Slashdot Mirror
A Galaxy-Sized Observatory For Gravitational Waves
KentuckyFC writes "Gravitational waves squash and stretch space as they travel through the universe. Current attempts to spot them involve monitoring a region of space several kilometers across on Earth for the telltale signs of this squeezing. These experiments have so far seen nothing. But by monitoring an array of pulsars throughout the galaxy, astronomers should be able to see the effects of gravitational waves passing by. They say such an array of pulsars should effectively shimmer as the gravitational waves wash over it, like a grid of buoys bobbing on the ocean. That'll create an observatory that is effectively the size of the entire galaxy. These observations should be capable of monitoring how galaxies and supermassive black holes evolve together, and shed light on the physics of the early universe. Best of all, the next generation of radio-telescope arrays should be capable of making these observations at a cost of around $66 million over ten years. That's a small fraction of the hundreds of millions that Earth-based observatories have already cost."
Just wanted to point out that the pulsar timing array approach will cover a completely different frequency range (~ 10^-9 to 10^-7 Hz) to existing ground-based detectors (LIGO, Virgo and friends), which operate in the 10^1 to 10^4 Hz range. In between are projects like LISA (http://lisa.jpl.nasa.gov/).
The different frequency ranges mean different astrophysical sources of gravitational waves; generally speaking, the more massive the system, the lower the GW frequency. LISA, for instance, would see the radiation produced by the supermassive black holes at the centres of galaxies, while the other detectors would be targetting much smaller systems.
A human landing on mars gives us pretty pictures and a bunch of cozy, warm feelings.
Understanding fundamental physics (and mathematics) gave us the computer age along with keeping Moore's "law" working for the past 40 years. What did physics ever give to you? Pretty much every major engineering invention since 1950 depends on it in some way or other.
It takes a man to suffer ignorance and smile
Be yourself no matter what they say
> We spend billions on observatories, but what's the point?
Calm down. There is a depression going on.
All that money enters the economy employing everyone from astronomer to shoe-shine guys. In the mean time some science gets done.
If your tag line is to be believed, you will forgive us if we wait till you are actually OUT of your mom's basement before we task you with prioritizing our national science budget.
Sig Battery depleted. Reverting to safe mode.
That's correct. Lack of evidence isn't enough to disprove a theory; what you need is evidence that directly contradicts the theory. In the case of gravity waves, it might be observation of an event that should produce detectable gravity waves, combined with our not detecting them.
And, while I'm at it, I'd like to point out that what Popper taught us was that a theory was useless unless there's a way to falsify it, at least in theory. If you can find a way to show that any conceivable experimental results can be viewed as confirming the theory, it's useless because it can't be tested. In the case of gravity waves, they're but one of many things predicted by General Relativity, and one of the few that's not been observed as yet.
Good, inexpensive web hosting
Since when does everything science accomplish have to have immediate material benefit to humanity? Science is the advancement of Homo sapien knowledge about the universe. If you're going to complain about spending money complain about throwing trillions of dollars at the people who brought down the economy. Some people need to grow up.
What do you mean finding absolutely nothing?
Judging by his links to thunderbolts.info, what I think he means is "I'm a crazy idiot who doesn't understand anything, and think this is a sound foundation to question the work of scientists everywhere. Solar wind is caused by an electric field! What do you mean it's a plasma with equal amounts of positive and negative charges, and a field can't move opposite charges in the same direction? No really, I have no idea what you're talking about because I never too physics in school! But my theories are right anyway!"
The enemies of Democracy are
Exactly. So, why should we be spending money that we don't have?
Finding gravitational waves isn't going to help 99.99% of the population.
How about you look at this this way instead:
There is a lot of money going around to try to help a flailing economy. Why should that money go ONLY to those who have been bad at their business? Automakers that don't make the right cars? Banks that don't have solid lending strategies? Why NOT give some of that money that's all going to the same economy to scientists who quietly go about their business and get things done?
Moved to http://soylentnews.org/. You are invited to join us too!
I seem to recall an experimental observation in the last few years involving Jupiter, through which they verified with about 90% certainty that the speed at which gravity propagates through space/time is equal to the speed of light.
A little googling turned this up:
http://www.nrao.edu/pr/2003/gravity/index-p.shtml
Even people that believe in pre-destiny look both ways before crossing the street.
A gravity wave, as derived from the theory of relativity, doesn't specify that the gravitational constant would oscillate - simply that the shifting of large masses, like co-orbital black holes and such, will distort spacetime in wavelike manner. Those perturbations of spacetime would travel from their origin outward at the speed of light.
It's best to think of it in terms of the bowling-ball-on-a-rubber-sheet analogy of space-time. If you take a large mass like a bowling ball and set it in the middle of a large rubber sheet, it will depress deeply nearby and taper off the further away from it you go on that sheet. If that bowling ball magically disappeared, there would be a wave that travelled across that sheet as well as if you had 2 bowling balls spinning around each other.
The way we've been trying to detect gravity waves so far (LIGO) uses lasers set up at right angles so if space were to compress or stretch in one dimension, the beams the were previously in phase would shift apart. This can detect a stretching of spacetime equal to a fraction of the wavelength of light used in the lasers.
In actuality, it is the change in the behavior of spacetime that lets us measure in that manner, but if the wave were to stretch spacetime in all dimensions, LIGO couldn't work. Hope that explains it.
Even people that believe in pre-destiny look both ways before crossing the street.
Personally, I don't believe in something like gravitational waves
Science: You're doing it wrong.
If gravity waves didn't exist, you'd have to find some other explanation for PSR B1913+16, which is a pulsar in orbit around another star. The pulsar and its companion are spiraling in together, losing energy in exact agreement with the phenomenon of gravitational radiation predicted by General Relativity. This binary pulsar system has been hailed as sufficiently convincing indirect evidence for the existence of gravity waves that Russell Alan Hulse and Joseph Hooton Taylor Jr. were awarded the 1993 Nobel Prize in Physics for its discovery.
No, it doesn't seem that the existence of gravitational waves is in any question here. The only thing is that there might be much yet we don't understand about gravity that is stifling our ability to observe them directly. It's obvious that General Relativity is far from being the final word on gravitation.
Qu'on me donne six lignes écrites de la main du plus honnête homme, j'y trouverai de quoi le faire pendre.