• Question: Can gravitational waves be detected experimentally?

    Asked by lakhn008 to Joel, Kristian, Tim, Venus, Zachary on 12 Nov 2013.
    • Photo: Kristian Harder

      Kristian Harder answered on 12 Nov 2013:

      Yes! when a gravitational wave hits an object, this object will stretch or compress a bit. Unfortunately this is such a small change in size that it is really really hard to measure. Plus, you have to learn how to tell gravitational waves apart from much stronger disturbances such as me driving past in a truck, minor earthquakes (happening all the time!) and a long list of other reasons for the apparatus to move.
      The most promising experiments are so-called interferometers, where a laser beam is sent back and forth between two mirrors a long distance apart, plus a second set of mirrors in a different direction. If a gravitional wave changes the length of this interferometer in one direction, but not the other, you can see the difference by comparing the laser beams. Even length differences smaller than the diameter of an atom can be measured this way. The difficulty really is learning how to control all other reasons for movement, and therefore I don’t think anyone has managed to observe gravitational waves yet.
      Check out the experiments LIGO and LISA (the latter doing the same thing in space, where you have less chance of me driving past in a truck). There is actually more than one LIGO, in different locations across the planet. That is actually *one* neat trick to distinguish road traffic vibrations from gravitational waves. Gravitational waves should hit all locations at a similar time, road traffic probably not. 🙂

    • Photo: Joel Goldstein

      Joel Goldstein answered on 12 Nov 2013:

      As Kristian has said, it is definitely possible and there are a couple of different experiments actually looking for them. The problem is that gravity is a much, much weaker force than the others we know about (electromagnetism and the two types of nuclear force). We know that our current experiments will only detect gravitational waves if they are very lucky.

    • Photo: Zachary Williamson

      Zachary Williamson answered on 13 Nov 2013:

      Yes they can. Gravitational waves distort space as travel. The effect is tiny but we’ve built two experiments to try and find this effect. Kristian’s already given a good description of what they do.

    • Photo: Tim Hollowood

      Tim Hollowood answered on 15 Nov 2013:

      yes they can be in principle…and pretty soon I’m sure we will see the elusive waves because we know they exists even though we haven’t seem them directly. That is because there are some binary star systems that are behaving just as if they were emitting gravity waves…the theory fits perfectly. So it’s only a matter of time.

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