Another one I have a hard time wrapping my head around deals with the whole accelerating expansion of the universe (space itself getting larger). I have several questions about this:
1) If all the galaxies are moving away from each other, will the Milky Way and the Andromeda galaxies still collide in the distant future?
This is a gross net effect, caused by universal expansion, our Local Group of Galaxies are 'gravitationally bound', which is to say the force between them from gravity overrides expansion. Expansion is roughly linear, double distance, double expansion rate, whereas gravity is inverse square, double distance, reduce force by a quarter. Hence inside a galaxy the expansion is effectively irrelevant. And unlike Stars or planets, galaxies aren't relative tiny dots on an empty ocean, but more like houses in a semi-rural area. We actually define the local group as those galaxies and satellites which will remain together (and eventually merge into one blob) till all creation sputters out.
2) Is the expansion of space effecting the space between star systems within each galaxy? If not, why? Is the Dark Energy effect only occurring to the space between galaxies? Will it at some point effect the space between stars, planets, asteroids, or even the space between my atoms and molecules?
No, again gravity is weak but not that weak. Hubble's Constant is at light year range amounts to about 20 mm/s per light year, or for context, 1 meter per 50 seconds, or 600 km a year, or 1 light year every 15 billion years or so. All the various stars flit around the galaxy under local accelerations and velocities relative to miles per second, not millimeters, at local galactic scale it's like a mule pulling against a team of horses, but inner-galactic it's like a cat pulling against a train. At the Galactic Supercluster scale, between those, the analogy reverses. Hence the universe is falling apart but it's individual sections remain coherent and would merge, minus some bits ejected by the merger.
3) Couldn't the acceleration of the expansion of the universe be explained in another way?
Probably, many have, I generally warn people of developing personal theories about it.
The intuitive mind is a sacred gift and the rational mind is a faithful servant. We have created a society that honors the servant and has forgotten the gift.
- Albert Einstein
King of Cairhien 20-7-2
Chancellor of the Landsraad, Archduke of Is'Mod
- Albert Einstein
King of Cairhien 20-7-2
Chancellor of the Landsraad, Archduke of Is'Mod
Science Question
13/10/2012 09:01:08 PM
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In general, effects of gravity on a nanoscale system are negligible.
13/10/2012 09:54:50 PM
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To get an intuition of how weak gravity is...
13/10/2012 10:33:14 PM
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Perhaps I say it as should not, but that is oversimplified to the point of inaccuracy.
15/10/2012 11:16:50 PM
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You can calculate gravity pretty precisely, but let me explain conceptually how we know
14/10/2012 03:54:40 AM
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thanks all (and some more Qs)
14/10/2012 07:30:04 PM
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You're welcome and some more A's
15/10/2012 01:40:01 AM
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Then I have another question
16/10/2012 05:52:33 PM
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He's talking about the Andromeda Paradox
17/10/2012 07:11:01 AM
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