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Whenever the Doppler effect is mentioned, it's typically in the context of sound waves or electromagnetic radiation. On the cosmological scale, red-shifting is also important because of the enormous speed of receding galaxies, thanks to the expansion of the universe.

Yet, red-shift is always discussed as the red-shifting of electromagnetic waves. Can gravitational waves be red-shifted? If so, could observations of them be used like red-shifted electromagnetic waves from distant sources are; that is, to figure out how fast an object is receding?

Qmechanic
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HDE 226868
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1 Answers1

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Yes, gravitational waves will undergo the same red-shift as any wave that propagates at $c$. There were probably very violent gravitational waves in the very early universe. If those waves hadn't been red-shifted, they'd be ripping us apart right now.

If so, could observations of them be used like red-shifted electromagnetic waves from distant sources are - that is, to figure out how fast an object is receding?

Gravitational waves have frequencies that vary over time and that also depend on the particular physical characteristics of the emitting systems. Therefore we don't know a priori what frequency a wave should have had when emitted. This is different from electromagnetic waves in a discrete spectrum.