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Nov4-06, 03:35 PM
P: n/a
In article <>,
Jonathan Thornburg -- remove -animal to reply <> wrote:
>I wrote:
>FearlessFerret <> 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.

Jonathan is exactly right. I just wanted to add one other point.
Even if a space-based experiment is ultimately necessary to get to the
science goals, it may be cost-effective to do the best you can from
the ground first, as a way of developing technology and working the
bugs out before mounting the space mission.

As an example, think of cosmic microwave background (CMB)
observations. The space-based missions (COBE and WMAP) were essential
-- no ground-based experiment could ever have done what they did.
(And we hope that we'll be able to say the same thing about future
satellite missions -- Planck soon and maybe someday a CMB polarimetry
satellite.) But COBE and WMAP could not have been as successful as
they were if they hadn't "stood on the shoulders of giants," namely
the incredible efforts of the ground-based and balloon-borne CMB

Just to be clear, I am not saying that the suborbital CMB experiments
were *only* technology pathfinders for the space probes; on the contrary,
they returned very important science of their own.

CMB science is one area in which a space-based mission was clearly "the
right way to go," but it would have been utterly crazy to neglect
the suborbital experiments in favor of a space mission. The right
thing to do was to push hard on the suborbital program while
simultaneously trying to make the case for a space mission.
I don't know for sure that the same is true for the gravitational-wave
business, but I suspect that it is.


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