Expansion of space

  • Thread starter Skeetss
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  • #26
Someone should correct me here if I'm wrong, but what you should think of when it's said that space is expanding is that the distance between any two given galaxies is, on average, expanding. Every galaxy is moving away from each other. Within a given galaxy, nothing changes at all. But the distance between, say, Andromeda and the Milky Way is getting larger.
 
  • #27
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Someone should correct me here if I'm wrong, but what you should think of when it's said that space is expanding is that the distance between any two given galaxies is, on average, expanding. Every galaxy is moving away from each other. Within a given galaxy, nothing changes at all. But the distance between, say, Andromeda and the Milky Way is getting larger.
Andromeda and the Milky Way are approaching each other, and will collide in about 4.5 billion years.


On any scale less than the local galactic supergroup (200 million lys) the effect of gravity overwhelms the force of expansion. It's only when you get outside the supergroup that you see expansion.
 
  • #28
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"If the universe is expanding, then why isnt the space between every atom expanding.."

Everyday matter is held together by forces that are incomprehensibly large compared with any local cosmological expansion. Like you or me trying to pull apart a steel rod. And the gravitational forces holding our solar system and our galaxy are likewise much stronger.

In contrast space, or space time, naturally contains a bit of cosmological constant, negative gravitational pressure, so it naturally expands.
 
  • #29
Andromeda and the Milky Way are approaching each other, and will collide in about 4.5 billion years.


On any scale less than the local galactic supergroup (200 million lys) the effect of gravity overwhelms the force of expansion. It's only when you get outside the supergroup that you see expansion.
Right. My bad. So replace the relevant parts in what I said with 'superclusters' or whatever could be called the minimum particle subject to expansion :P
 

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