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View Full Version : Discussion: Searching for Gravity Waves



Fraser
2005-Apr-05, 05:06 PM
SUMMARY: When he developed his General Theory of Relativity, Einstein predicted that the motion of large masses should create ripples in spacetime called gravity waves. Now 100 years after his theory, a precise instrument is being prepared that should be able to find out if he was right or not. A joint ESA/NASA mission called LISA (Laser Interferometric Space Antenna) will launch in 2012. It will consist of three spacecraft flying 5 million km apart, which measure their distances from each other precisely. LISA should be able to detect black holes and neutron stars as well as echos from the Big Bang.

View full article (http://www.universetoday.com/am/publish/searching_for_gravity_waves.html)

What do you think about this story? Post your comments below.

Ola D.
2005-Apr-05, 05:33 PM
LISA mission sounds cool. That's great!

TuTone
2005-Apr-05, 05:54 PM
If Einstein's theory is correct, then what? What does that mean?

The Near-Sighted Astronomer
2005-Apr-05, 07:23 PM
More importantly if there are no gravity waves it means that gravity moves instantaneously through the space-time continuum...

StarLab
2005-Apr-06, 12:11 AM
Dang&#33; Why&#39;s it gotta be so darned far into the future? <_<

TuTone
2005-Apr-06, 04:44 AM
I want to know how Einstein came up with this theory. What kind of measurements did he use to conclude that? He&#39;s never been out of space how would he know about ripples of gravity?

SCHNECK
2005-Apr-07, 11:35 AM
More parameters:

The atmospheric gravity wave induced airglow fluctuations of the Hydroxyl OH Meinel and other bands are routinely observed using CCD imagers operating in the near infrared wavelenght region.

The CO2 absoprtion bands offer a major advantage to eliminate albedo effects.

http://sprg.ssl.berkeley.edu/adminstuff/we...2000_grl_41.pdf (http://sprg.ssl.berkeley.edu/adminstuff/webpubs/2000_grl_41.pdf)

The 1999 solar eclipse provided a rare opportunity to observe the OH atmospheric photochemistry : Hydroxyl radical and ozone measurements (Oxidative Capacity)during the 1999 solar eclipse :Geophysical Research Letters Vol 27 NO 21 Pages 3437-3440, 2000

http://dx.doi.org/10.1029%2F2000GL012164

wstevenbrown
2005-Apr-07, 03:27 PM
Dear SCHNECK:
I enjoyed the Berkeley article hugely. I salute the authors&#39; ingenuity, and I see wide application for the method. But. There was a great deal of more basic material which was unsaid/assumed. Perhaps it&#39;s in the extensive reference list.

For instance: The patterns they were analyzing looked like solitons to me. A good &#39;solid&#39; analogy would be the yardang patterns in the Sahara and the Rubh Al Khali. How did the authors determine that the patterns under examination were in fact propagating gravity waves and not ordinary aeolian interference patterns? Is there any stereolocation data pointing to the source events? Would an array of such sensors provide same, like the lag times in gravity-lensing events?

I need a little help connecting the dots. A gentle nudge would suffice. :D Steve

kkurtlove
2005-Apr-07, 08:36 PM
Apologies I am not getting this. Well beyond me.
Please help.
I feel like a blind man in a dark room looking for a black cat that isn&#39;t there.

I guess the first thing is, "what is the wavelength of gravity?" is it smaller than a light year?.
Would it be a set or varying frequency? AM or FM.
With light, we talk FM, is gravity AM? Has that been determined? Does source size matter in frequency as it does intensify space-time curvature?
If the effect of gravity follows the inverse square rule for drawing power,
how could a gravity wave be at a different speed?
But are they talking about a gravity wave or rather a space-time wave.

Would the solar wind buffet the craft? How would you calibrate the interferometer?
Or just pick a time to start and measure variation.

How to we determine the source.
There are many galaxies out there and at different distances and vectors. How would you distinguish "a" wave?
How would the waves from M33 be distinct from our sun&#39;s waves?
The very next article in the mailing is "Starburst Galaxies Hide Black Holes". Would this be a reinforced wave?
Would there not be waves from every direction from every gravity source in the cosmos?

If all that is nonsense, I have more. 3 observation points?
By the wildest of probabilities, if the distances between the 3 points would be in phase with the wave length,
(I think the drawing shows this), and (wave speed = light wave speed)
would you see nothing?
Slight variations of phase, without knowing that wavelength, would also distort the measurement.

I think 20 craft would be better. Line them up at varying distances.
This would guarantee that no one phase would cause a problem.
How about using our sun.

What would happen if they used an atomic clock to send a timed laser pulses from each craft to a single receiver.
They could measure the differences in intervals.
A space-time wave may not wobble an object nearly as much as it may distort the clock intervals.

But again, not knowing the wave length would be an issue.


thanks for your help in this.

wstevenbrown
2005-Apr-07, 09:21 PM
LISA and experiments of the Berkeley type should be expedited. Much to the chagrin of the experimenters, ground-based experiments like GEO and ALLEGRO have so far detected long-haul truckers and lumberjacks.

http://lisa.gsfc.nasa.gov/Science/OtherLinks.htm

LISA in the near future should nail it down as to whether gravity-waves exist. The Berkeley-type experiments have at least detected something. Best regards-- Steve

Greg
2005-Apr-08, 01:59 PM
It would be amusing if a ground-based project scoops this mission by making the discovery first. A similar race against time between space and ground observations occurred with Gravity Probe B. So does this mean we should get these space based missions off the ground faster from the conceptual phase, or not bother at all and wait for ground based observations to get the desired results? Or does the competition between the initiatives spark better and faster science?

wstevenbrown
2005-Apr-09, 01:30 PM
Or does the competition between the initiatives spark better and faster science?

Competition yields evolution. Even negative results, which don&#39;t generate as much eclat, are good science. Best regards-- Steve