DarrenBaker, a gravity wave is not a change in the gravitational constant; it is a deformation of the space-time fabric itself. So it doesn't change the gravitational (attractive) force between masses but simply moves the "fabric" on which they lie.

Imagine a stretchy, rubber fabric that you pull/push or move upward/downward from one side such that a wave propagates through. Then two masses lying on this fabric, link ping pong balls that you would stick on, would move closer/further apart. That's basically the effect that people are trying to measure. Of course, if these "test" objects are perfect in such that they're infinitely small, everything behaves in a trivial way. The catch is when your object is not "perfect" anymore and possesses some finite size. This seems to be concept that you worry about and you are right. Because of it's finite size, the object itself would change size. However, it does not matter at all because this change is not significant. Here's why:

The amplitude of a gravity wave is express in a weird unit expressing the ratio of the spatial compression in one direction to the stretching in the orthogonal direction (see the nice animation here). A typical gravity wave would have an amplitude of 10^-20., which basically mean that any object would change size by this fraction. So this is practically undetectable unless you consider something really big like the "arms" of the LIGO gravity wave detectors or this pulsar timing array. The other thing to take into account is the fact that what you are trying to detect acts like a wave. Waves that this pulsar array is after have frequencies of nanohertz, or wavelengths of 3*10^17 meters (this is about 32 light-year!). For LIGO, frequencies are the order of 1 hertz, so 300 000 km. Hence if your object, the pulsar for the pulsar array, or the mirror/detector for LIGO is much smaller that the wavelength that you attempt to detect, it really doesn't have any effect on what you are trying to measure.

In fact that's what do they all the time, although they don't do it for the same reason that you were thinking about ;-) They typically run it for a couple months and then shut it down for a while to do some more calibration, tweaking and improvement. These results are from the fifth run.

I know it's probably a silly idea but since a lot of cows (at least milk cows) spend most of their time inside, wouldn't there be a way to have the air circulation system go through some kind of filter that would recuperate methane? Instead of just wasting it in the atmosphere farmers could at least use it as an energy source that would allows them to save electricity, which comes -- at least partly -- from fossil fuel?

BTW what's the status of methane recuperation from the big stacks of stinky manure sitting outside barns?

Hubble and Herschel's orbits are not even comparable to each other.

As pointed out earlier in a separated thread, Hubble is in a low, circular orbit about 560 km above the Earth. It has has a low inclination -- about 28 degrees with respect to the equator. You can actually see the orbital details and where it is in the sky on Heavens Above. The low Earth orbit was chosen so that the space shuttles could service it as they can't reach very far orbits basically due to limitation i how much fuel they can carry (bear in mind that at launch the shuttle engines are powered by the huge orange tank attached to it). It would have to be double checked but I think that the low orbital inclination was decided because it's was easier to launch -- Hubble is one of the most massive payloads ever carried by a space shuttle -- since you benefit from the fact that the Earth rotates so it effectively adds up to your velocity whereas for a polar orbit the contribution is basically null.

On the other hand, Herschel is orbiting 1.5 million km away from the Earth at the L2 point, in a direction opposite to the Sun -- the Sun - Earth - Herschel system forms a straight line. To give you an idea of the scale, the Earth-Moon distance is about 385 000 km so Herschel is located 3.9 times further. Therefore it's easy to understand why the mission is a one-hit wonder because there is no way someone is gonna go there fix it. To be more precise, Herschel is actually "orbiting" about the L2 point (see this diagram on Wikipedia) otherwise its orbit around the Sun-Earth-Moon system would be too unstable. The main reason for sending Herschel so far away from Earth is to optimize its infrared performances. Herschel observe at very long infrared wavelengths compared to, say, the the infrared camera of Hubble and near the Earth, even though you are in space, there is still a lot of thermal radiation coming from the Earth as well as the radiation belts that add up on top of what you want to detect. By being further away, passive cooling helps you and the liquid helium that keeps you cryostat cold heats up slower so your instrument has a longer life time. Also, "temperature" fluctuations are much smaller out there whereas they can be quite large near the Earth depending if your in the Earth shadow, crossing a radiation belt, etc. More stable environment means smaller systematics, which, in turns, imply better telescope sensitivity.

Finally, note that Hubble's successor, JWST will also hang out around L2 for similar reasons.

I felt like it was April's fool when I read this /.. Isn't ironic to read an article about Scientology being bashed when the Google Ads displayed at the top of the page is one about the Scientology Church? This made my day!