Quote:
Originally Posted by grant hutchison
I think the reason no-one knows is that it is an ill-posed question: you're inserting an assumption that there's a thing called "space" which must behave in one of these two ways.
In fact, the phrase "space expands" is just a metaphor for the mathematics, which describe a set of coordinates expanding, so that points within the coordinate frame move apart as time goes by.
By way of analogy: suppose I take a "mind-expanding" drug. During my mind-expanding experience, does extra mind appear, or does my existing mind simply get bigger? Most people would feel that such a question makes no sense, since they recognize that in this context both "mind" and "expanding" are metaphors for something we don't properly understand. I think the analogy with "space expanding" is quite tight, apart from the fact that we us a mathematical theory to describe "space", and subjective knowledge to describe "mind".
Grant Hutchison
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No, I don't think your analogy is in place. Why would scientists use metaphore?
No scientist working on drugs will use words "mind-expanding" while performing some experiment (on him/her selves for instance) and ceartanly not in a scientific journal.
Expansion of space causes a real effect - redshift. You can't back off in the realm of mathematics on this issue. It's like to say that Schrödingers cat causes neutron decay.
I don't expect that anyone says what space (or gravity or time..)
is, but I do expect that someone put the finger on "Expansion of space" because it's a behaviour cruical to photons. They expirience it. We have cause and effect relationship here.
We have a new force: space-force (dark energy) acting on both, matter and radiation.
Naming it force is apropiate especially now when that force causes accelerated
(but collisionless!) movement of massive bodies.
One more interesting thing:
In the regime of accelerated expansion, is it properly accounted for a redshift?
Haven't think about it much, but sounds to me as it could be nonlinear realtionship. (which troubles (1+z)^4 )
(Isn't the gravitational redshift non-linear?)
An excersize (for Jerry I guess :-)) which result could end in love-hate relationship (yes, there are no time dilation and yes, SNIa data are correct :-)).