Jan Panteltje wrote:
I was thinking, if I was to look for the most redshifted stars,
and did assume a big bang, and the redshift caused only by Doppler,
then the most redshifted stars would be the furthest away, but just
as old as our sun?
This is why I think that:

Origin of BB:
O

After some years, A and B are stars speeding away from the BB origin:
A O B


After even more years:
A O B



Now suppose we are on star B, then for us star A will move faster away
then any star in position O, so star A will be more redshifted.

So when we look at the most redshifted stars, we merely look at the ones
that are speeding away at the highest speeds, and that are those on
the 'opposite' (sorry 2D picture) of the BB origin.

But they often say: 'this (the most redshifted) is the oldest......'

So where am I wrong?


Assuming you are looking past the origin of the universe (there isn't
such a data point) to a star farther away. Unless you understand the
actual model of the universe, you will remain confused.

At an earlier epoch, all galaxies were closer than they are now. Stars
born at that time begin to live out their lives and shine into the
universe. In the time that it takes the light to reach us, the universe
has continued to expand. The light is redshifted because of that
expansion and the light we detect is also from that earlier epoch, not
from the current one. So, we are seeing the stars as they were at that
earlier epoch, not as they are now.

The stars shine continously over this time and the light they emit
becomes even more redshifted by the expanding space-time. It now has to
travel an even greater distance to reach us, which means we are still
seeing those stars as they were at earlier epochs, not as they are today.

The end result of all this is that those stars that are farthest from us
as determined by their large redshift (galaxies rather than individual
stars, for the picky!!) have had their light traveling the farthest
amount of time to reach us, being redshifted along the way and revealing
us as they were, not as they are.

Note that in this explanation that we may be the center of observation
but located randomly within the universe, so that the same observation
would be made no matter where one was in the universe. There need be no
center of expansion, just an apparent expansion from the point of
observation.