Biggest Detector To Look For Gravitational Waves 109
Hugh Pickens sends in coverage in the Telegraph of a joint NASA-ESA experimental mission, to launch around 2020. It involves three spacecraft orbiting the Sun, separated by 3 million miles, each with a payload of two lasers and a 4.6-cm cube of gold-platinum alloy. The point of it all is to look for gravitational waves. The mission is called LISA, a reasonably non-strained acronym for Laser Interferometer Space Antenna. The Telegraph makes a point of LISA being the largest experiment ever constructed (in terms of its dimensions). Neither that newspaper nor the project page at NASA mentions how much the experiment will cost, but it's almost certainly an order of magnitude or more above the $66 million estimated for a gravitational wave detector the size of the galaxy, which we discussed last fall.
not funded yet (Score:5, Informative)
I believe the slashdot summary and TFA are misleading, because they make it sound like LISA will definitely be built. According to the WP article [wikipedia.org], LISA is competing against two other space-based science projects for funding, and the decision won't be made until 2013.
Personally, I would love to see LISA fly. Gravitational waves were first predicted in about 1914. Most aspects of general relativity have been tested pretty thoroughly at this point, but almost a century later we still have no direct confirmation that gravitational waves exist (although there is very strong indirect evidence). And if they can be detected, then it opens up an entirely new way of doing astronomy: not with electromagnetic waves, but with gravitational ones.
Re:So I didn't RTFA (Score:5, Informative)
I guess they do carry energy, and we think we've seen proof of it: http://en.wikipedia.org/wiki/Hulse-Taylor_binary [wikipedia.org].
Re:not funded yet (Score:5, Informative)
The NASA and JPL mission pages don't make it clear that this is unfunded as of yet either, which is annoying since I've been reading up on this experiment for some time and am pretty excited about it!
I, too, would love to see LISA fly. We really do need robust tests of gravity waves, and a whole new world of observations will open up to us if it pans out.
One of the coolest things about the mission itself that I read about is the 'drag free' aspect. To ensure that the test masses are in free-fall around the sun without interference by things like the pesky solar wind, they're housed free-floating in a chamber inside the LISA spacecrafts themselves. The spacecraft absorbs the solar wind or other outside forces while measuring any change in relative position to the test mass and using micro-thrusters to keep itself centered on the mass and thus in the same free-fall drag-less orbit. Effin cool imo, even if I don't think it's first time it's been done. :)
Re:So I didn't RTFA (Score:3, Informative)
A gravitational wave is a "ripple in space-time".
Re:Unlike the "Galaxy sized detector" (Score:3, Informative)
...the huge scale of the equipment (3 Million Miles) is very significant -- the instruments will be able to make a fine measurement across this distance -- and comparing it with the size of the galaxy is not really a valid comparison.
It's a valid comparison because, when you're using pulsars to detect gravitational waves, the effective size of your detector is the distance from one pulsar to another, which is (some large fraction of) the size of the galaxy. Okay, pulsars aren't man-made - but if we deliberately set out to make the transmitter component of a galaxy-sized gravitational-wave detector, we wouldn't be able to produce anything nearly as suited for the task as they are. They keep time as well as our best clocks, and are trillions of times as powerful as any radio transmitter we could build (and they need to be, if we want to see them at these distances).
The snarkiness is entirely justified, I think, as a response to the Telegraph's claim that LISA is the largest gravitational wave detector, when it's not. This doesn't mean that it isn't useful, though. LISA and pulsar observations are sensitive to gravitational waves of different frequencies - about 10^-1 and 10^-9 Hz respectively - so they're complementary techniques in the same way that (say) optical and radio astronomy are.
LISA vs. Pulsar Observations (Score:3, Informative)
Re:not funded yet (Score:3, Informative)
But wouldn't that mean the cube's trajectory lead into the sun?
It'll be orbiting the sun, in an orbit much like earth's.
Re:So I didn't RTFA (Score:3, Informative)
What does gravity has to do with quantum mechanics?
Oh nothing at all. It's just one of the biggest unsolved problems in physics at the moment.
Re:Unlike the "Galaxy sized detector" (Score:4, Informative)
Hope this clears things up for you
Re:Costing (Score:2, Informative)