The LIGO detector, a US gravitational waves detector, will see a $205 million upgrade in the next seven years, making the Advanced LIGO 10 times more sensitive and boosting the number of observable galaxies from hundreds to tens of thousands.
While it might seem like a lot of money, the research on gravitational waves are very important for understanding one of the most fundamental parts (it’s one of the only four known forces) of our Universe: Gravity. Although gravity is probably the most intuitively well known force (just try to jump out of the window), we really don’t know much about it on a fundamental level, and it doesn’t fit in with the rest of the fundamental physics in the Standard Model. Einstein released his theory of General Relativity in 1916, and since then we have only verified the predictions of it, never disproven it. One of the predictions of General Relativity is the existence of gravitational waves, and we’ve been trying to detect them directly for a long time*. With the upgrade of the LIGO experiment, the probability of detecting gravitational waves will increase significantly. As the LIGO scientists says in the LiveScience article:
“With Advanced LIGO, it’d be very surprising from a relativity perspective if we didn’t observe anything.”
Not only can the gravitational waves help us investigate the gravitational force and why it doesn’t fit with the other forces further, it could also be a great tool for future astronomers and astrophysicists. The gravitational wave is shaped uniquely by its source and by traveling unhindered through space and time, they would enable us to investigate things like black holes, neutron stars and grand cosmic collisions in a way that is currently not possible by looking at the light (if any) from these objects.
* Gravitational waves have never been detected directly, but their existence has been proven indirectly by the observation of an exotic pulsar system. This system consists of a pulsar and a close companion and seems to be losing orbital energy that goes to making the gravitational waves, exactly as Einstein predicted that such a system would. This discovery was the basis of the 1993 Nobel Prize in Physics, and you should go read that press release if you’re more interested.
RSS Feed
April 15th, 2008 at 3:17 am
So how fast do gravitational waves move through space time?
April 15th, 2008 at 7:56 am
Sorry I forgot to mention…
Gravity, as described by Einsteins General Relativity propagates at the speed of light. But it’s actually very hard to measure this, for exactly the same reason that we are having trouble investigating gravity in the laboratory in general; it’s too weak for us to see it work on small scales.
So this was another great feat of the 1993 Nobel Prize winners, because the binary pulsar system allowed us to measure the speed of gravity by measuring the rate of energy loss, also called damping, of the orbital system. And of course, by using the framework of general relativity, the velocity was confirmed to be the speed of light to an accuracy of 1%.
So it still looks like Einstein nailed it pretty good the first time. Anyone who proves him wrong is guaranteed a trip to Stockholm for the Nobel Prize in Physics, you have my promise.
April 15th, 2008 at 12:18 pm
Good question, Jon B … my guess, is grav-waves propagate at 4c - four times speed of light. Have to “move” faster than light, for large black-hole to have grav influence externally. If grav-speed is only light speed, there is argument that planetary orbits would not be stable over multi-million year time frames - so a friend advises me, though have not checked the background. Finally, 4c is nice figure because if there were 4^3 = 64 times as much matter outside light-horizon, that would help explain the “dark matter” conundrum. Totally naive viewpoint on my part, but perhaps material for a few grad students to play around with some interesting hypotheses. KR
April 15th, 2008 at 12:32 pm
Forgot to mention how to do grav-speed estimation. The orbit decay problem arises because if grav-effect has finite speed (say it is c light-speed, for instance) then sun pulls earth from where it “was” 8 minutes previously - gradual effect. So if can measure orbital decay, can turn around and use that to estimate grav-speed.
Apply to very large systems, spiral galaxies, so have large group of observations. Perhaps can develop model to estimate grav-speed effect on structure, vs other causation hypotheses?
April 15th, 2008 at 12:36 pm
Ken, I dont quite follow you here…
Where did you get the 4c? Is this a new theory?
As gravitational waves carry information about the system that created them, they can not propagate faster than the speed of light without violating general relativity, causality and other nasty stuff. But of course if you’re talking about a new theory, this might not be valid. I think we really have to see some papers or authors to be able to say some more about it.
April 15th, 2008 at 1:58 pm
Hi Brink … 4c is just pulled out of hat, as reasonably good ratio grav/light to make progress on dark matter problem … ie if there were 64x as much grav-influencing mass as visible (inside light horizon) mass, then don’t have to look for dark matter in the “interstices” within light horizon. No basis for the ratio being integer 4, rather than say 3.5 or 4.5, except that integer value may excite additional hypotheses - eg maybe look at Fredkin (was that his name) propagation idea for the two types of information.
Clearly there is information “received” or “present” via gravitation, we get it now, since we invent “dark matter” idea.
Don’t have references. Just fooling around with ideas. Am retired from computers / math background, so no credentials for astro / physics. Hope to encourage someone to have fun.
Idea is “new to me” but most likely has been expored by some others. Don’t claim first, not playing that game. This is the sort of idea-fun that might occur at Sat eve group mtg, in my teens-twenties when we felt free to play with theory.
I agree would like to see papers / authors - hope someone mentions them for my info, or better, bright student writes them! The observational approach, study of spiral galaxies, may give avenues for interesting work by do-ers as well as formula lovers.
April 15th, 2008 at 2:12 pm
Well, we should definitely be brainstorming for ideas of how to solve some of the mysteries of science in simple ways, but…
Dark matter is almost certainly real. Recent observations of colliding galaxies and stuff makes it hard to explain by modifying the theory of gravity (gen. rel.), and I dont think there’s a lot of scientists today that doesn’t believe dark matter is some kind of elementary particle that we have yet to identify.
Maybe we get a step closer once the LHC start banging baryons together at enormous energies.
April 15th, 2008 at 5:40 pm
You write that $205 million might seem like a lot of money, but let’s put this in perspective, that’s for 10 years, and therefore the projects only cost $20.5 million per YEAR. The war in IRAQ is costing the US taxpayers $12 million per HOUR, day in, day out.
April 15th, 2008 at 7:45 pm
Well yeah, thats just insane… imagine all the great science we could be investigating.
And $205 million is a small amount compared to some of the biggest scientific experiment, eg. the LHC which will cost around $10 billion, but I still know a lot of people who think it’s a lot!