Why gravitational wave interferometers work

Mainly for my own benefit here’s a link to Amber Stuver’s Living LIGO blog answering why interferometers work as gravitational wave detectors given that GWs will also alter the wavelength of light as well as the interferometer arm length. I’m not going to rehash the answer, so go there for it (or for a rather more technical answer see arXiv:gr-qc/0511083 – which is a paper I found ages ago, but then forgot about until I saw Jorge Pullin’s comment on Amber’s post), but will just say that it’s something that’s easier to think about when using pulsar timing as your detector, because for that you actually do have the pulsars producing clock ‘ticks’.