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A comment on The path to detecting extraterrestrial life with astrophotonics.

Re:The path to detecting extraterrestrial life with astropho... by panki27 on Tuesday September 19, 2023 @09:22AM (#37569593)
> This will require measuring a velocity change in the speed of light of <50 cm/s and more likely 10-20 cm/s (1 part in 3 × 109).

Can someone explain to me why the speed of light changes?

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Re:The path to detecting extraterrestrial life with astropho... by perihelions on Tuesday September 19, 2023 @09:24AM (#37569634)
It doesn't; that language is garbled. It's the velocity of the star they're observing that changes by several cm/s. This translates to a Doppler shift in the starlight being detected: a change in its frequency and wavelength.

see also https://en.wikipedia.org/wiki/Doppler_spectroscopy

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Re:The path to detecting extraterrestrial life with astropho... by panki27 on Tuesday September 19, 2023 @09:29AM (#37569690)
Thank you! I was massively confused there for a second.
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