Wikipedia:Reference desk/Archives/Science/2015 March 1

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March 1

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

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, 28 February 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, 1 March 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, 2 March 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, 2 March 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, 3 March 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, 3 March 2015 (UTC)

The kinetic theory of gases, degrees of freedom, and distribution of kinetic energy

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

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

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)

• Objects have weight in proportion to their mass, which includes the relativistic mass of all subatomic particles within them. Wnt (talk) 15:37, 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)

It is always been assumed, that the distortions (displacements) of time space (of a space time’s continuum) are always been occurs in the case where the moving body for short periods of time is always been passed a different distance of path, regardless of the accelerations of the movements of this body.--83.237.213.252 (talk) 14:16, 5 March 2015 (UTC)

Board of multi national corporations

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)