Hacker Newsnew | past | comments | ask | show | jobs | submitlogin

So wait, individual stars aren't getting further apart? Galaxies aren't getting "bigger"/more diffuse?


Galaxies have enough gravity to counteract the expansion of the universe.


So do we see the expansion cancelled out by the gravity, or do we only see the gravity?

I mean, is it

    change = gravity
or

    change = expansion - gravity
Because this just made me wonder.. is "dark energy" simply the absence of gravity? i.e. just in regions where there is next to no matter/activity?


> do we see the expansion cancelled out by the gravity, or do we only see the gravity?

We see gravity overpowering expansion. Same way you can’t launch yourself into orbit by throwing lots of pennies at one a second.


Imagine the universe as a giant balloon. Inside are little miniature balloon stars floating around, tied with string into balloon galaxies. If we heat the air: the big balloon expands, the clusters of mini-balloons spread out from the other clusters, but the clusters don't get any more diffuse. The string is way way too strong to be overpowered by the separating force from the expansion of the gas over short distances.


I mean, this is tricky to even ask: is there still expansion INSIDE galaxies, BUT it's countered by gravity?

Or is there no expansion within galaxies at all?

i.e. is dark energy or whatever that causes expansion only present in the absence of matter, or is it present everywhere regardless of matter, but because matter also has its own gravity the expansion is not visible/relevant?


No, stars stay just as close to each other. Also even the nearest galaxies (Andromeda) are either getting closer or staying at roughly the same distance.




Guidelines | FAQ | Lists | API | Security | Legal | Apply to YC | Contact

Search: