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February 23[edit]

brightness of an inferior planet[edit]

Suppose you have in inferior planet like Venus. Assume that the planet orbits are circular and in the same plane. What is the equation of the apparent brightness of the inner planet as a function of where it is in its orbit? (When it is more than 1 AU away, more of it is lit but it is farther away, etc.) Bubba73 You talkin' to me? 02:12, 23 February 2015 (UTC)

Well, there's one formula for how brightness reduces with distance, another for what phase the body is in relative to Earth, and then the average insolation angle must also be considered. That is, is the sunlight reflected towards Earth from sun rays that hit the planet straight on, and are thus bright, or at a shallow angle, and are thus dim ? I suppose the average reflectivity of the place on the planet reflecting light towards Earth should also be considered, if it's not uniform for the planet. Mars has more reflective polar caps, but neither Mercury nor Venus do. StuRat (talk) 06:15, 23 February 2015 (UTC)
And assume that the planet is uniform. Bubba73 You talkin' to me? 08:24, 23 February 2015 (UTC)
I am really curious. What makes a planet inferior? That is a term I have never heard of when referring to a planet. (talk) 22:29, 23 February 2015 (UTC)
I think every planet is inferior to the Earth. :-) But astronomically it means that it orbits closer to the sun/star. In our case, Venus and Mercury are inferior planets, see Inferior and superior planets. Bubba73 You talkin' to me? 00:35, 24 February 2015 (UTC)
  • What will matter is the cross section of the plant visible, the planet's albedo, its distance from the sun (how much light is hitting it--which you are assuming is a constant, given a circular orbit) and how far from the earth it is (how much of that light is getting here. The lessening of the brightness will differ by the square of the distance. For an exact mathematically written formula you could pose this at the math desk. μηδείς (talk) 22:39, 23 February 2015 (UTC)
The actual albedo doesn't matter since it is assumed to be constant. Years ago I thought about working this out, but never got around to it. Maybe someone knows the answer to a simplier version - when is the inferior planet the brightest? Bubba73 You talkin' to me? 00:35, 24 February 2015 (UTC)
Well, yes, the albedo's constant, but two planets at the same distance will have different relative brightnesses as seen from earth if they have different albedos. In any case, I suggest you ask at the Math Desk, as someone will very quickly come up with an actual equation for your specified parameters.
(For example, I had an argument once over whether it made sense to run between shelters in a rainstorm. I argued that all other things being equal, the less time spent in the rain, the less wet you will get. But then we considered the effects of angle of attack. If you have a glass plate 1 meter square of negligible thickness (approximating an ideal windshield) and the plate is held horizontally and moves at a slow speed it ill get much wetter on the surface than a vertically held plate.
Paradoxically, if the plate is moving at the speed of light between shelters, it will get wetter when held vertically, because it will "scoop up" all the drops in front of it, whereas if held horizontally, it will get between shelters before many, if any drops can manage to fall on it. I posted that scenario at the Math Desk and quickly got a response that gave an answer for accumulated wetness depending on angle, speed and volume of rain per cubic meter and the angle and speed of the windshield.) μηδείς (talk) 18:27, 24 February 2015 (UTC)
Oh, an as to when the planet will appear brightest in the simplified question is a minimax equation that will be a function of the relative angle to the sun. As the planet gets closer to the earth it will shrink in appearance from a crescent to only showing the dark side when the angular difference is zero. As the angular distance increases, the amount of reflective face visibe t the earth will increase, but the brightness that reaches the earth will lessen in proportion to the square of the increasing distance. I don't know myself how to calculate the area of the visible crescent, so for the exact formula, again the Math Desk will be of help. μηδείς (talk) 18:35, 24 February 2015 (UTC)
Well, I found equations for the actual brightness of the planets in Astronomical Algorithms, by Jean Meeus, chapter 41. Bubba73 You talkin' to me? 19:15, 24 February 2015 (UTC)
OK, then let's mark this Q resolved. StuRat (talk) 19:23, 24 February 2015 (UTC)

Did the speed of light been a constant in nature?[edit]

The speed of light is been a constant only in the inertial closed physico-mathematical systems in which the observer and the light source are moved simultaneously, is it been so? I’m thinking that the speed of light in nature had an initial speed and final speed, is I’m right?-- (talk) 11:27, 23 February 2015 (UTC)

Read the article speed of light if this topic interests you. --Jayron32 12:08, 23 February 2015 (UTC)
Thanks! I’m assume that the speed of light is been a constant only in the case where the light source to constantly been in front of the observer.-- (talk) 13:18, 23 February 2015 (UTC)
Someone asked a similar question a while ago. It seems to depend on whether the light spectrum is an idea of optical or magnetic. I haven't seen that guy around in a while, but if you find him, he may be able to elaborate. InedibleHulk (talk) 13:31, February 23, 2015 (UTC)
In anyway cases, problems with the speed of light is always been solving in aggregate systems.-- (talk) 13:36, 23 February 2015 (UTC)
Like the gravel industry? Yes, asphalt can create some breathtakingly inferior mirages. Turns heat to water, at least as far as our optical systems are concerned. No electrical resistance, though. InedibleHulk (talk) 13:50, February 23, 2015 (UTC)
I'm talking about the fact that the study of the light is always been conducted in aggregate (totally) systems, that's why we been interested in aggregate (totally) sloving these problems.-- (talk) 14:29, 23 February 2015 (UTC)
The aggregate (totality) of tasks is always been determines the solution of the problem.-- (talk) 15:55, 23 February 2015 (UTC)
I have a bit of trouble parsing all of the question, but the speed of light in a vacuum (the thing we usually mean by "speed of light" and the thing thing that is constant for each observer) is constant for all observers, at least according to special relativity, which has been, to a very high degree, verified in nature. This includes unintuitive results such that two observers, one at rest with respect to a light source, and one approaching it at 1/2c in the frame of reference of the first observer will both measure the speed of a photon from that light source as the same constant c. --Stephan Schulz (talk) 16:21, 23 February 2015 (UTC)
If you watching the speed of light in different inertial systems, it will never been a constant, that's what I'm talking about.-- (talk) 16:41, 23 February 2015 (UTC)
No, if you are watching the speed of light in different inertial systems, it will ALWAYS be a constant. That's the basis for the various Einsteinian theories of relativity. --Jayron32 17:56, 23 February 2015 (UTC)
As I know, Albert Einstein solved the problem of relativistic quantum mechanics in the form of the closed inertial system which represents an aggregate (totality) of inertial systems. That’s why I think that Albert Einstein is been right in his particular case of physics which was been occupy whole physics.-- (talk) 18:51, 23 February 2015 (UTC)
There is been optics which based on the Laws of mechanics of the Isaac Newton, so why could exist the relativistic quantum mechanics which been based on the Laws of mechanics of the Isaac Newton?-- (talk) 21:07, 23 February 2015 (UTC)
By definition, optics involves light traveling through matter. That is, something not a vacuum. The speed of light in a vacuum is the universal constant. Light slows down when it travels through matter. --Jayron32 21:12, 23 February 2015 (UTC)
I’m thinking so, the optical medium is been a closed inertial system in which there is been an observer, and also to the same state of vacuums including the state of inert sparse vacuums are been unstable, so that the vacuum state is not been the ideal physical environment.-- (talk) 21:35, 23 February 2015 (UTC)
Everyone of those words is an English word, and yet that is completely nonsensical. Perhaps you'd have more success finding an "ask a question" website in your native language. It is hard for us to help correct your misconceptions when we can't tell your misconceptions from your impenetrably bad syntax. --Jayron32 00:53, 24 February 2015 (UTC)
Thank you! It is pity, but I was banned in the Russian version of Wiki. What from your point of view are being an optical mediums, it is a mediums which containing a light in self, or mediums which refract a light?-- (talk) 01:18, 24 February 2015 (UTC)
What be if we assumed that in nature the optical mediums are always been conductive environments, but not been dielectric environments?-- (talk) 02:41, 24 February 2015 (UTC)
As far as I know even Albert Einstein told that the cases of quantum mechanics been fully applied to the cases of conventional mechanics (mechanical movements of Isaac Newton), but I argue that this situation is been vice versa, that’s is been, the cases of conventional mechanics (mechanical movements of Isaac Newton) been generalized and complemented the cases of quantum mechanics.-- (talk) 17:03, 23 February 2015 (UTC)
From my point of vision, it is been natural, that quantum mechanics is been a part of conventional mechanics (mechanical movements of Isaac Newton)!-- (talk) 17:29, 23 February 2015 (UTC)
Can I recommend (again) that you seek the advice of the Language Desk on the proper use of the various parts of the verb 'to be'? It would make your posts here a lot more comprehensible. AlexTiefling (talk) 22:11, 23 February 2015 (UTC)

A Really Tall Ship, or how to "fly" a planet.[edit]

This is a question about flying an Earth-sized planet like a spacecraft.

The rules would be,

  • A roughly Earth-sized planet, not a gas giant. The latter would have lots of hydrogen and helium, which would make nuclear fusion more feasible than on Earth. However, if that's easier, an existing planet like Mars could be chosen, or even a plausible planet that doesn't exist (say, one halfway between Earth and Mars).
  • There should be mainly today's technologies, including everything we know but don't have in that quantity. Far future technology is forbidden; for example, with Honorverse technology and its near-magical gravity projection, flying a planet would be much easier, not to mention with Treknology.
  • Large-scale application is allowed and even encouraged. The planet might have an enormous number of fission plants for propulsion; however, the fuel needed must be plausible.
  • Efficiency figures can be estimated with some optimism; I'm not trying to fly away with Mars or anything based on replies on the internet. :)

The thoughts I came up with:

  • A "free" planet (not in the Lensman sense, just a planet that doesn't orbit a star) doesn't need a lot of acceleration; whenever it approaches a star, its inhabitants would see that for millions of years in advance, even with today's telescopes. That would, even if they were on a collision course with a star, open a very long time window to avoid that star. One millimeter per second is about 31km per year, or 1AU in 5000,000 years, so that tiny course correction would add up to a successful evasive maneuver. The disadvantage of the free planet is that it doesn't have access to cheap fusion, i.e. a star.
  • A free planet would also be much colder than Earth, and thus still have more hydrogen / helium in its atmosphere.
  • A "bound" planet like Earth could possibly use the solar wind to its advantage and slowly spiral in or out. Out being the way to go to counter solar expansion, but would it be fast enough? What I'm thinking of is a magnetic "sail" , a shaped magnetic field which deflects more particles to the direction from where the planet came than where the planet is going, and thus providing net momentum change. That would add to orbital velocity and cause the planet to spiral away from the star.

My question is if there are estimates, or maybe even scenarios on these cases, and if there are acceleration and/or delta v figures for bodies which fit my criteria. Or maybe some fatal flaws which would make my ideas fall flat.

Thanks in advance. (talk) 15:47, 23 February 2015 (UTC)

For a planet without an atmosphere (including where the would-be atmosphere is frozen or liquid), I like the idea of coilguns, pointing up from the surface. You could mine the planet for iron, accelerate it to the speed of light, and fire it in whichever direction you want to flee from. You'd have one main (fixed) coilgun, and smaller ones, which could be tilted, for maneuvering. Nuclear fusion would be a good power source. StuRat (talk) 16:05, 23 February 2015 (UTC)
(deleted - OP)
I didn't want any treknology or "accelerate it to the speed of light" magitech. See item #2 (talk) 08:08, 24 February 2015 (UTC) (OP)
That's not the way to comment on a reply even if it's off. StuRat probably meant "relativistic velocity". And he was talking about accelerating the iron to that kind of velocity, not the planet itself. Still a bit energy-intensive, though. - ¡Ouch! (hurt me / more pain) 09:27, 24 February 2015 (UTC)
Correct on all counts. OP, if you continue to behave like that, we may delete your Q and ban you from asking any more. StuRat (talk) 19:27, 24 February 2015 (UTC)
With enough guns, they need not even swivel. Most of the time, I imagine, "fire whenever the target acceleration vector is below your horizon" is enough control. —Tamfang (talk) 20:24, 24 February 2015 (UTC)
If none of the guns were tilted, then each would push the planet along a different vector, but none would rotate it so that the main gun could be used. You could have multiple guns with different tilt angles, as opposed to a smaller number (even just one) that swivel, but that would mean the vectors wouldn't be perfect, so you would waste some energy and matter that way. However, if making guns that can swivel is problematic, that might be the preferable solution. StuRat (talk) 20:31, 24 February 2015 (UTC)
You might find some fun stuff at this TV tropes page [1]. Lots of refs to sci-fi media, many of which at least wave their hands at the physics. SemanticMantis (talk) 17:45, 23 February 2015 (UTC)
I was thinking myself about Unicron. --Jayron32 17:54, 23 February 2015 (UTC)
These are fun. However, most depictions are just "bigger is cooler" stuff. In one old Japanese movie (1950s or early 1960s, and it's not listed at Planet Spaceship#Film), they used some huge chem-thrusters to move Earth, within months. (talk) 08:08, 24 February 2015 (UTC) (OP)
  • Alright, Earth gives you the problem figure: 5.97219×1024 kg = 3.0×10-6 solar mass (The latter is actually pretty amazingly high, when I think about it). To move that course, say, a km in a million years means an average transverse velocity of 1 mm/year (plate tectonics manages speeds this high, but only for thin little bits of crust, not the whole planet). That's an acceleration of ( 2 mm/year )/10^6 years (the 2 comes in because it only has top speed at the end...) So we need a force F = m a of 6 x 1024 kg * 2 x 10-6 mm/yr2 = 1.2 x 1019 kg mm/yr2. Now substitute 1 mm = 10^-3 m and 1 yr = (365.25)(24)(60)(60) s and we get ... 12 kg m / s^2 ?!. Hmmm, that's pretty remarkable. We're talking about, like, 1.2 kg of weight tugging on the planet continuously for a million years. Either I fouled up or this is more doable than I thought. Still, we have to bear in mind that to avoid a star you can't just move the planet by one km, but by some significant proportion of an astronomical unit, i.e. millions of kilometers. I think I'll pause and wait to be found out for an idiot before going on. Wnt (talk) 18:00, 23 February 2015 (UTC)
No it is quite practical, see [2] for instance. It won't turn the earth into a nippy Star Trek type spaceship but it could be used to for instance move the earth out to a safe distance as the sun gets hotter near the end of its life. Dmcq (talk) 21:08, 23 February 2015 (UTC)
IIRC, Master of Orion was the first computer game to feature a planet-sized starship. It was called "The Guardian". Coincidence? - ¡Ouch! (hurt me / more pain) 09:27, 24 February 2015 (UTC)
I was looking at a different approach: install some fission plants, power some big, probably city-sized ion thrusters and fire them when they are pointing the right way. This only assumes that the planet rotates at all, and doesn't have an atmosphere. For north/south maneuverability, one would need half a dozen thrusters and good timing. At the exhaust velocity of ion thrusters, vaporising the iron, or whatever, is only a minor power/efficiency issue before accelerating.
However, that "let a comet pull Earth forward a bit, and recharge it by letting Jupiter pull it" idea sketched in The Guardian looks really elegant. (talk) 08:08, 24 February 2015 (UTC) (OP)
(H:EC)Earth is about 6*1024kg, so we need about 6*1021kg m/s of momentum to get that 1mm/s velocity change.
It's well known that you need less reaction mass if you throw it out faster; OTOH, we're on a limited energy budget (again), and throwing it faster will use much more energy (4 times for doubled velocity).
OTOH^2, if we don't achieve escape velocity, which is about 11km/s, we won't change Earth's momentum, because the ejecta will return. It'd be a closed system.
The details are complicated, but an exhaust v which slightly exceeds escape v will result in a momentum change which depends strongly on how slightly we exceed escape v. I'll use 16.8km/s (1.5 times Earth's escape v ) from now on, which will result in about 12.6km/s "final" velocity.
So, we need to eject about 4.8*1017kg to get the desired delta v of 1mm/s.
Putting these together, we get m/2 v2 = (2.4*1017) (2.8*108)kg (m/s)2 = 6.7*1025 J.
One Joule is one watt-second, so 3.1*107Ws are a watt-year, and 3.1*1022Ws are a million gigawatt-years. If we could run 2200 gigawatt plants for one million years, we could eject all the matter necessary for 1mm/s.
With a bit of luck, we would invent a fusion plant before our fission fuel runs out. (With today's technology, we only have two sources of power: fusion and fission. Everything except fission fuel is ultimately solar fusion energy if you go all the way back. And solar fusion wouldn't be available on a rogue planet (that's what you called a "free" planet). I assume you don't want me to invent things as exotic as a p-brane tap, which would provide essentially unlimited energy.)
For a rogue planet, any encounter with a star is an opportunity; the closer you get, the more it will deflect your course. If you get close enough, you can use an early course adjustment in the range of mm/s to get a deflection in the km/s range.
"All I ask is a tall ship, and a star to swing her by." - ¡Ouch! (hurt me / more pain) 09:27, 24 February 2015 (UTC) BTW, I like that word. "Treknology".
Fun though this is, the Reference Desk isn't really here to engage in speculation. This question would be better asked of Randall Munroe in the "What If" section of his xkcd comic strip. RomanSpa (talk) 09:05, 24 February 2015 (UTC)
I suppose this is a valid RD question. For one, the IP didn't ask for speculation, nor "But what if we tried more power?" - ¡Ouch! (hurt me / more pain) 09:33, 24 February 2015 (UTC)
I think it's possible to defeat the OP's suggestion of using a thruster that is timed to fire only when the planet rotates into the right position, but alas, my physics-fu feels weak today. I'm thinking that there's no obvious drawback to realigning the rotation of a rogue planet however is convenient; and of course what's convenient is to have one pole facing in the direction you intend to thrust so that you can fire your thruster 24/7. (If you're using thrusters that is) Problem: how much energy does it take to realign a planet's axis? Well... I'm thinking it's not energy, but angular momentum... in theory, you ought to need very little energy I think, provided you're able to throw off enough sheer mass of propellant (because KE = 1/2 mv^2, but momentum is just mv, in this case multiplied by the torque arm) But what the practical minimum is, assuming some grand space elevator, balancing KE vs. lifting energy vs. escape velocity... that I don't know. It's also worth noting that angular momentum changes can sometimes be put on a planet from a fairly long range, as with the precession of the Earth's axis, and I don't know how clever and creative you can be with that. I'm thinking a better answerer could come up with a calculation to put those timed rocket firings right out of your mind, but that's just a guess. Wnt (talk) 23:01, 24 February 2015 (UTC)
The problems with using a thruster only when the planet rotates into the right position:
1) The thruster will only move in a circular pattern (well, precession of the equinoxes may eventually move it in a broader band, but that would take thousands of years). There's no guarantee that the direction they want will lie on that circle.
2) Obviously, you'd only be able to use the thruster a small portion of the time. This means either you would accelerate much slower, or you would need a far bigger thruster.
3) Turning the thruster on and off might create annoying tremors around the site, and eventually cause structures to crack and fail. (Presumably any thruster would need to be turned on and off periodically for maintenance, but hopefully not once a day.) StuRat (talk) 23:11, 24 February 2015 (UTC)
1) That's why I had a dozen or so in mind, not just a single thruster; that way, I could use a combination of the thrusters that come closest.
2)Yes, that would definitely be an issue, but I could use it for 6 hours a 24-hour day, if I could live with the partial cancellation of "diagonal" thrust near the beginning and the end of each burn. (Tamfang & StuRat suggested a similar approach, but with ~12 hour burns.)
3)I had a gradual ramp-up, maybe during one or two hours, and a corresponding power-off at the end in mind. I don't know if that would complicate or simplify thruster design and maintenance; maybe the thrusters don't work properly if they don't run at or near design specs? The worse angles near the beginning and end of each thrust cycle would exacerbate the diagonal thrust cancellation, too.
4)Sorry StuRat, for my rude reply yesterday. I got the "accelerate to light speed" part of your reply wrong, and overreacted. Thanks Wnt & Ouch! for the numbers. Fuel availability looks like the bigger issue; power demands look high but not prohibitive (at least if we assume high efficiency). And thanks for recognizing the "tall ship" reference.
With a captured planet like Earth, would the solar wind provide enough force to push Earth? The magnetic field idea looks quite good to me; deflecting the particles should be easier than coating Earth with solar cells. (talk) 11:21, 25 February 2015 (UTC)
Awww hell, this isn't what you meant but you gave me an idea... Iapetus orbits about 9.5 AU from the Sun, so it gets 1/90 * 1366 W/m2 (which is what the Earth gets) * [the 2D area] pi * 735 km^2 of light on it. That's roughly 2.6 x 1013 watts of power. When it is going away from the Sun, it bounces half of that power back out in a roughly hemispherical pattern I won't pretend to calculate accurately; I'll pretend roughly half of that is bounced straight back at the Sun. When it is approaching the Sun almost all is absorbed. (That's because it's the famous black-and-white moon) Adding another fudge factor I'll divide by, oh, 6, because it only really gets that extra push at one edge of the orbit. So that's, oh, maybe 2 x 1012 watts of power bounced off in such a way as to propel it faster in its orbit by light pressure. Energy = momentum x c, so 2 x 1012 W [kg m^2 / s^3] / (299792458 m/s) = roughly 7000 kg m / s^2. Divide by the mass of Iapetus = 1.8 x 1021 kg and you get a steady acceleration of ... 4 x 10-18 m / s ^ 2. To increase the moon's orbital velocity by 1 m/s it therefore should take 2.5 17 seconds / 31557600 = 8 x 10 9 (8 billion) years, which is indeed a slow, but not utterly insignificant effect. But to simply move it a meter forward in its orbit means you get to square the time, so inverting 2 x 10-9 /s means you need, oh, roughly 16 years. But since that just moves it in a circle it's not very noticeable. :) Wnt (talk) 18:15, 25 February 2015 (UTC)
So, a Pioneer anomaly writ large? - ¡Ouch! (hurt me / more pain) 09:55, 27 February 2015 (UTC)
Another link that could be useful: [3]. The grav assist is the highest on their list, too. But it doesn't work on rogue planets.
The magnetic field approach doesn't sound that bad. It's very low on the qntm page, but if you made a length of wire in orbit around the Earth, it could both create a magnetic field to "grab" onto the solar wind and grav-tractor us along. Solar cells could provide the power needed.
WAIT. If we're not trying to use an electromagnet to move the planet directly, but to grab onto the solar wind and to drag the planet along by gravity, it is not really method #1 (the least plausible), it becomes method #5, which is as plausible as it gets without resulting to blunt force (#6) or the already mentioned grav assist(#7). - ¡Ouch! (hurt me / more pain) 09:55, 27 February 2015 (UTC)
And another relevant article: Magnetic sail. It mentions a pressure of about 0.01mPa, so you need about one km² per kg-force of thrust. A large hoop around Earth would result in billions of kg-forces, or tens of giganewtons. The article confirms that although the solar wind is weaker than sunlight, it can be "harvested" using a lighter device because it doesn't have to hit solid matter to be deflected; this could well be the way to move Earth. Oops, I'm speculating... - ¡Ouch! (hurt me / more pain) 10:23, 27 February 2015 (UTC)


Am I right in thinking that when writing reports its not necessarily to reference anything that's common knowledge in that industry. So for example saying that using a clean room for any scientific experiment would reduce contamination is generally common knowledge as is using a certain type of microscope to look for certain things etc. (talk) 19:33, 23 February 2015 (UTC)

They could still be specific. For a clean room, they could specify exactly how clean, like "removes 99.999% of all particulates above a size of ...". StuRat (talk) 19:48, 23 February 2015 (UTC)
If the report was concerning clean rooms, they would probably be aware that cleanliness is categorised using standard methods.--Phil Holmes (talk) 14:06, 24 February 2015 (UTC)
Unless the experimenters directly checked this, they would probably just name the equipment, e.g. laminar flow hood. But I don't think that's often specified in tissue culture papers. Someone might use a lab manual reference for the kaboodle, i.e. "routine cell passaging and harvest was done per [1]" where 1 is Maniatis or something, whatever your lab prefers, and that book might have a section on recommended sterile procedure. Wnt (talk) 20:51, 23 February 2015 (UTC)
In a somewhat different context, cleanliness might be implied when specific guidelines are quoted, e.g. Association for Assessment and Accreditation of Laboratory Animal Care International. Wnt (talk) 21:01, 23 February 2015 (UTC)
Over citing rarely hurts anything, while under citing because of supposed "common knowledge" can lead to misunderstandings, possibly even accidents. You may wish to read Wikipedia:You_do_need_to_cite_that_the_sky_is_blue. SemanticMantis (talk) 20:13, 23 February 2015 (UTC)
The issue, as always, is common knowledge to whom? Wikipedia should be written for people who know nothing about the subject they are reading about. It should not consider common knowledge those things which are commonly known only among experts in the field. There's a difference between citing something like "the sky is blue" which depends only on basic human experience, and citing something which requires at least some background in the field of study. One may not always need to cite the former; the latter should ALWAYS be cited. --Jayron32 21:09, 23 February 2015 (UTC)
See also WP:POPE - do you really know what everyone who reads your report already knows and doesn't know? SemanticMantis (talk) 20:19, 23 February 2015 (UTC)
The PhD dissertations I've looked at have run to dozens or hundreds of pages to cover the same material that a couple page journal article would because of the need to reference and explain every little detail. Rmhermen (talk) 20:57, 23 February 2015 (UTC)
Sure, in a dissertation, 10 or 15 papers might be cited each covering a small point. In a journal article, the material might get one cite: (reviewed by Xu et al., 2013). But that's all the domain of academics. Context is important but "reports" for an "industry" doesn't give us much to go on. I'd hope that reports in the nuclear engineering industry are more heavily cited than reports in the fashion industry... SemanticMantis (talk) 21:16, 23 February 2015 (UTC)

Title lineage of University Physics[edit]

For the textbook University Physics by Sears, Zemansky, and Young, which the referenced article says is in its 13th edition, is the title "College Physics, 7th Edition" (of which I have a copy with those authors listed) with ISBN 0-201-17285-2, one of the editions, or was/is there a separate title line in which all editions are entitled "College Physics"? (talk) 20:08, 23 February 2015 (UTC)

I think it must be the same - Bookfinder doesn't seem to list an edition of University Physics earlier than the 10th edition. Bubba73 You talkin' to me? 01:13, 24 February 2015 (UTC)
They're different series. (Confusing, though.) See for example the 3rd editions of College Physics [4] and University Physics [5]. I believe, although I don't have them handy to check, that the secret code is "college"=algebra and "university"=calculus. --Amble (talk) 01:32, 24 February 2015 (UTC)
Oh yes, should have looked at reference #3. Bubba73 You talkin' to me? 01:52, 24 February 2015 (UTC)
And Hugh D. Young: "Young also wrote an algebra-based version named Sears and Zemansky's College Physics, which is currently in its 9th edition." Bubba73 You talkin' to me? 01:56, 24 February 2015 (UTC)

If beer and wine are acidic, then why do they taste bitter?[edit]

Why might have caused the bitter taste? Could it be a chemical compound, or could it be the taster's genes? (talk) 22:14, 23 February 2015 (UTC)

  • Alcohol itself is considered to be one of the tastes. Beer can be bitter because it has a quantity of roasted malt byproducts, and wine picks up some of its quality from the barrels it is aged in. μηδείς (talk) 22:32, 23 February 2015 (UTC)
Hops are used to give a bitter taste to beer - the details are explained here. Apparently the hops contribute a variety of acids that taste bitter. Mikenorton (talk) 22:40, 23 February 2015 (UTC)
I am not at all sure that is correct. Hops are the closest relative there is to the cognate hemp (Cannabis). I suspect the original reason was for effect, not a biter taste. μηδείς (talk) 05:34, 24 February 2015 (UTC)
Even the most casual reading of our own hops article shows your idea is nothing but nonsense. (talk) 17:35, 24 February 2015 (UTC)
The acidity gives rise to the sourness of beer and wine. As Mike says, the bitterness of beer comes mainly from hops, a bitter-tasting herb. The bitterness of wine comes mainly from tannins in the grape skins, and, for wine that is aged in barrels, from tannins in the oak. Looie496 (talk) 22:53, 23 February 2015 (UTC)
Simple, inexpensive white wines fermented in stainless steel will lack tannins, and will be about as sour and about as acidic as diluted lemon juice. Cullen328 Let's discuss it 22:58, 23 February 2015 (UTC)

The link claims that the bitter-tasting chemicals in hops are acids, specifically alpha acids, and our article seems to agree. I don't understand, though, how are these molecules acids? Where do the protons come from? If it's from the hydroxyl groups, why aren't they just as likely to split off an OH- as an H+ ?
Take a look at Vinylogy, which may help a bit. Mikenorton (talk) 23:17, 23 February 2015 (UTC)
Enol might be the better article, it's a bit easier to understand and the concept is the same. In any case, it's the alpha-carbon that loses the proton. shoy (reactions) 16:38, 24 February 2015 (UTC)
Also, I had the notion that bitterness was a marker of either alkalinity or reduced nitrogen (of course, they often go together), and these substances (assuming they're really acids) don't seem to supply either. So I'm missing something.... --Trovatore (talk) 23:03, 23 February 2015 (UTC)
Bitterness is not a simple chemical property. It is a measure of the ability of a substance to bind to a subset of taste receptors -- there are over 20 distinct types of receptor that contribute to the sensation of bitterness. Their biological function is to be activated by substances that have a high probability of being poisonous. Looie496 (talk) 23:14, 23 February 2015 (UTC)
Yep, we have an article on bitter taste evolution. SemanticMantis (talk) 20:41, 24 February 2015 (UTC)

To answer the point above, hops were originally used in beer as a preservative and to balance the sweetness of the malt. Now the type or blend of hops used is an integral part of the taste of bitter beer - see Hops. Richerman (talk) 10:28, 24 February 2015 (UTC)

Our article says that, with a cn tag added. I still think the reasoning is post hoc, propter hoc. I strongly doubt anyone ever said randomly, this beer is too sweet, I know, lets add some roasted hops to make it bitter. That's kind of like saying the reason you put gas in a car is to get rid of the new car smell. I suspect there was originally some other reason for adding the hops, and the bitter taste just became standard. Also, if one has had beer made with cannabis in place of the hops, it is no less bitter, but a little bit better. μηδείς (talk) 18:08, 24 February 2015 (UTC)
So 'twas better Betty Barter bought a bit of better bud? --Trovatore (talk) 18:52, 24 February 2015 (UTC)
You want to call citation needed on hops preserving beer!? Or that someone might want a more bitter brew?! I think you're just bitter because your first response was totally wrong ;) Malt is sweet, and has many sugars, including Maltodextrin, Hops are bitter, and they act as a preservative in beer. If you want a citation for the claim that hops preserve beer, check out [6]. If you think hops have have an "effect" that is not preservation or bittering (are you implying psychoactive?), then [citation needed] for that. Hops are in the same family as Cannabis, but so are hackberry spp, so [citation needed] on the claim that hops is the closest relative to Cannabis. Next, many people dislike sweet beers. Is it that hard to conceive of? Just google /beer to sweet/ for plenty of examples. Finally, taste does not say that alcohol is "considered one of the tastes", it says that ethanol tastes bitter. SemanticMantis (talk) 20:41, 24 February 2015 (UTC)
You seem to be freaking out on multiple fronts, SM, and I would appreciate some more focus on the issues, and less on me. For example, I did not add the cn tag to the hops article. You can take that up with the article's edit history.
If by Hackberry, you mean the town in Arizona, you are wrong. If you mean Celtis, you are still wrong. Hemp and hops are each other's closest relatives.
The speculation that soma, which was brewed by the early Indo-Europeans, used cannabis is of long standing (a not necessarily RS that at least mentions references). Given that cannabis was not native to Europe, but Humulus lupulus which resembles it is, it is quite possible the Europeans substituted the latter for the former. It's simply absurd Ockham's Razor to assume people started cultivating an uncommon plant to make their beer taste bitter. As for taste, the article mentions alcohol as bitter, but other studies on the net say its taste varies according to genetics, and I have indeed read where it has been proposed as a "basic" taste like fat and umami, although a quick google search was unhelpful. μηδείς (talk) 21:56, 24 February 2015 (UTC)
Hmmm, this conversation needs to be grounded in some technical discussions of gruit that are beyond my competence. While I suppose only the most die-hard aficionados of beer would say that restricting brewers to hops was Germany's worst purity law, it should be clear that beer was once a much more diverse and interesting set of multi-ingredient herbal preparations, complete with some rather alarming "narcotics" like henbane. Damn, I forgot all about one of my past daydreams to do Michurinist graft hybridization of hops onto cannabis rootstocks (now legal in some places and highly selected to produce certain chemicals) in order to see if the transferred small RNAs would create desirable changes (but not THC production!) on the hops. Wnt (talk) 23:31, 24 February 2015 (UTC)
My main point was the issue of the question, though thank you for your concern. I wanted to make sure readers knew not to trust your original response about bitterness in beer, because it is wrong. I think I have enough links now to support my case, so I'm done here. SemanticMantis (talk) 17:25, 25 February 2015 (UTC)

The relationship between acidity and taste is not straightforward. Coca Cola is very acidic. I even used it once to remove some rusty boults to replace a flat tire. But the taste of Coke is mostly sweet. And you can make a sour orange taste sweeter by adding a little salt. --Judithcomm (talk) 08:49, 26 February 2015 (UTC)

Comparing human and machine energy efficiency[edit]

Can humans or machines extract more energy from a gallon of fuel (food for the human, gas or diesel for the machine)? It's clear that maybe humans can walk, cycle or run a shorter distance due to all the heat being generated and lost. After all, maintaining life is more important than moving. But I'd like to know how the two compare, if we count all the energy humans are obtaining from food and all work done, not just locomotion.--Senteni (talk) 22:35, 23 February 2015 (UTC)

They both extract comparable amounts of energy, but what matters is the fraction of that energy that can be converted to kinetic energy, as opposed to the fraction lost to heat. The human body is generally thought to have an efficiency of energy conversion of around 20-25%. For machines the numbers vary so widely that it is impossible to generalize. Most gasoline-powered automobiles achieve efficiency comparable to the huma body, but diesel engines usually reach efficiencies in the 30-40% range.Looie496 (talk) 23:08, 23 February 2015 (UTC)

Poincare thought experiment[edit]

Martin Gardner in Relativity Simple Explained mentioned Poincare thought experiment, which says there would be no means to detect any change if the universe and everything in it tomorrow becomes proportionately larger (or possibly smaller). I had a quick thought: wouldn't we notice that it would take more (or less) time for the light to reach the Earth, for instance? That said, assuming the speed of light and time itself wouldn't change (a second would remain a second, a minute would still consist of 60 sec, etc), it should take more time (if the universe becomes larger) for the light to cover any distance, meaning we would notice the changed size of the universe, being accustomed to the previous size. Am I missing something? Brandmeistertalk 22:50, 23 February 2015 (UTC)

They were likely assuming the speed of light would change proportionately. StuRat (talk) 23:59, 23 February 2015 (UTC)
They explicitly tells you that everything would change, including wavelengths. The thought experiment is meant for you to realize a basic concept. In this case, you should ask yourself whether distance can be absolutely be measured or it is relative to other stuff.--Senteni (talk) 00:53, 24 February 2015 (UTC)
If I understand it correctly, a change in wavelength wouldn't imply change in the speed of light, but even if it also changes, we would certainly notice that it's not the same as previously. Brandmeistertalk 08:24, 24 February 2015 (UTC)
And how would you measure anything, if everything is half of what it was yesterday, including your ruler? If in a half-so-big universe the constants like speed of light are half of what they were, you'll have no chance of noticing a difference. — Preceding unsigned comment added by Senteni (talkcontribs) 15:13, 24 February 2015 (UTC)
I now suspect that something would definitely go wrong due to possible violations of baryon number and other fundamental constants, but that steps into the concept of fine-tuned Universe. Brandmeistertalk 17:22, 24 February 2015 (UTC)
can massless elementary subatomic particles within a single atomic structure be infinitely close to each other? (talk) 19:57, 24 February 2015 (UTC)
I assume you mean gluons which are the only known massless particles that that remain within the atomic structure (the others, photons and neutrinos are best regarded as waves for most purposes). I think they can be arbitrarily close, especially in a quark–gluon plasma. Dbfirs 21:10, 24 February 2015 (UTC)
But of course. (talk) 21:37, 24 February 2015 (UTC)
The point is that if you uniformly scale all the numbers that refer to distance, it's just like changing your base unit of distance, and has no physical consequence. If you can come up with an experiment that detects the change then you forgot to scale something. If you think the speed of light will be detectably different then you probably forgot to scale c. If you think the Compton wavelength of the electron will be detectably different then you probably forgot to scale h and/or c. Every quantity is scaled by the power of distance that appears in its units. For example c has units of distance/time so it should be scaled by k, the overall scale factor; h has units of mass·distance²/time so it should be scaled by k²; the diameter of the earth has units of distance so it should be scaled by k; and so on. -- BenRG (talk) 22:18, 24 February 2015 (UTC)
Thanx, those were the aspects that buffled me. Brandmeistertalk 09:24, 25 February 2015 (UTC)
you should be able to detect the change proportionally with respect to time in the the twin experiment. 2601:C:3600:46B:A926:7032:DCEE:D302 (talk) 09:32, 25 February 2015 (UTC)
Incidentally, I don't think you should try to learn special relativity from Martin Gardner, since I don't get the impression that he understood the theory himself. He was primarily a journalist, not a scientist, and certainly not a physicist. I'm a fan of Einstein's own Relativity: The Special and the General Theory. There are cheap printed editions available and you can download it free online since it's in the public domain. Einstein was an engaging writer and he understood the theory better than, frankly, the vast majority of later popularizers. I can't recommend his section on general relativity, though, since it's based on the "general principle of relativity" which is now a historical curiosity. -- BenRG (talk) 22:33, 24 February 2015 (UTC)
The flip side of this question is whether we "really" live in an expanding universe, or whether some of the underlying physics is changing so that atoms and various other things are getting smaller. I think I asked something along this line a while before here and basically the answer is that either you're in possession of a model by which your new paradigm makes it easier to work the math, or else you have some groovy bong-hit philosophy and your dick in your hand. :) For the original question, if we suppose that every aspect of the data (and therefore the math that underlies it, is unaltered, then the change in "actual" size, that we can't measure, has to be dismissed as unobservable. Otherwise, we start doing math on whatever observations change. Wnt (talk) 23:23, 24 February 2015 (UTC)
wnt, could you clarify what you mean by underlying physics is changing? Because I would say the physics does not have to change for that to be true. It is actually a perfect fit to help explain time. Delta t is delta shrink. That is how the universe differentiates now from now. (talk) 03:09, 25 February 2015 (UTC)

What does it take to set up a personal laboratory in the 21st century?[edit]

I have heard and read that in history, people just funded their own research, and if they were broke, then they're out of luck, unless they asked a wealthy person to finance their research project or invention. Now, in the 21st century, what does it take to set up a personal laboratory in the 21st century in order to conduct research? Is the person allowed to publish research papers even without any academic degrees? Does the researcher have to take into account of ethical/safety standards, or will he/she have to put his/her own life at risk? (talk) 23:40, 23 February 2015 (UTC)

It will depend greatly on what you want to research. If you want to compare the liver size in various frogs, that could be done pretty cheaply. If you want create a sustainable fusion reaction, that might cost a tad bit more. :-) StuRat (talk) 23:57, 23 February 2015 (UTC)
(ec)It depends on what sort of research you want to do. Amateur astronomy is easy to get in on with a small amount of investment. I'm guessing you're talking chemistry/biology/physics, though. There's a growing movement of DIY biology, including a growing number of hackerspaces with a science twist. Reagents and equipment can be obtained by private individuals from internet sites like eBay, or even from standard scientific suppliers. Keep in mind, though, that certain materials are illegal to purchase or possess without a license or some sort of official affiliation. This is particularly true for chemistry items, where the sale of things like Erlenmeyer flasks are restricted in some jurisdictions as "drug paraphernalia" (due to their use in meth labs). Regarding publishing, an institutional affiliation is not strictly required for publishing, but submissions from independent researchers are likely to be scrutinized more heavily than those from recognized institutions. Having a previous track record of scientific publishing would help in this regards - it's not that independent researchers can't do good science, it's just that the balance of probabilities are such that submissions from a non-affiliated researcher are likely to be from a crackpot, and no one wants to waste their time on improperly performed drivel. Independent researchers should take in to account ethical and safety standards - many journals will require ethical oversight of research, especially that involving humans or other vertebrates, and will refuse to consider research which doesn't have ethical oversight. Safety standards are less rigorously enforced by journals, but should be accounted for anyway - particularly as performing experiments without the proper safety precautions may be illegal in your jurisdiction. In *all* research, whether independent or institution-affiliated, a researcher should never perform experiments where their own health or welfare are put at risk - or where the health and welfare of others or the environment is put at risk. If an experiment can't be completed safely (or if it's unknown if the experiment is safe), it shouldn't be attempted in the first place. -- (talk) 00:19, 24 February 2015 (UTC)
Partly false. Researchers can perform experiments where their own health and welfare are put at risk; indeed, this is sometimes the only person they are allowed to perform the experiment on. The most famous example is probably this, which won the experimenter a Nobel prize. RomanSpa (talk) 12:35, 24 February 2015 (UTC)
30 years ago yes. Today may be a bit different. --Jayron32 13:34, 24 February 2015 (UTC)
  • It might help if you told us where you heard and read where such people existed. Was it natural historian? Were they sharecroppers, or clergy, heirs, and minor nobility? Have you read peer review? Have you read Einstein? He was published well before he earned a PhD. Give us some context so we can better assist you. μηδείς (talk) 05:28, 24 February 2015 (UTC)
  • In some subjects it is possible to do research with very few resources, and, yes, you can (though it is rare) publish without being affiliated to an institution, as your paper will be subject to the same peer review process. My mother maintained a small research effort into the reproduction and behaviour of various weevils on a kitchen worktop. Total area used was about 1 sq metre, and academic output was principally in the form of correspondence with the Royal Entomological Society. Amusingly, her interest was piqued by finding an infestation in a bag of flour.
My niece is currently breeding Drosophila melanogaster in her bedroom. Academic output so far seems to be a couple of essays for her school biology class. Cost is negligible, as she is now using her grandmother's microscope. RomanSpa (talk) 09:28, 24 February 2015 (UTC)
Perhaps it is instructive to point out that much research and development takes place in the private sector. If a private company wishes to hire and fund your research, they may choose to do so, irrespective of your credentials. Generally, well-credentialed people have an easier time getting other people to take them seriously, so it's very common to find that an academic degree is an "implicit" prerequisite. There are exceptions: one Peter Thiel will aggressively fund ideas and individuals of his choosing, provided that the youngster signs a contract obligating them not to take any academic training. This is a notorious exception: Mr. Thiel, however wealthy or successful he may be, is a crackpot. Nimur (talk) 15:09, 24 February 2015 (UTC)

February 24[edit]

Chemical composition of Steam[edit]

If I wanted to know if something was burned by steam , and the residue was carbon , what would the exact chemical composition(formula) be if it was tested , and steam or water was the cause or present , for instance if metal or an alloy was extremely hot and cooled down suddenly and shattered and left a carbon residue and was tested what would the chemical formula be does anyone know ??? or apart from everything else will H2O be present no matter what ?? — Preceding unsigned comment added by (talk) 06:40, 24 February 2015 (UTC)

If carbon residue is left by steam, it wasn't steam, it was smoke. Carbon residue means soot is present, and carbon is not water. Steam is gaseous water (H2O) has no carbon in it. If it leaves carbon, it had carbon to begin with. --Jayron32 12:28, 24 February 2015 (UTC)
You might also want to read about how real-world fire investigation uses forensic evidence to draw conclusions about a catastrophic event. NIST even offers a program on the topic, with several books listed as sources: Disaster and Failure Studies. Nimur (talk) 14:55, 24 February 2015 (UTC)

Is there a maximum time limit to a human courtship?[edit]

Courtship explains that in the UK, people court about 2-3 years. This does not mention statistical outliers. In that case, what is the longest human courtship known? 5 years? 10 years? 25 years? 50 years? (talk) 18:47, 24 February 2015 (UTC)

One famous outlier was Michael Winner who married 70-year-old Geraldine Lynton-Edwards when he was 75. They had been courting for 50 years, on and off. Dbfirs 18:56, 24 February 2015 (UTC)
Although he apparently had women in his life - including a prior marriage. Hard to count it as a courtship in the circumstances. Collect (talk) 19:10, 24 February 2015 (UTC)
This might be better asked on the Humanities desk. -- LongHairedFop (talk) 19:26, 24 February 2015 (UTC)
Collect's comment above along with Dbfirs example sort of hinted at this. I think this question (as with many) is basically impossible to answer, unless you come up with a precise and clear definition of courtship. (Well even then it's probably impossible to answer since it's unlikely to be something recorded.)

Our article uses, "Courtship is the period in a couple's relationship which precedes their engagement and marriage, or establishment of an agreed relationship of a more enduring kind. During courtship, a couple get to know each other and decide if there will be an engagement or other such agreement." It also mentions how courtship practices vary significantly.

Consider the example above, they seem to fit within this definition for the 50 years or so, yet a both Dbfirs and Collect hinted at, many wouldn't count the whole thing as courtship.

Or consider if two people meet as young kids, perhaps they become friends. They stay that way for many years. At some stage they realise they have romantic feelings for each other, and begin a dating. Under the definition used in our article, it would seem you should count the time from when they first met, but I think many would only count around the time they began to realise they have feelings.

Yet that isn't simple either. What happens if only one party initially develops feelings, and it takes a long time and a lot of effort before the other party does likewise (probably most such relationships end in disaster but you did ask for outliers)?

Or if you're taking the looser definition, what about if the couple meet as children and then lose touch for many years? What about if they meet and know each other but have only minimal contact?

As for my earlier point of differing practices, on Collect's point, even if not true for the above case, in some cultures polygamous (mostly polygynyous) marriages are acceptable. In such cases it may be acceptable for one partner to be publicly courting another person while already married. Of course in many cultures, publicly courting multiple woman may be acceptable at least at an early stage.

Our article mentions UK averages and also the earlier point "establishment of an agreed relationship of a more enduring kind". In the UK and some other countries, it isn't exactly uncommon for a couple to start cohabitating before even engagement. Are they still courting then?

It definitely doesn't fit many traditional definitions of courtship, even in these countries. Note in some countries, e.g. NZ such a relationship may have legal implications at some stage perhaps being treated very close to a marriage, but will legally never be a marriage without the formal process. And depending on the couple, the engagement and marriage, while perhaps important, may not be that important. (And also sometimes may only come after many years of cohabiting and describing each other as partner or spouse, kids, basically everything you'd expect in marriage except the certificate, except of course marriages themselves existed long before certificates and there are still plenty of places where it isn't necessary for something to be legally considered a marriage. In fact sometimes they may never get married, see my later point.) Yet if you count the cohabiting as the end of courtship, consider some may jump in to this extremely readily, and perhaps even stop doing it due to relationship problems a few times and not really consider their relationship anything that special at least the first time they are cohabiting.

Also are you only counting successful courtship? In other words, if a couple spend a lot of time together developing a romantic relationship but it ultimately doesn't work out, are you counting this or not? Consider if you require a successful marriage proposal, or even a marriage, you're ruling out for example, a case where a couple a courting and one party plans to propose to the other and the other party basically knows and tells several people close to them (and it's clear they will accept), but one of them dies before this can happen. (Or alternatively one person dies before marriage.)

Nil Einne (talk) 20:08, 24 February 2015 (UTC)

I know a couple who were engaged for more than thirty-five years. They were finally married in summer 2014. Not a dry eye in the house, apparently (I wasn't there myself - don't know them that well). RomanSpa (talk) 23:24, 24 February 2015 (UTC)
The second Google hit on longest courtship is from 1915 and says: "The longest courtship on record ... seventy-five years".[7] PrimeHunter (talk) 23:25, 24 February 2015 (UTC)
Note that both RomanSpa's and PrimeHunter's examples further illustrate the point above. In RomanSpa's example, the couple were engaged and I suspect their relationship was not that different before and after marriage, they were simply prevented by the laws of where they lived from being married. While it sounds like their marriage is very important to them and it's rather sad they were forced to wait so long, whether you want to call that period courtship will vary. It doesn't fit the definition from our article (and it would I presume not count in the survey). Conversely many such couples may have never had a formal engagement because they couldn't get married and didn't know when they were going to be able to. Are you going to count one as courtship, and one not, despite the fact the relationships before and after marriage may be similar? In the example mentioned in PrimeHunter's ref, although it calls it courtship, there's mention of how the bridal day was repeatedly deferred and ended up happening when one partner was dying. This suggests there could have been an engagement, or at least there were apparently some sort of specific marriage plans during the courtship. Nil Einne (talk) 16:10, 25 February 2015 (UTC)
I'm suspicious of PrimeHunter's example. It's next to another space-filling item saying that backgammon was invented in 1224, which it wasn't. The same story appears in newspapers as early as 1902, and none of them give the year of the alleged wedding, which is usually not a good sign. -- BenRG (talk) 22:54, 25 February 2015 (UTC)

Growing outside the womb[edit]

You know how some species like chickens lay eggs? Well, is it possible to make an artificial "egg" for a human fetus? At birth, will the human fetus have the ability to kick out of the shell? Who will nurture the child when it's born? (talk) 23:04, 24 February 2015 (UTC)

Artificial wombs are an appealing idea, but ... let's be realistic. Infant formula, replacing the seemingly simple nutritional recipe of breast milk, is so laughably deficient that many studies have found the babies to lose 5 or 10 points of IQ from the unwholesome substitution. Breast milk isn't even alive and we fall flat on our face trying to replace it. Much the same can be said of blood substitutes; whenever some group of luckless souls becomes the newest victims of the doctrine of "community consent" to some Frankensteinian experiment at the cellular level, double digits more people die than would have died if given normal blood transfusions. Now imagine that instead of trying to replace a mere fluid, you're trying to replace a living human woman, with many endocrine glands, bone marrow, digestive tract, even the occasional inscrutable but likely vital instinctive call for pickles and ice cream, all responding to the pregnancy. This is an idea that will be proposed ten thousand times but never happen. Wnt (talk) 23:14, 24 February 2015 (UTC)
Can you point me to at least one study that "found the babies to lose 5 or 10 points of IQ from the unwholesome substitution"? Ruslik_Zero 19:14, 25 February 2015 (UTC)
Infant formula#Health risks says: "Some studies have found an association between infant formula and lower cognitive development, including iron supplementation in baby formula being linked to lowered I.Q. and other neurodevelopmental delays; however other studies have found no correlation." You may wish to follow the references given there. -- ToE 16:59, 26 February 2015 (UTC)
What about babies that are breastfed AND cowmilk-fed? Does that decrease IQ? (I was one!) (talk) 23:33, 24 February 2015 (UTC)
Neglecting the hyperbole, the answers to your questions are: No, it is not possible to make an artificial "egg" for a human foetus; No, the child will not have the ability to kick out of the shell, because (a) the shell is likely to have to be fairly thick to hold the amniotic fluid in place, and (b) humans do not have that kind of instinctive kick reaction at the moment of birth; No-one will be needed to nurture any children born in such as way, because nobody is going to be born that way any time soon. Despite the previous comment, it is impossible to permanently rule out this technology, but it is unlikely to happen in the near future. A technology of this kind would certainly save lives (pregnancy carries substantial risks for the mother), but is a long way from being developed. RomanSpa (talk) 23:38, 24 February 2015 (UTC)
Agreed that just because we can't do it now, that doesn't mean we will never be able to do it. After all, we have artificial bone, teeth, and (temporary) skin. That said, this seems similar to the "living head in a jar" concept we often see in sci fi, which presumably is also a long way off. StuRat (talk) 23:57, 24 February 2015 (UTC)
  • The OP's question is about an egg, not an artificial decantable. The obvious answer is no. No egg could hold enough nutrients, store enough waste, or pass enough oxygen to carry a baby to term. That's why we have placentas and egg-laying animals don't. Consider the size at which marsupial larvae are born. They are so small because they cannot develop any larger with the support an egg can give. Look at newborn monotremes for the limit for mammals, and keep in mind these are small-brained and relatively cold-blooded mammals. 05:46, 25 February 2015 (UTC)
    • As you imply, the different ways that gestation and birth occur across different species are the result of evolutionary adaptation. In order to bring a human embryo to full term outside the womb, be it in some sort of egg or laboratory device, it would be necessary to recreate all the functionality of the uterus during pregnancy. Obviously, this raises various moral and ethical questions. But forgetting that, trying to achieve it successfully would likely prove a daunting task. ←Baseball Bugs What's up, Doc? carrots→ 14:21, 25 February 2015 (UTC)

February 25[edit]

How are contactless credit cards protected against electronic pick-pocketing?[edit]

Couldn't a tech thief adapt a credit card processing machine to collect payments in crowded places?--Senteni (talk) 00:29, 25 February 2015 (UTC)

Yes, they certainly could. So a second level of authentication, like a PIN, is needed. StuRat (talk) 06:01, 25 February 2015 (UTC)
But the PIN is only occasionally required, so presumably a lot of small amounts could be collected before a PIN was needed. Presumably the issuers of the cards have some security measures to detect repeated use in unlikely places since they are liable for any money falsely debited, but their ultimate protection is simply to reclaim the money from the authenticated bank account to which money is credited. The fraud wouldn't last long and the perpetrators would be easy to trace through the identification required when they opened the account. Dbfirs 08:38, 25 February 2015 (UTC)
(ec)::The whole point of a contactless transaction is that you don't need a PIN. However, there is a limit of a small number of transactions of less than £20 each day and I suspect the banks have to pay for any that you can show were fraudulent. But there was a possibility of fraud on a larger scale - at least with some of them - although that may have been fixed by now see [8]. Richerman (talk) 08:46, 25 February 2015 (UTC)
Not having to slide credit cards through that annoying reader is another advantage. I often have it turned the wrong way, or not quite far enough in, or slide it too slowly or too quickly. StuRat (talk) 14:52, 25 February 2015 (UTC)
The limit will be raised to £30 this year. They are playing it safe. (talk) 09:49, 25 February 2015 (UTC)
I also wonder about accidentally charging the wrong card. Consider people packed tightly in line, passing a street vendor and buying hot dogs as they pass. Your credit card may not be any closer to the reader than the next guy in line's credit card. StuRat (talk) 14:55, 25 February 2015 (UTC)
It's contactless in the sense that you don't need to swipe it. You still have to take it out of your pocket and wave it within an inch or so of the reader. The security comes from the fact that the RFID doesn't actually give you the credit card number (which the magnetic strip does, making it susceptible to skimming). So simply using an RFID scanner shouldn't give a thief anything useful. They would need an actual credit card payment terminal (or at least the software) which would presumably mean having to register with the credit card company (they have to know where to deposit the money), which should make spotting fraud rather easy. Mr.Z-man 15:28, 25 February 2015 (UTC)
I can think of a couple ways around that:
1) Hack the software.
2) Start some tiny business, say a pretzel stand (if they would even bother to check), and use that to get the scanner software, which you use to charge all the cards you've skimmed. Then withdraw the money as cash, leave town, and repeat the same thing in the next town. (If they have an alert out to not let you get another scanner, just use a bit of identity fraud to change your name each time.) StuRat (talk) 20:06, 25 February 2015 (UTC)
Hacking the software won't help. To be able to clone a card and use it, you need the account number, security code, expiration date, and possibly the cardholder's name and billing address. None of that is transmitted through the RFID chip on modern cards. The point of the software is to communicate with the processing network so that the credit card company can process the transaction. Only a portion of that transaction is done client-side on the terminal.
If you're going to go to the extent of #2, why even bother skimming RFID cards when you can just inflate charges on every transaction? It would probably be cheaper to just buy a gun and rob people directly. It doesn't protect against that either and the chances of getting caught are pretty similar. The money isn't deposited instantaneously, there can be a delay of up to a few days. Mr.Z-man 01:02, 26 February 2015 (UTC)
Are you sure about that? When I tested last year, I was still easily able to get I think the credit card number and possibly expiry date with this Android app [9]. The app details suggests new cards may not send the card holder name and transaction history feature is removed in new cards, but doesn't mention anything about removing the credit card number, nor for that matter expiry date. (These older refs confirm the app isn't lying about what has been transmitted [10] [11].) The card itself was relatively new (like 2014), but I am in NZ so may be a bit behind.
However as I understand it per [12] [13] [14] [15], the payment tokenisation spec was only published last year, it was rolled out in the US due to Apple Pay, but isn't in Europe or most of the world yet. As I understand it, it is the tokenisation process which will replace the transmission of the credit card numbers, even then it's as much to do with protecting terminals and for mobile payments, as protecting the contactless cards themselves from being "skimmed". (As per our contactless smart card article, the use did make contactless smart cards which were basically similar to magnetic stripe devices, but most of the world, and what I'm referring to are cards which are EMV.)
Your later reply above is partially correct. I think one thing which definitely isn't transmitted is the CVV. Or rather a CVV is transmitted, but it's unique to the transaction. And as my post mentioned, possibly the name isn't in some cards either. The CVV and general communication is the other important security as you sort of mentioned too. The problem with skimming on magnetic cards is that you not only can get all the data, you can easily generate a card (clone) which to someone else's system seems the same as a genuine card. So if you're using signatures like in the US people can use this to make rogue transactions in stores etc.
This has two problems from tbe banks POV, one is that antifraud measures are generally reduced for such transactions since they are considered lower risk, the other is that in many cases the bank is the one responsible for fraud in such card present transactions. (If you use PIN, you at least have to work out how to steal the PIN as well, which as shown in places like NZ, is possible but does take more work.)
I'm not disagreeing skimming all the details including CVV is a concern. E.g it can be used for card not present transactions. Hence why stuff such as the Target breach gets attention and why PCI-DSS etc are generally mandatory. But I think also something difficult to protect against, particularly since the details are generally published on the card. (Numberic billing address details are not, but my understand is they're not checked in many places besides the US.) With modern high speed, high definition cameras and good image recognition technologies, it's probably getting to the stage where a strategicly placed camera could capture both sides and the software could identify where the cards are exposed. (Perhaps OCRing them would be a step too far, but if you can reduce the amount of video that has to be scanned, you could easily hire someone in a developing country to steal the numbers for you.) Notably while most would advise you to protect PIN entry, it's rare that you're told to hide the card details, and for some people it may be difficult anyway. Of course even then this is still relatively expensive per card compared to stealing 40 million (or whatever) by breaching a Target's payment systems, but I'm not sure whether hiring someone to go around with a RFIC reader to steal details is much cheaper. (Contactless and modern contact systems often mean the card doesn't have to leave you hand, which is an advantage since you may hide the details even unintenionally and at least the staff can't just put your card in front of a camera.) Stuff like 3-D Secure and other antifraud measures by the bank, and stores (including using third party payment gateways like PayPal with their own security measures) who will take most of the cost for the fraud are likely to be an important part of stopping fraud for for card-not-present for quite a while I suspect.
Nil Einne (talk) 14:29, 26 February 2015 (UTC)

Can one get his entire/whole vas deferens removed?[edit]

As in, is it practically possible (for a doctor) to do this?

After all, vasectomies can fail, and thus, I am curious about whether or not it is practically possible to do this. Futurist110 (talk) 04:33, 25 February 2015 (UTC)

No matter how much of it they removed, they would still have to cauterize at each end, and if the cauterization somehow fails at both ends, theoretically some of the wiggly little guys might be able to get through. ←Baseball Bugs What's up, Doc? carrots→ 14:17, 25 February 2015 (UTC)
Yes, which, in turn, is why I asked about removing the whole vas deferens, rather than about only removing a part of it. Futurist110 (talk) 21:38, 25 February 2015 (UTC)
And I'm saying no matter how much of it you remove, you still have seal it, and that's where the risk for error comes in. And how would you define precisely where it starts and stops (or vice versa)? Are you talking about removing it all the way into the abdomen? I suppose that would do it. But the work could run into money. ←Baseball Bugs What's up, Doc? carrots→ 21:41, 25 February 2015 (UTC)
If removing it all the way up to the abdomen (I am sorry, but I don't know where exactly the vas deferens starts and stops) is what it takes to do this, then Yes, I am talking about doing that. Futurist110 (talk) 21:54, 25 February 2015 (UTC)
I'm at pretty much the limit of my anecdotal info. Aside from reading the vas deferens article, you should probably contact your urologist and pose this question to him, to get a thorough answer. ←Baseball Bugs What's up, Doc? carrots→ 22:53, 25 February 2015 (UTC)
  • Read first, do no harm. A physician is not going to do an unnecessary and damaging procedure for no reason, unless he's Doctor Robert. Given cutting the duct and cauterizing it works, there's no reason to remove the entire duct, and possibly do seven damage as a result. See also, Michael Jackson for the result of such unnecessary surgeries. μηδείς (talk) 22:54, 26 February 2015 (UTC)
The "first, do no harm" principle might have already been thrown out of the window by some/many doctors who are willing to turn women into Barbie dolls, et cetera. After all, if one follows the "first, do no harm" principle, then one shouldn't perform any elective cosmetic surgeries which carry any risk at all, correct? Also, I would argue that this surgery is necessary due to the fact that regular vasectomies, including with cauterization, can fail, and if a vasectomy fails, then this can certainly result in extremely unpleasant consequences for the male who gets it done. Plus, this is not to mention the possibility of individuals trying to perform surgery themselves and/or trying to get surgery performed in "back-alleys" if they are unable to get these surgeries performed in a safe, medical setting. Futurist110 (talk) 23:52, 26 February 2015 (UTC)
Which reminds me that there's a vas deferens between men and women. -- Jack of Oz [pleasantries] 23:02, 26 February 2015 (UTC)
Yes, well you've gotten my point about barbie dolls which I illustrated using Michael Jackson. But you are talking about removing the entirety of two foot-long ductsthat are intimately involved with the testicles, bladder, and prostate. I'll leave it up to you to contact a reputable surgeon and ask his advice on removing the entire duct, and the risks involved. μηδείς (talk) 00:17, 27 February 2015 (UTC)

Are there quantum effects having unexpected "memory"?[edit]

For instance: can a piece of information, which apparently got lost because of strong entropy, be recovered / restored - in quantum systems?

In macro-systems, I can hypothetically think about a "magician" who takes a random card out of a deck of cards, then puts it back in the deck, shuffles, and then takes out a random card which turns out to be the first card. Are there similar phenonema in quantum systems? HOOTmag (talk) 10:55, 25 February 2015 (UTC)

Not a quantum system, but in a macro-system, a better example than a magician is two cylinders with a thin layer of glycerin between them. Place a drop on ink in the glycerin, rotate one of the cylinders, and the ink disappears. Rotate the cylinders back into place and the ink drop reappears. This happens because the ink didn't evenly distribute itself in the glycerin, but rather was spread out over multiple layers of glycerin, due to laminar flow. StuRat (talk) 15:40, 25 February 2015 (UTC)
Quantum entanglement may be relevant. StuRat (talk) 15:44, 25 February 2015 (UTC)
My main purpose, is to inquire whether any quantum effect can overcome the increase in entropy, so I suspect your ink example is irrelevant - because it involves no real increase of entropy. As for quantun entanglement: yes, I'd thought about that, but I couldn't think about hypothetical experiments involving quantum entanglement that are relevant to "preserving memory" (by overcoming the increase of entropy). HOOTmag (talk) 16:51, 25 February 2015 (UTC)
either you should be more specific about what you mean when you say "piece of information " or I would say any actual memory that a person has in their brain would qualify. At the very least any recorded information that is stored on memory devices would qualify. Microprocessors are very small. And probably employ some quantum effects to record memory. (talk) 17:50, 25 February 2015 (UTC)
Quantum mechanics, in the basic sense that matter and energy levels are discrete, is an essential foundation to statistical mechanics and the modern understanding of entropy. In that regard, quantum mechanics is at the heart of entropy and what it actually means for a system to become more or less ordered over time. In the spirit of "If you think you understand quantum mechanics, you don't understand quantum mechanics" (widely attributed to Richard Feynman), I am not sure if there are examples of quantum mechanical systems that would satisfy you. However, I will note that even in the classical formulation, entropy always increases is only a statistical maxim and not an absolute law. Firstly, one can always locally decrease entropy through an expenditure of energy and a willingness to increase entropy elsewhere. Most complex living systems rely on the energy they bring in to maintain their complexity against entropy. Secondly, even in the absence of external energy, spontaneous declines in entropy do and will occur; however, the larger the decrease the more improbable the event. Atoms allowed to wander randomly will sometimes, by mere chance, return to their point of origin. The larger the number of atoms involved the less likely they all return at once, but there is nothing in principle that prevents it. In this sense, the increase of entropy is really a statement that the most probable spontaneous outcome is one that tends to maximize entropy. There is nothing about quantum mechanics that occurs to me that would tend to disagree with that or necessarily lead to magic tricks where one can intentionally reduce global entropy. Dragons flight (talk) 19:30, 25 February 2015 (UTC)
I'm not sure, but I think Ergodic theory and Poincaré_recurrence_theorem are relevant. If you have a box that is half full of air and half full of vacuum at time zero, eventually all the gas will happen to end up where it started, leaving vacuum in the other half (at least in terms of the mathematical model). SemanticMantis (talk) 22:14, 25 February 2015 (UTC)
I'm thinking of quantum entanglement and quantum teleportation. (These effects are less impressive than they sound, but basically they amount to information seeming to disappear yet being interrogable somewhere else) Wnt (talk) 19:34, 26 February 2015 (UTC)
@HOOTmag: the more I think about it, the more I think your question is precisely addressed by the Poincaré_recurrence_theorem#Quantum_mechanical_version - information can be lost due to entropy and other fluctuations, but still sort of spontaneously re-emerge. SemanticMantis (talk) 19:35, 26 February 2015 (UTC)

question (optics)[edit]

is F=R/2 is applicable in lenses — Preceding unsigned comment added by (talk) 14:25, 25 February 2015 (UTC)

I added to the title to make it actually useful. StuRat (talk) 14:46, 25 February 2015 (UTC)
Assuming he's referring to the focal length of a spherically curved mirror, Wikipedia's article titled Focal length contains all the information one needs to calculate the focal length of various lenses and mirrors. --Jayron32 15:31, 25 February 2015 (UTC)
(edit conflict) Looks like a variation on the Lensmaker's equation, for certain combinations of lense geometry (only one "R", so both faces have same curvature or else one face is planar) and certain types of materials (some unstated "n" optical density). DMacks (talk) 15:34, 25 February 2015 (UTC)


How many classes there are in Kingdom Animalia?-- (talk) 19:29, 25 February 2015 (UTC)

List of animal classes says roughly 108 classes in 34 phyla, though with the caveat that different authorities give slightly different classification schemes and hence the exact number of classes is somewhat ambiguous. Dragons flight (talk) 19:33, 25 February 2015 (UTC)

Physics: Gravitational Fields[edit]

Calculate the total energy of a communication satellite of mass 100kg in a stable circular orbit with a time period of 25 hr.

i have managed all the questions in the book but the question above is giving me problem, i keep getting the wrong answer and there are no solutions in the book.

I know that total energy = 1/2mv^2 + (-GMm)/r^2 Period(T)= (24 * 60^2) i have used this to find the radius = 1.03

if i could get some guidance or a clue on how to approach this it will help a lot. -Thanks86.183.65.110 (talk) 23:17, 25 February 2015 (UTC)

A few suggestions:
  1. Keep better track of units. You found a radius of 1.03 whats? Is that a number that makes sense?
  2. You have a 25-hour period in the problem statement, and a 24-hour period in your calculation. One of them must be incorrect.
  3. You appear to be mixing up the force of gravitational attraction (with r^2 in the denominator) with gravitational potential energy (with r^1 in the denominator).
If you check the units in your calculation, you will see that you're adding together two things with different dimensions -- one is an energy and one is a force. Make a habit of carrying units through the entire calculation so that you can easily check your work and spot this type of mistake. --Amble (talk) 23:26, 25 February 2015 (UTC)
What Amble said above is very good advice. You are right that the first step is finding the radius of the orbit. If you haven't already, maybe it's a good idea checking out Kepler's laws of planetary motion for this. - Lindert (talk) 23:43, 25 February 2015 (UTC)
If you use Google Calculator, WolframAlpha, or the units program, they will do the dimensional analysis for you, and show if you've used the wrong power somewhere. LongHairedFop (talk) 13:39, 26 February 2015 (UTC)

February 26[edit]

Genetics: Focal amplification[edit]

What does focal amplification mean?

— Preceding unsigned comment added by Blue down quark (talkcontribs) 00:20, 26 February 2015 (UTC)

In genetics, "foci" (plural of focus) are specific genes. Amplification is a type of gene duplication that causes the gene to overexpress itself. The term is usually used in reference to cancer cells; cancer is basically a somatic cell which is reproducing like crazy, and many common types of cancer are linked to specific sorts of gene amplifications. See Gene duplication, Gene expression which have some explanations of these concepts. Focal amplification just means a specific amplification of a specific gene. --Jayron32 01:18, 26 February 2015 (UTC)
We ought to have an article on gene amplification; what happens with something like MYC (or DHFR, in a different context) is far beyond what you usually think of as "duplication", because there's a process of natural selection for increased numbers of copies, and the presence of arrays of identical DNA may tend to make it easier for further changes in copy number to occur. Wnt (talk) 19:29, 26 February 2015 (UTC)

Spectral sensitivity[edit]

What optical spectral sensitivity is been more high, of the human eyes or optical (magnetic-optical) devices, and why?-- (talk) 05:10, 26 February 2015 (UTC)

Considering that we have cameras that can see ultraviolet, infrared, at night, and a single photon, I'd have to say the machines beat the human eye. On the other hand, the human eye has the advantage of being connected to the optical processing center of the human brain, which can do amazing things that computers still have trouble doing. StuRat (talk) 05:21, 26 February 2015 (UTC)
Thanks a lot! Any optical medium at first and foremost is always been magnetic environment, so I thinking that the conductivity of electric current of the magnetic environment is always been determines any spectral sensitivity, is I’m right?-- (talk) 06:46, 26 February 2015 (UTC)
So, I’m think that the conductivity of electric current, which is always been Ampere Force, is always been determining any spectral sensitivity of optical mediums. Is it right?-- (talk) 07:16, 26 February 2015 (UTC)
I came to the conclusion that in any cases, the physical phenomenon of the photoelectric effect which been discovered by Albert Einstein, is always been observing in all optics. Is it right?-- (talk) 08:08, 26 February 2015 (UTC)
So that’s, the all Laws of mechanics (optical mechanics) of the Isaac Newton are always been right, because the phenomenon (phenomena) of the photoelectric effect of Albert Einstein is always been observing in all optics.-- (talk) 09:26, 26 February 2015 (UTC)
Thus this, I concluding that Ampere Force always been determining all properties of optics, which always including (optical) properties of quantum mechanics (quantum physics). Is it been right, so?-- (talk) 11:51, 26 February 2015 (UTC)
I don't think optics necessarily has anything to do with electricity or magnetism. Film cameras existed for over a hundred years before digital photography. StuRat (talk) 15:47, 26 February 2015 (UTC)

Did the laws of mechanics are been identical to the laws of other sections of physics?[edit]

Did the laws of mechanics been identical to the laws of other sections of physics, if the Law of conservation of energy is always been universal, that is be, if some of physico-mathematical values of mechanics is always been directly proportional to the same (identical) physico-mathematical values of other sections of physics?-- (talk) 14:15, 26 February 2015 (UTC)

Please try to ask this question on a Wikipedia reference desk or other question-answering website in your own native language. Your English usage is so poor, that it's almost impossible to even understand your questions, and I have doubts that your English language comprehension is good enough to understand our answers fully, if we were to give them. Really, there are smart people in whatever language you grew up speaking. Seeking them out and asking them questions would be better for everyone involved. --Jayron32 15:21, 26 February 2015 (UTC)
I've known native English-speakers to ask similarly baffling questions. —Tamfang (talk) 09:45, 27 February 2015 (UTC)
There is an interdisciplinary approach to engineering that looks at the similarity in how mechanical, electrical, hydraulic, and pneumatic systems work (is it called systems engineering ?). For example, an electrical transformer has a mechanic equivalent in a lever. StuRat (talk) 15:53, 26 February 2015 (UTC)
I meaning that in physics, for example, the value of mechanical work is always been equivalent to the value of work of electric current, isn't it?-- (talk) 16:14, 26 February 2015 (UTC)
And so also, electric power (Watt's) is always been identical to mechanical power (Watt's), and so on.-- (talk) 16:24, 26 February 2015 (UTC)
Yes, they are the same watts. Other "equivalents" are less clearly defined. You might be interested in articles such as Hydraulic analogy. Dbfirs 22:26, 26 February 2015 (UTC)
Your English would be easier to read, Alex, if you completely avoid the word "been" (though just occasionally you might need it e.g. for Uses of English verb forms#Been_and_gone). Dbfirs 22:33, 26 February 2015 (UTC)
Oh don't be such a been-counter. - ¡Ouch! (hurt me / more pain) 12:00, 27 February 2015 (UTC)
I have repeatedly advised this guy to brush up his English, to no avail. It's getting wearisome. I fear an improvement in his English might reveal just how bad his physics is, though. He's allegedly banned from Russian Wikipedia already. AlexTiefling (talk) 00:21, 27 February 2015 (UTC)
Thanks a lot for all! Ultimately, in all sections of physics (in all physics) are been existed only the same (identical) mechanical movements which are been existing in mechanics (mechanics of Isaac Newton).-- (talk) 10:01, 27 February 2015 (UTC)
If according to the mathematical version of the Law of conservation of energy, the energy potential is always been proportional by the physico-mathematical units which expressed it, so then what is being the mechanical potential of energy (energy of mechanics)?-- (talk) 12:35, 27 February 2015 (UTC)
42. AndyTheGrump (talk) 13:14, 27 February 2015 (UTC)
It is worth considering why physics and chemistry for explain the physical and chemical phenomena used the mathematical theory which had not been proved by applied (practical) ways, this been leads to a false theory of physics and chemistry.-- (talk) 13:56, 27 February 2015 (UTC)
Colonel Mustard, in the library, with the lead pipe. AndyTheGrump (talk) 14:36, 27 February 2015 (UTC)
Free access to education (reliable educational information), that is no secrets to the reliableness (authenticity) of educational information is always being the key to the success of any society - humanity.-- (talk) 15:12, 27 February 2015 (UTC)
Mersey Docks and Harbour Board... AndyTheGrump (talk) 15:28, 27 February 2015 (UTC)


Are all dinosaurs canivore in this superfamily?-- (talk) 14:17, 26 February 2015 (UTC)

According to to Benson et al 2010 (see ref in article you linked to) almost all large-bodied predators belong to either Megalosauroidea or Allosauroidea after the Middle Jurassic. So not even all large-bodied carnivores were in that superfamily - this doesn't cover any small-bodied carnivores or any carnivores before the Middle Jurassic. Mikenorton (talk) 14:47, 26 February 2015 (UTC)
I read the OP's question as being equivalent to "Were any Megalosauroidea not carnivores." Sadly, I don't know the answer. {The poster formerly known as} (talk) 14:55, 26 February 2015 (UTC)
yes;I mean if all species belonging to this superfamily are carbivore.-- (talk) 15:01, 26 February 2015 (UTC)

Are humans instinctively able to ensure that the phallus goes into the correct orifice for successful mating?[edit]

I am not sure if the penis-vagina intercourse is supposed to be instinctive. Do men guide their penises with their hands during sexual intercourse, or do they allow their penises to become erect by themselves? I mean, I've seen a dog mating with another dog, and the male dog does not seem to care where the penis is. Is this what goes on in the human mating process? (talk) 15:22, 26 February 2015 (UTC)

Data would indicate that successful mating has occurred in the human species. I don't feel the need to link to anything, as you and I are here, which is evidence enough that it works. --Jayron32 15:37, 26 February 2015 (UTC)
That just proves that mating occurs, not that it's instinctive. In other animals, they likely just watch older animals to learn how. But, since people mate differently (usually face-to-face) and in private, watching other humans may not have historically been possible. With the advent of widespread porn, it now is. Sex education is another way to learn. And, of course, it's only the case of two virgins where not knowing the mechanics might be an issue. But, given enough time, I'd expect two virgins with absolutely no knowledge of sex would eventually figure it out on their own. StuRat (talk) 15:43, 26 February 2015 (UTC)
As to your last statement, the fact that we're all still here means that humans can successfully mate, even if they weren't taught how to by porn or formal sexual education. Those things have only existed for a tiny fraction of humans for a tiny fraction of history. And we made it through thousands of years of human history before we got to the point where porn and sex ed classes existed. That's evidence enough that people have figured out, all on their own, how to put tab A in slot B. --Jayron32 15:46, 26 February 2015 (UTC)
If you go back far enough, adults wouldn't have had sex in private (before there were houses with individual rooms, doing so would have been difficult), so children would have learned that way. StuRat (talk) 15:58, 26 February 2015 (UTC)
So, do men hold the penis or not during copulation? (talk) 15:50, 26 February 2015 (UTC)
I'm sure some do and some don't. There's lots of ways to have sex in the world, and it's all probably happening right now. If you can think of it, people have done it. --Jayron32 15:51, 26 February 2015 (UTC)
So, humans don't have an evolved method? (talk) 16:01, 26 February 2015 (UTC)
Well, the human vagina is part of evolution, you might like this article on the evolution of the mammalian vagina [16]. Humans do tend to have sex a bit differently (and with more variation in positioning) than other primates [17], in part due to differences in angles and hip structure. SemanticMantis (talk) 16:46, 26 February 2015 (UTC)
I found the article about sex positioning very informative, SemanticMantis. In addition, I have read that the female can become impregnated without penetration at all, as long as the semen is somewhere close. So, this may give some hope to those who can't seem to conceive. (talk) 17:28, 26 February 2015 (UTC)
Do humans have to take off their clothes during sexual intercourse? (talk) 17:36, 26 February 2015 (UTC)
Only the relevant bits of clothing. I get the impression people might have left more clothing on in the olden days, when taking off all a women's clothes could take an hour (this might also explain the bodice ripper stereotype of tearing off the woman's clothes in a fit of passion). Also, when it's cold, people might tend to keep more clothes on. StuRat (talk) 17:56, 26 February 2015 (UTC)
For example, see Temple garment. ←Baseball Bugs What's up, Doc? carrots→ 17:59, 26 February 2015 (UTC)
If you stop and think about it, only a virgin and/or a resident of central Ohio would be asking all these questions sincerely. (As in "Nudge-nudge, wink-wink... What's it like?") ←Baseball Bugs What's up, Doc? carrots→ 17:47, 26 February 2015 (UTC)
No, the occurrence of instinctive behavior in humans is a serious, and extensively debated, issue. The sad part is that, due to certain ethics impediments where it comes to raising babies in isolation cells, we really don't have any good experimental methods to use to get to the truth of it. But we do know that when making, say, germ-free mice in a way that involves separation from their non germ free parents, they seem able to figure it out. Wnt (talk) 19:41, 26 February 2015 (UTC)
Didn't The Blue Lagoon (1980 film) adequately explain the matter? Jim.henderson (talk) 19:49, 26 February 2015 (UTC)
(Edit Conflicts) While I can't point you to specific references right now, I can tell you that that I once attended a talk given by someone who, amongst other things, provided counselling to couples (in the USA, I believe Texas) who had failed to have children. She asserted that in a significant percentage (at least 10%, but I can't recall precisely) of these cases, questioning established that the couples involved had not, in fact, been having sex involving penile penetration of the vagina, because they had never received sufficiently specific advice in the matter. The unsuccessful targets involved included between the thighs (most commonly), the navel, and in at least one instance the urethra.
This suggests that the necessary manoeuvres of sexual intercourse (as opposed to the general desires) are not instinctive in humans. Regarding your observations of dogs, I also know, from conversations with dog breeders, that inexperienced male dogs not infrequently need physical guidance: dogs are of course domesticated, and some biologists argue that humans can be regarded as self-domesticated, which might be of some relevance. {The poster formerly known as} (talk) 20:03, 26 February 2015 (UTC)
So, really, conception is a matter of trial and error. Since it's easy to miss the target, this may also explain the prevalence of anal sex and the replacement of the opposite-sex partner with a same-sex partner. (talk) 22:04, 26 February 2015 (UTC)
That reminds me of the story of a couple that had been married for several years but without children. When asked, the husband said, "Well, we've tried, but she never can seem to swallow that stuff." ←Baseball Bugs What's up, Doc? carrots→ 20:21, 26 February 2015 (UTC)
The urge to embrace seems to me to be pretty universal, and everything else leads on from there, and you only need to get it approximately right to reproduce, if you do it enough times. The alignment of anatomy means that PIV sex is quite a lot easier than the alternatives. 100% success in not necessary to propagate the species, as not everyone needs to reproduce for the species to survive. -- The Anome (talk) 20:26, 26 February 2015 (UTC)
  • I'll just point out that historically, brother-sister incest has happened and produced babies. Certain body parts smell good, and rubbing them together is pleasurable. I can't think of any famous child incest cases, but of course we know it does occur, otherwise it wouldn't be necessary to segregate pubescent children who haven't been given explicit instructions on producing babies. μηδείς (talk) 22:45, 26 February 2015 (UTC)
weird question that sounds like it's coming from a person that doesn't realize there is another person involved that also has instincts. --DHeyward (talk) 00:30, 27 February 2015 (UTC)

Buried by time[edit]

Might be a silly question. When archeologists dig ground to uncover ancient settlements or other artifacts of ancient societies they have to remove a few feet of dirt and other material. The same is true for paleantology. Where does this matter come from? Thanks, --AboutFace 22 (talk) 16:57, 26 February 2015 (UTC)

It's not a silly question at all, but rather a fascinating and important one. The best articles to look at are Law of Superposition, Stratigraphy (archaeology), and tell. They come from layers of sediment that build up over time. You can sort of think of them as being like rings in a tree. They help us to date stuff and determine how different pieces of material evidence relate to each other. We also have times when people have put modern top soil over a site (which is as annoying as it sounds). We don't always have to dig deep though, sometimes things are close to or on the surface and we just have to remove an inch or two of top soil and then we get to the good stuff. Sir William Matthew Flinders Petrie | Say Shalom! 7 Adar 5775 17:04, 26 February 2015 (UTC)

There's some useful information about a specific and accelerated type of this phenomenon at Tell (which I personally think should be spelled 'tel', but what do I know). --Dweller (talk) 17:13, 26 February 2015 (UTC)

Both are correct spellings. Tel is a Hebrew transliteration, whereas Tell is an Arabic one. They're used interchangeably in archaeological publications and it's not uncommon to see both spellings in the same article. Sir William Matthew Flinders Petrie | Say Shalom! 7 Adar 5775 17:16, 26 February 2015 (UTC)
I never could tel. --Dweller (talk) 17:27, 26 February 2015 (UTC)
There's also material placed there by later generations of people. In many cases, they build a structure on top of an old one. At other times, it's a trash heap, with pieces of broken pottery and food residue (with seeds, bones and shells still remaining). Then there's human excrement, which turns into dirt. StuRat (talk) 17:32, 26 February 2015 (UTC)
The articles linked above don't really answer the question. I think this tells you a lot more. It's things like: decayed vegetation (especially leaves), wind-blown soil, sand and other debris, silt washed from higher ground during floods, volcanic ash etc. etc. Richerman (talk) 18:20, 26 February 2015 (UTC)
Yep, a mixture of excrement and melted mudbrick in some cases. Often we lick bones to determine if they are in fact bones (if your tongue sticks it's probably bone or pottery) and try not to think about the excrement aspect. Sir William Matthew Flinders Petrie | Say Shalom! 7 Adar 5775 18:46, 26 February 2015 (UTC)
In the case of tells, it's also melted and decayed mudbrick. The thing is we're also talking about different types of sites here. I'm referring to cities built on tells that range from Bulgaria to the Punjab which have little vegetation initially, and I think what you're referring to is more European sites. I think we both might be forgetting that there's a lot of variability in archaeological sites. Sir William Matthew Flinders Petrie | Say Shalom! 7 Adar 5775 18:46, 26 February 2015 (UTC)
Depending on the site, and at risk of stating the obvious, the "stuff" comes from other places. It gets to the site via Aeolian_processes#Transport, and Fluvial processes, and also a tiny bit from things like animal transport (e.g. zoochory and excrement). SemanticMantis (talk) 19:05, 26 February 2015 (UTC)
If you were referring to my use of stuff in your quotes, in both cases my use would encompass finds such as material remains, architecture, coprolites (fossilised poop, which smells like chocolate oddly enough), faunal remains (animal remains), flora, etc. so it's easier to say stuff, haha. One of the problems with discussing your own field is that you sometimes forget to specify terms that would seem obvious to you, but aren't to others as you're far too used to them. The end result is that you cause more confusion than clarification... Also, I realised I directed this topic away from palaeontology. Sorry about that. Sir William Matthew Flinders Petrie | Say Shalom! 7 Adar 5775 19:40, 26 February 2015 (UTC)
Yeah, I just meant the same stuff you did. Whether it's soil, plant, animal matter, etc, the stuff gets their mainly by aeolian and fluvial processes, with a bit of animal (including human) transport mixed in. SemanticMantis (talk) 22:13, 26 February 2015 (UTC)
Though in the case of tells, it's mostly human activity (building, filling, warfare that destroys the city) and rain. James Mellaart found the latter out the hard way when he was excavating Çatalhöyük and the mudbrick walls of the areas he had excavated started to melt during the winter (destroying some lovely bull murals in the process). They built shelters after that. Sir William Matthew Flinders Petrie | Say Shalom! 8 Adar 5775 00:31, 27 February 2015 (UTC)
Also, the traces that archaeologists find often started off underground anyway; it's often only the foundations of a building that survive. In the UK, it was common for later generations to recycle the stones and bricks from older structures, sometimes digging them out right down to the footings, leaving only a robber trench. Alansplodge (talk) 14:32, 27 February 2015 (UTC)

If whales were fish[edit]

"Fish" in the modern, scientific sense (Osteichthyes, or Pisces if you want to be old-fashioned) in a paraphyletic group, because it excludes tetrapods.

How would you describe, taxonomically, the pre-modern definition of "fish" that included cetaceans?

Is it polyphyletic? The acticle on Polyphyly gives two definitions, the first of which would apply to "Pisces + Cetacea" ("phenotypes which have converged or reverted so as to appear to be the same but which have not been inherited from common ancestors").

The second definition ("multiple ancestral sources") doesn't though, as the most recent common ancestor of fish and whales was also fish. How then, if you use this definition, would/could you describe to the group "Pisces + Cetacea"? Iapetus (talk) 17:12, 26 February 2015 (UTC)

If a large-prey eating whale (an orca) was a fish, it would be a shark (most kinds). If a filter feeding whale was a fish, it would be a whale shark. The only type of whale which (I believe) lacks a shark equivalent seems to be the group that scoops up large quantities of fish in a mouthful. StuRat (talk) 17:44, 26 February 2015 (UTC)
I would just call pre-modern "fish" (i.e. Pisces + Cetacea) a polyphyletic grouping and call it a day. Nobody is going to say that you're wrong, and if pressed, yo can explain. Really, Pisces + Cetacea is about the same as nocturnal primates, the example of poyphyly given in the article - because a dolphin and a tuna both swim, but the dolphin has plenty of ancestors that didn't swim. Also, while the MRCA of Pisces and Cetacea may well be a pre-modern "fish", I don't think that really matters in terms of the cladistics, because the whole point is that this grouping is not a clade. You might be interested in the recent phylogeny described at Sarcopterygii#Phylogeny. If you like, you can consider your group polyphyletic and paraphyletic, the latter since we can form pre-modern fish by lopping off several monophyletic chunks from the clade formed by the MRCA of Pisces and Cetaceans...
The main point is, unless you're speaking at a technical conference for systematists or something, polyphyletic is a fine label. If you are presenting at a technical conference for systematists, ask your colleagues or advisers, because they surely know more than us :) SemanticMantis (talk) 18:58, 26 February 2015 (UTC)
I'd go with "fish" (old sense) being a habit (biology). It seems a bit odd to put it like that, mostly because the actual uses as given in the article are more specific and, well, technical-sounding. Wnt (talk) 19:19, 26 February 2015 (UTC)
But a habit isn't a grouping, it's a concept (e.g. a behavior, growth form, etc). Looking at the definition of polyphyly given in monophyly, pre-modern fish are definitely polyphyletic, because the cetaceans did not inherit their swimming habit from a common ancestor with Pisces. Probably the definition in polyphyly should be subtly changed to match the language in monophyly. Another option would be to say that pre-modern fish are a type, just as the modern sense of fish is, as explained in that article. SemanticMantis (talk) 19:31, 26 February 2015 (UTC)
  • There's also the question of who's doing the classifying PIE has various fish words, and *(s)kwalos means shark and whale in various dialects. The *peisk- root is believed to be related to a word for spotted, referring to species like the trout. *dhghu- (ichthys in Greek) seems to be a more general term with a wider Eurasiatic etymology.
"Fish" in the biblical sense basically refers to any sea creature, including turtles, crabs, etc. There, kosher law defines only fish with scales and fins to be edible. The whale and the crab might be fish in this sense, but lacking scales they are not kosher. Sea turtles actually do have scales and fins, and at least for Catholics they were edible on Fridays as "fish" when normal meat was forbidden.
Any sort of scientific taxonomy is a relatively recent innovation. Herman Melville wrote the best part of a whole chapter in Moby-Dick, debating whether a whale was a fish or a mammal. He decided in the end that it was definitely a fish. Alansplodge (talk) 14:51, 27 February 2015 (UTC)
Biologicaly, the most recent group including at least some fish and the whale is the Sarcopterygii, which also includes lungfish and the Coelacanthμηδείς (talk) 02:37, 27 February 2015 (UTC)±

Pronunciation of "agRP"[edit]

I'm making a video and I need to know how to pronounce the abbreviation for agouti-related protein (i.e., "agRP"). In the video, I also talk about POMC, CART, and NPY, and I'm only using the abbreviations. I tried to find a pronunciation on Google, but somehow Google didn't know what I meant. I would appreciate any suggestions. (talk) 18:01, 26 February 2015 (UTC)

This is just of the top of my head: Over reliance on abbreviations can be sometimes be a problem when spoken. If you pronounce it əˈɡuːti RP , (or agoo tee RP) then people in that discipline (which you are addressing in the English speaking World) will understand perfectly. [18] Agrp is not a memorable sound in English regardless of how it is pronounced. It sounds too much like Klingon (my apologies to any Klingon readers here – I think you language is wonderful – when spoken on your own planet!). Keep your language clear, simple and unambiguous. Reliance on abreviations requires the listener to realize that this is not a word but an abbreviation.... and then.... remember what it stands for. As a communicator, one should short cut that extra brain-work in order to keep one audience’s attention. I learnt this when I studied Industrial Communications.--Aspro (talk) 18:33, 26 February 2015 (UTC)
Using an abbreviation without ever defining it seems like a bad idea to me. When people want to pronounce things like agRP, they usually insert a schwa. So something like /agərp/ or /agrəp/ might work. But I have to wonder how you know what these things are without ever having heard someone else talk about them... SemanticMantis (talk) 18:40, 26 February 2015 (UTC)
You have it the nail on the head of what I'm saying. I became an expert in instrumentation and other things once; much of what I knew came from text books, research papers etc. When I had first found I had to talk to a audience (managers and the CEO) I was lost for how to say the abbreviations - I'd never heard many of them voiced. In these instances, one needs to take a step back and talk in the clearest prose and vocabulary as possible. In print, one can quickly scan back to find out what an abbreviation means but in a verbal presentation one has to carry the whole audience along with you – all at the same time. If they have trouble following your presentation, it is not because they are stupid (some had enough degrees to get a job as a laboratory thermometer) but it due to one's lack of speaking in a vernacular that they understand and can comprehend.
I'm puzzled why you don't just say it as it's written, ag R P, in three syllables/letters, as everybody else does. (talk) 18:57, 26 February 2015 (UTC)
AG is the root. AG can stand for other things as well. Too much brain work involved to just say AGRP.--Aspro (talk) 19:06, 26 February 2015 (UTC)
I would go with just spelling out A G R P; I'd avoid splitting between a full name (agouti) and an acronym (RP) unless RP were some sort of "action" done to agouti, which isn't the case. Even then you wouldn't usually mix and match (not "estrogen R" or "E receptor", not "IRF-4 BP" or "I binding protein") though I imagine you could find a counterexample with enough looking. Wnt (talk) 19:16, 26 February 2015 (UTC)
In this 2011 Youtube video, Richard Palmiter from the Allen Institute for Brain Science pronounces each letter individually, saying A G R P neurons. --NorwegianBlue talk 19:21, 26 February 2015 (UTC)

Thanks for all of your ideas! (talk) 20:30, 26 February 2015 (UTC)

If I was making a presentation, I would probably just say the full name, "agouti-related protein". That's just about as easy as reciting the initials. If I needed something shorter, I would probably say "agouti" unless that's ambiguous, and explain it the first time I did it. In any case the main thing to remember is that your goal is to be understood by your audience, not to be formally correct. Looie496 (talk) 15:06, 27 February 2015 (UTC)

Name of a tree in Miami[edit]

Here's a picture of a tree in Miami, Florida:

What is the name of this tree? This may be too easy for those who live there, but I don't have such trees near where I live. (Never mind the squirrel on photo.) -- (talk) 21:10, 26 February 2015 (UTC)

Maybe a gumbo tree? ←Baseball Bugs What's up, Doc? carrots→ 21:19, 26 February 2015 (UTC)

No idea

  • It's very hard to tell without seeing the leaves, flowers or fruit. American sycamores and eucalyptus have bark that peels in this way, but from what you can tell the leaves are not like eucalyptus and the growth form of the trunk is unusual for the very upright and tall sycamore. μηδείς (talk) 00:10, 27 February 2015 (UTC)
    • Could also be really large crepe myrtles. Again, without leaves or flowers, or the like, we're just throwing darts blind, though. --Jayron32 02:13, 27 February 2015 (UTC)

Bird identifciation[edit]

My parents' birdfeeder has drawn that attention of some large black passerine birds, presumably corvids. They are as long as crows, but not so robust. Strangely, they look like Brown-headed cowbirds in reverse. Their heads are black with a strong navy blue sheen, and the shoulders of their wings have a bronze highlight. So the contrast is not a striking as the cowbird, but the blue and bronze on black is quite clear.

I've read List of birds of New Jersey and the bird is not included, presumably it is a transient. Any suggestions as to the identification? Thanks. μηδείς (talk) 22:39, 26 February 2015 (UTC)

You know the common grackle, right? That's what it sounds like, but it's a very common bird, and resident to NJ year round... Boat-tailed grackle would be very distinctive with the long tail. What type of feeder are they using, how many do you see at once? Are they otherwise foraging on the ground? Any note on eye, beak, or leg color? SemanticMantis (talk) 22:45, 26 February 2015 (UTC)
No, actually I knew of the name and had seen the birds very rarely, but as I have mentioned earlier, the birdfeeder my mother got for Christmas 2013 has been so successful we have seen dozens of species. I am fairly sure it is indeed the common grackle, however, thanks. μηδείς (talk) 00:03, 27 February 2015 (UTC)

February 27[edit]

NASA's beautiful new denoising algorithm[edit]

Anyone seen [19] [20]? Titan has never looked so good. It traces back to [21] which is locked up. Do we have any good (and hopefully more approachable) explanation to what the algorithm is? Specifically, I'm wondering if it could work on pre-existing immunofluorescence images and the like. Wnt (talk) 02:34, 27 February 2015 (UTC)

A horribly formatted draft of the JGR article can be downloaded here (found using Google Scholar). It cites "A non-local algorithm for image denoising" by Buades et al., which can be downloaded here. The latter paper says "the denoised value at x is a mean of the values of all points whose gaussian neighborhood looks like the neighborhood of x"—in other words they are blending together similar-looking regions of the image to reduce noise. This seems similar to advanced upscaling algorithms like Genuine Fractals™ that use the image itself as a codebook. It strikes me as very dangerous to use this kind of algorithm as a prelude to image analysis, as these authors do, since there's a good chance that the details it "reveals" are not really there. -- BenRG (talk) 06:21, 27 February 2015 (UTC)
BenRG describes a bilateral filter, or an enhancement along those lines. Nimur (talk) 15:36, 27 February 2015 (UTC)
It's actually quite easy to design your own denoising algorithm with a performance that is far better than anything that is implemented in standard software. I use my own algorithms on my raw picture files which yields far better results than the in-camera noise reduction or anything that photoshop has to offer. Basically, what I do is I use a model for the a priori probability distribution of the set of grey values of the pixels in the picture (the prior probability of a picture in the absense of noise). The parameters describing that model will behave in a certain way under scaling, which allows me to estimate these. Then I have a good model for the noise which includes correlations and outliers. I can then solve for the most probable picture iteratively starting with an approximate guess. That guess is obtained by eliminating the outliers in some simple way (e.g. local median) and approximating the noise + picture model by a Gaussian model, allowing one to use Fourier transform methods to get to an approximate solution. Then this is the first approximation that can be improved iteratively.
On a fast pc, denoising properly takes a long time (hours, not minutes) and it requires quite a lot of preliminary calculations to do the model estimation before you can run the program. E.g. the point spread function should be specified, it matters if you specify the picture as perfectly sharp or if the point spread function is more spread out and the picture is not sharp at the level of the pixels. And, of course, when you are done you need to do the demosaicing and the transforms to e.g. SRGB colorspace before you have a picture, but the results are worth it. Count Iblis (talk) 14:00, 27 February 2015 (UTC)
Count Iblis describes a non-local means estimator, e.g. a spectral estimation filter or an iterated statistical estimator an enhancement along those themes. This is a statistical signal processing method.
It does not necessarily require hours to compute one of these, in its most basic form; but if you are iterating for the purpose of optimizing some kind of model fit, you can iterate as long as you wish. If you have an incredibly elaborate model, each iteration could take a very long time.
Nimur (talk) 15:33, 27 February 2015 (UTC)
Wnt, you should definitely find a way to read this article, which was published in IEEE Signal Processing about two years ago: A Tour Of Modern Image Processing. Nimur (talk) 15:43, 27 February 2015 (UTC)

Latex gloves[edit]

Do latex gloves go through a water test like condoms? And are latex gloves equally permeable? (talk) 04:06, 27 February 2015 (UTC)

Yes, the gloves that are used for sterile surgical procedures or for handling hazardous material go through a water test. I don't know about permeability. See Looie496 (talk) 14:49, 27 February 2015 (UTC)

Physics: How can any black hole move?[edit]

Give reference please!A. MohammadZade Iran -- (talk) 06:44, 27 February 2015 (UTC)
As per our article, "there is no observable difference between the gravitational field of such a black hole and that of any other spherical object of the same mass". Presumably they would therefore interact with spacetime the same as any other object except within the event horizon. In other words, they move the same as anything else. Remember, black holes aren't vacuums; if our sun were magically replaced with one of the same mass, it would get dark and cold on Earth, but that's pretty much the only difference, gravitationally speaking. Our orbit wouldn't change. Mingmingla (talk) 06:59, 27 February 2015 (UTC)

Equatorial bulge and viewing distant objects[edit]

Since the Earth has an equatorial bulge where the Earth's curvature is at its greatest and the poles are the flattest points of the Earth's curvature, does that mean that we get to see things at greater distances at the poles than in the equator, especially when looking from North to South and vise versa? Let's say we are standing at the North Pole and there is a ship 5 miles away that we can barely see because of the distance. Only its masts are visible because of the Earth's curvature. Then, let's say we and the ship go near the equator and the same expanse and visibility are as clear as when we stood at the North Pole and the same ship is there at exactly at the same distance, will the ship be seen just as barely as it was in the North Pole, or will the whole ship be out of sight because it will be hidden under the Earth's curvature due to the equatorial bulge? Has such experiment ever been done near the poles and then near the equator? Willminator (talk) 06:58, 27 February 2015 (UTC)

I'm having a surprisingly hard time finding a reference for this. Earth bulge#Distance to horizon (bulge has a different meaning here) and Horizon#Distance to the horizon both seem to deal only with a spherical Earth, as, I was amazed to discover, does Bowditch. Online I found this Distance to the Horizon university page which at least mentions that "Numerically, the radius of the Earth varies a little with latitude and direction; but a typical value is 6378 km (about 3963 miles)." and proceeds from there with a spherical Earth.
My impression from this is that the difference must not be significant, but let's try a calculation. Note that we are interested in the radius of curvature, not the actual distance to the center of the Earth. Earth radius#Radii of curvature just says to see Spheroid#Curvature, and that's more math than I wish to deal with at the moment. Assuming that the radius of curvature along a meridian at the equator is about equal to the semi-major axis at the pole and vice-versa, then the distances to the horizon should differ by about 1 part in 600 because the flattening of the Earth is about 1 part in 300 and there is square root in the formula in Horizon#Geometrical model. (sqrt(1-x) ≈ 1 - x/2 for small x.) But Horizon#Effect of atmospheric refraction says that with standard atmospheric conditions, refraction adds about 8% to the value calculated from the geometric model, and in unusual atmospheric conditions the distance to the horizon will vary by much more than the 0.17% difference we get from the varying geometric model from equator to pole.
So yes, it differs, but not enough to be noticeable. Sorry that I can't find any good references here. -- ToE 10:00, 27 February 2015 (UTC)
My assumption regarding the radii of curvature was a poor one as it significantly underestimates the difference in the radius of curvature along a meridian from equator to pole. Radius of curvature (mathematics)#Ellipses tells me that with a flattening of 1 part in 300, the two radii of curvature will vary by 1 part in 100. Thus the distance to the horizon from our geometric model will vary by 0.5%. This is still small compared to effects of unusual atmospheric conditions. -- ToE 10:20, 27 February 2015 (UTC)
Left open is the question of whether this has ever been observed experimentally. Perhaps, instead of taking separate measurements at equator and pole, it would be best to conduct such an experiment only at the equator, where the radius of curvature along the equator is 2 parts in 300 greater than the radius of curvature along a meridian. This yields a 0.33% difference in the calculated distance to the horizon. I suspect that during periods of settled weather the atmosphere would be sufficiently azimuthally isotropic for this difference to be detectable. -- ToE 10:39, 27 February 2015 (UTC) I'm 12.5°N. If only the seas were calmer and I had two equally nerdy friends with sailboats.

Is there a scientific consensus on how long people who existed the Stone Age lived?[edit]

Is there a scientific consensus on how long people who existed the Stone Age lived? If so, what is the consensus? Fanddlover5 (talk) 10:07, 27 February 2015 (UTC)

There is a huge consensus among the scientific community that, during the Stone Age, humans had a lifespan of 30 years. Icemerang (talk) 10:13, 27 February 2015 (UTC)
Is that maximum typical longetivity, or life expectancy at birth? (I.e. is it including or ignoring infant mortality?) Iapetus (talk) 12:34, 27 February 2015 (UTC)
I found The neolithic revolution and contemporary variations in life expectancy which (looking at the graph on page 2) suggests that life expectancy might have dipped below 25 during the Neolithic period, to increase again later. Alansplodge (talk) 13:14, 27 February 2015 (UTC)
Figures in the 25-35 year range are almost certainly life expectancy at birth, see also my links below. SemanticMantis (talk) 15:05, 27 February 2015 (UTC)
"Huge consensus" is an overstatement. Life expectancy is not so easy to calculate. You have to assume that the distribution of skeletal remains accurately reflects the distribution of the population, and there are a variety of reasons why that might not be correct. Looie496 (talk) 14:39, 27 February 2015 (UTC)
Here's an open access journal article on the topic, which also includes many references [22]. At birth, estimates usually fall in to the 25-35 year range. However, most of that low age is due to extremely high infant mortality. If you were a neolithic human who survived to ~18 years old, and survived childbirth if female, then the expectancy goes way up, and it wouldn't have been that odd to see a few 65 year old people around. Probably not as many as today. The main idea is that the oldest neolithic people lived about as long as the oldest people in the modern era, but that the high rates of infant mortality and death-by-birthing bring the average expectancy way down compared to modern life expectancy. However, Maximum_life_span hasn't changed nearly as much. SemanticMantis (talk) 15:04, 27 February 2015 (UTC) (p.s. I see that Alansplodge has already linked the the same article as I did)