Re: Detection of Gravitational Radiation



I wrote:
The (overwhelming) consensus among experts is that no gravitational
waves (of any waveform shape) have yet been directly detected.

FearlessFerret <ff@xxxxxxxxxxxxxxxxxxxxxxxxxx> wrote:
I've always been of the opinion that terrestrial GW detectors are a
complete waste of effort (except maybe as an interesting engineering
problem) when you can put one in space and make it millions of times
bigger without any noise problem.

Not that a space-based system could be built for the same cost, but here
on earth you're hamstrung by the signal-to-noise ratio.

If gravitational-wave detector people had as much money to play with
as (say) the pentagon, they probably would build lots and lots of
detectors in space. Alas, in the real world you have to do the best
science you can within (very) finite budgets, and doing things in
space costs a *lot* of money.

Of the major ground-base GW detectors now running or almost-running:
* In (very) round numbers, the US spent around $300 million to build
the 2 LIGO detectors (ground-based).
* I'm less knowledgable about the budget of the French/Italian Virgo
detector, but I would guess it's on the order of 100 million Euros.
* The UK-German GEO600 detector was very cheap, perhaps 15 million Euros
(it's 1/5 the size of LIGO and Virgo, and used a lot of volunteer
labor to help keep costs down).
* I don't know the budget of the Japanese TAMA300 detector.

There is indeed a project underway to build a space-based GW detector.
It's a joint US-European project called LISA (Laser Interferometer Space
Array). It's designed to be sensitive to a much lower frequency band
than the ground-based detectors (milliHertz instead of 100s of Hertz).
LISA should be *very* sensitive, and do *great* science.

However, LISA won't be launched until 2015 at the absolute earliest,
and its total budget will probably be close to 1000 million dollars
or Euros. And alas, the most recent US budget proposals would *not*
provide funding for US LISA development in the next US fiscal year.
There are hopes that the US may have funding available starting in
their 2009 fiscal year.

See the LISA web sites
http://sci.esa.int/science-e/www/area/index.cfm?fareaid=27
http://lisa.jpl.nasa.gov/
http://www.lisa-science.org/newsletter
for more information.

I think we need *both* ground-based GW detectors (which are running
now, and can do excellent science at moderate cost) *and* space-based
detectors in the future.

[Conflict-of-interest disclosure: My institution operates GEO600,
and has a major role in LISA. My boss's boss is chair of the LISA
science working group.]

--
-- "Jonathan Thornburg -- remove -animal to reply" <jthorn@xxxxxxxxxxxxxxxx>
Max-Planck-Institut fuer Gravitationsphysik (Albert-Einstein-Institut),
Golm, Germany, "Old Europe" http://www.aei.mpg.de/~jthorn/home.html
"Washing one's hands of the conflict between the powerful and the
powerless means to side with the powerful, not to be neutral."
-- quote by Freire / poster by Oxfam

.



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