Who disputes that gravity is related to mass?
Posted on 10/29/2002 10:42:41 AM PST by RightWhale
Gravity waves analysis opens 'completely new sense'
PRESS RELEASE
Washington University in St. Louis
St. Louis, MO. -- Sometime within the next two years, researchers will detect the first signals of gravity waves -- those weak blips from the far edges of the universe passing through our bodies every second. Predicted by Einstein's theory of general relativity, gravity waves are expected to reveal, ultimately, previously unattainable mysteries of the universe.
Wai-Mo Suen, Ph.D., professor of physics at Washington University in St. Louis is collaborating with researchers nationwide to develop waveform templates to comprehend the signals to be analyzed. In this manner, researchers will be able to determine what the data represent -- a neutron star collapsing, for instance, or black holes colliding.
"In the past, whenever we expanded our band width to a different wavelength region of electromagnetic waves, we found a very different universe," said Suen. "But now we have a completely new kind of wave. It's like we have been used to experiencing the world with our eyes and ears and now we are opening up a completely new sense."
Suen discussed the observational and theoretical efforts behind this new branch of astronomy at the 40th annual New Horizons in Science Briefing, Oct. 27, 2002, at Washington University in St. Louis. The gathering of national and international science writers is a function of the Council for the Advancement of Science Writing.
Gravity waves will provide information about our universe that is either difficult or impossible to obtain by traditional means. Our present understanding of the cosmos is based on the observations of electromagnetic radiation, emitted by individual electrons, atoms, or molecules, and are easily absorbed, scattered, and dispersed. Gravitational waves are produced by the coherent bulk motion of matter, traveling nearly unscathed through space and time, and carrying the information of the strong field space-time regions where they were originally generated, be it the birth of a black hole or the universe as a whole.
This new branch of astronomy was born this year. The Laser Interferometer Gravitational Wave Observatory (LIGO) at Livingston, Louisiana, was on air for the first time last March. LIGO, together with its European counterparts, VIRGO and GEO600, and the outer-space gravitational wave observatories, LISA and LAGOS, will open in the next few years a completely new window to the universe.
Supercomputer runs Einstein equation to get templates
Suen and his collaborators are using supercomputing power from the National Center for Supercomputing Applications at the University of Illinois, Urbana-Champaign, to do numerical simulations of Einstein's equations to simulate what happens when, say, a neutron star plunges into a black hole. From these simulations, they get waveform templates. The templates can be superimposed on actual gravity wave signals to see if the signal has coincidences with the waveform.
"When we get a signal, we want to know what is generating that signal," Suen explained. "To determine that, we do a numerical simulation of a system, perhaps a neutron star collapsing, in a certain configuration, get the waveform and compare it to what we observe. If it's not a match, we change the configuration a little bit, do the comparison again and repeat the process until we can identify which configuration is responsible for the signal that we observe."
Suen said that intrigue about gravity waves is sky-high in the astronomy community.
"Think of it: Gravity waves come to us from the edge of the universe, from the beginning of time, unchanged," he said. "They carry completely different information than electromagnetic waves. Perhaps the most exciting thing about them is that we may well not know what it is we're going to observe. We think black holes, for sure. But who knows what else we might find?"
On the contrary, they prove that more local public funds need to be allocated to science education in public schools, and that the Federal Dept of Education should be disbanded.
Excellent question. If they have mass (do they?), presumably they can't escape. But obviously a black hole generates (so to speak) a lot of gravity, so ... as I said, an excellent question.
The square the sine of gravity waves = gravy waves/2(pork chops x mashed potatoes) + 3(high gravity Steel Reserves).....
And that is the real cause of my recent weight gain.....
We need to be careful to distinguish between the gravitational field and gravitational waves.
The gravitational field is fixed to the black hole. In a nutshell, the gravitational field is the curvature of spacetime caused by the black hole. This curvature is defined everywhere in space, all the way up to the singularity at the center of the black hole; it is even defined inside the event horizon.
Gravitational waves are changes in the gravitational field. If a black hole is accelerated, obviously the field as it exists at some arbitrary point is going to change over time. This is perfectly analogous to the way electromagnetic waves are caused by the acceleration of electrical charges. If you move a charge around, the field associated with that charge will also be moved around. These changes in the field are propagated as a wave.
So in answer to your question, don't think of gravitational waves as radiating outward from a black hole like light from a bulb; rather, think of the gravitational field as being fixed to the black hole, with changes in the motion of the black hole thereby causing changes in the field.
The fact of the inverse square law of gravity demands that gravitational radiation be massless.
presumably they can't escape.
Light is massless, but still that can't escape from a black hole.
You need to think in terms of inertial frames. Event horizons, for example, exist between locations not because there is some physical barrier between them, but because the difference between the inertial frames exceeds the speed of light. Signals from one point to the other can't run fast enough to catch up. It's a question of point-of-view.
Gravitational waves are also a point-of-view thing. The Earth, for example, radiates gravitational waves into space as it whips around the sun. The planet Mars, for example, feels (however feebly) the changing gravitational field of the Earth as it wobbles back and forth in its orbit. We here on Earth, however, can't feel those waves. It doesn't make sense to talk about measuring them as they travel from the center of the Earth on their way to Mars, for the simple fact that the waves don't travel along any such path. From where we're sitting, the gravitational field of the Earth doesn't change at all; there are no such waves to measure, from our point-of-view.
No higher than the speed of light...unless Einstein was wrong about the fundamental assumption in his relativity theories. Of course if he was then using his theories to predict the shape of gravity waves would seem to not be very productive. Regardless, we are bound to learn something from all this.
To an observor outside of and away from the hole, time for the matter falling into the hole slows down as it approaches the event horizon. At the instant the matter reaches the event horizon, "its" time "stops" (again, for an observor away from the hole). All the matter that fell into the hole over its history is "at" the event horizon, not "inside" it, to an observor outside.
It is different for a co-moving reference frame with the matter approaching the horizon. In that reference frame, time continues and it goes right across - while time in the rest of the universe, looking back out, speeds up. Matter crossing an event horizon is "falling out of our space-time", not just going somewhere inside of it.
Who disputes that gravity is related to mass?
I just finished it. A good read!
I don't completely understand what you're saying, here. (The statement "the field actually increases but is still non radiating" is probably wrong.) There is a gravitomagnetic effect caused by special relativity, but it's pretty subtle because, unlike electromagnetic field, the gravitational field has no dipole moment.
All orbiting charge does not radiate, for example the electron orbiting the atom. What causes the earth to radiate or not radiate when it orbits the sun?
Electrons don't always radiate when they orbit around the atom because they're hard up against the Heisenberg Uncertainty Principle; there's no lower energy state available. There is no such consideration when it comes to the Earth in its orbit. It will radiate gravitational waves continuously.
What gives the phase quadrature components so it doesn't radiate? Or what are the in phase components to give the radiation? Gravity then must have a wavelength and phase in order to radiate.
Again, I don't really understand what you're saying. "Gravity" doesn't have a wavelength, as it's a field. (Geek alert: if gravity can be described by a quantum field theory, then the field could be decomposed into an infinite superposition of quantized virtual gravitational waves, just as the EM field can be described as an infinite series of virtual photons. But that doesn't mean that the field would in any sense have a wavelength.) Gravitational waves--that is, changes in the gravitational field--would have definite wavelengths. It's a whole new spectrum.
The difficulty in detecting gravitational waves is primarily due to their long wavelengths. For example, the gravitational waves radiated by the Earth have a wavelength of exactly one lightyear, because it takes the Earth exactly one year to complete one cycle. Measuring such a wave would require an apparatus of about that scale. LIGO is designed to measure much shorter wavelengths, but the processes that generate gravitational waves with such a short wavelength are few and rare.
For one thing, the sky looks incredibly different when you look at different frequencies of photons. If you look at visible light, you have the enormous powerhouse of the sun, the band of the galaxy, the Magellanic Clouds, and some very bright stars. If you look at gamma rays, you see an isotropic distribution of point sources. If you look in the far infrared, you see the galaxy, the dipole anisotropy caused by the proper motion of the Earth with respect to the cosmic background radiation, and the cosmic background radiation itself. The x-ray and radio bands show you other things besides.
I would expect that the appearance of the gravitational sky would also be strongly frequency-dependent. Quasars, binary pulsars and galactic clusters would figure prominently, I imagine, as would the rapidly moving stars at the center of our galaxy. The most interesting possibility is that the brightest sources may well be sitting back at the inflationary epoch, far earlier than anything we can see with electromagnetism.
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