Wikipedia:Reference desk/Archives/Science/2010 May 6

From Wikipedia, the free encyclopedia
Jump to: navigation, search
Science desk
< May 5 << Apr | May | Jun >> May 7 >
Welcome to the Wikipedia Science Reference Desk Archives
The page you are currently viewing is an archive page. While you can leave answers for any questions shown below, please ask new questions on one of the current reference desk pages.


May 6[edit]

epson salts[edit]

how come the epson salts article dosent explain how it helps sore joints. —Preceding unsigned comment added by Tom12350 (talkcontribs) 00:57, 6 May 2010 (UTC)

It's sort of mentioned in the talk page... Maybe it's because no one can find a good reliable source to make it worth including? Vespine (talk) 06:20, 6 May 2010 (UTC)
Perhaps because it does not generally help sore joints. I know it's personal research but I have never heard that Epsom salts relieves sore joints. However if you have a reliable source for that claim then you might consider adding it to the article. Be bold! Caesar's Daddy (talk) 06:21, 6 May 2010 (UTC)
They're a fairly standard ingredient for many bath salts - which are the standard home remedy for sore joints. http://www.google.co.uk/search?q=epsom+salts+sore+joints&hl=en&start=0&sa=N
The epsom salt council suggests that it is magnesium that is effective. http://www.epsomsaltcouncil.org/about_better_health_through_soaking.htm 77.86.68.186 (talk) 17:01, 6 May 2010 (UTC)
Is that source to be trusted, though? I've read that it is not very effective. 67.243.7.245 (talk) 19:16, 6 May 2010 (UTC)
Could be a placebo effect - there's a vast amount of people claiming they are good though. Who knows? It's an unwanted product of the chemical industry.. Conspiracy theory perhaps??77.86.68.186 (talk) 21:03, 6 May 2010 (UTC)
I could certainly believe that soaking in warm water could help - relaxing the muscles - taking the weight off the joint and allow neutral bouyancy to support the limb, calming and mentally relaxing the patient because while in the bath they aren't being hassled by the perils of daily life. So it wouldn't surprise me if the whole business of using epsom salts had nothing whatever to do with it! If this hypothesis is correct then people will doubtless claim that soaking in an epsom salt bath helps their ailment - not realising that it's the bath - not the salts - that's really doing the job. Without a proper double-blind trial, I don't think we could say for sure...but the idea that magnesium salts migrate through our skins (which are pretty water-tight stuff!) through layers of fat and muscle to reach the knee - and then somehow acts to help the pain without all sorts of dangerous chemical imbalance side-effects - is one hell of a stretch! SteveBaker (talk) 01:59, 7 May 2010 (UTC)
There's a study here http://www.epsomsaltcouncil.org/articles/Report_on_Absorption_of_magnesium_sulfate.pdf
If you don't like the idea - how about a Magnesium salt lick , or just eat your greens :)
77.86.68.186 (talk) 11:01, 7 May 2010 (UTC)
That is one seriously flawed study!
  1. It was funded by the "Epsom Salt Council" who are hardly an unbiassed source of information.
  2. They only used 19 test subjects. That's not a good enough statistical sample.
  3. Their test subjects were all young and healthy without joint problems. Is it not possible (if magnesium is indeed implicated in joint pain) that the entire reason older and less healthy individuals suffer joint pain is because whatever mechanism for magnesium uptake is responsible for the rises measured in this experiment is broken? That would completely invalidate the entire set of conclusions.
  4. Their findings for one or two baths are less than their error bars and only after weeks of this treatment did they get an actual, measurable effect. An occasional bath in this stuff is useless - even by their own evidence. Do they tell people to bath in the stuff for weeks at a time? No.
  5. They did no placebo controls and their "control" experiments are not explained. That's a huge "no-no".
  6. The experiment was not done 'blind' - much less 'double-blind' - so some kind of placebo effect is a possibility here.
  7. The amount of Epsom salts they needed to use to produce a measurable effect were over half a kilogram per bath! So two or three bottles of the pretty scented stuff you can buy in big glass jars or ten packets of the stuff you buy in a boring cardboard box at the supermarket in each bath - for weeks and weeks! Their main web page says to use two cupfulls per bath - which is below the level that this study says has any measurable effect! So one major conclusion should be "In normal amounts, Epsom salts have no measurable effect on magnesium levels in the blood of young, healthy individuals even after two weeks of use".
  8. The "paper" hasn't been peer-reviewed, the experimental results have not been duplicated and no major scientific journal has published the study. They have not released the raw data for other people to analyse with their own statistical tools. So it's clearly not acceptable science yet.
  9. Then we have to ask how long the stuff stays in the blood and whether increased magnesium levels in the blood is even any good for you in the first place! Their own article points out that the body normally carefully regulates magnesium levels in the blood - there is probably a very good reason our bodies do that!
  10. They explain that the test subjects found bathing in the required high concentrations of epsom salts to be unpleasant. What happened to the "warm relaxing bath" thing?
  11. They conclude "Bathing in Epsom salts is a safe and easy way to increase sulfate and magnesium levels in the body" - but none of those conclusions are actually found in the body of the paper. Where did they follow the subsequent health of these volunteers? Maybe they all dropped dead right after the study - or will have long-term health problems as a consequence.
This is a classic example of "junk science" and it should be ignored. SteveBaker (talk) 14:42, 7 May 2010 (UTC)

Curvature of the earth[edit]

Not a big deal, but I was wondering just now if it is known how much a certain area of earth's surface (assuming a perfectly flat area) is curved. Is there any measurable curvature within, say a mile? –Juliancolton | Talk 01:19, 6 May 2010 (UTC)

Divide the number of miles in the circumference, about 24000, into 360°. This will tell you how many miles it takes to produce one degree of curvature. --Chemicalinterest (talk) 01:29, 6 May 2010 (UTC)
That makes sense. Thanks! –Juliancolton | Talk 01:39, 6 May 2010 (UTC)
Not quite. That assumes the Earth is perfectly spherical, but it is actually a bit of a flattened sphere. Over a small distance like a mile, this imperfection can be discounted, but on a large scale it has to be considered. 76.199.153.83 (talk) 01:49, 6 May 2010 (UTC)
Not quite. If you wish to take flattening of the ellipsoid into account, then variations in distance per unit curvature as a function of latitude is as (or slightly more) noticeable for small distances then it is for large distances. 58.147.58.122 (talk) 15:50, 6 May 2010 (UTC)
Yes. The earth's diameter is about 24 miles bigger at the equator than from pole to pole because of centrifrugal force. --Chemicalinterest (talk) 15:40, 6 May 2010 (UTC)

Look at a map of one of the plains states in the US, like North Dakota or Nebraska, and you will see lots of places where a road, or a series of successive county boundaries, forms a straight north-south line that jogs to the west every so often as you go north. In Canada the boundary between Manitoba and Saskatchewan is an even better example, having the same sort of shape for hundreds of miles with no further irregularities. The reason for this is that both the Public Land Survey System in the US and the Dominion Land Survey System in Canada were based on dividing the land into squares with specific sizes -- squares whose boundaries run north-south and east-west. For example, a 1-mile square on this system was called a section.

But of course that's impossible on a curved planet. The way it was really done was that they made the shapes almost square, with true north-south sides, running north and/or south from an east-west baseline until they got too far from the desired size; then they jogged all the boundaries to one side (by an amount that depended on how far they were from a principal meridian) and continued north or south from there. So for example each of the stairstep points in the Saskatchewan-Manitoba border is the same distance west of a principal meridian that runs north and south more or less through Winnipeg. The jogs in this case are about 24 miles apart. Look at a map of Manitoba and you can see how much the curvature of the Earth affects things. --Anonymous, 02:15 UTC, May 6, 2010.

To really get a gut feel for it - imagine you're standing on the end of a long, straight, "flat" road (we have to put "flat" in quotes - because it follows the earth's curvature). Over the distance between where you're standing and where the horizon is - the difference between a 'flat earth' and the real curved earth is exactly the height of your eyes from the ground. Within a mile, this "curvature" distance is about 8 inches...which is quite measurable. It gets bigger fast though! Within 3 miles, it's about 6 feet of curvature...which is why (if you happen to be a little over 6' tall) the horizon is about 3 miles away on dead flat, level ground. SteveBaker (talk) 03:18, 6 May 2010 (UTC)
Pages 774-779 of an old science book from 1887 give an approchable understanding of the Earth's curvature. If the diameter is 8000 miles, then in 1 mile there is 8 inches of curvature. The "drop" increase more than 8 inches in the 2nd mile,to 32 inches, and to 72 inches at 3 miles, and 128 inches at 4 miles, 66 feet at 10 miles. Observers watching a ship see it go "hull down" with only the mast or superstructure visible, through a telescope, when it is several miles away. One old source claims "optical depression" of only 6 inches in the first mile at sea, with similar geometric increases in dip per mile. Only the top of a tall hill or mountain will be visible from a distance. If you note the setting of the sun from the ground floor of a skyscraper, then ride the elevator to the top floor, you might see it once again partly above the horizon. Edison (talk) 03:38, 6 May 2010 (UTC)
Another example of this effect is to look at a city skyline from across a wide body of water; if you're familiar with the relative heights of the different buildings, you can tell that their bottoms are missing. I have noticed this when riding toward Hamilton over the Garden City Skyway on a day when the air was clear, and observing the Toronto skyline across part of Lake Ontario. --Anonymous, 04:20 UTC, May 6, 2010.
Fascinating stuff. Please excuse my stupidity - why are the "drop" numbers not increasing at a constant rate? Steve said '"It gets bigger fast, though!"' -- why? 218.25.32.210 (talk) 05:46, 6 May 2010 (UTC)
Think of a ball. Put your finger on the center top. Move it sideways and watch as it also moves down. At the beginning it moves down slowly, but as you get closer to the edge it moves down faster and faster. Ariel. (talk) 07:10, 6 May 2010 (UTC)
Ahhh... most helpful! I see now that the constant rate drop I was expecting would mean I was standing on a planar surface - such as the hypotenuse of a triangle (if imagined in 2D). Thank you! 218.25.32.210 (talk) 07:54, 6 May 2010 (UTC)
Civil engineering surveyors also notice on very large man made structures such as the Humber Bridge ”The towers, although both vertical, are not parallel, being 36 millimetres (1.4 in) farther apart at the top than the bottom as a result of the curvature of the earth.”--Aspro (talk) 11:28, 6 May 2010 (UTC)
Thanks for the responses; Steve's explanation is particularly enlightening. –Juliancolton | Talk 18:41, 6 May 2010 (UTC)
Some of the old books say the curvature can be noted in the plains of the US, but when I am driving on a long straight highway and see things behind falling below the horizon, I always figure it could be due to rising and falling terrain. As a child I saw a book showing a man watching through a telescope as a ship sailed out of sight, gradually disappearing below the water, and wondered how he knew the ship was disappearing over the horizon and not simply sinking. Edison (talk) 19:13, 6 May 2010 (UTC)
Well, the idea is that you look for ships that are sailing towards you - then, when they reach land you can ask them whether they were miraculously recovered from sinking or merely hiding behind the planet! :-) The ocean (or, better still, a nice calm lake to avoid big waves getting in the way) is a better place for testing these ideas than on land because you can be sure that there aren't any hills worth mentioning! SteveBaker (talk) 01:50, 7 May 2010 (UTC)
"How do you know it's not sinking?" Maybe it is! When the Titanic was sinking, there was actually another ship within sight, the Californian, which had stopped for the night due to the ice hazard. Its radioman had already gone to bed when the Titanic hit the iceberg, but its crewmen saw the Titanic's distress rockets. However, its captain said, in effect, "Well, maybe they're not distress rockets," and decided to do nothing. When the Titanic could no longer be seen, they didn't know it had sunk, because it could have just sailed away. They found out what had happened when the radioman got up. (At least, this is the most widely accepted version of the story, but it certainly has been disputed. Wikipedia has something at RMS Titanic#SS Californian inquiry and SS Californian#Captain Stanley Lord and other places.) --Anonymous, 06:37 UTC, May 7, 2010.

can Blue cheese produce penicillin?[edit]

Just curious. If the cheese could produce penicillin then it might be bad to those that are allergic to penicillin. --121.54.2.188 (talk) 05:20, 6 May 2010 (UTC)

I'll leave it to a biologist rather than speculate, but I can link you to Penicillium roqueforti, the fungus used in the making of blue cheese; Penicillium, our article on the whole genus; and this Straight Dope column from 2004, which claims that "most cheeses contain relatively small levels of antibiotic mold relative to that found in concentrated pharmaceuticals". Comet Tuttle (talk) 06:47, 6 May 2010 (UTC)
Nobody has mentioned the traditional folk medical practice of using mouldy bread or grain in poultices. Bread supports some penicillium varieties. The practice of using mould has been recorded way back, including of course -mouldy cheese. Moulds in folk medicine--Aspro (talk) 17:30, 6 May 2010 (UTC)

inverse square law and electromagnetic force[edit]

If the distance between two positively charged nuclei is halved, the inverse square (of Newton's law of gravity) says that the gravitational force will increase (by a factor of four) (i.e. become more positive/stronger) and the inverse square (of Coulomb's law) says that the electrical force will decrease (also by a factor of four) (i.e. become more positive/weaker). Is this correct? I am having trouble with the semantics of saying that something (electrical force) which becomes more positive is actually decreasing in force/strength. This also doesn't seem to fit with my (fairly poor) understanding of magnets, whereby the force required to bring two repelling magnets together seems to increase (my numbers aren't bearing this out?).

The more I think about it, the more it appears illogical that a decrease in separation also equals a decrease in the net force. But my head gets so screwed up with these negative numbers. I've done the calculations for the original distance and the halved distance, and my net force has moved from a –x10-27 to a –x10-26. Can that be right?

Does this mean the electric force can eventually become a net positive? Why do I think this should all be working the other way around? Any tidbits, filling in the gaps, overviews, corrections, numbers, calculations, examples, etc very welcome. Thank you. Differentially (talk) 06:48, 6 May 2010 (UTC)

Thanks to Ariel for an answer, but I've just finally realised that –x10-27 is a smaller repulsive force than –x10-26. As soon as it's that way around, it makes sense! Differentially (talk) 08:19, 6 May 2010 (UTC)

Force is not positive or negative. Force is force, and it has a direction (it's a vector, not a scalar). A negative force is a positive force pointing in the other direction. Don't think of negative forces, just think of the direction of the force. Ariel. (talk) 07:08, 6 May 2010 (UTC)

Who's on first? ("Extraterrestrial life(forms)") (done)[edit]

Greetings Earthlings! The article Extraterrestrial life mentions people and schools who thought first about life beyond earth but there is no informationen who coined (used for the first time) the English expression "Extraterrestrial life(forms)". So - please no Greek, no other language - who (which book, which article) used this term first? I do not know the answer myself, but I have a bet going on, that it was rather a literary person than a person of science. Am I right? I appreciate any clues (going back in time). Grey Geezer 07:36, 6 May 2010 (UTC) —Preceding unsigned comment added by Grey Geezer (talkcontribs)

This would probably do better in the language reference desk, but I found this published 1870. And this in 1854. Yet this claims 1868, which is clearly wrong. I think you won't find a definitive answer. Google scanning books has actually caused a revolution in etymology finding much earlier uses that were currently known for many many words. Edit: Even earlier 1848 Ariel. (talk) 09:06, 6 May 2010 (UTC)
I searched GB before and got unsatisfactory results. It is the combination of life and extraterrestrial. I think I will move to "Languages". Thanks! Grey Geezer 12:03, 6 May 2010 (UTC)
Google Books is absolutely unreliable in their claimed publication dates, since their system may report the first date found in a work. If it is the 2010 volume from some organization founded in 1660, it usually cites the publication as being from 1660, so it is essential to page back to the title page or equivalent to determine the publication date. They do not even have a channel for reporting incorrect date attribution. Edison (talk) 19:21, 6 May 2010 (UTC)

Mathematics of Kepler's laws[edit]

Hi,

I have the following comments about the mathematics of Kepler's laws.In this concern the original paragraphs were edited as follows: Please let me appreciate your editing for this article.Thanks.

TASDELEN's arugments for why Kepler's Laws are wrong

Kepler’s laws are wrong.[edit]

Kepler’s laws do not explain why the celestial bodies cycle around a barycenter, while Newton’s mechanical laws explain this cycling and give the shape of the orbits.

General[edit]

When two bodies are in the empty universe (even n-body in a system)

m1*r1=m2*r2 where (r1+r2)=d

F=G*m1*m2/d^2 means F*d^2=Ct (this is an hyperbola on Cartesian)

Transporting the axes, we write:

(f+f0)*(d^2+do^2)=Ct

When f=0 dmax^2=(Ct/f0-d0^2) and then the attraction force=centrifugal force

So, dmax has a limited, fixed value. Also the barycenter is fixed.

First law: The orbits are not elliptical.[edit]

Why the bodies cycle around a barycenter?

Consider the velocities of the bodies in the attraction field

V^2=Vp^2+Vr^2 where

Vr is the radial velocity and Vp is the tangential (perpendicular) velocity

Consider Newton’s law F=G*m1*m2/d^2.We write

F=G*m1*m2/d^2=m1*Vp1^2/d=m2*Vp2^2/d then,

m1*Vp1^2=m2*Vp2^2 where (d) is eliminated.

For the equilibrium of the bodies in motion we see that:

Vp1 and Vp2 should exist. This explains the cycling around a barycenter.


How looks the shape of this cycling?

Consider Newton’s F*dt=m*dv.This is,

F*r*dt=m*r*dv (energy conservation equation), then we write

1/2*m*Vr^2+m*gr*r+1/2*I*w^2=m*r*dVr (total energy with g variable)

This is a differential equation

dr^2+K*dt^2=2*r*d(dr)

with solution

r=-a*t*(t*tmax)+K where K=2*gr*r+I*w^2/m=-a^2*tmax^2/(1+4*a)

On Cartesian, the graph of (r) is a parabola.

On Polar this graph is a cardioidal looking spiral: billions of spirals.

Expanding then after compressing; with a max.point, only one max.point.

Located on a paraboloid surface along the orbit of the Sun in its galaxy.(our Milky Way)

This is the shape of the orbits. No sign of ellipse, no sign of aphelion, no sign of perihelion.

See the spirals on Nasa’s galaxies photos. The barycenter is not at one focus of an ellipse.

Second law: the areas swept out in equal time are not equal[edit]

Kepler says the Vp velocities are variable, the areal velocities are constant.

No.Vp velocities are constant since the existence of the body. This is an innate velocity.

Consider the mass m1,and the velocities Vp11,Vp12,…Vp1n for different values of r1:

From V^2=Vr^2+Vp^2 we write

V11^2+Vp11^2+2*g11*r11=Ct (energy conservation). (I*w^2 is invariable, is innate)

V11^2+Vp11^2+2*g11*r11=V1n^2+Vp1n^2+2*g1n*r1n=Ct

In an attraction field, Vp doesn’t matter. So,

Vr11^2+2*g11*r11=Vr1n^2+2*g1n*r1n (energy conservation, with g variable),therefore

Vp11=Vp12=Vp13…..=Vp1n= Ct

That is to say:

Vp at dmax has the same value as at d0: invariable until the body reaches to the barycenter.

Same reasoning for m2.

Third law: periods (P1/P2)^2=(r1/r2)^3 is correct.[edit]

In 1609 Kepler said, orbits are elliptical. Then in 1618 he gave the law of periods. But this last law is valid only and only when the orbits are circular. How Keplerian solid elliptical orbits could be transformed to circular orbit according this law of periods? Simply the orbits were not elliptical. Kepler himself has pronounced his orbital reasoning change with this period’s law: the actual orbits were not elliptical but another shape which could reach to circular orbits. These are spiraled orbits. Sun near the barycenter, no elliptical focus, no closest farthest point in one cycle of the body around the Sun, no aphelion, no perihelion, no equality of swept out areas.

TASDELEN (talk) 17:47, 8 May 2010 (UTC)=== Consequences: ===

As (r) is variable in the spiraled orbits theory:

P^2/r^2 =Ct is no more valid. It is variable

If today 1 year=365 days, billion years ago it was for example 15 days.

Light-year distance has no sense. Years have different quantity of days.

Light-day or 1000 LD has a meaning, since I*w^2 is constant, is innate.

Newton do not confirm Kepler as say the mathematicians.Etc,…TASDELEN (talk) 08:34, 6 May 2010 (UTC)

I've taken the liberty of reformatting your post and adding a collapse section so it doesn't take up a large portion of the page.
To be blunt, almost every bit of mathematics you try to derive above is wrong. Kepler's Laws are a strict mathematical consequence of Newton's Law of Gravitation when one has only two point masses. A complete derivation is given in the article at Kepler's laws#Derivation from Newton's laws, though I don't really expect that you will be able to follow it. Dragons flight (talk) 09:16, 6 May 2010 (UTC)
Without doubt, TASDELEN's mathematics are incorrect. Probably the first issue I spot is his first line, an equation for what appears to be a ... moment of inertia, or something ... but does not define distance from any particular location (presumably he meant to specify the center of mass, but critical steps are missing and/or rely on erroneous, unstated assumptions). The next line introduces a value, Ct, without explanation or justification. These sorts of skips and jumps are not permissible in a proper physics derivation. For a correct version of these derivations see our article on the two-body problem, specifically how to reduce it to a 1-body problem. Once you have mastered these equations, which are indisputably correct and have been verified by thousands of mathematicians and physicists during the last four centuries, you may be able to expand the theory; but the current work you have presented above is full of physics and mathematical error. Nimur (talk) 15:01, 6 May 2010 (UTC)


I agree - I'm sorry but what you've presented above is wrong - both physics-wise and mathematically. You can't just make stuff up - that's not how science works! If you attempted to add this to the article, it would be reverted instantly. Heck - I'll personally revert it if you did that!
But it doesn't actually matter whether your ideas are right or wrong. We simply don't write Wikipedia by having clever, original ideas and writing articles about them - that's just not how Wikipedia operates. In fact, we have a specific rule: No Original Research which actively prohibits you from writing about your own ideas...right or wrong. Instead, we have to write about things for which solid, reliable outside references can be found. Third party, peer-reviewed scientific papers, published in reputable journals are required for science articles like this one. So if you look at the bottom of the Kepler's laws article - you'll see all of the learned scientific papers that were referred to when writing that article.
So to get your ideas into Wikipedia - you'd first have to write this up as a formal scientific paper. Then you'd need to present your paper for publication at (let's say) "The Journal of Celestial Mechanics and Dynamical Astronomy" (that's a real journal by the way). They would examine your paper, have several other celestial mechanics experts read it - and only if they agreed with your findings and found the math plausible - would they allow it to be published. That's called "peer review" and it's a tough test to pass. If you did get published - then it would be appropriate to go to the talk page of the Kepler's Laws article and suggest a revision to include these new findings - along with a proper link to your article in the journal.
But the problem with doing that is that your math and science are hopelessly, naively, catastrophically wrong! (I'm sorry - but there is no polite way to express just how wrong it truly is!) Hence, the journal of celestial mechanics are going to write you a polite letter telling you in no uncertain terms that your paper is worthless and they won't publish it. That means that Wikipedians couldn't write about it - even if we agreed that the guys at that journal were clueless and you were the next Einstein (which we don't!).
So, no - there is no possibility whatever of your change being kept in the Kepler's laws article - or anyplace else in Wikipedia for that matter.
If you are unconvinced by what I say - please read WP:FRINGE - which covers how we handle these kinds of 'fringe theory'.
SteveBaker (talk) 15:19, 6 May 2010 (UTC)


Hi,

Many thanks for the comments.Dear commentors:

Dragons flight (talk) 09:16, 6 May 2010 (UTC)

Nimur (talk) 15:01, 6 May 2010 (UTC)

SteveBaker (talk) 15:19, 6 May 2010 (UTC)


“…almost every bit of mathematics you try to derive above is wrong. Kepler's Laws are a strict mathematical consequence of Newton's……”

If I say 2*2=7, then you say “No.You are wrong; 2*2=4”. So, you prove that I am wrong. Otherwise I must ask you “where is the wrong point ?”.Please, show me the wrong point of my mathematics.

“…Derivation from Newton's laws, though I don't really expect that you will be able to follow it.”

Thanks for the compliment. Really I am unable to follow this. This why, I have to repeat my Newton’s derivation so that you can point out the wrong expressions. I think you are mathematicians, dealing with physics, or astronomer. I am a mechanic, diesel engine repairer.

Newton’s F=G*M*m/d^2

is explaining,why the masses have to orbit around their barycenter. Vpm and VpM (the perpendicular velocities to the attraction direction) should EXIST for cycling. In fact F=G*M*m/d^2= m*Vpm^2/d= M*VpM^2/d, that is Attraction Force = Centrifugal force: m*Vpm^2=M*VpM^2, So the cycling is a MUST, due to these velocities.

Newton’s F*dt=m*dv gives

the shape of the orbits: Consider F*r*dt=m*r*dv

F*r*dt is the energy conservation expression’s left side .This is

F*r*dt=1/2*m*Vr^2+m*gr*r+1/2*I*w^2 (total energy, where Vr is the radial velocity).Then

1/2*m*Vr^2+m*gr*r+1/2*I*w^2=m*r*dv (we assume g variable,gr)

Vr=dr/dt and dVr= d(dr/dt)/dt

1/2*m*(dr/dt)^2+m*gr*r+1/2*I/w^2=m*r*d(dr/dt)/dt simplifiying

(dr)^2+ K*dt^2=2*r*d(dr) a differential equation, with solution

r=-a*t*(t*tmax)+K where K=2*gr*r+I*w^2/m=-a^2*tmax^2/(1+4*a)

On Cartesian, the graph of (r) is a parabola. On Polar, this graph is a cardioidal looking spiral: billions of spirals. No sign of ellipse! And this is due to Newton’s laws. Please edit and show the wrong points, before saying “…almost every bit of mathematics you try to derive above is wrong. Kepler's Laws are a strict mathematical consequence of Newton's……”

When speaking of areas

and considering the mass m, the total energy of the body is constant due to energy conservation law of Newton. That is:

Assuming V^2=Vr^2+Vp^2 (radial and perpendicular components of the velocity V)

1/2*m*Vr1^2+1/2*m*Vp1^2+m*g1*r1+1/2*I*w1^2=Constant=C1 (conservation)

1/2*m*Vrn^2+1/2*m*Vpn^2+m*gn*rn+1/2*I*wn^2=Constant=C1 (conservation)

1/2*I*w1^2=1/2*I*wn^2 ( as innate=nothing added to the mass,no modification of w)

In an attraction field a work is done ONLY in the direction of attraction. So,

1/2*m*Vr1^2+m*g1*r1=1/2*m*Vrn^2+m*gn*rn , then

Vp1=Vpn=Constant =C2

That is:

Vp perpendicular, to Vr, is constant at every level of the distance (r).Vr is variable.

When Vp is constant (that is the Vx in Cartesian) no equality of swept out areas in equal interval of time.So, what about Newton’s confirmation of the old mathematicians? Is this is a correct confirmation or a tricky confirmation? Have you controlled this confirmation yourself or just copy-pasted the confirmation of the old mathemeticians? Try it yourself.

“Once you have mastered these equations, which are indisputably correct and have been verified by thousands of mathematicians and physicists during the last four centuries, you may be able to expand the theory; but the current work you have presented above is full of physics and mathematical error.” Where are this errors?

I know it is difficult

to change the perception of the community with such contradictory arguments.And no one of the Keplerian religion will agree with these last Newtonian religion.

“Third party, peer-reviewed scientific papers, published in reputable journals are required for science articles like this one. So if you look at the bottom of the Kepler's laws article - you'll see all of the learned scientific papers that were referred to when writing that article.”

This is not

a scientific article.I do not know how to design a scientific article.I am sure Peer-reviewers will prefer to keep their position in Keplerian religion.But if you start to believe to my mathematics,then someone should help me write a scientific version of my evaluations.

Regards.TASDELEN (talk) 17:47, 8 May 2010 (UTC)

I did read much of your derivation, so I'll just point out the first couple of mistakes. First, you said that the gravitational attraction is equal to centripetal force (actually, you said centrifugal force, but you meant centripetal) - that is only true for circular orbits where d is constant. In general (and in reality) Keplerian orbits are non-circular ellipses. Second, you said "F*r*dt=1/2*m*Vr^2+m*gr*r+1/2*I*w^2". That equation has to be wrong because one side has a differential in it and the other doesn't - every term needs to be of the same order for it to make sense. You clearly don't understand differentials, so I suggest you avoid them. They are very confusing and completely unnecessary for this. Stick to derivatives (ie. don't say F*dt=m*dv, say F=m*dv/dt). --Tango (talk) 18:20, 8 May 2010 (UTC)

Dear Tango (talk) 18:20, 8 May 2010 (UTC)

By attraction force I mean "attraction towards the barycenter" and by centrifugal force I mean "the force in the contary direction".

When you make the unit analysis of the equation's terms

"F*r*dt" =1/2*m*Vr^2+m*gr*r+1/2*I*w^2 = m*r*dv you have

(dr)^2+ K*dt^2=2*r*d(dr) that is

(metre)^2+K*dt^2= metre*metre= metre^2 which means "terms are of the same order,on left side and on rigth side"

and K=2*gr*r+I*w^2/m=-a^2*tmax^2/(1+4*a)=metre/sec^2*metre= metre^2/sec^2

therefore K*dt^2= metre^2

So,the terms are of the same order.No discrepancies.

"You clearly don't understand differentials, so I suggest you avoid them. They are very confusing and completely unnecessary for this. Stick to derivatives (ie. don't say F*dt=m*dv, say ...." is not valid.I am not mathematician but I know to make "unit analisis".I hope you will appreciate my knowledge.ThanksTASDELEN (talk) 15:50, 9 May 2010 (UTC)

There is no force in the opposite direction. There is gravity pulling the objects together, that is it. I'm not talking about units, I'm talking about the differential order - basically, count the d's. F*r*dt has one d. 1/2*m*Vr^2 has no d's. That means having both terms in the same equation doesn't make sense. --Tango (talk) 22:30, 9 May 2010 (UTC)
Dear TASDELEN, I wonder if you have read our article on Johannes Kepler. It explains that he chose his mathematical model (after several failed models) to match the observations of Tycho Brahe. Good scientists always choose a model to match observations. If you can come up with an orbital equation based on spirals that comes as near to matching observations as does the standard Newtonian derivation of Kepler's model, then perhaps someone will take your theory seriously. It is always interesting to read new viewpoints and alternative theories, but they have to be based on real mathematics, and they have to match observations. I suggest that you take another unbiased look at your theory, check it with any mathematicians or physicists that you know, and then find a more profitable outlet for your abilities. Sorry to be so blunt, but I think you are wasting your time on this. Dbfirs 17:34, 10 May 2010 (UTC)

living species which appear to have stopped evolving[edit]

Is their a list of species such as sharks, crocodiles, palmetto bugs and ants which are not extinct but which appear to have evolving or which appear to have reached an apex of evolution, excluding my neighbor Billy Bob? :-} 71.100.0.29 (talk) 09:55, 6 May 2010 (UTC)

There is no such concept as "apex of evolution", evolution doesn't work that way. Living fossil may be of interest. How can you tell if an animal "stopped evolving" without being able to predict the future? Ariel. (talk) 09:59, 6 May 2010 (UTC)
Silly person. Because you do not need to predict the future to answer the question since the question only concerns itself with the present and the past. In fact even if you have a crystal ball I'm not interested in what it shows you. 11:45, 6 May 2010 (UTC) —Preceding unsigned comment added by 71.100.0.29 (talk)
The closest sensible version of the question might be: What species appear to have changed the least in the last 100 million years? Is that what you are asking? alteripse (talk) 10:33, 6 May 2010 (UTC)
It could simply be that they fill their ecological niche so well. Their present morphology is undoubtedly successful at preventing other species from taking over due to Competitive exclusion.--Aspro (talk) 10:41, 6 May 2010 (UTC)
Exactly. If the environment doesn't change, then the species won't change either. That's why Australian species have been preserved unchanged for so long: there were no changes in the enviromental condition, and there was no external influences that changed them (like new species that migrated from a different environment). Then the European arrived to Australia and introduced new species (rats and rabbits, among other), and existing species had to change or die. --Enric Naval (talk) 11:02, 6 May 2010 (UTC)
"That's why Australian species have been preserved unchanged for so long" [citation needed]. Who says they were unchanged? Do you have any evidence that the rate of speciation in Australia was markedly different than similar areas? Australian species are different because they evolved independently for a very long time, but on average they most definitely evolved. It just happened that evolution often took different paths than in other parts of the world. Even in the absence of migration the continent has still experienced large climate shifts (along with the rest of the globe) since it became an isolated island, and that is plenty of impetus for evolution. And even in the absence of external pressure genetic mutations still sometimes create new traits that are so successful they can disrupt established ecosystems anyway. Dragons flight (talk) 11:52, 6 May 2010 (UTC)
(edit conflict) Minor correction - it is probable that humans had a major impact on the Australian environment well before the arrival of Europeans - see our article on Australian megafauna. More significant correction - the engine room of evloution is random mutation, and there is no reason why this should stop or slow down just because a species has filled a comfortable niche in a stable environment. Even in a stable environment, species will tend to differentiate and specialise. Gandalf61 (talk) 11:57, 6 May 2010 (UTC)
100 million years is an exceptionally long time. Almost no species last that long. Either they die out entirely, or they evolve sufficiently new traits that they come to be labeled as a new species. The typical duration of a species level taxon is only a few million years. Higher level categories like families and classes are more robust, but individual species are usually ephemeral. Probably less than 1% of species would be expected to persist for 100 million years. Dragons flight (talk) 11:52, 6 May 2010 (UTC)

So if the environment is really changing then you are likely to see a reflection of those changes if species that have stopped evolving all of the sudden begen to change again. geez. 71.100.0.29 (talk) 11:49, 6 May 2010 (UTC)

You can't tell if a species stopped evolving, because you don't know what it will do in the future. Living fossil is probably the best answer available for your question. Ariel. (talk) 12:02, 6 May 2010 (UTC)
Reading some of the examples should also help. An example I like to use is the tuatara. As our article notes:
Tuatara have been referred to as living fossils,[2] which means their group retains many basal characteristics from around the time of the squamate - rhynchocephalian split (220 MYA).[19] However, taxonomic work[20] on Sphenodontia has shown that this group has undergone a variety of changes throughout the Mesozoic, and a recent molecular study showed that their rate of molecular evolution is faster than of any other animal so far examined.[21][22] Many of the niches occupied by lizards today were then held by sphenodontians. There was even a successful group of aquatic sphenodontians known as pleurosaurs, which differed markedly from living tuatara. Tuatara show cold weather adaptations that allow them to thrive on the islands of New Zealand; these adaptations may be unique to tuatara since their sphenodontian ancestors lived in the much warmer climates of the Mesozoic.
Although as a caveat to the rate of evolution I'll add [1] [2] [3] [4] [5].
Another interesting example is the case of the Wollemia (of which the location of the only known wild specimens is still being kept secret AFAIK [6], again the article helpful as are the references and external links e.g. [7]
Speaking more generally, if subject to a major environmental change, the rate of evolution may change (or more likely the species will just die off) but it doesn't mean that they ever 'stopped evolving'. That's primarily a simplistic and flawed creationist idea which doesn't get much consideration from evolutionary biologists.
Nil Einne (talk) 14:23, 6 May 2010 (UTC)
100 million years is really just a blink of the eye. Bus stop (talk) 14:28, 6 May 2010 (UTC)
No, it isn't. 100 million years is 100 millions years, which is a significant amount of time, even speaking geologically. The earth is about 4.5 billion years old, which makes 100 millions years a span of slightly more than 2% of the total - if each blink of your eyes took 2% of your life, you'd miss out on quite a bit, I think. And multicellular life is "only" about a billion years old - of which 100 million years would represent 10% of the span. It's important to emphasize the realities of deep time, but exaggerating it does no service. Matt Deres (talk) 16:37, 6 May 2010 (UTC)
Well, the age of the universe is 13.75 billion years. That's about 3 times older than the age of the Earth. Bus stop (talk) 17:04, 6 May 2010 (UTC)
True, but what's your point? The discussion at hand is about rates of evolution and speciation and so on, so the age of the universe is pretty much irrelevant. 100 million years is a very long time indeed and you're not doing anybody a service by telling them otherwise. Matt Deres (talk) 20:26, 6 May 2010 (UTC)
In a sense, these animals haven't stopped evolving at all. They will still be getting genetic change from mutation and the general genetic diversity within the species - but what is happening is that any changes that happen are having a negative effect - so the mutated animals are not surviving as well as the unmutated population.
What we need here is a good analogy - and the one I'm about to give is a classic. Imagine all possible sets of genes as being laid out on a large map with the similar gene makeups close to each other and the less similar ones further away - and imagine that the reproductive success/survival rate of a hypothetical animal with a particular genetic makeup to be represented by the elevation of this 'genetic terrain'. Then there will be hills and valleys all over the place on this map - with many of the hilltops being populated by particular species of real animals that have that particular makeup...but with other hilltops representing possible kinds of successful animals that don't happen to exist in the real world.
As particular animals mutate - their genes change which "moves them" to a slightly different location on the map...typically not far from their parents. Hence, individual animals appear that are a little way away from the others of their species - but because all of the members of the species share most of their genes, they come out as a small 'fuzzy' group of dots on this landscape. If some members of the species are positioned at a lower elevation (ie less reproductively successful) than the others higher up the hill - then they'll be out-bred and eventually die out leaving the ones on the higher elevations who survive. If the species is not quite at the top of the hill yet - then a random change could produce an animal that's higher up the hill (ie more successful at breeding and surviving) - and that animals' ancestors will come to dominate the population. Over many generations, you'd therefore see the members of the species gradually climbing to the top of the hills and then staying there because "when you're at the top, the only way is down".
So after enough time has passed, you'd see little groups of animals huddled together at the tops of their respective hills - having evolved to be there and all having genetic makeups that can't be improved upon.
Now, the nature of this process is that once on a 'hillside' the population will climb to the top of that hill. That doesn't mean that the hill is the highest one around. If there is a species in the same environment that's managed to get to the top of a higher hill - then the lesser species will be out-competed and die off - being unable to evolve to be any better without getting worse first.
It's also possible that there may be other hilltops nearby that are higher than the one they are currently sitting on. But they can't evolve over to that higher hill because any small genetic change just moves the animal off to lower ground where it gets out-bred by the ones higher up in the genetic landscape. A little further away, there will almost certainly be some higher mountains - sets of genes that are much better for survival than the present makeup of these animals. However, if those higher peaks are further away than a few generations of genetic change will reach - then the animals are effectively trapped with their present genes. Any small genetic change makes them worse off - but the huge genetic changes that would get them to a higher hill and allow them to evolve up that new slope are too far away.
If the slope of the local landscape is shallow enough - then it may be possible for a few generations of mutated animals to survive despite not being so great as the others and drift across that shallow genetic valley onto the slopes of the higher peak. When that happens, they'll rapidly climb that peak and suddenly you have a new species that's much better than the old one.
But if the slopes are steep then any animal that shifts it's genetic makeup far from the local peak will end up in a deep valley and will die off before it can get onto higher genetic terrain.
However, this is a statistical matter - it's possible that some really unlikely mutation could change the animal enough to transport it's genetic makeup to the slopes of a quite distant and much taller peak - and then you'd find a sudden shift in the population to a significantly different animal...probably a different species. But if it happens that these animals are on a really steep-sided hill in the middle of a vast plain - then it's possible that no 'reasonable' amount of genetic change will get them to a higher peak - and they will (in effect) have stopped evolving. That's evidently what's happened with these 'static' species. Any small genetic change in a crocodile makes a worse crocodile - and the necessary change to have six legs (or whatever it would take to be a better crocodile) is too large to happen in a single generation. So they are stuck on their little steep-sided hill - unable to evolve in any direction.
But the thing is that the world changes. If the environment changes (due to global warming, for example) - then that re-prints the map! Genetic positions that used to be hills could now become valleys, other genetic hills will get taller - and the animals will spontaneously start evolving to find the new hilltops. This sudden 'scrambling' to get to the higher genetic peaks is what drives these sudden bursts of new species that pop up after a major environmental change.
There are other places in this genetic landscape where there are relatively flat, high plateaus. In that case, there are lots of small changes that can happen to the species which are neither better nor worse than their present genes. The animals spread over the plateau because no place is particularly better than any other - and you see considerable diversity within the species. Humans are kinda like that - we have genes for different hair, eye and skin color - genes for lactose tolerance and intolerance - all sorts of variations - but none of those are having much of an impact on our survival rates - so you see people with all kinds of different skin/hair/eye colors surviving equally well.
If you take another situation, the dark skinned people of Africa had a problem with malaria - and a local 'peak' in the genetic landscape corresponded to having a particular gene that conferred protection against the problem...albeit at the cost of some individuals getting two copies of the gene and dying young with sickle-cell disease. However, this was a local peak and evolution took those people up to it. Now, transport those same people to a region where there is no malaria, or add medical treatment that makes the value of natural malaria immunity 'go away' - and the genetic landscape changes. The peak caused by the malaria problem goes away - revealing a valley due to the sickle-cell issue. Logic says that we should see this gene becoming less common over coming generations as those groups of people evolve back up the sides of that new valley to the top of whatever is the nearest local peak.
SteveBaker (talk) 14:54, 6 May 2010 (UTC)
For people who wish to do further research, does that classic analogy have a name? Does Wikipedia have an article about it?
-- Wavelength (talk) 15:38, 6 May 2010 (UTC)
That's a good analogy, but it would be better if you turned it upside-down. Better genes should be lower down. That reflects the fact that species will naturally move towards them, just as objects in real space naturally move downwards. They then reach the bottom of a local depression and are stuck there. Getting to a deeper depression would involve climbing over a ridge, which is difficult. --Tango (talk) 17:02, 6 May 2010 (UTC)
It sounds like something used in The Blind Watchmaker by Richard Dawkins, but with a bit of chemistry/physics thinking mixed in. The analogy lacks enough of a genetic drift element, to my mind. Even without the landscape changing, populations evolve through genetic drift. Not just a few places on the landscape having plateaus (and anyway, this gets a bit weird because we don't have enough dimensions to keep track of all the variables we're talking about), but almost all the places have plateaus for some parts of the genome. And this genetic drift can even alter the shape of the landscape without anything happening externally, leading to selection pressure on this species and others. This is why species continue to evolve, even when conditions don't change. 86.178.228.18 (talk) 19:29, 6 May 2010 (UTC)
You're close - it comes from Dawkins - but you got the wrong book: "Climbing Mount Improbable". But Dawkins isn't really the originator of this analogy. The general idea of mathematical optimisation is usually visualised that way - and optimising algorithms are sometimes called Hill climbing for that very reason. The way genes evolve is a lot like that mathematical process. When you do optimisation using 'hill climbing' math inside a computer program, you 'climb' a slope until you hit a local maxima...and you have the same problem that an evolving species has - that you may successfully reach a local maxima - yet miss a much better optimisation that's further away - but an overly rigorous algorithm might never be able to descend into the valley and cross the intervening space to find a higher peak. Computers can be programmed to do smarter things like "Shotgun hill climbing" and "Random restart hill climbing" - which involves occasionally injecting some randomness into the process to hopefully jump you over to somewhere on the map where you'll find a better hill. Real world species fail to do that - so it's interesting to note that evolution isn't the perfect algorithm that some people think it is...without the ability to somehow look for yet higher mountain on the other side of nearby valleys - you'll rarely hit upon the best possible solution. Genetics can't do that...computer programs can! SteveBaker (talk) 01:34, 7 May 2010 (UTC)

Okay, so we are talking about a landscape called an environment and organisms on that landscape. I mean this analogy seems to have paralleled the real world exactly. As for dimensions we have all sorts of things, temperature and light and moisture level and turbulence and you name it all of which can change, with the organisms themselves in this terrain representing the genetic code they contain. The mountains or valleys are just places where the environment comes closest to fulfilling the requirements of the genes and vice versa. So if the environment does not change and a change in the genes occurs that does not bring the organism closer to matching the environment then its numbers will decrease due to reproduction. It all makes sense that while a palmetto bug might do better outside due to temperature and rotten vegetation and dead worms, etc. except for spiders and birds and lizards it still comes inside to find enough hidden crud or crumbs to do well. What I'm looking for, however, even though genes will change and the environment will change is a list of organisms which have adapted to both through all kinds of changes and yet remains essentially the same as it always was. If I were designing a tank this is the tank I would want to design. One that is exposed to all sorts of change but is still functioning in the end due to the flexibility or stamina or shape, etc. of the initial design. I just need a list of organisms that are living today and the amount of time since their last notable change or origination as a new species. 71.100.0.29 (talk) 21:04, 6 May 2010 (UTC)

The original question was sensible, except that it should have used a term such as "local optimum" instead of "apex of evolution". There are a few species such as the cockroach, horseshoe crab, and coelecanth that appear to have changed very little over the last 100 million years, but I'm not aware of a list of such species. (Not that I would know, not being an evolutionary biologist.) Looie496 (talk) 21:39, 6 May 2010 (UTC)
I've wondered about this--so modern horseshoe crabs resemble fossils from hundreds of millions of years ago, so one could say their appearance has not changed much, right? But couldn't there have been all kinds of change that does not get fossilized? Our page says they use Hemocyanin in their blood to carry oxygen. Would one be able to tell, from fossils, when the use of Hemocyanin in horseshoe crabs began? Was it there all along? ..there must be all kinds of important stuff that is lost in the fossil record. Wouldn't it be impossible to make any claims about the actual genetics of fossils? Or when a new species evolved? Like, a modern horseshoe crab could breed with an ancient one from how long ago? Seems like the best that could be done is making statements about appearance, no? Pfly (talk) 02:17, 7 May 2010 (UTC)
The entire thread appears to be a tl;dr situation, although the above two posts try to give an answer. My two cents: Triops. 220 million years. ~ Amory (utc) 03:43, 7 May 2010 (UTC)

Chemical explosive rail-gun-better than electric?[edit]

If a massive gun had a series of explosive chambers at right angles all the way along it's length, and after a projectile (a manned rocket perhaps) was set moving with an initial explosion at the start of the barrel, would a series of timed chemical explosions in the side chambers speed the projectile up even more, enough to escape Earth orbit without the G-force killing the astronaut, or could it be a more compact and powerful equivalent to an electric rail-gun for military use? Would the speed be higher than any other method? [Trevor Loughlin]80.1.80.12 (talk) 11:43, 6 May 2010 (UTC)

You are describing something very similar to the Nazi V3 weapon of WW2 [8]--Aspro (talk) 11:58, 6 May 2010 (UTC)
It's better than one large explosion, but not as good as electric. Electric is constant acceleration, this would be a series of jerks. Humans wouldn't like that. The force is lower for each explosion, but now you are shaking the person violently - this might actually damage them more than a single larger explosion. You could maybe add a buffer to stretch out the force for each explosion - a heavy pusher plate on a spring maybe, with the explosions carefully timed for when the pusher is just about to switch from compressing the spring to stretching it. But an explosion is not really the most efficient way to accelerate something, a constant fire would be better. Ariel. (talk) 12:08, 6 May 2010 (UTC)
We have, of course, an article at V-3 cannon. To escape from Earth, the projectile needs to reach the second cosmic velocity or escape velocity, which for Earth is 11.2 km/s (call it 10km/s). Assuming perfectly constant acceleration, at 1 g (call it 10m/s), you need to accelerate for roughly 1000 seconds to reach escape velocity. At 10 g, 100 seconds. In that time, your projectile will have traveled approximately 500 km. That's a mighty long barrel for a gun... --Stephan Schulz (talk) 12:16, 6 May 2010 (UTC)
The idea reminds me of Project Orion which was to be a spaceship powered by detonating atomic bombs behind a large 'pusher plate' behind the craft. The issue of peak versus average acceleration was handled by large shock-absorbers. In the case of our OP's idea, you could use a larger number of smaller charges to even out the acceleration still more - and even approximate continuous thrust that way. The difficulty (as others have pointed out) is that you effectively need the rail to be as long as distance travelled by a conventional rocket while under power - and that's going to be a very long 'rail'. Rail guns are a more practical proposition for unmanned launches where the g-forces can be higher...but their main advantage is re-use and the fact that they could be powered by electricity - making them feasible for things like doing mining operations out on the asteroids or on the moon where solar power is cheap but rocket fuel (or explosives) might be unobtainable - and the escape velocities are much lower. SteveBaker (talk) 14:02, 6 May 2010 (UTC)
Another problem with relying on a series of explosive chambers is the choice of propellant. The lower the molecular mass of the combustion products the faster it will expand (and push on the projectile). The railgun avoids this issue completely and can already achieve (so we are told) 3,600 meters per second (with a hydrogen filled barrel). Railgun#Tests. Faster speeds are theoretically possible to 7,000 m/s. Light gas guns can already achieve this using pure high pressure hydrogen -the lightest of the lot. Using multiple chambers on their own therefore, would not I think, ever be capable of beating this. So, I suppose the answer to the OP's question is no. --Aspro (talk) 15:00, 6 May 2010 (UTC)

I should point out that there are theoretical limits to how fast a projectile can be fired out of a cannon with smokeless powder. The limit is around 1600 m/sec. The Paris Gun came about as fast as a projectile is going to get when fired from a classic style cannon. A railgun on the other hand has a theoretical limit of 6 KILOMETERS/sec. So to answer your question, even with multiple charges, there's no way you can compete with railguns. Besides, having multiple charges in a cannon would only work on one projectile instead of multiple ones, and that's assuming it would even work at all, which I doubt. ScienceApe (talk) 01:12, 12 May 2010 (UTC)

Electrolysis of CuSO4[edit]

Is sulfate oxidized to SO4 when CuSO4 is electrolyzed? My chemistry teacher in 11th grade keeps saying that, but I don't think it does. Thanks. --Chemicalinterest (talk) 13:04, 6 May 2010 (UTC)

persulfate is a possibility SO52−. But SO4 is not realistic. But I do not know if it is formed this way. Graeme Bartlett (talk) 13:21, 6 May 2010 (UTC)
I think that the reaction is: 2 CuSO4 + 2 H2O → 2 Cu + O2 + 2 H2SO4 The sulfuric acid may react with additional copper sulfate to form copper bisulfate. They said that the reaction was: CuSO4 → Cu + SO4 --Chemicalinterest (talk) 13:36, 6 May 2010 (UTC)

Here is how you would figure this out. You have three species in the beaker: Cu2+, SO42-, and H2O. Figuring out the anodic and the cathodic reactions is actually very easy. Just look on any table of standard reduction potentials, like Standard electrode potential (data page) and then look up the potentials for each reaction. Possible cathodic reactions are:

  • SO42− + 4H+ + 2e ⇌ SO2(aq) + 2H2O Eo = +.17
  • Cu2+ + 2e ⇌ Cu(s) Eo = +.340
  • 2H2O + 2e ⇌ H2(g) + 2OH Eo = -.8277

Possible anodic reaction are:

  • 2H2O ⇌ O2(g) + 4H+ + 4e Eo = -1.23
  • 2SO42−S2O82− + 2e Eo = -2.010

You need to choose a reaction for each electrode. You always choose the one with the highest (most positive) electrode potential, that gives us a cathodic reaction of:

  • Cu2+ + 2e ⇌ Cu(s) Eo = +.340

and an anodic reaction of

  • 2H2O ⇌ O2(g) + 4H+ + 4e Eo = -1.23

So, we double the first, and combine to get an overall reaction.

  • 2Cu2+ + 2H2O ⇌ 2Cu(s) + O2(g) + 4H+ Eo = -.89

Meaning that, assuming 1 molar concentrations you'd need a minimum of 0.89 V to make the electrolysis extensive. Where your teacher messed up is that they forgot that water was present; in any electrolysis, you need to consider whether or not water is more likely to electrolyze than your other reactants. At the anode, it turns out that the water is far more likely than the sulfate to electrolyze.

This assumes aqueous-phase electrolysis. You can also do liquid-phase electrolysis, but that requires liquid copper(II) sulfate, which isn't usually done in your high school chem lab. In that case, you'd need the liquid-phase electrode potential data; I don't have that at my finger tips, but the method is identical, except you don't have water present, so you'd need a liquid-phase half reaction for the oxidation of the sulfate ion into sulfur trioxide gas and oxygen gas. --Jayron32 15:40, 6 May 2010 (UTC)

CuSO4 decomposes before it melts into SO3 and CuO. Thanks. Another questionable reaction was that: Zinc and copper are placed in a sodium chloride solution. The sodium ions accept electrons to produce sodium, and the chloride ions give away electrons to produce chlorine. --Chemicalinterest (talk) 15:47, 6 May 2010 (UTC)
Bullshit. There's nothing you could do to an aqueous solution of sodium chloride to produce sodium metal or chlorine gas, especially not with Zinc metal or Copper metal. Sodium is far more active a metal than Zinc or Copper. You can compare the ionization energy for the metals, or you can look at the electrode potentials for either of them. Putting zinc metal in a salt solution will get you a wet, salty piece of zinc metal. There are corrosion reactions that can occur here, but these involve oxygen and water. Sodium ions can act as a catalyst for these reaction via ion exchange, but you never get sodium metal in the presence of water. It just doesn't happen. Oh, and I looked over your reaction; its pretty much the same as the one I came up with; just that sulfate is a spectator ion to the overall reaction, so I left it out of my analysis, and you kept it in yours. Either way, its correct and your teacher is incorrect. --Jayron32 15:53, 6 May 2010 (UTC)

Planets in Universe[edit]

why is it important to find out if there is anther planets in the universt ? —Preceding unsigned comment added by 90.149.184.157 (talk) 14:47, 6 May 2010 (UTC)

People like to see whether there is other life in space. See SETI. --Chemicalinterest (talk) 15:22, 6 May 2010 (UTC)
A lot of people consider understanding the universe to be important. There isn't necessarily any practical reason to do it, it's just human nature to want to understand things. Finding out about planets around other stars may help us understand our own solar system better (which may or may not be actually useful). --Tango (talk) 15:34, 6 May 2010 (UTC)
Pragmatism. The planet cannot sustain the current population growth levels of humans. At some point, either human population growth is going to have to level off (and the mechanisms for that will involve aggessive competition for resources, i.e. wars where lots of people are killed) OR we're going to have to find some other place to live. One of the things about finding life outside of the earth is it allows us to understand how to survive in other environments, either in our own solar system (like Mars) or, how life can be made to work in completely different environments. Furthermore, the prospect of finding a peaceful, but technologically advanced alien race would be quite helpful. Learning how to effectively travel interstellarly is something that seems impossible given our current understanding of the universe, but if another alien race has figured it out, we could too, and that would open up MANY possibilities for human colonization of the galaxy. Even if we were to figure out how to do that on our own, knowing what life, if any, existed outside of our solar system is a handy bit of knowledge. Trying to colonize a planet whose already intelligent inhabitants aren't interested in us doing so is something we'd want to know before we showed up. --Jayron32 15:58, 6 May 2010 (UTC)
I disagree with your parenthetical assertion. There seems to be a natural reduction in birthrate as standard of living increases (most of the developed world would be showing population decline if it weren't for immigration from the rest of the world). If we can increase the standard of living in the rest of the world, we may well find our population problems disappear. --Tango (talk) 16:53, 6 May 2010 (UTC)
Oh, yes, if we could raise the standard of living in the rest of the world, that would go a long way towards ameliorating overpopulation problems. How's that been going so far? --Jayron32 17:06, 6 May 2010 (UTC)
Well, we solved world hunger, then we solved global warming. What's next? Vimescarrot (talk) 18:30, 6 May 2010 (UTC)
Jayron, you laugh condescendingly at the idea of raising the standard of living in the third world, but you think colonizing other planets can solve overpopulation? -- BenRG (talk) 00:25, 7 May 2010 (UTC)
With any forseeable technology, of course, there is no way to send enough folks to another planet to make even a dent in population. What it is just barely conceivable that we might be able to do, though, is create a self-sustaining population somewhere else, in such a way that if worse comes to worst on this planet, the species will nevertheless survive.
But a flip side of that has occurred to me. It is possible that, on one planet, no one will deploy (or at least detonate) a weapon that would make the planet uninhabitable, because they themselves would have nowhere to go. With two planets, they could fire them at each other.... --Trovatore (talk) 00:31, 7 May 2010 (UTC)
No ecological catastrophe could make Earth nearly as uninhabitable as the Moon or Mars are already. Whatever technology might allow people to survive there long-term, you might as well just deploy it here. Put it underground or at the bottom of the ocean if you have to; that's still much, much easier than putting it on Mars. -- BenRG (talk) 03:48, 7 May 2010 (UTC)
Well, there's something to that argument, but I don't completely buy it. A sufficiently large body colliding with the Earth could indeed make it more uninhabitable, for one thing. Granted that impacts that large are pretty rare. But even in the case of a less-badly-wrecked Earth, one thing you could have here that you don't have there are the people who were left out of the ark. They might be tempted to attack it. --Trovatore (talk) 08:25, 7 May 2010 (UTC)
A large impact might make the Earth less inhabitable than the Moon for a short period of time (a few years, maybe) but after that time it would go back to being easier to inhabit. Really, the only thing that might be better about the Moon than the Earth is the absence of a dust cloud blocking out the sun making solar power impossible. As long as you have some other way of generating power, the Earth will probably be easier to inhabit within a couple of days of the impact (once the shockwaves have dissipated, for example), and generating power is easier on the Earth than the Moon (you can use geothermal energy, wind energy, tidal power, etc. on Earth, even after a big impact, but not on the Moon). --Tango (talk) 18:29, 8 May 2010 (UTC)
You won't live long enough to get to the time when the Earth is easier to inhabit. I'm talking about really big impacts, say of the sort that split the Moon off in the first place. --Trovatore (talk) 19:52, 8 May 2010 (UTC)
Well, I wouldn't use the word "uninhabitable" to describe that situation. I would say that just a collision is fatal, not that it makes the Earth uninhabitable. Habitability is a long term thing, not an instantaneous one. There aren't going to be any collisions as big as the one that created the Moon anyway - that object is believed to have been about the size of Mars. There are only 8 objects that big in the Solar System (including the Earth and Sun) and none of them is going to collide with us before the Sun renders the Earth uninhabitable in about a billion years. --Tango (talk) 03:10, 9 May 2010 (UTC)

To understand our local solar system. We have a sample size of 1. This is not enough to know if our solar system is unique, unlikely, or common. So we look for others and try to get more information about solar systems. Ariel. (talk) 20:10, 6 May 2010 (UTC)

Incidentally, the wording of your question is a little hard to understand, but suggests that you may not realise that we have already found out if there are other planets in the universe (beyond the other 7 in our own Solar system); so far we have detected over 450 Extrasolar planets, and the number is climbing as fast as we can improve our instruments and methods. 87.81.230.195 (talk) 21:10, 6 May 2010 (UTC)

Do airlines use ground length measurements for their mile programs, or air length?[edit]

since airplanes travel at an altitude of somewhere near 30,000 feet, wouldn't that add a few miles to the length when compared from measuring from the ground? I know 30,000 feet is insignificant to the radius of the earth, and would only add a couple miles on really long trips, but i like to argue with airline companies. —Preceding unsigned comment added by 76.21.237.247 (talk) 16:05, 6 May 2010 (UTC)

They use "marketing-ese" to measure the mileage. I think they will tell you this in blunt terms, if you try to dispute a mileage number. They have a standard to determine how many "miles" a particular flight is worth to a frequent-flier program. Think of those as "points", not "miles" in the true sense. The pilots have much more accurate measures of the flight distance than the airline reports to you, the lowly customer; see air speed and ground speed. Integrating either air speed or ground speed will give you a different measure of the total trip-length; air-speed does account for the vertical distance, but is much more significantly affected by wind. Nimur (talk) 16:44, 6 May 2010 (UTC)
Back when I flew United constantly and obsessed over miles, I found that their FF mileages were extremely close to those from this great circle calculator. That would correspond to the shortest path, along the ground. But in terms of arguing with them, I agree with Nimur: They disclose how many miles the trip gets you, and that's it. They're more of an abstraction than an actual distance. -- Coneslayer (talk) 16:51, 6 May 2010 (UTC)
From the point of view of the customer, mileage should be calculated as shortest distance between points of departure and arival. The actual path taken, and height travelled, is somewhat irrelevent for your calculations since frequent flier miles are calculated by great-circle distances between airports. And for pilots, the air-mileage is also largely irrelevent. Far more important, for calculation of fuel consumption, is the intergrated air speed, as noted by Nimur. Fuel consumption will be directly related to integrated air speed, which is "virtual air miles travelled", basically the sum of the actual air miles traveled combined with the effect of headwinds or tailwinds. I doubt that anyone has any practical use for calculating the actual miles traveled through the air. It is trivial to calculate it, its just not very useful for either the customer or the airline to know it. --Jayron32 17:04, 6 May 2010 (UTC)
Here's the thing: Suppose you took a piece of string, long enough to stretch tightly all around the equator. If you then wanted to lift it up and put it on top of 10' poles all around the world - how much more string would you need? It sounds at first like it would be a lot - but in fact, it's pi times 10' - so it's just 31.4 feet extra. So for your airplane at 30,000 feet - the total extra distance if it flew all around the world would be pi times 30,000 feet - so 93,000 feet extra. That's a little over 17 miles. But if you're only flying (at most) halfway around - the difference is only around 8 miles - and for most flights the difference between "air distance" and "ground distance" is going to be just one or two miles. It's really completely irrelevent which they choose. When you consider that the plane is probably flying at between 300 and 400 mph - it's covering a mile every second ten seconds! You'd only have to be off-course by a few seconds half a minute to wipe out the error! SteveBaker (talk) 00:04, 7 May 2010 (UTC)
Steve, I think you need to re-check the number of seconds in an hour :-).
By the way, most commercial flights are traveling over 400 mph, and often as much as 600 mph, at cruising speed. --Trovatore (talk) 02:26, 7 May 2010 (UTC)
Oopsie! Thanks...fixed it. SteveBaker (talk) 03:35, 7 May 2010 (UTC)
Also, the height you give is added to the radius of the earth, not the diameter. Therefore, a plane flying at 30,000 ft would add 188,500 ft to an around the equator trip, for a total addition of 36 miles. 36 miles of 25,000 is still pretty much negligible for the purposes of the original inquiry, especially since the longest non-stop flight I know of is from LAX to Sydney, which is under 1/3 of the earth circumference, and would thus add less then 12 miles. Googlemeister (talk) 13:29, 7 May 2010 (UTC)

Snow accumulating in above-freezing temperatures?[edit]

A friend in Bethel, Alaska tells me that they had an accumulation of 5 inches (130 mm) of snow a few days ago, even though the temperature was above freezing. How is this possible? I understand that snow can fall when it's above freezing, but (1) how can it possibly accumulate so much when the air is above freezing, or (2) if enough is falling to accumulate this much snow, how doesn't the large amount of snow cool the air to a temperature below freezing? I should note that my friend is trustworthy; I have no reason to believe that she's making this up. Nyttend (talk) 17:10, 6 May 2010 (UTC)

It could simply be that the latent heat heat that the snow needed in order to melt was in sort supply due to the specific heat capacity of the air being so low (maybe it was dryish air too). The only other place the heat could come from is the ground and maybe that was very chilly as well. In other words the heat gradient was very small. Also, in the absence of wind there could very well be a laminar boundary layer of much colder dense air close to freezing - covering the snow. Just like the open top freezers in supermarkets.--Aspro (talk) 17:52, 6 May 2010 (UTC)
Additionally (expand above) if it had been very cold previously the ground itself could still be sub-zero - but the atmosphere above zero - which would delay melting, and cause the near ground temp to be lower..77.86.68.186 (talk) 19:26, 6 May 2010 (UTC)
Also, it is easy to overlook the amount of heat required to melt five inches of snow. It equals about half an inch of solid ice. To melt that, you need about the same number of calories as you need to bring half an inch of water up to boiling point. Being snow, it also reflects most infra-red heat and the air above it is an insulator. It is going to take time.--Aspro (talk) 19:48, 6 May 2010 (UTC)
The heat content of air is very small, but snow is wetter when it falls in warmer temperatures. It forms bigger flakes. --Chemicalinterest (talk) 20:44, 6 May 2010 (UTC)
Isn't snow stable up to about 4 °C, as long as it is kept out of direct sunlight? —Preceding unsigned comment added by Csmiller (talkcontribs) 21:29, 6 May 2010 (UTC)
If the frozen precipitation is heavy enough, it can accumulate when the surface temperature is well above freezing. Of course, lighter showers will melt at more than a few degrees above freezing. It doesn't surprise me that 5 inches fell, but it would be good to know how much above freezing the temperature was. –Juliancolton | Talk 02:32, 8 May 2010 (UTC)
If I remember rightly (can't access it anymore, since this was several days ago now), Weather.com said that it was in the high 30s °F. Nyttend (talk) 02:50, 8 May 2010 (UTC)
That's definitely possible, then. Snow can fall at temperatures exceeding 40° given the right conditions. –Juliancolton | Talk 03:20, 8 May 2010 (UTC)

metal differentiation[edit]

I am having some difficulties differentiating two metal samples. They have the same dimensions and density, though the metal alloys are quite different, with one sample containing nickel, and the other sample does not. Neither sample is magnetic. I can not damage the samples, so using chemicals that would react to nickel would not be feasible. For the same reason, I can not test the hardness or tensile strength of the alloys. I tried using a multimeter to determine if there is a difference in the resistance, however since both are metal, the multimeter gives only a very low Ω value which is lower then the multimeter can use. Are there any other ideas? Googlemeister (talk) 18:38, 6 May 2010 (UTC)

Have you considered X-ray fluorescence analysis?--Aspro (talk) 19:19, 6 May 2010 (UTC)

also Atomic_emission_spectroscopy#Spark_and_arc_atomic_emission_spectroscopy ? 77.86.68.186 (talk) 19:22, 6 May 2010 (UTC)
Have you got the composition of the two alloys and have to tell A from B, or is the only info you have is that one contains nickel.?
There are surface tests for nickel (specifically usually for jewelry for people are allergic) - this would not substantially damage the sample. ie you just wipe a swap on the surface...77.86.68.186 (talk) 19:20, 6 May 2010 (UTC)
Sadly, I do not have equipment for XRF available to me, though I would love such a device. Also, the surface test mentioned is not a good idea since even minor damage would be unacceptable. How about thermo effects on the material? Perhaps I could determine one sample heats faster then the other under the same circumstance, or one is a better conductor of heat? Googlemeister (talk) 19:31, 6 May 2010 (UTC)
I usually find that if I need a bit of equipment, somebody else has needed it so bad that they have actually purchased it. If they have already purchased it, I can always think of lots of reasons why they should allow me use it. So just because you can't afford one, is not what I consider a legitimate excuse ;-) Aspro (talk) 20:39, 6 May 2010 (UTC)
Sample A is 75% copper and 25% nickel, and sample B is 56% copper, 35% silver and the balance in Manganese. Googlemeister (talk) 19:33, 6 May 2010 (UTC)
You could measure the specific heat of the metals. Heat them both to identical temperatures, drop them into identical, insulated containers filled with the same amount of the same temperature water. Watch for the final temperature of the water. You wouldn't even need to calculate the final specific heat, since you know the identity of the two samples (but not which is which), you would just need to know which had the higher specific heat, and compare to the expected values. The one with the higher specific heat will heat the water to the higher temperature. --Jayron32 19:41, 6 May 2010 (UTC)
I would expect B to be yellow or yellowish in color - if one is more yellow/orange then that is definately B. (or maybe not): At the risk of appearing facetious it sounds like you are trying to tell apart nickel coins.. Nickel_(United_States_coin)#Wartime_nickels - if so - would the date on the coin be a give away? :) 77.86.68.186 (talk) 19:50, 6 May 2010 (UTC)
Technically - measuring compressive tensile strength is non destructive too... the silver allow should be weaker. or not.. really need a table of values for both.77.86.68.186 (talk) 19:46, 6 May 2010 (UTC)
Not if you suspect that they used the incorrect materials when they made the coin. Googlemeister (talk) 19:53, 6 May 2010 (UTC)
Are the coins 'as new'.. if not a photo would help - I claim to be able to spot silver patina at long range.77.86.68.186 (talk) 20:00, 6 May 2010 (UTC)
You said the density of both is the same, yet my simplistic calculation[9][10] shows sample A to have a density of 8.917 g/cm^3 and B is 9.339 g/cm^3. (Does alloying metal change the density, like dissolving salts does?) Ariel. (talk) 20:30, 6 May 2010 (UTC)
Not sure. All I know is that the weight is identical, and the external dimensions are identical. Googlemeister (talk) 20:33, 6 May 2010 (UTC)
If the weight is identical to the level of accuracy of the scales you've got, but isn't accurate enough to distinguish the above method ... you can use a simple balance (diy) - it's easy (use a knife edge as the pivot) - a 10cm arm will easily distinguish weight differences of 1mg. —Preceding unsigned comment added by 77.86.68.186 (talk) 20:51, 6 May 2010 (UTC)
If you've got an ideal material, you can find the Young's modulus non-destructively, but finding the yield strength and failure strength is a destructive process. In practice, most metals behave non-ideally, so even measuring the Young's modulus is a destructive test. (When I worked in a mechanical testing lab, our compressive test specimens would typically be 1/40" shorter after testing). --Carnildo (talk) 01:54, 7 May 2010 (UTC)

Alloys have density as a weighted average of the individual metals composing it. --Chemicalinterest (talk) 20:48, 6 May 2010 (UTC)

According to http://www.ukcoinpics.co.uk/metal.html the two allows also have similar electric resistances. I can't find any physical data for the Mn alloy - presumably because it was a one off.77.86.68.186 (talk)
The US national mint probably has the data - should be obtainable since USA has freedom of information acts. Not sure exactly where you would write to? 77.86.68.186 (talk) 21:36, 6 May 2010 (UTC)
What about microscopy - comparing them against known control samples?77.86.68.186 (talk) 20:52, 6 May 2010 (UTC)
I don't think density is a weighted average (by %composition) of the component densities unless the volumes literally add. But alloys aren't individual blocks of the components, more like a solution where atoms of one can fit in spaces between others in a packing different than either one alone (for example, nonideal Volume of mixing, so the volume of the alloy is not exactly the volume of the two pure metals being mixed). DMacks (talk) 21:59, 6 May 2010 (UTC)
Yes you may be able to discern crystal structure or corrosion products with a microscope. Another test is the speed of sound. This will change the pitch of the clink when you tap the sample, and if they are truly the same dimensions should differentiate. This can reveal the compressibility since you know the density. Graeme Bartlett (talk) 22:11, 6 May 2010 (UTC)
Besides specific heat, you can measure thermal conductivity. That should differ between different alloys. Electrical conductivity might also differ, but you need to be more creative than to just use a multimeter to measure resistance. Rather than just asserting "Neither sample is magnetic" you need to characterize their exact degree of Paramagnetism, Diamagnetism or Ferromagnetism. Copper and silver are diamagnetic, nickel is ferromagnetic, manganese is paramagnetic (no idea how alloys will come out). Such testing goes far beyond trying to pick them up with a magnet. A powerful electromagnetic field and sensitive measurements of effect are needed, but it should be a good test. Getting or making a known standard sample of one of the possible alloys would be very useful if that is possible. Edison (talk) 15:55, 7 May 2010 (UTC)

Cold, flu, etc season/s[edit]

Is there one cold, flu, allergy or etc for the whole world or 2 separate ones for all of them?

Basically, I always wonder about this.--Jessica A Bruno (talk) 22:14, 6 May 2010 (UTC)

I'm not sure I understand what you are asking? They are all 3 different medical conditions, with different causes, though their symptoms can overlap:
  • The common cold is caused by a number of different viruses which usually infect the nose and upper respiratory tract, called rhinoviruses. Rhinovirus meaning "virus that infects your nose".
  • The Flu, or Influenza, is caused by one of the group of influenza viruses, usually Influenza A or Influenza B. There are other medical conditions which get called flu (such as a "stomach flu") which are unrelated. Commonly (but not always) flu symptoms are more intense than cold symptoms (though sometimes a cold can be really bad, confusing the two). The other difference is that the Flu can be vaccinated against via the flu vaccine and there are antiviral drugs, like Tamiflu, which can fight the infection. The types of viruses that cause a cold are too varied for effective vaccination and treatment under current technology.
  • Upper respiratory allergies, sometimes called "Hayfever", properly termed Allergic rhinitis, which is doctor speak for "allergy that causes stuffy nose", is caused by allergens (usually small little bits of dust or pollen) that iritate the nose and trigger a histamine response; such histamine responses usually cause similar symptoms to a cold or flu, however usually absent the fever.
Hope that helps. --Jayron32 21:12, 6 May 2010 (UTC)
The article Vitamin D and influenza suggests that there are two seasons, one for each hemisphere. Pollen allergy obviously oscillate between the two hemispheres. Colds? Pass! A submariner told me that for the first couple of weeks of a new tour, everyone has the sniffles. This can not be due to the lack of vitamin D as the body can store quite a bit and so it wont run out so suddenly. However, they are in a very enclosed space. The carbon/ electrostatic filtration system is obviously of little help in this regard. UV lamp sterilizers might help though.--Aspro (talk) 21:14, 6 May 2010 (UTC)

Thank you and interesting.--Jessica A Bruno (talk) 22:14, 6 May 2010 (UTC)

Night Vision[edit]

Is it possible to read a book in the dark with night vision goggles? —Preceding unsigned comment added by 71.104.119.240 (talk) 21:13, 6 May 2010 (UTC)

I don't know why it wouldn't be possible. --Chemicalinterest (talk) 21:16, 6 May 2010 (UTC)
The output of image intensifiers suffer from scintillation (speckling) , which may make it hard to make out fine details, which is needed for reading. However active IR night vision will probably work, as long as paper is IR reflective, and the ink absorbs IR. CS Miller (talk) 21:27, 6 May 2010 (UTC)
As above. Yes, if it is not active IR it will need some other light source (unless you have a generation 3½ device or something). --Aspro (talk) 21:33, 6 May 2010 (UTC)
IIRC, the first image intensifiers (in passive mode) need moonlight to work, the latest will work with starlight on a cloudless night. I'm not sure if the resolution of these devices is enough to read standard size print.
It goes with out saying that the body-heat night vision systems won't let you read a book. CS Miller (talk) 21:46, 6 May 2010 (UTC)
I've just tried out a class one device (i.e., cheap and cheerful) on a newspaper and I can easily read the news print. The thing I did notice, was that the optics are so poor that only the centre of the image was in sharp focus. This would make reading slow. Whilst it's possible to buy a reasonably good pair of binoculars for under a hundred dollars these days, if you want a good monocular night scope you might need to spend a thousand or so.--Aspro (talk) 21:57, 6 May 2010 (UTC)

Thank you, everyone - special thanks to Aspro for doing the experiment. Where do you go to buy them, anyway? I know they can be ordered online but it would be nice to try before I buy. 71.104.119.240 (talk) 22:45, 6 May 2010 (UTC)

I used a Tchibo nachtsichtgerät (night vision aid) tonight. This is a German company (the Nazis had nachtsichtgerät way back during the second world war) that buys job lots and markets them under its own brand. Good enough, if one wants to protect one's night adapted vision, (which would be washed out by the use of an electric lantern). Unfourtunatly, it does not respond fast enough to be able to follow bats and other critters that move quickly. They just don't show up! If you live in Virginia I don't know where you could try some out ( Norfolk Naval Base perhaps). I'd recommend getting one that has adaptations so that you can stick it on your SLR camera/ video camera. It is really nice to be able to record some of the things you see -just as you would, if they happened in daytime. Google around until you find an emporium that stocks them. If you have a specific use, then Google around for other people that would use them for the same thing. They will know which are the best ones to buy. Note: they are very sensitive to light, so it is not practical to try one out in a retail store. You will wreak it! If your just curious to try one out, buy a cheap one. A big benefit, that I have already mentioned is that you can still see ( it takes two hours for your eyes to become fully night adapted). Where as, using a torch to ensure you don't fall a*** over t** into the nearest ditch, would also alert any critters of you presents. Military scopes are great, but not worth the money IMHO for just exploring the back yard. --Aspro (talk) 00:11, 7 May 2010 (UTC)


Hmmm, if there is moonlight you can read a newspaper at night without any device (I would guess the Moon needs to be more than half full). Even on moonless skies, you can read newspaper headlines if there is significant light pollution, see here

Class 8: City sky. The sky glows whitish gray or orangish, and you can read newspaper headlines without difficulty.

Count Iblis (talk) 23:24, 6 May 2010 (UTC)

I too have read using one of these. There are really two problems - one is that they have a very narrow field of view - the other is that they are generally focussed out to infinity (or at least beyond a few tens of feet) - so it's hard to have things be in focus close-up. SteveBaker (talk) 23:54, 6 May 2010 (UTC)

Longevity of a species[edit]

Perhaps I failed to make my previous question clear so I apologize. Now what I am asking is where can I find a list of species and the amount of time the species existed or the age of the species. In other words if man is a species than how old the species of man is.


For example:

Man 1 million years
Palmetto Bug 350 million years


Thanks in advance. 71.100.0.29 (talk) 21:36, 6 May 2010 (UTC)

For old ones - Category:Living fossils (you'll need to get the dates yourself - and it's not exactly what you asked - but it's a start...) (misc. Anenomes are immortal).77.86.68.186 (talk) 21:44, 6 May 2010 (UTC)
Are you talking about the plants, the animals, the song or the actress? 71.100.0.29 (talk) 22:24, 6 May 2010 (UTC)
The rock pool animal.
For a overview (and earliest possible date for classes of species) Timeline of evolution is a good start.77.86.68.186 (talk) 22:39, 6 May 2010 (UTC)
It does not appear capable of surviving an oil spill. 71.100.0.29 (talk) 22:46, 6 May 2010 (UTC)
link ? 77.86.68.186 (talk) 23:10, 6 May 2010 (UTC)
Only if it could digest bunker c would I call it immortal. 71.100.0.29 (talk) 00:22, 7 May 2010 (UTC)

classification characteristics[edit]

Is there a table of characteristics which define Phylums within Kingdoms, Classes within Phylums, Orders within Classes, Families within orders, Genus within families, and Species within Genus such that one could determine by querying the table what sort of species they had in hand? 71.100.0.29 (talk) 22:21, 6 May 2010 (UTC)

For all species? Do you know how big that would be? 71.104.119.240 (talk) 22:42, 6 May 2010 (UTC)

Computers now-a-days should be able to handle not only the table but the queries. 71.100.0.29 (talk) 22:48, 6 May 2010 (UTC)
The key word is "taxonomic key" or "dichotomous key" or "identification key" - I've not seen one that goes all the way down in one book.
If there are 2 million species that would be about 22 questions in depth to get to a single species.77.86.68.186 (talk) 22:57, 6 May 2010 (UTC)
No problem. In fact it could probably be pre-programmed and made into a child's game here: http://www.20q.net/ 71.100.0.29 (talk) 23:02, 6 May 2010 (UTC)
Try the "Tree of Life Web Project" http://tolweb.org/tree/ - it has many keys for different groups - I don't know if it is complete.77.86.68.186 (talk) 23:04, 6 May 2010 (UTC)
I see the project and the structure, the names and the individuals that have been included... but alas, not the criteria or the characteristics. 71.100.0.29 (talk) 23:21, 6 May 2010 (UTC)
Another incomplete key here http://en.wikibooks.org/wiki/Dichotomous_Key/Start 77.86.68.186 (talk) 23:36, 6 May 2010 (UTC)
That's more like what I had in mind but I fear biological taxonomists will see it as a threat to the realm of biological taxonomy and as an act of biological taxonomic terror. 71.100.0.29 (talk) 00:04, 7 May 2010 (UTC)
I'm surprised that nobody mentioned our very own WikiSpecies over on http://species.wikimedia.org/wiki/Main_Page - it has the taxonomy for about a quarter million species. Of course that's really only a drop in the bucket. SteveBaker (talk) 00:36, 7 May 2010 (UTC)
Unfortunately the wikispecies project has the same problem as the tree of life web project. One must already be an expert to use it. Using characteristics you need not be an expert in the field but instead rely upon the expertise built into the system to which your job is to present measurements or observations. Why are these projects duplicating taxonomic systems only experts can use instead of making the system the expert that everyone can use? What unmitigated and self-serving hypocrisy I observe. 71.100.0.29 (talk) 01:45, 7 May 2010 (UTC)
I think that's a bit over-the-top. Bear in mind that Wikispecies is not a stand-alone project - like Wiktionary and other such projects, it's designed to complement Wikipedia. You can do formal navigation of the taxonomy tree using Wiktionary - and get to articles written in Wikipedia...or vice-versa. If you want to find an article about Giraffe - use Wikipedia - if you want to find where Giraffa camelopardalis rothschildi fits into the taxonomy tree - use Wikispecies. The reason it uses cold scientific latin terms throughout is that there are no language-specifiec Wikispecies branches as there are for Wikipedia. A German reader should be able to use WikiSpecies with little or no trouble. You can't traverse a modern taxonomy with 'characteristics' because there can be similar - or even identical features in unrelated species that happen to have evolved some similar characteristic. The characteristic: "Has simple eyes" would find the branch of the tree with fish and mammals in it - but it would also have to include cephalopods, annelids, crustacea and cubozoa - which all have eyes that evolved in completely separate ways. The most recent common ancestor of (say) humans and squid didn't have eyes at all. So there is no single point in a taxonomic tree where "has eyes" is a distinguishing characteristic. So a modern evolutionary-based tree can't be navigated that way. About the closest you could come to that would be to query genetic sequences - but that would be even tougher than the latin names! SteveBaker (talk) 02:18, 7 May 2010 (UTC)
The points you make support the need to ultimately replace the current taxonomic system with DNA sequence classification for animals and plants. (Show me a plant or animal that does not contain minerals or the non-existence of an animal which can photosynthesize.) Regardless, DNA sequences classification will still require classification of associated characteristics that can be measured, observed and described. To prepare for such a system we need to start now by developing a 30 characteristics based query system to permit identification by measurement, observation and description of what characteristics we have already observe. 71.100.0.29 (talk) 06:48, 7 May 2010 (UTC)
The taxonomic system (you mean 'shared characteristics' or Phenetics) is being replaced by cladistics or phylogenetic classification (as you request)..
Nevertheless it's still possible to create a decision tree system to result in a phylogenetic classification - in recent times species are being re-assessed to place them in the tree according to their evolutionary heritage (derived from DNA mostly) - more info Biological_classification#Modern_systems. 77.86.67.180 (talk) 11:16, 7 May 2010 (UTC)
I think there is a problem with attempting to make a single global decision tree for classification (which might still exist) - in that classification isn't a completely precise science - and that classifications are based on a number of factors per branch rather than a single binary decision (ie the decision tree isn't in itself the classification system..)- maybe that's why the biologists don't seem to have produced such a thing. 77.86.67.180 (talk) 11:53, 7 May 2010 (UTC)
I agree to the extent that:
  1. query order be dynamic and use many-valued independent variables
  2. emphasis be on keys which provide the greatest separatory value
  3. multiple systems, each designed with respective users in mind
    1. Humans
    2. robotic probes
Biologist have had computer technology such as:
Wikibooks has a book on the topic of: Optimal Classification

available to them for only a (relatively) short period of time. 71.100.0.29 (talk) 12:43, 7 May 2010 (UTC)

How many humans a asteroid would be able to have?[edit]

How large an asteroid population would be able to be?

I tried to find this info on net but was not able to. —Preceding unsigned comment added by 187.116.80.68 (talk) 23:10, 6 May 2010 (UTC)

Zero. Except for Ceres, the largest known asteroid, none are large enough for humans to live on. Ceres appears to have enough mass that you won't drift off into space if you try to walk around, but its is leagues away the largest asteroid, so much so that some people have started characterizing it as a "dwarf planet" due to its size. For the "average" asteroid, most are no more than a kilometer or two across, and the simple act of walking on them would generate more than enough escape velocity to send you drifting off into space. --Jayron32 23:16, 6 May 2010 (UTC)
I think it depends on your imagination. Colonization of the asteroids covers this topic nicely. You might have a hard time living on the outside of one - but you could hollow a small one out, fill it full of air and spin it to make artificial gravity. A C-type asteroid would contain maybe 10% water, plus all sorts of useful organic compounds. It could be hollowed out while mining the ice for drinking water, oxygen for breathing and oxygen/hydrogen rocket fuel. You'd just need a heck of a lot of solar panels to make electricity to first melt the ice, then convert to oxygen & hydrogen for fuel and breathing. As you dig, you'd fill the resulting chamber with air and use the rocket fuel to start spinning it up to speed - a slow process, to be sure - but maybe you can have robots do that part for you and you can just move in when it's all ready. The rock and dirt that comes out of the 'dirty snowball' would be what you'd need for growing food in and for processing into silicon (or whatever) to make more solar panels and other things. The organic compounds would also be good for food production. It's doubtful that you could get one full 'g' of gravity by spinning it because it would fall apart - but something much less than that might be enough for comfortable living conditions. If you picked your target asteroid well, you might find several in similar orbits - the low gravity would make finding and mining other asteroids for metals and other useful substances attractive. When your population gets too big - you can just move to another one. I think asteroids make pretty good homes for technologically advanced humans. SteveBaker (talk) 23:43, 6 May 2010 (UTC)
Oh - yes...and actually answer the question! It's hard to estimate how many people you could house this way - it depends too much on the actual resource availability and the size of rock you pick. But hollowing out the asteroid into swiss-cheese-like holes with tunnels between them, the surface area of the interior (being three-dimensional) could be much larger than the surface area. But the sustainability issue becomes a problem with having to grow food using predominantly artificial light generated from solar power (or maybe nuclear power if you can find the right materials locally). The acreage of solar panels would have to be many times greater than the acreage of crops planted (because you're essentially condensing large areas of sunlight to account for the fact that the asteroid belt is so far from the sun. So the actual farmable space might be ten times less than the outside surface because of that. Asteroids come in all shapes and sizes - so it's tough to know which size you'd choose. I'd guess a thousand people on a reasonably sized (say 20 mile across) asteroid. SteveBaker (talk) 23:50, 6 May 2010 (UTC)
As for the solar panels, under the feeble gravity of an asteroid, they could be extended great distances into space, couldn't they ? If the asteroid is spinning, that might present more of a problem, but perhaps light energy could be beamed down to receiver stations on the asteroid, by solar panel satellites orbiting it. StuRat (talk) 21:50, 7 May 2010 (UTC)
If you imagine something like The Little Prince then it's fiction and doesn't work for a number of reasons. For one thing, there wouldn't be enough gravity to hold on to an atmosphere so you would need to keep air in a closed space like a spacesuit, a building or a hole inside the asteroid. If humans ever get on to an asteroid then it may be a very expensive science, mining or diversion operation relying on supplies from Earth, and not a permanent settlement. The number of people would likely be determined by the task and how many supplies you want to spend resources bringing in, and not on what the asteroid could theoretically support. PrimeHunter (talk) 00:19, 7 May 2010 (UTC)
The prime examples of fictional hollowed-out asteroids would be Fred Pohl's Gateway and Star Trek: The Original Series's "For the World Is Hollow and I Have Touched the Sky". Clarityfiend (talk) 00:45, 7 May 2010 (UTC)
Or for a total nut-job take on the idea, it's hard to beat Hollow Earth! SteveBaker (talk) 02:02, 7 May 2010 (UTC)

dinosaur o2 requirements versus mammals and others[edit]

In a previous question no one seemed to think that the extinction of the dinosaurs 65 million years ago was due to asphyxiation by carbon dioxide even owing to the deaths of animals and humans known to have died after collapsing within seconds of entering a ravine or other enclosure or depression where co2 has accumulated. Since the avail dinosaurs (birds) survived, however, I was wondering whether or not extinction of 65 million years ago may have been due not to a low-to-ground atmosphere of pure co2 but simply the absence of sufficient mixture of oxygen which the grounded dinosaurs could not overcome. Of course this idea might also account for the fact that some dinosaurs occupied mountainous areas high enough to escape the co2 but too high to provide enough o2. In other words a layer between the area too high in co2 and too low in o2 for a dinosaur to survive. Could then the lack of sufficient oxygen be the cause of mass dinosaur extinction whereas what was available was enough for avail dinosaurs, insects, mammals and the rest? 71.100.0.29 (talk) 23:56, 6 May 2010 (UTC)

I'm sure toxic gases played a role after the impact, but large levels of O2 would have been required for the growth of the dinosaurs. In fact, high levels of diatomic oxygen gas are required for all of the fabulous processes of mammals, and while early mammals may have needed far less than we do now their requirements surely could be on par with current rodents. ~ Amory (utc) 03:33, 7 May 2010 (UTC)
I think the extinction was more likely due to the impact sending huge amounts of water vapor and particulates into the air, causing worldwide nuclear winter: those creatures that could adapt to the cold temperatures survived, whereas dinosaurs, being essentially huge two-legged cold-blooded lizards, could not adapt (lizards need outside heat for their bodies to function, and dinosaurs need a lot of heat because of their size), so they died out. FWiW 67.170.215.166 (talk) 05:29, 8 May 2010 (UTC)
Actually the reverse is true. The amount of energy required to support a large animal's BMR is less: e=m^(3/4). 71.100.0.29 (talk) 20:21, 8 May 2010 (UTC)