Re:A new Einstein cross is discovered
by btilly on Monday March 25, 2019 @05:07PM
(#19486740)
I haven't heard the cupcake version. It does have something to recommend it, though raisins don't crawl. So that may make it harder to visualize the difference between how fast you're expanding versus how fast you're moving versus local space. Which is the whole point.
[ Parent
| on HN ]
Re:A new Einstein cross is discovered
by vanderZwan on Monday March 25, 2019 @05:44PM
(#19487012)
What I find confusing is that the space inside the ants/raisins should expand as well. Why do we not experience this expansion locally?
Re:A new Einstein cross is discovered
by function_seven on Monday March 25, 2019 @06:00PM
(#19487135)
Space is expanding everywhere, but the matter that resides within it is bonded to other matter, or gravitationaly attracted together, so it holds.
Back to the balloon analogy, the surface of the balloon is expanding, even under the ant's feet. But the ant doesn't grow.
And since the even the whole groups of galaxies are gravitationally bound, it seems that the galaxies, including our own galaxy, are not "stretching" but remain the same size. And, based on the same principle, everything inside of them also, including us.
So back to the cupcake analogy, the raisins are the whole galaxy groups.
Also:
https://medium.com/starts-with-a-bang/this-is-why-we-arent-e...
"As physicist Richard Price once put it, “Your waistline may be spreading, but you can’t blame it on the expansion of the universe.”"
https://www.newscientist.com/article/dn8082-cosmic-expansion...
Here "bonded to other matter" means "electrostatically attracted together".
It's not strong enough to overcome the forces keeping us together.
But that might not be the case for forever: https://en.wikipedia.org/wiki/Big_Rip