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Big Bang question



 
 
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  #1  
Old February 28th 18, 08:51 PM posted to sci.astro.research
John Heath
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Posts: 13
Default Big Bang question

There are 2 rocks in space. As a result of big bang the universe
is expanding. Is it the vacuum that is expanding therefor the
distance between the rocks or is it the vacuum and the size of the
2 rocks that is expanding. That's it . Did not want to clutter this
question with too many details . Is it the vacuum or is it the
vacuum and the rocks that are expanding?

[[Mod. note -- This is a FAQ, and is one of the entries in Ned Wright's
excellent "Frequently Asked Questions in Cosmology":
http://www.astro.ucla.edu/~wright/cosmology_faq.html
-- jt]]
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  #2  
Old March 1st 18, 09:16 PM posted to sci.astro.research
John Heath
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Posts: 13
Default Big Bang question

On Wednesday, February 28, 2018 at 2:51:05 PM UTC-5, John Heath wrote:
There are 2 rocks in space. As a result of big bang the universe
is expanding. Is it the vacuum that is expanding therefor the
distance between the rocks or is it the vacuum and the size of the
2 rocks that is expanding. That's it . Did not want to clutter this
question with too many details . Is it the vacuum or is it the
vacuum and the rocks that are expanding?
=20
[[Mod. note -- This is a FAQ, and is one of the entries in Ned Wright's
excellent "Frequently Asked Questions in Cosmology":
http://www.astro.ucla.edu/~wright/cosmology_faq.html
-- jt]]


Nice link.

Quote

Are galaxies really moving away from us or is space just expanding?

This depends on how you measure things, or your choice of coordinates.
In one view, the spatial positions of galaxies are changing, and
this causes the redshift. In another view, the galaxies are at fixed
coordinates, but the distance between fixed points increases with
time, and this causes the redshift.

end quote

This is getting warmer but in this case it is a little tricky as
the observation of the rock is made at two different times. 300
million years ago and now. I can predict the size of the rock 300
million years ago as this rock is a dragonfly fossil. It should
have been 6 to 12 inches max if atmosphere pressure was 20 times
higher with lots of oxygen. Today that rock fossil is a 3 foot
monster dragonfly that puts beyond feasibility to fly from a physics
point of view. This raises the question did the dragonfly grow to
3 feet or was it the fossil that grew to 3 feet. Knowing if a rock
expanse while the universe expands will answer that question.

[[Mod. note -- You're misunderstanding the situation: Bound systems
(including rocks, solar systems, and galaxies) don't share in the
cosmological expansion to any significant extent. So (absent other
physical processes to change them) those rocks are essentially the
same size now they were 300 Myr ago.

The FAQ entry you quoted is discussing the distances *between*
bound systems (galaxies).
-- jt]]
 




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