- #1

Naty1

- 5,606

- 40

http://en.wikipedia.org/wiki/Metric_expansion_of_space

Anybody know the source or a similar plot with some explanations? What do you make of it?? What does it purport to show? Is it in the correct section [Theoretical basis and first evidence] of the article...If so which is it: do you think the plot represents a 'theoretial basis', a prediction, or does it suggest 'first evidence' , experimental confirmation..?

The y-axis is p(a) and the x-axis a(t)...is (a) cosmological scale factor??...so where "today" on the chart is about 3ct

_{0}...or 42B years or so?

I can see that radiation density falls off most rapidly (proportional to 1/a

^{4}, matter density falls off with volume, curvature as 1/a

^{2}, and dark energy density remains constant...is it obvious the first three decline linearly?

So far I haven't found a title, explanation, legend, or anything else...Apparently it was posted March 12, 2012... so it seems pretty new. Maybe Muhammad the author will add more..

Why are matter and radiation shown at a common starting point with equal densities...?

Why that point was selected? I'm guessing it's because nobody knows the radiation density at the big bang, so its convenient..or is that where linear change can be approximated for those two variables??

thanks...