I want to determine the radius vs time for the universe (observable
today) but using universe ages starting with age =3D 0.721 Gyr and
moving forward in Gyr increments. Ned Wright's calculator gives values
but from our current perspective, looking outward into the surrounding
universe, whereas I want to go back in time and am not sure I can use
the values.

Using the calculator, I got the below values for radius of the universe
as a function of the distance out I look using z values to give Gyr
increments with default settings for co moving radius:

If I did this right, the following are the co moving radii for the
universe out to the same co moving radius (that we see today) applied
to different ages of the universe starting at 0.721Gyr and increasing by
1Gyr per data point up through present at 13.721Gyr. To the same co
moving radius of the universe, the current value is 30.79GLyr, whereas
to that same co moving radius at 0.721Gyr age, the co moving radius
would have been 14.21GLyr if I did this right.

But I used the modern co moving radii, then just multiplied by the ratio
of universe age, and am not sure the inversion is correct....ie, that
the expansion is (I think the term would be) reversible / self similar??

14.214956
14.7706565
15.35837267
15.998686
16.7039454
17.48512767
18.36849871
19.37748225
20.56168078
21.9975072
23.83462436
26.39463033
30.79097946

But it's different to look backward from the present, compared to
looking forward from the past. ie, if we today were in the universe at
age 0.721 Gyrs, would the co moving radius back then have been
14.21Glyr? And today, due to expansion, the co moving radius is now
around 30.8Glyrs.

Not sure this is a legitimate transformation.

rt