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Contents

March 1[edit]

How much hydrogen do I need to float a 200,000 ton blimp?[edit]

Or can it even be done?

The question is based on the slightly dubious story of Skydon, but here, let's assume the blimp is made of stretchy and untearable hypothetical material. Basically the same shape, though, longer than tall or wide. InedibleHulk (talk) 23:26, February 28, 2015 (UTC)

Hydrogen can lift about 1.2 kg/m3. So for a total mass is 200,000 metric tons, you need about 167000000 m3. That is a cube with a side length of 550m - large, but maybe not impossibly so. Or make it a cylinder 1500m long, with a 350m diameter. --Stephan Schulz (talk) 00:39, 1 March 2015 (UTC)
When you consider that the LZ 130 Graf Zeppelin II used 200,000 m3 of hydrogen, 167,000,000 m3 does start to look like rather a lot.
835 of the largest airships the world has ever seen is HUGE by any measure! SteveBaker (talk) 01:35, 1 March 2015 (UTC)
It's not even an order of magnitude orders of magnitude! --Stephan Schulz (talk) 08:47, 1 March 2015 (UTC)
It's also reasonable to think of it in terms of linear dimensions. If you need 835 times as much gas, you need it to be cube-root-of-835, which is about 9.4, times the length, width, and height. Of course, this is not exact because you also have to consider how the structural elements scale with increasing size. However, the cost of the gas will be proportional to the volume! --70.49.169.244 (talk) 05:01, 2 March 2015 (UTC)
Thanks. That's a lot of gas. InedibleHulk (talk) 06:49, March 1, 2015 (UTC)
The Hindenburg was slightly larger than either of the Graf Zeppelin airships, but be that as it may, the load on this ships was typically rather small - up to maybe 120 people along with the weights of the gondolas, cargo, engines, and frame. Not a very efficient mode of transportation, but supposedly extremely smooth, aside from the occasional explosion. ←Baseball Bugs What's up, Doc? carrots→ 19:19, 1 March 2015 (UTC)
The original poster specified a blimp, not a dirigible. No rigid frame required. --70.49.169.244 (talk) 05:01, 2 March 2015 (UTC)
I'd actually forgotten they were different things. But no, I don't want a dirigible. I don't really want a blimp, either. No metal at all. Too sparky. No jet fuel or gasoline or any of that craziness. Basically just a very dense balloon, maybe with a chair. InedibleHulk (talk) 12:15, March 2, 2015 (UTC)
I think this would be just right for you. ―Mandruss  12:18, 2 March 2015 (UTC)
Helium...bah! But yeah, he's alright. InedibleHulk (talk) 12:29, March 2, 2015 (UTC)
Actually, a blimp (such as the Goodyear blimp) and a Zeppelin are both "dirigibles", as that word means "steerable",[1] or "directible" if there is such a word (as opposed to a hot air balloon, which is at the mercy of the wind). The Zeppelins were called rigid airships because they had an underlying metal framework, which I think was usually made from aluminum, which is light and doesn't particularly conduct electricity. Of course, it added weight to the structure. What we call blimps are mostly just balloons, but they also have some rigid elements to maintain their shape. For the idea in question, I think the balloon would have to be spherical. I don't see how you could maintain a cigar shape without some underlying structures. And by the way, it was the skin of the Hindenburg which helped feed the flames, as it was coated in a flammable material. So be careful what you make it out of. ←Baseball Bugs What's up, Doc? carrots→ 15:35, 2 March 2015 (UTC)
Football-shaped is good enough. They seem to make those without metal, somehow. Round up the synthetic pigs! InedibleHulk (talk) 13:21, March 3, 2015 (UTC)
  • It's true that "dirigible" is derived from a word meaning "steerable", but despite what Wikipedia claims, the word is now normally used for rigid-framed airships. See also etymological fallacy. --70.49.169.244 (talk) 23:23, 2 March 2015 (UTC)
Aluminium is actually a very good conductor of electricity, which is one of the reasons we make high-voltage power lines from it. Copper has better conductivity, but is much heavier. Tin, which we use for soldering contacts, has nearly three times higher resistance than aluminium. --Stephan Schulz (talk) 17:45, 2 March 2015 (UTC)
Well, in that case it's double jeopardy. ←Baseball Bugs What's up, Doc? carrots→ 17:59, 2 March 2015 (UTC)
Maybe I'm confused now. Typically, you want good electrical conductivity, so that charge inequalities can easily equalise without creating sparks. And in Zeppelins, the lifting gas was carries in separate gas cells inside the main structure, so that a surrounding cage of conductive material would work as a Faraday cage, further reducing the risk of sparks. --Stephan Schulz (talk) 18:15, 2 March 2015 (UTC)
For my task, I wouldn't need electricity. No steering, no motors, no soothing airship music. Just want it to float safely away from civilization. InedibleHulk (talk) 13:24, March 3, 2015 (UTC)

The kinetic theory of gases, degrees of freedom, and distribution of kinetic energy[edit]

Back when I was in school, I had a chemistry textbook that had an explanation of the kinetic theory of gases. In one of part of the analysis, it stated, but without explaining, that (statistically) kinetic energy is distributed equally among the 3 degrees of freedom of a gas molecule. I've always wondered why. Can someone help? Thanks. --173.49.77.202 (talk) 00:09, 1 March 2015 (UTC)

Read Equipartition theorem for more information 79.237.93.71 (talk) 01:13, 1 March 2015 (UTC)
I know of the theorem. What I'm looking for is a simple, intuitive, explanation of the why. Is there a simple explanation? --173.49.77.202 (talk) 01:32, 1 March 2015 (UTC)
I'm not sure what you want to be explained. The three degrees of freedom refer to the three spatial dimensions, and the fact that a molecule's motion can be described entirely as a combination of those three dimensions. Plasmic Physics (talk) 04:30, 1 March 2015 (UTC)
Cartesian coordinates are more difficult to imagine as orthogonal directions are not favored over others. Think of a radius with 360 rotation and 360 degree incidence and a sphere is a more satisfying shape for the the 3 degrees of freedom. --DHeyward (talk) 05:20, 1 March 2015 (UTC)
The 3 degrees of freedom referred to in the textbook are not the spatial dimensions, but the different forms of kinetic energy carried by gas molecules can take. Translational and rotational k.e. form the first two of them. The third one I can't remember, but it could be vibrational k.e. In the book, it was stated but not explained that kinetic energy is distributed equally among the three forms. It's not obvious to me as to why, and that what I'm trying to understand. --173.49.77.202 (talk) 06:22, 1 March 2015 (UTC)
Vibrational is the third. --Jayron32 20:14, 1 March 2015 (UTC)
Think of this definitionally, rather than intuitively. A "degree of freedom" is defined as a mode in which energy can go. If energy could not get into that mode, it wouldn't be a "free" parameter: it would be a constraint.
Whether your degrees of freedom are the x,y,z positions of the centroids of each free-to-move mass; or if they are generalized as "translational" and "vibrational" is purely a choice of your coordinate system. You can use algebraic geometry to turn one scheme into the other. See generalized coordinates for an overview.
Nimur (talk) 17:38, 1 March 2015 (UTC)

The simplest way is to count all the degrees of freedom in two ways. Given some molecule, you are free to consider it as a system of point particles. So, if you have n atoms in a molecule, you can also consider it as just n atoms which therefore only as 3 n translational degrees of freedom, each of which will on average contain the same amount of energy. But you can also consider it as a molecule that has just 3 translational degrees of freedom, 3 rotational degrees of freedom and 3n - 6 vibrational degrees of freedom. For linear molecules there are only 2 rotational degrees of freedom, because the rotation parallel to the symmetry axis corresponds to a spin of atoms which we didn't count in the composition of the degrees of freedom in terms of the atoms (so, the book keeping of the degrees of freedom will then yield 3n-5 vibrational degrees of freedom).

Then, one takes into account that a molecule will have a binding energy realtive to all the atoms being free, the potential energy describing this can be approximated by a harmonic potential (a quadratic form, just like in case of a spring). Each vibrational mode then not only has the kinetic energy that you also have in case of a free system of unbounded atoms, but you also have the consider the ptential energy realtive to the ground state of the molecule. The two contributions are the same (in the harmonic approximation) assuming validity of classical mechanics. This means that the 3 n - 6 (or 3 n -5) vibrational modes will contain double the energy on average compared to the other modes (there is no contradiction with the energy according to the picture where the atoms are free, because now you have put the atoms in a potential well and are calculating the energy relative to the bottom of that well using a harmonic approximation and this approximation will have to break down if the atoms are far enough removed from each other). Then, quantum effects will modify this picture, at low temperatures the degrees of freedom are frozen. According to quantum mechanics the energy in each mode is quantized and if the energy of the first excited state is of the order of k T or more, then the mode will be frozen in the ground state. At room temperatures, the vibrational modes are frozen, at liquid nitrogen temperatures the rotational modes start to get frozen. Count Iblis (talk) 14:41, 2 March 2015 (UTC)

Polar vortex[edit]

How come the west coast is unaffected by the polar vortex? — Preceding unsigned comment added by 199.7.159.20 (talk) 01:56, 1 March 2015 (UTC)

Strictly, the whole earth is affected by the polar vortex in each hemisphere. You're probably referring to recent usage of the term "polar vortex" to represent what is more properly called a cold-air outbreak. The short answer is that the Rocky Mountains block the propagation of cold air toward the U.S. and Canadian west coast. Short Brigade Harvester Boris (talk) 02:06, 1 March 2015 (UTC)
You may want to specify the West coast of where you're talking about..... 82.21.7.184 (talk) 02:22, 1 March 2015 (UTC)
The OP geolocates to British Columbia. ←Baseball Bugs What's up, Doc? carrots→ 02:37, 1 March 2015 (UTC)

The west coast of North America. — Preceding unsigned comment added by 199.7.159.20 (talk) 03:42, 1 March 2015 (UTC)

The West Coast of North America is also warmed by the Pacific Ocean. Extremely cold temperatures are more common in the center of continents than on the coasts. StuRat (talk) 08:19, 1 March 2015 (UTC)
Basically, yup. We here in Vancouver don't know what "real" Canadian weather is like. This whole winter was T-shirt and light jacket weather for me. It's all due to oceans and mountains. As for the rest of BC, some of it is affected, at least a bit. It's a very big province. Mingmingla (talk) 18:32, 1 March 2015 (UTC)

The east coast was hit by the vortex though wasn't it? — Preceding unsigned comment added by 199.7.159.16 (talk) 20:24, 1 March 2015 (UTC)

Please again be careful with the terminology here. The polar vortex exists all the time, regardless of the time of year. What happens is that, during some periods of some winters, at some specific locations in the Northern Hemisphere, the vortex loses its regular shape, spinning off huge chunks of cold air into lower latitudes. The news media has latched on to these outbursts as "polar vortex", which is wrong, the vortex still always exists even when it isn't unusually cold in the eastern third of North America. These outbursts are properly called Rossby waves, which are undulations of the path of the jet stream. Rossby waves also always exist, but tend to become more pronounced in the winter over eastern North America because of the local geography. The relatively unbroken, flat land along the Canadian Shield, Great Plains, and Midwestern U.S. allow these outbursts. They tend not to happen in the west because the Rocky Mountains and the mediating effects of oceanic climate prevent it. A related concept is the Alberta clipper, which is what happens when these outbursts of cold air interact with a simultaneously timed influx of moisture from the Gulf of Mexico. All of these interactions are highly dependent on where you are located on the landmass, and do not just occur randomly, but occur because of the specific interactions of land, oceans, and air. --Jayron32 20:36, 1 March 2015 (UTC)

Accelerations of the electrons[edit]

Could be the accelerations of an electron(s) changed (changes) the gravity of the electron(s)?--83.237.201.100 (talk) 03:29, 1 March 2015 (UTC)

If you asking whether F = ma applies to electrons, then yes; gravity, if acting as a net a force, will cause a electron upon which it is acting, to accelerate in the direction of the centre of mass. Plasmic Physics (talk) 04:24, 1 March 2015 (UTC)
What if it is accelerated to a relativistic speed - the inertial mass increases, but what about the gravitational mass? Bubba73 You talkin' to me? 04:26, 1 March 2015 (UTC)
Gravity is a combination of rest mass plus kinetic energy. That's any object with a rest mass, not just electrons. Incidentally, this feature is how frames of reference can differ. --DHeyward (talk) 05:25, 1 March 2015 (UTC)
If so, why did the physico-mathematical value of units of accelerations is always been identical to the physico-mathematical value of units of gravity, I think they always had one and the same potential of energy, thus this they are always been directly proportional to each other, is it I’m right?--83.237.201.171 (talk) 05:30, 1 March 2015 (UTC)
I'm not sure what your question is. Absent an external frame of reference, gravity and acceleration are indistinguishable forces. Applying a force over a distance exerts energy. That turns into velocity or heat. If the energy is not lost as heat, it's converted into relativistic mass in the form of velocity. As velocity increases to near light speed, the mass increases to the point where the relativistic mass dominates the conversion to velocity. The object will grow to infinite mass before it reaches the speed of light. --DHeyward (talk) 05:58, 1 March 2015 (UTC)
Did the mass of electron(s) is always been a constant in nature, if a mass in nature had lesness inertia?--83.237.208.252 (talk) 06:51, 1 March 2015 (UTC)

Note: The section electromagnetism of physics usually told that the mass and speed (accelerations) of an electron(s) is always been a constant, so that Volt’s are always been proportional to Ampere Force.--85.141.236.202 (talk) 07:37, 1 March 2015 (UTC)

I’m thinking that in nature a mass is not been empty, it is had lesness inertia!--83.237.210.18 (talk) 06:38, 2 March 2015 (UTC)
I believe that accelerations and gravity are always been one and the same form of mechanical energy, so according to the Law of conservation of energy in nature, could the accelerations to done the work of gravity, and so gravity to done the work of accelerations?--83.237.201.12 (talk) 17:13, 1 March 2015 (UTC)
I’m thinking that the speed of the electric current could be absolute, since as in nature the speed of the electric current is been such that, if the gravity of the physical environments (molecular substances) in which been distribution (conducting) the electric current been reached the absolute values (the value of maximum).--83.237.207.37 (talk) 18:40, 1 March 2015 (UTC)
The force of attraction due to gravity between an electron and another subatomic particle is a calculable, but not meaningful, number. As far as the mass of an electron due to its acceleration, yes, electrons do gain a small bit of mass when they are accelerated (due to increases in kinetic energy), but they also lose energy (and thus mass) because of the Larmor principle which notes that accelerating electric charges shed energy, in the form of photons (usually radio-frequency photons). This is all inconsequential however. As I tried to start saying above, you can make any of these mass (and force, and energy) calculations regarding gravity and electrons, and get a number you can write down. That number will be so tiny that it in no way affects the behavior of anything. Congrats, you just wasted time making a calculation that tells you nothing about the universe. But you're free to make it. --Jayron32 20:13, 1 March 2015 (UTC)
1) Did the laws of relativistic mechanics is been applicable to magnetic and electromagnetic mechanics?--85.141.233.119 (talk) 03:28, 2 March 2015 (UTC)
2) In addition without absurdities. Could in physics, the work is always been done identically to the laws of mechanics, that is, did in the nature the energy is always been existed only in the form of mechanical energy?--85.141.233.119 (talk) 03:28, 2 March 2015 (UTC)
1. the laws of relativity are actually derivable from Maxwell's equations. so the answer is yes.
2. Potential energy is also important. Mass energy can happen when energy is converted to mass. Graeme Bartlett (talk) 07:26, 2 March 2015 (UTC)
1) Did it meaning that magnetism and electromagnetism propagate (conducting) with the speed of light, which been means that the speed of the electric current in these environments may had be as minimum the value of the speed of light, and as maximum what value been?--83.237.209.71 (talk) 08:34, 2 March 2015 (UTC)
2) Potential energy is always been a particular case of the kinetic energy in which the value of the masses is always been empty, is I’m right?--83.237.209.71 (talk) 08:34, 2 March 2015 (UTC)

Note: I’m thinking, that particular cases of the Law of conservation of energy did not had existed in nature, so that all cases of the Law of conservation of energy are always been subject's to rational mechanics, that is, the Law of conservation of energy always had’s an ideal mechanical expressions, so the Law of conservation of energy is always been constantly universal.--83.237.196.60 (talk) 11:07, 2 March 2015 (UTC)

1) Read speed of electricity. The start of electricity flow will happen on the surface of a conductor on a vacuum at the speed of light. It will not be faster than the speed of light. However phase velocity can appear to be faster than the speed of light, though energy will not move at that speed.
2) No, potential energy is distinct from kinetic energy. If you look at the limit as the mass of your particle is reduced, speed will have to increase to carry the same energy. You will have to consider special relativity as you approach the speed of light. At the speed of light you will need a massless particle. The energy in light will not be called potential energy. Did you read conservation of energy? Graeme Bartlett (talk) 21:40, 2 March 2015 (UTC)
Thank you a lot of much for your answer. I believe that any energy in nature is always been preserved (conserved) only in the form of kinetic potential, that is, the energy is always been preserved (conserved) in nature only in the form of already completed (done) work.--85.141.236.1 (talk) 09:03, 3 March 2015 (UTC)
In any cases, the energy is always been preserved (conserved) in nature, not through the law of conservation of mass, because the masses in the kinetic potential of energy are always been empty (the empty multiplier).--83.237.204.105 (talk) 10:01, 3 March 2015 (UTC)
So, based on the above said’s, what is been the gravity of elementary particles, which described as kinetic potential of energy?--83.237.204.105 (talk) 10:16, 3 March 2015 (UTC)
Based on your statement above I will not answer the question, due to its inclusion of a term that you made up that suggests incompatibility with mainstream physics. Read Satisfiability and Gravity. Graeme Bartlett (talk) 11:00, 3 March 2015 (UTC)
Much thanks! May be, If the nature of the electric current in nature is been constant and physics been proved that the electron mass in nature is been a constant in all environments, however, the electron mass could not done the work, and if we exclude the magnetism (electromagnetism) from the nature, so it turns out that the gravity of the electric current is always been made the work of light, that is, the gravity of the electric current is always been the energy of light (the speed of light), which is been constant in nature, because it is always been a work (speed) of the electric current.--85.141.236.12 (talk) 11:57, 3 March 2015 (UTC)
What be happened, if we exclude the magnetism (electromagnetism) from the nature and would represent that the speed (work) of the electric current in nature always had an absolute physical-mathematical value?--85.140.140.139 (talk) 12:49, 3 March 2015 (UTC)

Note: There is no been never relativistic mass, but there is been only a work (speed) of the electric current!--85.140.129.92 (talk) 14:23, 3 March 2015 (UTC)

For the correctly solution of the problem in the calculations we always need the mechanics which was been before the invention of relativistic mechanics, in which the moving body form short periods of time is always been passed the same distance of path, regardless of the accelerations of the movements of this body.--85.140.137.119 (talk) 16:26, 3 March 2015 (UTC)
In my mind understanding, the gravity is always been a work of the kinetic potential of energy!--83.237.220.253 (talk) 20:47, 3 March 2015 (UTC)
You can work out the speed of light from Maxwell's equations. An important part of this is magnetism. In Classical electromagnetism and special relativity you can read how electric and magnetic fields transform between reference frames. There you will see you cannot just have an electric field without magnetic field in some other frames. To see what happens with electric current in gravity read Four-current and then Maxwell's equations in curved spacetime. Graeme Bartlett (talk) 21:03, 3 March 2015 (UTC)
Why did the magnetism (electromagnetism) always allowing to extending (moving) an electric current with absolute speed, and the light which was always had in self an electric current, always did not had an absolute speed, so solar panels (battery) did not generate a powerful electric current (much Force of Ampere)?--83.237.217.204 (talk) 08:08, 4 March 2015 (UTC)
The speed of light depends on the response of the vacuum to an electric field and a magnetic field. The changing of one causes the other in the electromagnetic equations. You can think of an oscillating electric current as the source of electromagnetic radiation. This happens in a radio transmitter antenna. Graeme Bartlett (talk) 11:15, 4 March 2015 (UTC)
Why did the light as approved, had’s an absolute speed which never been reached the speed (work) of the electric current, it turns out that the work performing by the speed of light could never been perfect (ideal), because the speed (work) of light could never been identical to speed (work) of the electric current, thus, quantum physics is not been physics of the ideal model, because quantum physics been complied with the Law of conservation of energy in expressions of the particular case of the mechanics.--83.237.203.97 (talk) 10:35, 4 March 2015 (UTC)
Quantum electrodynamics is what you should read. But your comments on magnetics suggest that you are not taking in Four-current. Graeme Bartlett (talk) 11:15, 4 March 2015 (UTC)
1) Thank you Graeme Bartlett! If the nature of the electric current is always been constant as magnetic and as also electromagnetic, so that what did the nature always had a light, the magnetic or electromagnetic, if the movement of the electric current is always been possible as in magnetic environments, and as also in electromagnetic environments?--83.237.192.21 (talk) 11:42, 4 March 2015 (UTC)
2) The movement of the electric current is identical (equal) in magnetic environments and electromagnetic environments?--83.237.217.69 (talk) 12:19, 4 March 2015 (UTC)
Note: Agreed, that the distinction between magnetism and electromagnetism is always been consisted only in the fact that the electromagnetism always had’s the most expression properties, than magnetism.--85.140.141.148 (talk) 16:13, 4 March 2015 (UTC)

Board of multi national corporations[edit]

How much direct control do the boards of multinational corporations have over its day to day activities (both at high level and lower levels) and long term strategies? — Preceding unsigned comment added by 194.66.246.7 (talk) 19:18, 1 March 2015 (UTC)

Wikipedia has an article titled Board of directors. You're allowed to read it and reach your own conclusions. --Jayron32 20:07, 1 March 2015 (UTC)
They could have as much control as they wanted. However, decisions made by committee are often slow and inconsistent, and most board members have better things to do with their time than micromanage the company, so are glad to delegate responsibilities, unless there is an obvious problem with the CEO or other executives which needs to be addressed. StuRat (talk) 09:12, 2 March 2015 (UTC)

March 2[edit]

Why are my coffee mugs too hot?[edit]

I often reheat plunger coffee that's gone cold by putting it in a mug in the microwave. I long ago worked out that 3 minutes on High works best. By that time the coffee is the right temperature for drinking, and the mug is comfortably warm. This system has worked dandily for at least 8 years. But over the past few weeks, the mug has been coming out way too hot, and I need a protective cloth to hold it. And the coffee is boiling, which is not what I want. I want hot, not boiling. I have an eclectic selection of mugs, some as old as the microwave (about 12 years), others acquired more recently. But it doesn't seem to matter which vintage or variety of mug I use, it always comes out too hot now, when it never did before. I haven't changed the microwave, the settings or the time. I could just reduce the time, but I want to understand what's suddenly changed. Is this overheating perhaps a symptom of impending microwaval menopause, or even failure/death? Has it become unsafe? Or would I need a technician to pull it apart to be sure? -- Jack of Oz [pleasantries] 08:47, 2 March 2015 (UTC)

I'd agree that it was the microwave oven, except that, in my experience, old microwaves become less efficient, so you would get cooler coffee. Could it be that the voltage delivered to your house from the mains has gone up ? I'm not positive that this would make the microwave run hotter, but it certainly does make incandescent light bulbs burn hotter and brighter. My aunt had this problem. I noticed that her incandescent bulbs burnt out very quickly and in some cases scorched the fixtures, so I put a monitor device on an outlet and found her voltage was indeed running way above spec. If you have any incandescent bulbs left in your house, do they seem brighter ? StuRat (talk) 08:59, 2 March 2015 (UTC)
We replaced them all last year, Stu. If it's relevant, we live in an area where blackouts are a way of life. Mostly they last only a few seconds, but sometimes they're many hours long. Also, our broadband connection goes down too often for my liking, often preceding rainy or stormy weather. Our TV reception is mainly good, but occasionally not. But we've never had any particular problems with our general electricity supply and I'm not aware of any fluctuations in power. -- Jack of Oz [pleasantries] 09:13, 2 March 2015 (UTC)
If you can dig up an old incandescent light, that might be worth a test. Of course, the power company won't accept that as proof that voltage is too high. For that you will need a device like this: [2]. That one is for the US market, though, and you will want one for Australian outlets. Your local home improvement store might have one.
Note that excess voltage could indeed be dangerous, potentially causing a fire. Basically, every wire carrying an excess voltage will be a bit hotter than normal, and, depending on your initial margin of safety, that just might make something hot enough to catch fire.
More likely, some of your smart appliances may refuse to turn on with a voltage out of spec, while others might shut down after a few minutes, due to an over-temperature reading (some will turn back on as soon as they cool down, while others require hitting a reset button).
Those numerous short power outages you mentioned also fit the pattern of poor maintenance, which could lead to an over-voltage situation. The system is doing some type of automatic switching to get your power back after each, but it may not verify the voltage range, as a human repairman hopefully would. StuRat (talk) 09:23, 2 March 2015 (UTC)
I'd recommend getting a plug-in voltage/power meter, such as the Kill-A-Watt (other manufacturers' devices are available, such as the Floureon TA-836A), and check what the voltage of your mains power supply is. If you are in the United States, then the voltage should be 120V, and the frequency 60Hz. I'm not sure what the tolerance is, but it's probably within 5%. LongHairedFop (talk) 16:24, 2 March 2015 (UTC)
This all makes a great deal of sense, and I'm very glad I asked. Thanks, Stu. I'll be calling someone tomorrow. -- Jack of Oz [pleasantries] 10:05, 2 March 2015 (UTC)
If you mean you will call the power company, they certainly wouldn't do anything here unless I had better evidence than "my coffee is too hot". If you mean an electrician, then they could indeed measure your voltage, probably using the same type of devices we mentioned. However, they are likely to charge far more than the $20 for the device. (If you're worried that you need to be an electrician to use such a device, don't be, just plug it in and read the numbers.) StuRat (talk) 16:56, 2 March 2015 (UTC)
I remember that some older models used mechanical timers to turn off after the chosen time. If you're relying on one of these, is it still accurate? Bazza (talk) 11:18, 2 March 2015 (UTC)
Are you placing the mug in a different place inside the oven? (See recent what if). If the oven has a rotating plate, is it rotating normally - gunk in the works or something? 88.112.50.121 (talk) 13:17, 2 March 2015 (UTC)
Oh dear, MICROWAVING coffee? This is a cardinal sin against this noble beverage. I'm afraid a trouting is in order. Sir William Matthew Flinders Petrie | Say Shalom! 11 Adar 5775 17:10, 2 March 2015 (UTC)
Seconded. And remember to microwave the trout first. - ¡Ouch! (hurt me / more pain) 13:16, 4 March 2015 (UTC)
I don't think there's any way we can rule out some degeneration in the electronics regulating the power consumed by an unknown microwave that could lead to an increase in the microwave output. On the other hand, could more ions in your coffee make it more conductive? (like if some salt gets in from a new water softener or something?) Sure it might have to do with house voltage but I'm really skeptical. I don't think you'll get a trustworthy answer here. Wnt (talk) 19:15, 2 March 2015 (UTC)
  • I tend to microwave X in one container, then decant it into another room-temperature container. Does that solve the problem? μηδείς (talk) 22:59, 2 March 2015 (UTC)
Not really. It doesn't address why the mug historically never got too hot while now it always does, under exactly the same conditions. -- Jack of Oz [pleasantries] 21:32, 3 March 2015 (UTC)
If the machine has a clockwork timer like my ancient microwave, then possibly it is sticking, as Bazza suggested above, but perhaps you've checked that it still takes no longer than three minutes when set to three? Dbfirs 21:49, 3 March 2015 (UTC)
I have to agree with Wnt and others that it seems a bit hard to believe this is mostly due to overvoltage, primarily because I think there's a good chance you would have noticed other problems if it's sufficient to cause a big difference to the microwave heating. For starters, most fans will go fast. You're in Australia and it's summer (okay technically may be autumn under some definitions now), do you have no fans that you would have likely noticed if going faster? Also since you're in Australia so the voltage is probably nominally 230V, and if you're noticing a significant difference the mains voltage is likely a fair amount higher than the upper limit of 264V. I think many devices with power supplies, possibly including any compact fluourescent lights, are going to start having noticable problems. (In the US, it's probably a lot more resonable you won't notice, because many devices nowadays are 100-240V, so even if the voltage is significantly above tolerances, for anything not using the 240V double live outlets, it'll have to be very high before devices should have problems, theoretically at least.) Nil Einne (talk) 11:40, 4 March 2015 (UTC)

Is it safety to enter a dog or cat into the emergency room or hospital?[edit]

I'm looking for scientific articles about. Thanks 149.78.32.22 (talk) 14:04, 2 March 2015 (UTC)

Well, dogs are sometimes brought into hospitals to make elderly and other patients happy. I doubt if they would be allowed into emergency rooms though. http://www.petsastherapy.org/

217.158.236.14 (talk) 14:16, 2 March 2015 (UTC)

  • There's also the question of the difference between the emergency room entrance and lobby and the actual treatment area. Presumably a blind person with a broken hand who walked in would be allowed access to the lobby and the staff would follow protocol on how to deal with the dog (contact a guardian/emergency contact, presumably) and put the patient in a wheelchair so she didn't need the dog to go with her in the treatment area. I would suggest calling a hospital main directory, and asking. μηδείς (talk) 17:18, 2 March 2015 (UTC)
Yes, in certain circumstances - see: APIC State-of-the-art Report: The implications of service animals in health care settings and Animal-assisted activity and infection control implications in a healthcare setting. This policy has been developed using those two papers. Richerman (talk) 17:54, 2 March 2015 (UTC)

Total eclipse and light levels[edit]

Does a solar eclipse make the sky noticeably darker? — Preceding unsigned comment added by 194.66.246.88 (talk) 14:20, 2 March 2015 (UTC)

It certainly does! http://www.eclipse2017.org/2017/what_you_see.htm 217.158.236.14 (talk) 14:22, 2 March 2015 (UTC)
The more the sun's disk is covered by the moon, the darker things get. It's not like cloud cover. It's like the sun is on a dimmer-switch. ←Baseball Bugs What's up, Doc? carrots→ 15:25, 2 March 2015 (UTC)

Exact date of previous total eclipse visible from the North Pole on the first day the Sun appeared above the Horizon after the end of the Polar Winter[edit]

Exactly such an eclipse will happen on March 20 this year. What was the previous date this has happened? Count Iblis (talk) 15:36, 2 March 2015 (UTC)

An interesting question that I cannot answer. Looking at Fred Espenak's eclipse pages on the NASA web site, under this page there is an atlas of total and annular solar eclipse tracks covering the 5,000 years from −1999 (i.e. 2000 BC) to 3000, in the form of 250 GIF files each covering a 20-year period. I used wget to download the entire set and looked at each one. Because they are Mercator projection maps, they cannot show the North Pole itself, but they go up to about latitude 85°N. So I looked for all eclipse tracks sometime in the month of March that ran off the north edge of the map and therefore might reasonably reach the Pole.
Now, I was doing this by eye, so it's possible that I missed a few, but it's a fairly easy thing to look for. It's also possible that there were solar eclipses with such a short track that they were only visible in the immediate area of the Pole and did not come onto the map at all—but not very likely. It's also possible that I miscopied some dates.
Be that as it may, these are the only ones I found. (The longitudes given on each line are my estimate of where the track's centerline runs off the north edge of the map.)
  • March 28, −1056: total, 65°W
  • March 21, −428: annular, 50°E
  • March 14, −189: total, 45°E
  • March 24, −171: total, 0°
  • March 23, 228: total, 70°E
  • March 27, 480: annular, 20°W (?—see note)
  • March 15, 1382: annular, 150°W
  • March 17, 1616: total, 90°W
  • March 20, 2015: total, 25°E
  • March 26, 2267: annular, 55°W
  • March 23, 2536: total, 80°E
  • March 29, 2788: annular, 135°E
Note: Two tracks run off the top of the same map near this position and the labels are so placed that it's hard to tell which one goes with the date in March.
I have not attempted to determine the dates of sunrise at the North Pole in these years, but if any other events of the type being asked about occurred or will occur in the 5,000-year period, it would seem that they should be on one or more of these dates. Perhaps there is astronomy software available that will allow the specifics of these eclipses to be explored. --70.49.169.244 (talk) 19:13, 2 March 2015 (UTC)
User:Count Iblis are you sure that 20 March is the first day of sun at the North Pole? Both the US Navy (form B) and the Canadian Research Council (Choose location by longitude and latitude) using 90N 0W and UTC time show the first sun as 18 March.

Denoising cine film[edit]

Many times when watching old b/w film clips on the tv, I wonder whether it is possible to remove all the scratches and other noise electronically ( maybe by spectral subtraction). If it is possible, how long to repair 1 hour of b/w film? --86.190.191.136 (talk) 15:39, 2 March 2015 (UTC)

Have you read our article on noise reduction? It covers several classes of techniques. The first step would be to digitize the old footage, so that it can be processed via digital signal processing. Here's a discussion of how to denoise old film using a filter and the program handbrake -[3]. SemanticMantis (talk) 15:46, 2 March 2015 (UTC)
Professional film restoration is labor-intensive even if done digitally. I think it can take man-months per hour of film. Automated noise reduction, which is all that the noise reduction article seems to cover, can't reliably tell scratches and noise from detail that should be there. -- BenRG (talk) 01:51, 3 March 2015 (UTC)

Why no exact date for the Toba eruption?[edit]

According to our article the eruption ccurred 69,000 to 77,000 years ago. Why can't we tell the exact date from the Greenland ice cores? Count Iblis (talk) 15:42, 2 March 2015 (UTC)

This Nature paper gives 73,500 years ago [4]. You'd probably have to read the full paper and perhaps some of the cited work if you want to work out methods they used to calculate or the estimated error. Probably this figure could be added to the article. The older Nature paper cited in the article is from 1978 and only gives "~75,000". SemanticMantis (talk) 15:51, 2 March 2015 (UTC)
As for the second question, you'll never get an exact date from an ice core. Our article ice core discusses some of the sources of error. My understanding is that a modern specialist could probably give a much smaller range, but nobody will ever seriously claim the data shows that the eruption occurred e.g. 9:32 AM local time on some Thursday in March... SemanticMantis (talk) 15:55, 2 March 2015 (UTC)
According to [5] the current best dates come from Ar-Ar radioactive dating of the debris and are 73.88 ± 0.32 ka BP and 75.0 ± 0.9 ka (1-sigma uncertainty). The paper also says that so far no one has definitively identified the Toba eruption in either Greenland or Antarctic ice. That's not to say that evidence of the eruption isn't there, it is more likely that it is there but no one knows which volcanic layer belongs to Toba. The paper then goes on to discuss 9 different volcanic layers in ice cores as possible Toba candidates during a 2 thousand years interval. Toba was an equatorial eruption, and even the very largest equatorial eruptions will leave smaller traces in ice cores than moderate eruptions that came from volcanoes near the ice sheet. So even though Toba was massive, you can't simply look for the largest ice core spike and call it a day, one has to carefully figure out which layer belonged to Toba, and apparently no one is sure of that yet. Dragons flight (talk) 16:36, 2 March 2015 (UTC)
I think I know what order of magnitude means, and what per annum means, but not how they go together here. —Tamfang (talk) 03:10, 3 March 2015 (UTC)
I believe this usage traces its etymology to dog Latin. Nimur (talk) 15:00, 3 March 2015 (UTC)
  • Looks like some folks here might be barking up the wrong tree. The full-length reference given at Toba catastrophe theory is giving me a 404, but the locked-up version at [6] at least gives an abstract that the 1000-year period is dated +- 5000 years. So it would seem like GISP2 is not well correlated to the actual date, as of 2012? Maybe there are unconformity(ies) in the ice? Wnt (talk) 02:11, 3 March 2015 (UTC)

Double slit observation[edit]

In our grade 12 physics class, our teacher taught us about the matter-wave duality by discussing the double-slit experiment using electrons, light, and small forms of matter, which all produced interference patterns on a screen. He also brought up how, interestingly enough, if one tried to observe which slit the electron/photon/particle goes through, the pattern collapses and one simply sees two bands on the screen. I would like to know: what did my teacher mean by "observing"? Does he mean scientists simply stared at the slits and the pattern collapsed? Does he mean they tried to detect it using a device? If so, what device? Thanks for your help. 74.15.7.133 (talk) 17:35, 2 March 2015 (UTC)

In a typical experiment you set up a fluorescent detector behind the slits, which emits a flash of light whenever a particle strikes it, and you use a camera to capture the flashes. Looie496 (talk) 17:40, 2 March 2015 (UTC)
We have a "double-slit experiment" article that includes lots of details (at various academic levels). In particular, there are some sections about the effects of trying to detect which "which way" the wave/photon goes. Regarding your actual question, I think you mean you would not see the two-slit pattern if the pattern collapses? Presumably you would only see the pattern from the one slit through which a particular photon goes rather than two-slit interference? There are some interesting experiments discussed in the article that speak against the strict claim that it's completely unobservable. DMacks (talk) 17:49, 2 March 2015 (UTC)
He said instead of seeing an interference pattern, one would simply see two bright bands (I've corrected it in my original question), which is why I was wondering through what means would cause this to happen. And thanks, I will read up on it. 74.15.7.133 (talk) 17:56, 2 March 2015 (UTC)
Your teacher was wrong when he said that you'd see two bright bands on the screen. If that were true, there would never be interference in the first place.
The rule in quantum mechanics is that you get interference between different "histories" that lead to the same final state. That's the same final state of everything, not just the particle going through the slit. So if the particle leaves any record of which slit it passed through, there's no interference, because although the particle itself may end up in the same place on the screen, the record of which way it went is different.
If the particles going through each slit end up in different areas of the screen—which is the only way you'd get two discrete bands on the screen—then there will be no interference between the slits in any case because there are no histories involving both slits where even the particle itself ends up in the same place, never mind the rest of the universe.
Looking at the slits won't do anything. Your eye can't reach out into the world and measure anything at the slit; it can only detect light that passes through the pupil of the eye. If that light contains information about which slit the particle went through, then the existence of that information means there will be no interference pattern, whether or not your eye is there. If it doesn't contain that information, then you won't be able to see which slit the particle went through. -- BenRG (talk) 17:12, 3 March 2015 (UTC)

Can sexual arousal cause a penis fracture in a fully clothed man?[edit]

If a man is sexually stimulated by some visual or auditory stimulus, and then he gets aroused, will his penis become erect and make him feel uncomfortable while having a layer of clothes on him that prevents penis movement? At this point, is this the reason why the man would intentionally disrobe in order to allow some movement for the erecting penis? 66.213.29.17 (talk) 17:44, 2 March 2015 (UTC)

You may be interested in reading our article on chastity belts. SemanticMantis (talk) 19:29, 2 March 2015 (UTC)
Does that mean that a man can actually control an erection, if he were just wearing pants? 66.213.29.17 (talk) 19:54, 2 March 2015 (UTC)
It means that experiencing penile fracture due to arousal with concurrent spatial restrictions is (ETA: PROBABLY) unlikely. (ETA: Note that we do not give medical advice here, and this comment shall not be construed as such by any reasonable party. Especially because no details of any case are given, and all discussion is purely hypothetical in nature. SM claims no medical expertise, and no warranty is provided, expressed, or implied, for the accuracy or correctness of any comments made by SM. See here [7] for more info.) Discomfort is another issue, and highly subjective. If you are a man, I suggest you do some WP:OR. If you are not a man, you might find one who is willing to help you learn and experiment or at least discuss (provided that you both consent and you are above the age of majority in your jurisdiction). SemanticMantis (talk) 20:05, 2 March 2015 (UTC)
And for that gratuitous comment, I have not only begun an ANI complaint against SemanticMantis, I have vowed to WP:STALK his every edit for the next year. Ha. Ha. Ha? μηδείς (talk) 22:49, 2 March 2015 (UTC)
What? I've updated my response to make it clear that I am not giving any medical advice. If you disagree or think my comment violates some rules or guidelines, feel free to delete it. SemanticMantis (talk) 23:57, 2 March 2015 (UTC)
Thanks. I asked this question, because I read a news article about people having sex in a public office. I figured that the woman might have triggered sexual arousal, which made the man's penis erect, and then the erection led to disrobing semi-consciously, and then that led to sexual intercourse. I mean, disrobing in a public place with huge windows even when you think that no one is watching doesn't sound very instinctive. Though, that case just shows that people can have sex anywhere. 66.213.29.17 (talk) 20:32, 2 March 2015 (UTC)
See Peyronie's disease (NSFW) for our article, incidentally. Tevildo (talk) 22:45, 2 March 2015 (UTC)

Awareness of erect penis[edit]

When a man is sexually aroused and his penis becomes erect, is he aware that the penis is erect without seeing it? 66.213.29.17 (talk) 21:38, 2 March 2015 (UTC)

Very much so, yes. --Stephan Schulz (talk) 22:55, 2 March 2015 (UTC)
It's actually not unusual for males to sometimes get erections even without becoming at all aroused, sometimes from sitting down for a long time, sometimes just after waking up. Especially for young males, some of my most embarassing memories are from my youth having erections at inconvenient times.. In any case, whatever the cause, it's usually quite obvious to the user because of several different sensations, not just one. Firstly you can feel the blood engorging, you can feel the swelling, you can feel pressure against your clothes, if you are wearing them, if it is due to arousal there is usually several other associated sensations in the general "nether regions", like a low down butterflies sensation. It's all quite hard to miss. Having said that, i wonder if there's some proprioception disorder which would make it possible to have an erection while being completely unaware of it. Vespine (talk) 23:18, 2 March 2015 (UTC)
Wouldn't that be priapoception??? - ¡Ouch! (hurt me / more pain) 13:17, 4 March 2015 (UTC)

Livestock breeding, estrus cycles, and artificial insemination[edit]

While horses tend to breed during spring or summer and rarely in late fall or winter, they may have a more limiting breeding season than cows. Also, horses are allowed to reproduce with stallions, but cows - which can reproduce year-round - must be artificially inseminated with collected semen from a bull to produce milk? Why aren't commercial cows allowed to breed with bulls? 66.213.29.17 (talk) 22:26, 2 March 2015 (UTC)

See Dairy cattle#Reproduction. Artificial insemination is the most common method, but a small number of dairy farms still keep a bull for this purpose. Tevildo (talk) 22:52, 2 March 2015 (UTC)
There's no real use for dairy bulls, apart from siring. Beef bulls can be farmed, but they are dangerously unpredictable, and their meat is tougher. Stallions can be ridden, and thus are worth keeping. Thus its cheaper to use one bull to inseminate several herds of cows, and artificial insemination is easier than transporting the bull around the herds. LongHairedFop (talk) 16:14, 3 March 2015 (UTC)


March 3[edit]

Rapidly turning on and off an LED lamp[edit]

I remember as a kid I was always told not to turn the lights on and off rapidly because it would make the bulb burn out faster. Is the same true for LED lamps or is it safe to rapidly turn them on and off without any adverse effects? ScienceApe (talk) 00:41, 3 March 2015 (UTC)

The answer is not appreciably. In fact one the very things that make LEDs so useful is their ability to turn on and off very rapidly, such as in fiber optics or optocoupler. Also, since an LED is either on or off, you can't reliably make it "half as bright" like a lightbulb by giving it less current, the way you typically controll an LEDs brightness is by using Pulse-width_modulation which also turns the led on and off typically in the KHz range, which surprisingly is not mentioned in the article, but does not appreciably reduce the life of the LED.. Vespine (talk) 04:15, 3 March 2015 (UTC)
Not true. LED brightness is almost linearly related to drive current. There's lots of discussion (some of it wrong) on the web, but this gives some graphs. Typically, LEDs are run at high current with low duty cycle to give them a high perceived brightness. However, they could also be run at 100% duty cycle and variable current to provide varying brightness.--Phil Holmes (talk) 10:46, 3 March 2015 (UTC)
Ok, I did get that one fact wrong, but it doesn't invalidate my response to the OP. It is true that typically, LED brightness is adjusted using PWM, especially in applications where the LED brightness needs to vary, i.e. is not fixed. LED drivers for displays use PWM, not varying current. Vespine (talk) 22:52, 3 March 2015 (UTC)
I just read Phil's user page :) Let me just add, I'd trust him more than me on this subject. :) Is the rest of my response "roughly right" Phil? I'm actually a big fan of LEDs and I have made a few LED projects, one I'm particularly proud of but it's a far cry from making lasers and pin diodes in a professional capacity ;) Vespine (talk) 22:58, 3 March 2015 (UTC)
It's certainly true that a key feature of LEDs is their ability to be switched on and off quickly. It's made optical communications (and therefore telecommunications/the internet) what it is today. I would say that, as a general rule, LEDs are used as being either on or off: it's not common to modulate their intensity. However, given that they are almost always pulsed in use, then using pulse width modulation would certainly be an option if you wanted to do this.--Phil Holmes (talk) 10:36, 4 March 2015 (UTC)
Reading your question again, my reply specifically refers to the diode part, however an "LED LAMP", especially one you can stick into a domestic light socket is typically far more than just "a lighe emitting diode" or two. It's usually a bunch of components, resistors, capacitors, rectifiers, if it's fancy even some sort of control IC. These components might very well be far less forgiving to fast switching and fail far sooner than the actualy LED part of the lamp. Vespine (talk) 04:21, 3 March 2015 (UTC)
I agree that you might hypothetically be right - but LED's are DC devices and we're feeding them with AC current - so there must be some circuitry to take care of that - which probably slows down switching transients to the point where they're not a problem. At any rate, if there is a problem, it is entirely negligible compared to the issues of rapidly switching incandescent lamps. SteveBaker (talk) 04:03, 4 March 2015 (UTC)
Basic science: Switching incandescent bulbs off and on stresses the glass-to-metal seal, thus, leading to an early lose of vacuum.--Aspro (talk) 00:25, 4 March 2015 (UTC)
I'm gonna call [citation needed] there (it's possible, but I can envision other possibilities too). There are lots of mechanical details that could potentially fail, and possibly due to changing thermal stresses. It seems like it would be easy to determine which one is most common. DMacks (talk) 18:18, 4 March 2015 (UTC)

Why didn't this hurt? (Not medical advice)[edit]

So here's a question I've had for a while and I don't think it qualifies as medical advice as it's something fully In the past that no longer affects me in any way (except that I do have a fantastic scar). Anyway, at the start of last summer, I managed to cut open the radial artery in my right hand whilst in Israel. For those who want to survey the damage to give a better answer/like seeing this kind of thing, here's a lovely picture of it popping up to say hi to everyone. After six hours and losing a litre of blood, the doctors (who spent most of the time bickering with each other as Israeli doctors are known to do) finally managed to get the artery cauterised and the wound stitched up. I was prescribed beer (to drink only with my left hand), and sent back to my friends' house without painkillers or any supplies.

Now an odd thing about this particular injury is that I never felt pain from it any point. Not when it was cut open (though there was a feeling of warm liquid on my hand and something draining out of me at times), not when I had it wrapped in paper towels and a hand towel, not when the doctors ran it under water for no good reason, nor when they unwrapped my bandage and had me hold my hand over a sink so they could argue with each other while I watched my life fountain out of my hand into the drain and nearly passed out from blood-loss, etc. In fact, the only time I felt anything was the searing intense pain when the doctor cauterising the artery—which really does smell like chicken—accidentally touched a bone.

I could attribute this to shock (as the whole time I was making morbid jokes and feeling loopy), but even the next day I felt no pain (remember there were no painkillers), and not any time after. There was no nerve damage, and there was still glass in my hand (as evidenced by the glass I pulled out a week later even though my hand had been x-rayed twice). Occasionally if tried working with my bandaged hand in the first week of digging (which started three days after the incident) to pick up a pickaxe or use a handpick, it would hurt from the vibrations, but otherwise nothing.

So, anyway, my question after all of this is this: why the heck didn't I feel any pain from this thing? Again, I don't want any advice on what to do as it's a nice healthy scar that doesn't unthreatening me in any way, shape, or form, and I don't plan on opening up any more arteries as I hate not being able to do heavy work on digs for two week. I just want to know why it never caused me pain even though it was a potentially fatal injury. Sir William Matthew Flinders Petrie | Say Shalom! 12 Adar 5775 01:51, 3 March 2015 (UTC)

Some parts of the body are less sensitive than others. Consider getting a flu shot or whatever. It's a needle poking into your arm, but it's not particularly painful. ←Baseball Bugs What's up, Doc? carrots→ 02:04, 3 March 2015 (UTC)
When I was 5, I managed to put my arm through a window and slice it open. I had stitches and still have a scar, but, like you, there was no pain. I do recall the stitches itching, though. So my theory was that there was nerve damage. I have full nerve function there now, so, perhaps due to my young age, I was able to regenerate those nerves. StuRat (talk) 04:25, 3 March 2015 (UTC)
This one basically cut through the artery and somehow avoided the radial nerve. I only felt some loss of sensation between the knuckles of my index and middle fingers (which came back after four months–I'm 25, so don't know if that helped). They tested for nerve damage (which felt weird because I had to watch and it felt like something would pop out of the hole in my hand) and found nothing wrong. My stitches also itched a bit (especially as they got covered in sweat). Sounds like a badass scar though, Stu. Maybe it's a sort of prolonged shut-down response (after shock has subsided) so your body doesn't process what should be agonising pain? We're not talking minor pin-pricks in either case, but rather massive damage. Sir William Matthew Flinders Petrie | Say Shalom! 12 Adar 5775 04:49, 3 March 2015 (UTC)
Oh, come on Sir William Matthew - you may feel like you're only 25, but by my reckoning you're almost 162 years old! Richerman (talk) 10:50, 3 March 2015 (UTC)
Have you read Acute stress reaction? How about Nociception#Regulation, or Pain#Theory? Also check out pain tolerance and the distinct pain threshold. I doubt you can get conclusive answers, but food for thought at least. Also I thought at least one person should provide some references, and wanted to congratulate you on your injury :) SemanticMantis (talk) 15:15, 3 March 2015 (UTC)
I'm also wondering now about how 'clean' the wound was. WP:OR: getting sliced by a razor hurts way less then being mauled by a saw, no matter where on the body it occurs... cuts from very sharp objects are generally preferable to those incurred by dull blades, in terms of healing time, scarring, stitches, pain, etc. SemanticMantis (talk) 01:04, 4 March 2015 (UTC)

Reference 4 in 'Malnutrition in South Africa'[edit]

Hi there,

I am looking for the actual reference for reference 4 in 'Malnutrition in South Africa', as the link is unfortunately invalid. ( http://en.wikipedia.org/wiki/Malnutrition_in_South_Africa#cite_ref-Malnutrition_in_South_Africa_4-1 ) The reference is ""Malnutrition in South Africa". Retrieved10 December 2012." The invalid link is http://myfundi.co.za/e/Malnutrition_in_South_Africa

Thank you very much for your time. I am currently looking into volunteering for Wikipedia myself and really appreciate your help.

OliviaOlivia Beth G (talk) 11:46, 3 March 2015 (UTC)

Hi Olivia, a few things: First, welcome to Wikipedia! Feel free to be WP:BOLD, and if you see a problem, WP:SOFIXIT - WP only exists because people like you want to make it better. If you need help learning how to edit the article, include the citation, etc, you can ask at WP:HELPDESK. You can also try this tutorial/game thing called Wikipedia:The_Wikipedia_Adventure.
Now, for this issue - the best place to post this problem (which is link rot) is on the talk page for that article [8]. But it is also fine to post it here.
As for the broken link - we could probably use the wayback machine to find the version of the page that as originally cited, even though the link no longer works. Another alternative is to find other references that say similar things. For instance, here [9] is a journal article that found 27.3% incidence of anemia among 2-year-olds in South Africa. Probably better references can be found (this one is a little old), but that's the first one I got. If you need help accessing the full article (or other similar), you can ask at WP:REX. Good luck, and thank you for helping to make WP better :) SemanticMantis (talk) 16:02, 3 March 2015 (UTC)
I've checked the wayback machine, and unfortuanatly, the page isn't archived by it. I've added a { {deadlink} } to it. This records that the link is broken, and puts it on a list of pages to be fixed, but there is a sizable back log. LongHairedFop (talk) 16:06, 3 March 2015 (UTC)
You can try asking the folks at WT:WikiProject South Africa, we're friendly and some of us have a talent for finding good sources. Roger (Dodger67) (talk) 17:41, 4 March 2015 (UTC)

Why does hyperglycemia not cause necrosis?[edit]

The whole question is: why when administrating glucose in the vain and it's going outside the vain (para) it causes to necrosis while hyperglycemia (more than 500 mg/dl) doesn't causes necrosis? (It's about the explanation of this phenomenon. not medical advice). Thanks 11:52, 3 March 2015 (UTC) — Preceding unsigned comment added by 149.78.32.22 (talk)

Intravenous sugar solution is 5% = 5 g/ 100 ml = 5000 mg/dl = 50g/l. Hyperglycemia is dangerous over 300 mg/dl. I think the effect of missing the vein is simple osmotic shock from that very high concentration of solute in the sugar solution, which is required in order that a reasonable volume have an effect on the entire blood supply. Wnt (talk) 14:04, 3 March 2015 (UTC)

When the glucose outside of the cell, which one pumps the other?[edit]

When glucose found in high concentration outside the cell, which one pumps the other? Is the cell pumps the glucose (and in this way the cell is going to die) or the high concentration of the glucose pumps the cell's content (and in this way the cell is going out of life). Thanks — Preceding unsigned comment added by 149.78.32.22 (talk) 12:01, 3 March 2015 (UTC)

Read the article titled Glucose transporter. --Jayron32 12:04, 3 March 2015 (UTC)
Your question "which one pumps the other" is unclear. According to the article Jayron32 linked to, the process is facilitated diffusion, not pumping (which would require energy). Glucose enters cells if the concentration is higher on the outside than the inside, which is usually the case for an energy-consuming cell. Glucose doesn't kill cells, as you seem to imply. Cells use glucose as fuel, and some cells additionaly build large glucose polymers (glycogen) for use as energy storage. In diabetes the problem is dysregulation of the facilitated diffusion, resulting in a surplus of glucose on the outside of cells that are starving. The "pumping" or rather "facilitated diffusion" is catalyzed by proteins that sit in the cell membrane. Some cells can synthesize glucose (gluconeogenesis), and release it to the environment for the benefit of other cells. Some cells, especially liver cells, assemble glucose into glycogen when supply is high (after a meal), and break down the glucose and release it between meals, thus keeping the glucose concentration in the blood fairly constant. In the kidneys, glucose is actively reabsorbed from the pre-urine against a concentration gradient (i.e. "pumped", to avoid loss of an important nutrient) in a process that requires energy (see Glucose uptake for the details). --NorwegianBlue talk 18:01, 3 March 2015 (UTC)

Can humans live with other apes?[edit]

Considering that there’ve been anthropologists who’ve lived with foreign people, has anybody ever attempted to live with non‐human apes in the wild? And while I’m at it, is it possible for chimpanzees and humans to co‐exist pacifically? Sorry if these questions sound weird but considering how similar hominids are, I thought that it might still be at least possible. --66.190.99.112 (talk) 20:43, 3 March 2015 (UTC)

Jane Goodall is a good starting point. Sir William Matthew Flinders Petrie | Say Shalom! 12 Adar 5775 21:12, 3 March 2015 (UTC)
Yeah, I was going to suggest Goodall and Dian Fossey, but neither actually lived with them, per se. Besides Tarzan I'm not aware of anyone who has. ―Mandruss  21:18, 3 March 2015 (UTC)
Generally, in the real world, humans are bad for non-human primates and their survival outlook. Habitat loss, poaching, etc. The International_Gorilla_Conservation_Programme will have a lot more info on the anthropogenic threats to gorillas.
A few human people do spend a lot of time with apes, the most famous are probably Jane_Goodall and Dian Fossey. To those that say they didn't "live with" the apes, I'm pretty sure they would have been camping right near by, and all the local troop members would have known them by sight and smell. A colleague of mine spent a whole summer in Africa camping next to Geladas, and I would describe that as basically living with them... Anyway, you can still easily get Fossey and Goodall's books and read their research papers to see how close they got, and Gorillas in the mist was also adapted into a movie. Chimpanzee#Interactions_with_humans has some relevant info, as does Gorilla#Interactions_with_humans.
It's also good to think about what can happen when chimps live with humans. Travis_(chimpanzee) ripped someone's face off, and Oliver_(chimpanzee) made many sexual advances on human females [10]. SemanticMantis (talk) 21:23, 3 March 2015 (UTC)

March 4[edit]

risk of cancer from oral sex[edit]

According to Wikipedia on oral sex there is a 250 percent increased risk of cancer if one has one to five oral sex partners. What is the average lifetime risk for developing head and neck cancer in percentage? — Preceding unsigned comment added by 199.119.235.240 (talk) 01:17, 4 March 2015 (UTC)

What article did you get that 250% info from? ←Baseball Bugs What's up, Doc? carrots→ 01:21, 4 March 2015 (UTC)
With two cites no less! Sir William Matthew Flinders Petrie | Say Shalom! 13 Adar 5775 01:27, 4 March 2015 (UTC)
We can't give medical advice, see your doctor, and mention that according to our archives you have a compulsion to ask this question every few months [11] [12] in public fora, because he can probably also help you with that issue as well. c (talk) 03:07, 4 March 2015 (UTC)

What are you talking about I have a compulsion? — Preceding unsigned comment added by 199.119.235.240 (talk) 03:39, 4 March 2015 (UTC) This is the first time I've posted her. — Preceding unsigned comment added by 199.119.235.240 (talk) 03:41, 4 March 2015 (UTC)

Instead you could be more polite and simply say we don't give medical advice instead of implying a personal attack that I'm mentally ill.

Your style is similar to that other user that you claim not to be, so it's not difficult to jump to a conclusion. As to mental illness, nobody said that except you. It's time to see your doctor. ←Baseball Bugs What's up, Doc? carrots→ 08:20, 4 March 2015 (UTC)

Apologies for the would-be Internet cops who clearly don't realize that this is a common fear, getting more popularity since various celebrities have been reported to possibly have throat cancer (e.g. Val Kilmer), and people nowadays recognize the link with human papillomavirus - to which a vaccine, trade name Gardasil and Cervarix, is available (though many right-wingers indignantly refuse to vaccinate their kids; I think their thinking is wrong but I have to agree with their point that schoolkids shouldn't be forced to take vaccines that don't affect disease transmission at school). There's an interesting anomaly that Gardasil is apparently not promoted to protect against throat cancer, but HPV 16 causes much throat cancer and is a target of the vaccine - I assume that this is because of the relative rarity of the condition but I don't actually know. Wnt (talk) 13:18, 4 March 2015 (UTC)

[citation needed] on the implication that those who come from right-wing backgrounds are less likely to vaccinate their children against this (or any) disease? Let's avoid making generalizations along ideological lines unless it's a sourceable statement that might be of use to our OP. Last I heard about the statistics on this issue, people were much more divided primarily by nationality on this issue, first and foremost; the biggest uptake in participation in HPV vaccination has been Australia, which has a strong conservative movement and has seen increasing ubiquity of vaccination amongst women. And within a given nationality, it's often along different lines than the "right vs. left" divide. You seem to be speaking to the American context, but you know what? You'd probably be wrong even there, because, while the tendency is the U.S. may be to see conservatives as more apt to deny consensus science, it's actually been observed broadly in journalism on the specific issue of the anti-vaccine movement in the U.S. that it's strongest base is composed largely of those who identify as being on the left... Mind you, I warrant the issue is somewhere in the middle, but as to your assertion, I'd recommend striking it if you don't have a source. Otherwise it's just subjective WP:OR judgement/guesswork. Snow I take all complaints in the form of epic rap battles 14:36, 4 March 2015 (UTC)

Well, sorry for overreacting to that person. — Preceding unsigned comment added by 199.119.235.240 (talk) 13:27, 4 March 2015 (UTC)

When he said that i should see a doctor about my compulsion I thought he was accusing me of ocd. — Preceding unsigned comment added by 199.119.235.240 (talk) 13:45, 4 March 2015 (UTC)

I don't defend the way Medeis handled this, but on the other hand, they and BB weren't the only one who came to that conclusion. I wouldn't have said anything because I didn't think it mattered (I wasn't aware at the time the editor in question had been blocked for sockpuppetry), but I also didn't bother to properly read the question and so wouldn't have said anything. My point is that without defending the way tis was handled, there is a potential net benefit here since me, and perhaps others may be willing to WP:AGF when you say you aren't the same editor yet I and perhaps others may have just ignored your question otherwise.
Anyway a simple search for 'life time throat cancer risk' will probably find either [13] or [14]. The former says "Lifetime Risk of Developing Cancer: Approximately 1.1 percent of men and women will be diagnosed with oral cavity and pharynx cancer at some point during their lifetime, based on 2009-2011 data". The later has 1.55% for men for "Oral cavity and pharynx", and 0.67% for women. The risk of dying from it is also present. These are only some of the cancer types covered under Head and neck cancer. The later link seems to have larynx. It doesn't seem to have trachea, it's possible this is too rare, or alternatively it's included in the other stats. The former ref doesn't have larynx directly, but if you browse around the site view the other "more cancer types" , you should end up at [15] which will link to larynx [16]. It doesn't have trachea either, not particularly surprising since these are different subdomains of the same site so I expect their data may be the sme. Also this is for the US, not other countries.
If you're asking specifically about the lifetime risk of head and neck cancers for people who have had "one to five oral sex partners", I have strong doubts that level of detail has even been studied sufficiently to provide a reliable answer, but I could be wrong.
Nil Einne (talk) 14:06, 4 March 2015 (UTC)
There's evidence enough the two are the same person, but the issue here is, if the OP is worried enough about the topic he should see a doctor who can examine him, vaccinate him, and assure him much better than we can. μηδείς (talk) 16:57, 4 March 2015 (UTC)
Note that a 250% increase on 1.1% is 3.85%. Even if you believe the numbers from the study apply to the real world (they never do), you can have all the oral sex you want and still have a 96.15% shot at not getting throat cancer. Or greater, considering a good chunk of that 1.1% were already having oral sex. InedibleHulk (talk) 20:14, March 4, 2015 (UTC)
This is a very good conceptual point to make. We can multiply very tiny percentages of incidence by huge numbers, and still get tiny incidence rates. E.g. I wouldn't mind increasing my risk of lightning strike sometime in my life by 1000% [17]. SemanticMantis (talk) 20:28, 4 March

Will I be able to find the lifetime risk for people with more than 5 partners (I misread the article) by simply adding 250 percent to 1.1 percent?

Why does stuff have color?[edit]

OK, the short answer is that different materials absorb different wavelengths of light, but why do different materials absorb different wavelengths of light? And how materials that are totally different have the same color, and things that all most the same have different color?--Noopolo (talk) 01:34, 4 March 2015 (UTC)

  • Read color (and quantum mechanics if you want). Basically, the color you perceive depends on lighting, how the material absorbs and reflects wavelengths differently, and how your brain interprets that in the context of surrounding visible materials. μηδείς (talk) 03:11, 4 March 2015 (UTC)
Color has much more to do with human biology than it does with physics. I always recommend this video, made by an alien, for a funny (and very accurate!) explanation of color. --Bowlhover (talk) 08:56, 4 March 2015 (UTC)
  • As noted above, color is a psychological/neurological effect, and not a physics one. It is influenced by physics, of course, but it isn't primarily a physical phenomenon: it is primarily a function of how your brain interprets the images coming into it, and your brain does a LOT of funny stuff to give you impressions of color. See Qualia, particularly the quote from noted physicist Erwin Schrödinger regarding color. --Jayron32 14:18, 4 March 2015 (UTC)
  • Eh, that's the third person whose supplied an answer here which is technically correct but not very helpful to the exact issues inquired about by the OP. And mind you, I'd be the first person to take the discussion in the direction of colour perception, as visual cognition with regard to this topic is very much my wheelhouse. But the OP is clearly inquiring as to the materials science side of things--that is, the physical phenomena rather than any interaction between stimulus and visual sensorium. No aspect of the mechanisms of the eye or the visual centers of the brain explains why two different materials have the same colour; if a photon strikes a photoreceptor, the receptor doesn't differentiate based on the material which reflected the light. All that matters is the wavelength and so long as that is identical, and it struck the receptor in the exact same manner, the perception would be identical in both events.
Noopolo, please see chromophore, optics, pigment and (of course) color and let us know if you have any more specific inquiries. Snow I take all complaints in the form of epic rap battles 15:00, 4 March 2015 (UTC)
Emission spectrum describes the spectral lines that compounds emit. There's a large set of articles linked from them, but I couldn't find a good layman's overview. LongHairedFop (talk) 15:17, 4 March 2015 (UTC)
Yes, the issue (however) is that with the fact that something has an emission spectrum which has a specific color in it has little to do with our perception of color. Here are just a myriad of issues with thinking about spectral lines as "color"
1) There's no functional difference between spectral lines which have wavelengths our visual systems can perceive and those that don't. That is, because a spectral line happens to lie in the UV range or IR range doesn't mean anything physically. It's a total coincidence
2) There are lots of other sources of light than electronic transitions (i.e. Bohr model stuff). For example, blackbody radiation, reflection, absorbtion, Iridescence, fluorescence, phosphorescence, etc.
3) Even with all of that, there's very little physical connection between our perception of a color, say "yellow", and say a coherent light of 580 nm wavelength. Yes, we would perceive that light as yellow, but we would ALSO perceive as yellow lots of things, many of which may not have any light of that wavelength. We can even perceive colors which have no spectral equivalences, things like brown and purple and the like. Plus, there's various ways in which the environment a material is in that affects what color we see. This page shows ways in which even the "matrerial science" answer is entirely inadequate. Even with all of the same physical factors, simply putting an object next to different objects changes what color it is.
Simply put, there is no "physics of color" in any meaningful sense. Again... don't take my word for it. Erwin Schrödinger, a physicist who has far more importance to the physics world (and the study of light and waves and all sorts of physicsy stuff) said "The sensation of color cannot be accounted for by the physicist's objective picture of light-waves. Could the physiologist account for it, if he had fuller knowledge than he has of the processes in the retina and the nervous processes set up by them in the optical nerve bundles and in the brain? I do not think so." What seems like a simple question, like "What makes something yellow" just cannot be answered with a simple discussion of wavelengths of light. --Jayron32 15:39, 4 March 2015 (UTC)
Eh, that's a little pedantic, in my opinion. Don't get me wrong, I'd happily talk about colour as a perceptual/cognitive/conceptual/contextual (look through the archives and you'll see just how verbose I can be on those topics, which have consumed a not insubstantial part of my life), but again, that's just clearly not what the OP is seeking here. Here's his direct inquiry: "Why do different materials absorb different wavelengths of light? And how materials that are totally different have the same color, and things that all most the same have different color?" He's asking specifically why certain materials reflect certain wavelengths of light. That question is answered purely through the language of physics; psychophysiology can't inform upon the topic of colour until the light reaches the eye.
So yes, of course a complete understanding of colour as a complete phenomena is deeply predicated upon physiological and cognitive mechanisms of the person who perceives it (I believe I stipulated as much in my first comment and it's hardly something I'm about to deny), but looking at Noopolo's question, he is clearly talking about how objects composed of matter emit or reflect the light properties they do. And it's not a trivial distinction. Other creatures have photoreceptors which are keyed to different wavelengths or neural networks (not always brains) which process them in different ways and cause a different subjective experience. Even amongst humans, there's noticeable variation in a difference in perception between individuals and context. But the light in question still has general physical principles that remain the same, no matter the different responses it elicits in different organisms, and that is what this thread (at least in-so-far as it is defined by the OP's question) is about. Snow I take all complaints in the form of epic rap battles 17:17, 4 March 2015 (UTC)

Moon floating away[edit]

What would happen if the moon were to float away from the earth? Would the effects be catastrophic? — Preceding unsigned comment added by 199.119.235.240 (talk) 05:51, 4 March 2015 (UTC)

Well, it would take a huge force to cause it to do that, and that force would likely effect Earth, too. But, ignoring that, the absence of the Moon would mean greatly reduced tides (the Sun would still cause minor tides). The intertidal zones would be greatly disrupted, and many plants and animals dependent on those tides would die. Salinity would be reduced in-shore, without tides to bring in salt-water, and that would favor some plants and animals over others. Some animals, like moths, may also use reflected moonlight to find mates, etc. So, it would cause a disruption, but life would adapt. StuRat (talk) 06:57, 4 March 2015 (UTC)
The Moon is actually currently floating away from Earth, at (I think) 4 cm per year. Earthquakes and volcanic activity is decreasing frequent. Earth will become tidally locked to the Sun - always facing the same side. A tidally locked Earth is a barely survivable scenario, scorching hot on the day side and polar winter on the night side, and chaotic weather on the twilight zone. I dare say yes, it will be catastrophic - life will be surviving instead of thriving. Plasmic Physics (talk) 12:07, 4 March 2015 (UTC)
Careful you don't mix up your tidal locks! It's true that the earth-moon distance is increasing, and the earth's rotation is slowing, due to the tidal locking effect between the earth and the moon. It's already the case that the same side of the moon faces the earth all the time, and that will eventually be true of the earth as well -- that is, the moon will stay over one spot on the (rotating) earth the whole time. At the very least this will be very sad for all the other parts of the earth that won't have a moon to see at all any more, but it's got nothing to do with the earth becoming tidally locked to the sun. That would take muuuuuuch longer. (In fact, according to our tidal locking article, the earth won't even become tidally locked with the moon before the sun becomes a red giant and engulfs us both.) —Steve Summit (talk) 14:08, 4 March 2015 (UTC)
What evidence is there for a reduction in frequency of either volcanic activity or earthquakes? Mikenorton (talk) 12:32, 4 March 2015 (UTC)
The same tidal effect that makes the ocean move up and down a couple of times a day is also exerting a force on the rocks below our feet. Those forces contribute to the likelyhood of that kind of activity. SteveBaker (talk) 15:32, 4 March 2015 (UTC)
I'm aware that even minor effects such as unusually heavy rainfall have been known to trigger earthquakes (not cause them - they would have happened anyway eventually), I was just questioning Plasma Physic's assertion that earthquakes and volcanoes are less frequent, although I'm not clear over what timescale that claim is being made. Mikenorton (talk) 20:39, 4 March 2015 (UTC)
I meant 'trigger'. Plasmic Physics (talk) 11:14, 5 March 2015 (UTC)
See this BBC documentary at YouTube: Do We Really Need the Moon?. ―Mandruss  12:12, 4 March 2015 (UTC)

Tidal effects stopping tectonic plates fusing[edit]

Inspired by the above question, does the Moon's tidal effect, which flexes the Earth's crust slightly, help stop the tectonic plates fusing together? LongHairedFop (talk) 12:27, 4 March 2015 (UTC)

That question is addressed here, concluding that tides do influence plate tectonics. Mikenorton (talk) 12:37, 4 March 2015 (UTC)
I'm not sure whether a tidal affect is required for plate tectonics, but I do know that the Earth will die without it. Plate tectonics are required to prevent the outer core from solidifying like what happened to Mars. When that happens, the planetary magnetic shield collapses, allowing the protective ozone layer to be overwhelmed and depleted by incoming ionizing solar radiation. All life, except for extremophilic microorganisms, will die from radiation. Overtime, the Earth's water will be radiolysed to hydrogen and oxygen. The resulting hydrogen in the atmosphere will be gradually depleted, blown away by space wind, to use common language. So, Earth will dry out and even those extremophiles will eventually die out, and Earth will look very much like Mars does today. Plasmic Physics (talk) 11:35, 5 March 2015 (UTC)

Why do physics textbooks come in "with Modern Physics" and "without" versions?[edit]

I checked the latest editions of Sears, Zemansky, & Young; Serway; and Halliday & Resnick-- they all do it, where the two books are identical except about six or seven chapters on relativity, quantum mechanics, nuclear physics, and cosmology are in the "with" versions. Why? 20.137.2.50 (talk) 16:54, 4 March 2015 (UTC)

One version for college and the other high school? Roger (Dodger67) (talk) 17:36, 4 March 2015 (UTC)
Accreditation! Thanks to the arcana of academic politics, textbooks are designed to fit into either a 2- or 3-course long series on physics. Textbook publishers segment the material along these lines: first, mechanics; next, electromagnetics; and finally (the optional third segment) on "modern physics." Most accredited universities in the United States are able to offer a "minor in physics" by teaching only the first half or the two-semester course, and eventually granting a Bachelor of Arts in (Something) with a Minor in Physics. The very same class can serve as the first two-thirds of an introductory physics track for major students or engineering students.
Nimur (talk) 17:40, 4 March 2015 (UTC)
The other advantage to the publishers is selling two books/editions, instead of one. Sort of doubles their market. In theory, the shorter courses could use the longer book, but not over all of it. Similar to the idea of coming out with a new edition every year that features only minor updates and some new homework problems. Some related info at Textbook#New_editions_and_the_used_book_market, [18]. SemanticMantis (talk) 20:03, 4 March 2015 (UTC)


March 5[edit]

Jet stream clouds?[edit]

Can a long, straight cloud like this be associated with the jet stream (upper left to lower right)? It went for as far as I could see in both directions. This was the widest I could get with the lens I had on. This is today's jet stream and the blue area in the southeast US is where I took the photo. (Sorry, it won't let me put in a shortened URL.) Bubba73 You talkin' to me? 00:39, 5 March 2015 (UTC)

That's a jet contrail, not a cloud. Clouds are never that long, straight, and narrow. ―Mandruss  00:45, 5 March 2015 (UTC)
But jet contrails can cause clouds to form in their wake. Those clouds are initially long, straight, and narrow, but then tend to diverge in shape. StuRat (talk) 00:57, 5 March 2015 (UTC)
Resolved

Thank you. Bubba73 You talkin' to me? 00:47, 5 March 2015 (UTC)

When I see such a long URL, I like to try deleting each field to see which of them are redundant. —Tamfang (talk) 08:59, 5 March 2015 (UTC)

final question[edit]

Will I be able to find the lifetime risk for people with more than 5 partners (I misread the article) by simply adding 250 percent to 1.1 percent? — Preceding unsigned comment added by 199.7.159.115 (talk) 00:55, 5 March 2015 (UTC)

Lifetime risk of what ? What article ? StuRat (talk) 00:58, 5 March 2015 (UTC)
Apparent continuation of #risk of cancer from oral sex. There is no need to start a new section, just add to the existing one. ―Mandruss  01:01, 5 March 2015 (UTC)

Venus and Uranus conjunction[edit]

There was a conjunction of Venus and Uranus today, when they were only about 0.1 degree apart (see List_of_conjunctions_(astronomy)#2015). I tried to photograph (just my camera - no telescope) it about 5-1/2 hours after closest approach, but I don't know if I got Uranus or something else. I got something other than Venus. I measured the distance in the photo, considering my camera and lens, and came up with 0.29 degree separation. Since it was about 5-1/2 hours after the closest point, could they be 0.29 degrees apart, or was the next-brightest object something other than Uranus? Bubba73 You talkin' to me? 04:24, 5 March 2015 (UTC)

How long was your exposure? There is a very easy way to resolve this if you install a program like stellarium. I have it at home but won't be home for a few hours. In this program you simply put in your location and the time and it shows you exactly what the sky looked like. From there you shold be able to compare your photo and fairly confidently say if what you captured was in fact uranus or not. Vespine (talk) 05:56, 5 March 2015 (UTC)
The exposure times ranged from a fraction of a second to about 1 minute. I'll check out that program. Bubba73 You talkin' to me? 06:03, 5 March 2015 (UTC)
Ok, that is a nice program. That program shows that they had moved a little farther apart. Uranus looked like the right direction from Venus, but the distance seemed wrong. But there was nothing else it could be. Then I realized that when I did my calculations based on my lens' field-of-view, I forgot to take into account the extra factor because the camera uses an AP-C sensor. So it is Uranus. Bubba73 You talkin' to me? 06:33, 5 March 2015 (UTC)

What is the thing that causes to contact lenses to be connected to the eyes?[edit]

Is it the surface tension?149.78.32.22 (talk) 10:57, 5 March 2015 (UTC)