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Post by principled on May 8, 2011 1:58:51 GMT 1
Read the following article about the latest confirmation of Einstein's Theory of General Relativity by Nasa's Gravity Probe B project. But can anyone explain to me exactly what Gravitational Radiation is? i've googled a few sites but unfortunately the explanations leave me not fully understanding what it is and why it occurs.  P Link to article: www.guardian.co.uk/science/2011/may/07/scientists-prove-einstein-right |
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Post by StuartG on May 8, 2011 7:20:54 GMT 1
Here's an explanation: The Nobel Prize in Physics 1993 Russell A. Hulse, Joseph H. Taylor Jr. "One of the most fascinating predictions of relativity theory is that massive objects in vehement motion emit a new kind of radiation, known as gravitational radiation. This phenomenon is also described as a wave motion, as ripples in the curvature of space-time, and we speak of "gravitational waves." No one has yet succeeded in recording a gravitational wave in a terrestrial or extraterrestrial receiver, but the Hulse-Taylor pulsar has convinced us that this type of radiation actually exists. This is because the orbiting period of the pulsar around its companion gradually diminishes with time — extremely little, but in exactly the way the general theory of relativity predicts, as a result of the emission of gravitational waves. " Full text of speech: nobelprize.org/nobel_prizes/physics/laureates/1993/presentation-speech.htmlwww.davis-inc.com/relativity/Here's a resource .pdf arxiv.org/ftp/gr-qc/papers/0211/0211084.pdfNASA site: www.nasa.gov/pdf/162789main_gpb_fs.pdfwww.nasa.gov/mission_pages/gpb/gpb_results.htmlMicrosoft Academic Search: academic.research.microsoft.com/Search?query=gravitational%20radiation&s=0Pretty picture source: upload.wikimedia.org/wikipedia/commons/b/b8/Wavy.gifen.wikipedia.org/wiki/Gravitational_Radiation#Astrophysics_and_gravitational_waves"Imagine the Earth as if it were immersed in honey. As the planet rotates, the honey around it would swirl, and it's the same with space and time," said Francis Everitt, GP-B principal investigator at Stanford University. " Jillian's Guide to Gravitational Waves: www.gothosenterprises.com/gravitational_waves/parallels.htmlA bit of history, with pics: homepage.mac.com/stevepur/physics/riding/Riding_session_5.pdf |
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Post by StuartG on May 8, 2011 7:58:11 GMT 1
You'll be pleased to know that any experimentation with this phenomena will not end with a visit from the Anti-terrorist Squad: "JASON was asked by staff at the National MASINT Committee of ODNI to evaluate the scientific, technological, and national security significance of high frequency gravitational waves (HFGW). Our main conclusions are that the proposed applications of the science of HFGW are fundamentally wrong; that there can be no security threat; and that independent scientific and technical vetting of such hypothetical threats is generally necessary." www.fas.org/irp/agency/dod/jason/gravwaves.pdf |
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Post by speakertoanimals on May 9, 2011 15:31:32 GMT 1
Gravitational radiation is really rather like electromagnetic radiation.
Move some charges back and forth (like a current moving backwards and forwards in a radio antenna), and you get em waves (radio waves). These carry energy, and radiate out from the source at lightspeed.
Move a mass backwards and forwards, and in a similar way you generate gravitational waves, that radiate out from the source, and carry energy.
Except to get anything really significant in terms of grav wave energy, you need a fairly vehement motion. Hence extreme objects like colliding black holes, or binary pulsars.
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Post by principled on May 10, 2011 3:17:55 GMT 1
So, in simple terms it's a bit like a salt shaker that contains damp salt, unless you shake it hard enough nothing comes out!  Seriously, what do the maths say about this motion? Is there a specific frequency of oscillation (pulsation) above which this occurs? How is mass loss linked to gravity radiation? P |
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Post by speakertoanimals on May 11, 2011 12:45:15 GMT 1
All frequencies.
you can compute the energy lost to an orbiting system via gravitational radiation (see Wiki page). So, for earth and sun, lost power is apparently only 200 watts. To get appreciable lost power and measurable orbital decay, you need large masses at small distances.
Earth and sun are eight light minutes apart (which is a measure of distance, time light takes to cross the gap). If you have two solar mass neutron stars about half a light second apart, THEN you start to get a decent loss through gravitational radiation.
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Post by principled on May 12, 2011 3:56:16 GMT 1
STA
Thanks
P
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Post by StuartG on May 19, 2011 22:06:29 GMT 1
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Post by buckleymanor1 on May 20, 2011 0:10:33 GMT 1
I designed this over 12 years ago and applied for a patent I feel ripped off.
I named it G.I.O. gravitational interferometry observatory.
Listed a number of reasons why L.I.G.O. and and it's contemporary instruments would not detect GW and how G.I.O would.
Damn I feel cheated.
I can prove this!
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Post by robinpike on May 20, 2011 12:50:35 GMT 1
In the described experiment, it uses light passing down two paths at right angles to each other, and back again, to detect gravity waves - with the gravity wave causing stretching / compressing of the two paths. But doesn't the light travel at a constant speed with regards to the space? So won't the light not see any change in the length of the two paths?
If that basis is correct (is it?), is it that the experiment works by detecting a change in frequency of the light in the two paths?
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Post by buckleymanor1 on May 20, 2011 13:21:26 GMT 1
In the described experiment, it uses light passing down two paths at right angles to each other, and back again, to detect gravity waves - with the gravity wave causing stretching / compressing of the two paths. But doesn't the light travel at a constant speed with regards to the space? So won't the light not see any change in the length of the two paths? If that basis is correct (is it?), is it that the experiment works by detecting a change in frequency of the light in the two paths? The arms which contain the light as it passes down stretch and contract as a gravity wave passes. Which in turn should cause an interference pattern shift where the two beams recombine at the observation point(they are in a state of phase). It can be used to detect the Moon passing above,the arms contract and expand as expected and the pattern shifts. The trouble with the present longbase interferometers is they are not sensitive enough to detect GW yet. |
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Post by StuartG on May 20, 2011 17:20:48 GMT 1
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Post by StuartG on May 20, 2011 17:37:39 GMT 1
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