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DanS
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Kickball Capital of the World
Jan 1970
time: 00:21
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This is like a far-out physics trifecta...
As the following article points out, the effects of dark energy -- which composes some 75% of the universe's mass -- are being seen all around us rather than merely in distant galaxies. We don't know what this energy is, but it seems to have some sort of repulsive effect (I'm repulsed just thinking about it -- hardeharhar).
Then we have the general observation that contrary to what was generally theorized, at the temperature of 0 Kelvin, atoms do not come to rest, but still jump around and as such still contain energy, but not the gravitational effects normally associated with energy.
Then we have Tesla's notion that there is an "ether" of energy that permeates everything. Rather like the ancient Greek philosophers theorized.
Could somebody with knowledge about physics explain to me in laymen's terms why these three observations/theories are probably unrelated? Is it merely the matter of anti-gravitational effects being seen with regard to dark energy, but not with regard to zero point energy, and who-knows-what impact on gravity of Tesla's energy ether?
http://www.msnbc.msn.com/id/3217961/
quote:
Mysterious effect detected in galactic back yard
March 16, 2005 | 8:45 p.m. ET
Dark energy is near: For years, scientists have known that we don't know all that much about the universe. In fact, ordinary matter the kind we can detect with telescopes and other observational tools accounts for only about 5 percent of the universe's content. About 25 percent consists of "dark matter," which can be sensed only by its gravitational effect. The other 70 percent is tied up in "dark energy," a mysterious quality that is apparently speeding up the expansion of the universe.
Astronomers first picked up on dark energy's influence on the edges of the observable universe, but now they have found evidence closer to home, in the relative motions of the galaxies around our own. The research indicates that dark energy isn't just a way-out-there quirk, but is truly a property that permeates all of space, including our own galactic neighborhood.
"It's like traveling from Seattle to Portland, Ore., rather than from Seattle to New York, to measure the earth's curvature," said Fabio Governato, a professor at the University of Washington and a researcher at Italy's National Institute of Astrophysics.
Governato and his co-authors the University of Zurich's Andrea Maccio and Cathy Horeliou at Sweden's Chalmers University of Technology report their results in a paper to be published by the Monthly Notices of the Royal Astronomical Society (PDF file).
To look for dark energy's signature, the team ran a series of supercomputer simulations of the universe's evolution, varying the parameters to reflect situations with and without dark energy.
"The computer crunches models for a few weeks, and then we compare the properties of our virtual universe with those of the real ones," Governato told me today.
The researchers looked at the actual motions of the Local Group galaxies with respect to each other a complex pattern that is influenced by the mutual gravitational attraction between the galaxies as well as the repulsion caused by the expansion of the universe. They found that the only way to explain the galaxies' motions with their computer model was by including an extra factor for cosmic expansion.
"If you leave out the dark energy, you miss the data by a factor of three or four," Governato said. "But if you include the dark energy, theres a match."
So what is dark energy? That's the 64,000-quatloo question and one that researchers cannot yet answer. Some theorists say dark energy is simply an unchanging property of the universe, the so-called cosmological constant that Albert Einstein proposed, then rejected. Others say it may be "quintessence," a form of energy that changes over time.
If we had more precise data about the motions of galaxies, could Governato's model make more headway on such questions?
"In theory, yes," he said. "We could see how this 'flow' of galaxies is related to the properties of dark energy. ... The more accurate we are with this measure, the more precise we can be with our models."
Check out the University of Washington's news release about the research, as well as Science magazine's report on the dark side of the universe. |
Last edited by DanS on 17-03-2005 at 22:34
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Cruddy
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Love this subject - thanks for the links.
I don't see it being terribly useful on planets, but orbital possibilies are quite staggering...
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Cruddy
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quote:
Could somebody with knowledge about physics explain to me in laymen's terms why these three observations/theories are probably unrelated?
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The zero energy thing I had explained to me in laymans terms - take a volume of space, and empty it of all material.
There will be a low level of energy output from it.
This energy is produced when a particle of matter pops into existence spontaneously. However, there is just as much chance as a particle of anti-matter spontaneously arriving in the same spot - the particles collide and disappear, leaving behind the zero state energy.
Dark Energy is again speculative and theoretical - imagine a force like gravity which instead of attracting, actually repels massive objects.
Dark matter is probably the most solid of the lot - physicists spent a long time deciding on the approximate mass of the universe and couldn't find nearly enough by direct observation.
So they just decided "it must be there - we just can't see it".
Hope this lot helps.
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Bill3000
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of Soloralism
Jul 1999
time: 00:21
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*Pops back into Apolyton roughly 4 or 5 years after he last posted*
First of all, gravity is really differenty from the other fundamental forces; In General Relativity, it is caused by the curvature of spacetime being warped by the presence of matter. (For instance, the acceleration due to gravity on earth is mostly because of time dialation rather than an actual force.) Thus, it cannot have a real potential energy function. However, it is theorized that like electromagnetism, there can be a form of radiation caused by the flucutation of the spacetime fabric. Still, gravity is the weakest fundamental force, and thus it's very hard to even remotely observe this time of radiation (Actuall, it would be a form of length contration and such rather than radiation like light.)
The idea of the rest energy (Don't confuse this with the energy from the rest mass; I mean the energy when the temperature is at absolute zero) was theorized, rather easily using quantum mechanics. But I'm not getting to the point. 
The modern version of the "ether" is ironically, the vacuum itself. Quantum field theory is based on the fact that particles can be created from vacuum flucuations (And it is these particles, called virtual particles because they cannot be observed by definition, that cause the forces) The vacuum energy does exist, but still - the point is that even when you include all of the normal mass of the universe and its energies, it only accounts for 5% of the total mass/enegy of the universe. The vacuum energy is actually very small (Believe it or not, 10^-120 smaller than originally predicted) so it cannot account for dark matter and dark energy.
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DanS
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Kickball Capital of the World
Jan 1970
time: 00:21
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Hey Bill. Sure been a while. Welcome back! Hopefully, your beard is a little grayer. 
I understand your post only slightly, but I'm trying to get all I can out of it.
quote:
The modern version of the "ether" is ironically, the vacuum itself. Quantum field theory is based on the fact that particles can be created from vacuum flucuations (And it is these particles, called virtual particles because they cannot be observed by definition, that cause the forces) The vacuum energy does exist, but still - the point is that even when you include all of the normal mass of the universe and its energies, it only accounts for 5% of the total mass/enegy of the universe. The vacuum energy is actually very small (Believe it or not, 10^-120 smaller than originally predicted) so it cannot account for dark matter and dark energy. |
OK, so if I'm understanding this correctly, we may have two "ethers", one being dark energy and the other being vacuum energy? Or is it unwarranted to ascribe a possibility to something for which we know little to nothing about (e.g., we don't know enough about dark energy to assume that it is uniform across space)?
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Bill3000
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of Soloralism
Jul 1999
time: 00:21
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quote:
Originally posted by DanS
Hey Bill. Sure been a while. Welcome back! Hopefully, your beard is a little grayer.
I understand your post only slightly, but I'm trying to get all I can out of it.
OK, so if I'm understanding this correctly, we may have two "ethers", one being dark energy and the other being vacuum energy? Or is it unwarranted to ascribe a possibility to something for which we know little to nothing about (e.g., we don't know enough about dark energy to assume that it is uniform across space)? |
About the vacuum energy, yes. However, dark energy we simply don't understand at all. It doesn't even have to be a type of energy but rathyer be a way that gravity acts on a very large scale. For instance in M-theory, gravity is hypothosized to actually be as strong as electromagnetism. However, we would live in more than 3+1 dimensions. (10+1 to be precise) The universe would be located on a brane, basically something akin to the thin layer of solid stuff on a stew. Normal matter/energy (e.g. most of the forces, all of matter, etc) cannot move out of the brane, but gravity can. So, gravity would leak out of the brane and it would seem weak to us. This is an example of how gravity could act differently; actually, there's an article on this possibility to describe dark energy. I should probably post a link to it.
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Provost Harrison
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The farce is strong with this one.
Feb 2000
time: 05:21
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quote:
Originally posted by Bill3000
*Pops back into Apolyton roughly 4 or 5 years after he last posted*
First of all, gravity is really differenty from the other fundamental forces; In General Relativity, it is caused by the curvature of spacetime being warped by the presence of matter. (For instance, the acceleration due to gravity on earth is mostly because of time dialation rather than an actual force.) Thus, it cannot have a real potential energy function. However, it is theorized that like electromagnetism, there can be a form of radiation caused by the flucutation of the spacetime fabric. Still, gravity is the weakest fundamental force, and thus it's very hard to even remotely observe this time of radiation (Actuall, it would be a form of length contration and such rather than radiation like light.)
The idea of the rest energy (Don't confuse this with the energy from the rest mass; I mean the energy when the temperature is at absolute zero) was theorized, rather easily using quantum mechanics. But I'm not getting to the point.
The modern version of the "ether" is ironically, the vacuum itself. Quantum field theory is based on the fact that particles can be created from vacuum flucuations (And it is these particles, called virtual particles because they cannot be observed by definition, that cause the forces) The vacuum energy does exist, but still - the point is that even when you include all of the normal mass of the universe and its energies, it only accounts for 5% of the total mass/enegy of the universe. The vacuum energy is actually very small (Believe it or not, 10^-120 smaller than originally predicted) so it cannot account for dark matter and dark energy. |
Jesus Bill, where did you get all that from?! Welcome back BTW...all that is needed is the return of The Brain and then armageddon will have commenced 
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Ramo
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Austin, Texas, USA
Oct 1999
time: 23:21
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Well, the ZPE comes from the idea that over short times, there's uncertainty in energy (which is a result of the Hamiltionian operator not commuting in general with an arbitrary observable, rather <[H,A]> = i(hbar)d< A>/dt, if you were curious ), causing particles to pop in and out of existence. So, there's a vacuum energy density due to these particles that permeates space. Because pressure can be thought of as -dE/dV, and because energy actually increases when the volume of a given vacuum increases, the pressure due to the vacuum energy density is negative. Now, Einstein's field equations impose a dependence on pressure as well as mass, so imply that the vacuum energy density, in the absence of mass or positive pressure, would cause an outward acceleration.
ZPE is a form of "dark energy." Another form is called quintessence, which is somehow based on temporal variation some scalar energy field, and something I know nothing about.
Dark matter is the stuff theorized to account for what's seen as missing mass.
I've never heard of a Telsa energy.
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17-03-2005 22:27
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