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Universe Expansion Representation Inconsistency
Name: George
Status: other
Age: N/A
Location: N/A
Country: N/A
Date: N/A
Question:
I have just read the Wikipedia article on the
Metric expansion of space. In that article, the writer presents the
raisin bread analogy and says "The dough between raisins in this
model acts as the space between galaxies while the raisins as
"bound objects" are not subject to the expansion." I have wondered
for 30 years why scientists consider the locality of mass as being
bound -- exempt from expansion. In other words, the ant on the
balloon can measure the expansion of his two dimensional space
using a yardstick -- which is exempt from the effects of the
expansion of space. It would seem to me that the yardstick would
expand, the raison would expand, as well as the ant. This results
in our small observers not being able to detect the expansion of
space in any way. However as light progresses toward us from a
source nearly 12 billion years ago, it travels through space that
is expanding and is consequently red shifted. Somehow the energy of
each photon is spread out over a greater "distance", its energy
reduced, and wavelength increased. I can nearly buy that explanation.
Replies:
It is not so much that galaxies, stars, and people are "exempt" from
metric expansion of spacetime as that the forces holding them
together are strong enough to hold them together despite the metric
expansion of spacetime. If you pull one raisin to the right and
another to the left, the raisins will move apart form each
other. On the other hand, if you pull the right side of a raisin to
the right and its left side to the left, you will not get a bigger
raisin unless you pull really hard - a lot harder than you need to
just move two raisins apart.
Your visualization of red-shift is pretty good, at least as far as I
understand it.
Richard Barrans
University of Wyoming
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Update: June 2012
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