View Single Post
marcus
#20
Nov5-08, 02:01 PM
Astronomy
Sci Advisor
PF Gold
marcus's Avatar
P: 23,236
Quote Quote by oldman View Post
...Neither do I like labelling what is going on in our evolving universe "an expansion phase"...


We are in a phase of widespread increasing distances between objects at CMB rest, according to pattern called Hubble law. So what better do you propose to call it? Would you feel comfortable saying we are in a:

1. Hubble phase, or Hubble law phase. (accurate, but too technical to communicate to many listeners)

2. increasing-distances phase (accurate, but too many syllables).

It is easier to say expansion (3 syllables) than increasing-distances (6 syllables). So what's wrong? As long as people don't misunderstand and over-extend the analogy with material substance. Aren't you being a bit fussy about words here?

The basic point is you either buy GR or you offer a better mathematical model of how geometry evolves. If you buy GR then you have no right to expect distances to stay the same. In fact you expect us quite possibly to be in an increasing-distances phase. And the kicker is the idea of being collectively at rest with respect to the matter in the early universe---at rest relative CMB.
Modulo small proper motions and possibly some drift, but on the whole a remarkable collective stationarity.

Well these are the most obvious features of the universe. What words would you like better? I'm flexible about words as long as the mathematical model clearly underlies them. Interpretation is just verbal trimmings. So as long as the words are easy to say, and fairly descriptive, I'm cool.

So what words do you like?