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Physicists hope the ambitious mission will allow them to prove the existence of gravitational waves – a phenomenon predicted in Einstein's famous theory of general relativity and the last piece of his theory still to be proved correct. The mission, a collaboration between Nasa and the European Space Agency, will use three spacecraft flying in formation while orbiting the sun, with each housing floating cubes of gold platinum.
Laser beams fired between the spacecraft will then be used to measure minute changes in the distance between each of the cubes, caused by the weak waves of gravity that ripple out from catastrophic events in deep space. Einstein's theory of general relativity predicted that when large objects such as black holes collide, ripples in space and time flow outwards. These ripples are called gravitational waves.
Professor Jim Hough, an expert on gravitational waves at Glasgow University and a member of the committee that drew up the plans, said: "Gravitational waves are the last piece of Einstein's theory of general relativity that has still to be proved correct. "They are produced when massive objects like black holes or collapsed stars accelerate through space, perhaps because they being pulled towards another object with greater gravitational pull like a massive black hole.
Scientists have already been able to prove a number of predictions made by Einstein's theory of general relativity, including that light is bent by gravity, gravity travels at a constant speed, that time can be warped by gravity and that space and time can bend. Einstein's other theories including his most famous formula E=mc2 have also withstood scientific testing.
The Laser Interferometer Space Antenna, or LISA as the new space based mission is called, will be able to detect gravitational waves of very low frequencies due to the huge distance between the three spacecraft. It will be the largest detector ever built. A smaller test mission called LISA Pathfinder, which is being built by British engineers at space company Astrium EADS and is due to be launched next year, is to pave the way for the more ambitious mission by demonstrating the technology to be used to detect the waves.
I want to know how God created this world. I'm not interested in this or that phenomenon, in the spectrum of this or that element. I want to know His thoughts, the rest are details.
The orbit has decayed since the binary system was initially discovered, in precise agreement with the loss of energy due to gravitational waves predicted by Einstein's General Theory of Relativity.
Originally posted by Phage
reply to post by rhinoceros
A null hypothesis applies to theories for which a falsifiable experiment can be performed. The theory is that gravity waves exist. The null hypothesis is that gravity waves do not exist.
By detecting gravity waves it can be demonstrated that they exist, it only takes one detection to prove the theory true and the null hypothesis false.
But it may not be true (I don't know) that the failure to detect gravity waves with LISA would prove that they do not exist. Gravity waves have not been detected by other methods. This does not mean they do not exist, or else the search would not continue.
This experiment is not a test of the null hypothesis. It is a test of the base hypothesis, that gravity waves exist and are detectable with LISA.
[edit on 5/11/2010 by Phage]