Observations

To begin considering the size and age of the Universe, we first need to understand the techniques used to measure it. The only data that we have are photons, but the way they are interpreted is contentious.

 

 

 

Light green boxes: Technique applicable to star-forming galaxies. Light blue boxes: Technique applicable to Population II galaxies. Light Purple boxes: Geometric distance technique. Light Red box: The planetary nebula luminosity function technique is applicable to all populations of the Virgo Supercluster. Solid black lines: Well calibrated ladder step. Dashed black lines: Uncertain calibration ladder step.

Notice that all of these methods (supposedly) are double-checked by redshift. Pretty much everybody agrees that redshift can be caused by a relative velocity between the light emitting source and the observer, because this can be verified here on Earth, and in near-field astronomical measurements (i.e., within our own solar system).

 

In a steady-state Universe, all other factors being the same, we'd expect an average redshift to be 0, and for those objects that happened to be moving away from us showing a redshift as a direct function of relative velocity, while objects moving toward us would be blueshifted. But this isn't what we're seeing. Rather, just about everything (except very near objects that are definitely moving toward us) is redshifted.

 

Various types of "standard candles" appear to undergo redshift, as well as attenuation in luminosity, at roughly the same rate. So nearer standard candles show less redshift, while the distant ones show more redshift.

 

Fingers of God

High/Low Redshift Conjunctions

Redshift Dependencies

What are the implications of redshift?

What causes redshift, if not universal expansion?