From an article in Fermilab Today:
Our universe is as mysterious as it is vast. According to Albert Einstein's theory of general relativity, anything that accelerates creates gravitational waves, which are disturbances in the fabric of space and time that travel at the speed of light and continue infinitely into space. Scientists are trying to measure these possible sources all the way to the beginning of the universe.
The Holometer experiment, based at the Department of Energy's Fermilab, is sensitive to gravitational waves at frequencies in the range of a million cycles per second. Thus it addresses a spectrum not covered by experiments such as the Laser Interferometer Gravitational-Wave Observatory, which searches for lower-frequency waves to detect massive cosmic events such as colliding black holes and merging neutron stars.
The absence of a signal provides valuable information about our universe. Although this result does not prove whether the exotic objects exist, it has eliminated the region of the universe where they could be present.
(Score: -1, Troll) by Anonymous Coward on Saturday April 11 2015, @08:14AM
Its Evolutionary Force
Not To Be Stopped By Anyone
And Its Beauty
Yes This Is A Happy Place To Stay
Filled With Harmony And Cosmic Joy
A Free Place Where Men Can Express Themselves
And Be As When They Were Born
All This Because Someone Cares
Because Someone Looks After Us
When We Sleep
When We Play
When We Act Natural
This Is A Movie
About Those Who Risk Life And Partners
To Guarantee A Wonderful And Free Universe
This Is A Movie About The GAYNIGGERS from OUTER SPACE
(Score: -1, Troll) by Anonymous Coward on Saturday April 11 2015, @08:29AM
Ooooh, Spooky Forest Lady,
You Are As Mysterious As You Are Beautiful!
It's Amazing!
I've Graphed Your Mystery And Beauty Over Time -
See How Well They Match!
And Then She Just Vanished?
That's Right
Without Fucking You?
Yeah!
After You Showed Her The Graph?
I Know! Who Understands Women?
Nobody. They're As Mysterious As They Are Beautiful
Within A Three Percent Tolerance
(Score: 2) by dltaylor on Saturday April 11 2015, @09:47AM
With a total dearth of evidence for gravitational waves, maybe we're on the verge of REALLY learning something.
It's going to take a very brave physicist to take on the hallowed (and amazingly often correct) Einstein, but I hope to see a verified alternate theory of space-time-gravity that explains WHY we don't detect gravitational waves more than a humdrum "yeah, we found them".
There are a lot of 'hand waving" explanations for phenomena, and many, many really bright people trying to solidify those, but here's a couple for those of you in the field: is the expansion of space quantized, and, if so, what is the quantum? Does space expand inside atoms, inside protons or other multi-quark particles, inside neutron stars or other degenerate matter, or does it only happen in volumes of low particle density (and, therefore, lower gravity)? If inside multi-quark particles, for example, what is the source of the energy to overcome the strong force?
(Score: 5, Interesting) by maxwell demon on Saturday April 11 2015, @10:48AM
While I'm not in the field, I think I understand enough of it that I can answer at least some of your questions:
I don't think anyone can give a definitive answer to that question yet, since we still don't know what is the right way to quantize spacetime (or if it should be quantized to begin with). But if it is quantized, the expansion should be quantized, too, and the quantum would be the quantum of volume (most probably something of the order of the Planck volume).
It expands everywhere (at least in non-quantized spacetime, no idea how quantized spacetime would enter), but that doesn't mean that the atoms grow because the size of the atom is determined by Coulomb attraction and quantum mechanics; imagine having an object on a treadmill, but held by a rope; despite the treadmill, the object won't move because the rope holds it back.
Now if you look closer, you'll find that the rope, while not expanding over time, will actually be slightly longer than if there were no treadmill since it the force needed to keep the object from moving slightly extends the rope due to the rope's elasticity. As far as I understand, the same happens in principle in atoms, however the difference is too small to measure. However if the expansion gets large enough, it should be sufficient to even rip atoms apart. Given that we observe an accelerated expansion, it has been hypothesized that this might indeed happen some time in the future; that scenario is known as Big Rip.
Now here things get interesting. I've never heard considerations about that; but from QCD we know that confinement cannot be broken, but as soon as you apply to add enough force trying to separate the quarks, new quark-antiquark pairs are generated, so you actually get two colour-neutral particles again. However if expansion is high enough to do that, it should immediately try to rip those apart again, causing the generation of even more quark-antiquark pairs. So it seems that the universe would ultimately get filled with quark-gluon-plasma. But then I wonder if all that new matter would not affect the further expansion of the universe; also, would the dark energy be used up for generating that matter? I guess to say more here we would need a real expert in that stuff.
The Tao of math: The numbers you can count are not the real numbers.
(Score: 2) by HiThere on Saturday April 11 2015, @06:48PM
Sounds like you've explained the source of the big bang. Which is rather interesting, and implies that the universe didn't start with the big bang, only the observable universe.
I don't know whether that would work out, but it may imply that the original creation of the universe is an indefinite number of big bangs ago, and thus it could be an EXTREMELY unlikely event. Sort of the kind of thing that's less probable than a Boltzman brain.
It's not clear to me, though, that this would imply we shouldn't expect to detect gravity waves.
Javascript is what you use to allow unknown third parties to run software you have no idea about on your computer.
(Score: 2) by kaszz on Saturday April 11 2015, @11:11AM
Perhaps there's a phenomena that blocks or disperse gravitational waves? And thus "we detected none".
Or they could be of such different magnitude of frequency that current equipment doesn't stand a chance to detect.
(Score: 2) by Immerman on Saturday April 11 2015, @03:49PM
Well, I could be wrong, but I believe that current most broadly-accepted hypothesis is that space expands everywhere at a constant rate, with the apparent acceleration being due simply to the fact that with every bit of expansion there is now more space between bodies to further expand. Assuming of course that there's no force pulling them together faster than the the space between them is expanding. But the effect is so small it really only becomes noticeable at intergalactic scales. It's estimated at ~74 km/s/megaparsec, (1 parsec ~= 3 million lightyears), or in somewhat more human terms, about 8 micrometers per century per kilometer. Little enough to be completely lost in the noise of any N-body problem, even with such a weak force as gravity. I suspect it will be a *very* long time before we can formulate instruments sensitive enough to determine whether space is actually expanding within galaxies, or only in deep intergalactic space where it's relatively flat.
It is an interesting question though, and I could see an argument to be made that, at the least, the expansion of space might be effected by the energy field density in the area, in an analogue to QM's virtual particles preferentially becoming "real" in energetically favorable situations: if space is quantized, then any time you create a "bit" of space between two attracting bodies you increase the potential energy between them. Deep in intergalactic space the change in potential energy associated with a newly-formed space-bit would be much smaller, and hence it's formation would appear much more energetically favorable.
As for expanding within atoms - it wouldn't matter. The subatomic particles can only exist at certain quantized distances from each other so if, say, the space between the electrons and nucleus expanded, the electrons would simply fall down to it's stable distance, possibly emitting an extremely low energy photon completely atypical of the atom's normal emission spectra, and then everything would be normal again. (I couldn't begin the guess the actual mechanics, but that's what I assume would happen if you suddenly crammed an extra "space-bit" inside it).
It also wouldn't matter if space expanded within a planet: atoms would move slightly further away from each other, giving a little more mobility, but nothing would stop them from immediately settling back down into a tightly-packed configuration due to gravity. It might keep the planet a little more tectonically active than it would otherwise be, but the rate of expansion is so slight that nothing will ever remotely approach escape velocity.
Orbital mechanics is pretty much the only thing operating on scales of time and space where it might make a difference, but with an orbital radius of 780 million km, the distance between Jupiter and the Sun would still be expanding at a rate of only 59m/yr... okay, I'll admit that's a LOT bigger than I assumed, but I just redid the math and it seems right... Hmm. So, I naively see two possibilities: either space is not expanding within the solar system, or it *is* expanding, but the planetary orbits are actually spiraling in at the same rate - i.e. what appears to be a stable orbit would actually be unstable in Newtonian space, suggesting that the sun is actually slightly more massive than Newtonian calculations from planetary orbits would suggest. It seems like we would have noticed such a thing with our probes though, especially considering the minuscule fluctuations in Voyager's acceleration that we've been able to detect. So that would seem to suggest that space doesn't actually expand locally (or at least expands much more slowly).
(Score: 2) by dltaylor on Sunday April 12 2015, @02:53AM
I appreciate the elucidations, but they rather prove my point. What force stretched the rope? Is that force detectable in some way? Similarly, the emission of very low energy photons as electrons resume their ground state having been displaced by the expansion of space should be detectable. Very interesting numbers about the possible effect on planetary orbits (which are not 100 % stable, BTW, due to tidal effects and drag from the solar wind); we should really be able to measure that, if expansion is occurring within the Solar System.
So, back to my initial posting: I think we may learn more from the lack of gravity waves than we would if/when we find them.
(Score: 3, Informative) by cosurgi on Saturday April 11 2015, @10:36AM
you can check the "evening lecture A" and "Lecture 27" and "Lecture 28" on https://www.youtube.com/channel/UCUHKG3S9N_QeIE2jQXd2-VQ/videos [youtube.com] they are less mathematical and quite explanatory. They are given by the director of gravitational wave detection institute.
#
#\ @ ? [adom.de] Colonize Mars [kozicki.pl]
#
(Score: 1) by inertnet on Saturday April 11 2015, @10:52AM
it has eliminated the region of the universe where they could be present.
Nuking them from orbit wasn't sufficient?