Re: 'moving through space' vs 'space expanding'

From: Greg Neill (gneillREM_at_OVE.THIS.netcom.ca)
Date: 12/31/04 

Date: Fri, 31 Dec 2004 00:47:51 -0500

"RichD" <r_delaney2001@yahoo.com> wrote in message
news:1104466548.340949.62730@z14g2000cwz.googlegroups.com...
> Modern cosmology has introduced the concept of
> 'expanding space'. Cf. the inflation theory of
> creation,

Careful, it's not a 'Creation' theory.

> and recently the dark energy 'negative
> gravity' hypothesis. In these scenarios, it is
> posited that the expansion can actually be faster than light.
>
> This bugs me,

What bugs you? Inflation, or the fact that expansion can
occur at speeds greater than light speed?

> because from an instrumental viewpoint,
> things move apart, right? All motion is relative.
> Then, what is the difference between 'A and B are
> separating by moving through space', and 'A and B
> are separating as space expands'?

On difference is that bodies in the universe can be not
only separating, but accelerating with repect to one another,
yet they will not experience any net force!

>
> (Some will object to the concept of moving through
> space, but I think it's clear in context)
>
> Let's put it another way. Suppose we observe
> Andromeda flying away at .8 c. Is it possible to
> say, "Andromeda is really moving at only .6 c;
> the extra .2 c comes from space expanding".
> Is that meaningful in any way? I don't get it.

Andromeda is next door. It's gravitationally bound in our
local group, so it won't participate in universal
expansion (relative to us).

>
> In particular, if space expands at greater than
> c, wouldn't this represent a catastrophe for relativity?

Not at all. General Relativity does not place a speed limit
on how fast space can expand.

Relevant Pages

  • The speed of light in a vacuum and other trivia
    ... Here we have the absolute precision of Special Relativity and the absolute maximum of the speed of light in a vacuum. ... That case is that uniform acceleration of motion is indistinguishable only if the universe is an infinite vacuum in say the +x,+y,+z direction and an infinite mass in the -x,-y,-z direction. ... It does not mean our solar system or galaxy is expanding because these objects are bound by gravity. ...
    (sci.physics)
  • Re: moving through space vs space expanding
    ... it's not a 'Creation' theory. ... > the extra .2 c comes from space expanding". ... General Relativity does not place a speed limit ...
    (sci.physics)
  • Re: moving through space vs space expanding
    ... If a ship takes off from mars moving - through space - ... > separating by moving through space', ... > the extra .2 c comes from space expanding". ... wouldn't this represent a catastrophe for relativity? ...
    (sci.physics)
  • Brad
    ... do you believe in the inflation theory of the universe from some ... it "bang" in and if it's expanding what is it displacing as it expands? ...
    (rec.org.mensa)