- #1

Froglet

- 11

- 0

Say I observe the spectrum of a galaxy, and I calculate its redshift. I then use the Hubble Relation to find its distance, which is, say, ten billion light years.

So far so good ... but doesn't this also mean I'm actually observing the galaxy as it was ten billion years ago, so in the intervening time it will have receded further with the expansion of the Universe, so isn't the real distance much greater? Would this affect our current estimate for the age of the Universe?

Put another way, I understand how Hubble's Law can apply to relative distances in space, but I'm not certain how we can calibrate it with an accurate distance at the present time if we are always looking into the distant past when we observe.

Many thanks.