Talk:LIGO
We need to add a subsection with a description of the interferometers and how its possible for them to measure such small distances.
Two things strike me about this summary. First, how do the detection facilities account for the overwhelmingly powerful effects of even very minor earthquakes that occur every day at multiple locations around the earth?
- Multiple detectors in several locations of same cosmic event. Allows one to subtract local noise. (Not just earthquakes, this experiment detects slamming doors.) Someone who knows more, add more. GangofOne 07:00, 7 August 2005 (UTC)
Second, the last paragraph of this summary is a thinly disguised plagarism of the LIGO-detectors web summary. If I pulled that in my work it would be ixney-on-hombre if you catch my drift...maybe someone with a good technical grasp of this could re-write it in a more "original" context instead of rewording a website summary. - JS 6-10-05
I added an external link on discussion of vibration and interference.
ligo
I have a question on why study the gravitational waves? What do we gain from it?? User:Sjml9
- Why did Maxwell waste his time studying Electromagnetism. Everyone knew it wasn't good for anything back in 1864.
- Actually, although you weren't taught it in either high school or college, Maxwell's development of what are now known as Maxwell's equations was far more important than any other single event (or group of events) in the 19th century! The Mexican-American War—trivial. The American Civil War; in spite of what you were taught—trivial. The abolition of slavery in much of the world; well that's a little more important, but still small shakes compared to Maxwell's equations.
- Maxwell's equations, developed in 1864, set the stage for electric lights powered by AC current, radio, television, computers, space flight, and almost everything we consider routine today. You'd still live in a world lit by fire without Maxwell's equations!
- No one can assure you we're not wasting our time and money looking for gravitational waves. But your great-grandchildren (who will think your life was as primitive as you think your great-grandparents lives were) will live in a different world than you can even imagine.
- Williamborg 03:52, 1 July 2006 (UTC)
- And finally, I must admit I've been awaiting with some impatience the experimenters publication of some discovery. Once we actually detect gravitational waves we'll get some sense of the significance of the event...
- Hmm, I'm not sure any of these replies actually answer the user's question. The study of gravitational waves are needded to explain and/or confirm a number of phenomenon more directly. Some are entirely hypothetical, others only indirectly observed. This part from the article, recently updated by me thanks to a great online lecture by Kip Thorne himself (co-founder of LIGO), should help answer your question: -- Northgrove 05:34, 1 January 2007 (UTC)
Predicted significant emissions of gravitational waves are expected from binary inspiral systems (collisions and coalescences of neutron stars or black holes), supernova collapses of stellar cores (which form neutron stars and black holes), rotations of neutron stars with deformed crusts, and the remnants of gravitational radiation created by the birth of the universe. The observatory may in theory also observe more exotic currently hypothetical phenomenon, such as gravitational waves caused by oscillating cosmic strings or colliding domain walls. Since the early 1990s, interferometer physicists have believed that technology is at the point where detection of gravitational waves—of significant astrophysical interest—is possible.
- The following text, below, is a copy of a post I found around the internet somewhere. I would like the answer to this also, so I copy post it here, to be mulled over, digested and hopefully, answered! --87.115.10.14 (talk) 07:05, 19 January 2008 (UTC)
Just getting back to LIGO for a while (sorry if this isn't strictly on topic), I understand that two long laser beams, at 90 degrees to each other, split from one laser source originally by a semi-silvered mirror, are re-combined at a sensitive detector to see whether their wave forms are cancelling or reinforcing. A passing gravity wave will sequentially lengthen and shorten the wavelength of only one of these light beams because the space-time continuum is distorted in only the direction of travel of the gravity wave. This, it is assumed, will cause the interference of the two laser beams to vary also - causing a variation in the light level measured at the detector.
I still don't see why LIGO will work because a gravity wave is indiscriminate in the way it distorts things. Everything is embedded in our 4-space, including the laser light waves lying along the direction taken by the gravity wave. As the gravity wave compresses and then dilates space-time, the LIGO tube and the laser beam within it will compress and dilate in perfect synchrony. Even the human observers' heads will compress and dilate as the gravity wave passes! The number of light waves per unit length of the LIGO tube (the laser wavelength) will appear unchanged because the actual physical length of the tube will shorten and lengthen as the light waves do, and as the eyeballs of the experimenters do too. If the waves of the re-united beams were re-inforcing peak-to-peak before the gravity wave arrived, they will remain peak-to-peak as the gravity wave passes through also. This alteration in the length of the tube, or arm, of the LIGO experiment, together with the variation in the wavelength of the laser beam, will be completely undetectable for that reason. It's not a case of the gravity waves being too weak to detect, their influence is universal within our frame of reference and therefore cannot be directly detected .. by definition!
The above is the way I see the situation. But dozens of scientists have spent billions of dollars designing LIGO, so I have to conclude I'm completely incorrect in my reasoning.
Can anyone tell me how you can measure a distortion of space-time (4-space) if you, and every tool you use to measure the distortion, including light, are part of the same space-time being distorted? ???