What do the cosmological supernova data really tell us?

Understand

Not much by themselves, aparently.

• We try to reconstruct the scale factor $a(t)$ of the universe from the SNe Ia data, i.e.
• the luminosity distance $d_{L}(z)$, using only the cosmological principle and the assumption that gravitation is governed by a metric theory.
• In our hence "model-independent," or "cosmographic" study, we fit functions to $d_{L}(z)$ rather than $a(t)$, since $d_{L}(z)$ is what is measured.