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Enjoy galaxy season while it lasts?


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Here is a subject I don't often think about these days. Youtube recommended this for me. They must have known the weather has turned...

 

 

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Just had a thought.

This expansion means that we should be able to detect density change in observed galaxies as we look further away?

Space is expanding and galaxies were earlier closer than they are now. As we look further away - we are also looking back in time.

If we assume homogeneity of universe - and there is expansion of universe - well, when we look at distant galaxies - they should be much more bunched up than we would assume from density of near by galaxies.

Is this so?

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8 minutes ago, vlaiv said:

If we assume homogeneity of universe - and there is expansion of universe - well, when we look at distant galaxies - they should be much more bunched up than we would assume from density of near by galaxies.

Pretty sure that’s correct Vlaiv, although someone with far more knowledge than me would have to confirm.

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I think it is what we see - think of the Hubble Deep Field and Ultra Deep Field  - it's like every available parking space has been taken by a Galaxy .  Having said that there will also be the factor of the timeline for the rate of Galaxy formation - no doubt some complicated maths will describe the interplay there. I love this video - music fits perfectly (Shine On Crazy Diamond) .  Oh ignore the hack partway through - Ill try find a better one. 

Jim 

 

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Here's a question - can we actually compare galaxy density , any spatial measurement really, between back then and now?  What I'm getting at is given that spacetime was/is expanding then are we able to compare a standard unit of spatial measurement across the universe's evolutionary epochs (don't know if that is right word) ?  Are these measurements invariant in that way ? 

Jim

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I don’t believe a word of it! Solid state universe, zero expansion. Existence makes so much sense this way. Why complicate things with a Big Bang?

Just think how many problems could be solved if all the people trying to find dark matter looked for real stuff😁

Marv

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On 05/05/2021 at 22:59, saac said:

Here's a question - can we actually compare galaxy density , any spatial measurement really, between back then and now?  What I'm getting at is given that spacetime was/is expanding then are we able to compare a standard unit of spatial measurement across the universe's evolutionary epochs (don't know if that is right word) ?  Are these measurements invariant in that way ? 

Jim

Yes but they will be model dependant . Currently the best accepted model is the LCDM one.

Regards Andrew 

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