![]() |
![]() |
The Bok globule Barnard68, seen in optical wavelenghts (on the left),
and in the infrared (on the right). Source : ESO |
The most recent measurements seems to agree with a value of about 65 km/s/Mpc.
We know that v is proportional to the distance with
the Hubble formula, so
we can obtain the distance as a function of the redshift :
The higher a body's redshift is, the further it is. Light travels
at a finite speed, so when you look far away in space, you also look far away
into the past.
If we look at an object located 10 billion light years away, we see it as
it was 10 billion years in the past.
There exists another redshift, called gravitational redshift, which
appears when the light source is inside a gravitational field.
This is the size of the horizon of a black hole, beyond which nothing can escape, not even light.