

Ask HN: Is our universe constantly expanding or constantly shrinking? - jmtame

Just read the book Zero, does their final conclusion still hold up? They say our universe is gradually expanding, which will inevitably leave to a freeze of everything? Did anyone else read this? What did you think?
======
russell
The latest theories say that the rate of expansion of the universe is
accelerating due to the effect of dark energy which overcomes the attractive
force of gravity over cosmic distances. There are competing theories that
don't involve dark energy.

------
vaksel
i'm on the side that its expanding. I reason that if big bang was an explosion
that created everything, then the blastwave or whatever is still expanding
indefinitely

------
Allocator2008
Oh, I just had another thought here. I would so very much prefer it if the
Hoyle steady state theory were correct, the idea that as galaxies expand, new
matter is created in the inter-galactic spaces formed by the expansions, and
this new matter makes new galaxies, ad infinitum, so there would not be a big
bang (a beginning) or a final state of dissolution into radiation that one
finds in the eternal expansion model (an end).Also it is a clean, beautiful
theory mathematically. But as Kepler found, when discovering that the planets
use ellipses and not circles when orbiting the sun (circles were thought more
"perfect" aesthetically at the time), the universe might not much care what we
like or prefer or find to be beautiful or aesthetically pleasing. :-) In the
case of steady state, it is hard to see how that can still be viable, given
the microwave background radiation discovered in the early 60's, and the more
recent discoveries of quantum density perturbations in the background, which
is consistent with the big bang model.

------
Allocator2008
I did not read that book, though I do know prevailing cosmological models say
that the universe is expanding continually. If it keeps it up, eventually, no
galaxy will be able to see any other galaxy, because the distances between
them have increased so much. Later, galaxies all collapse into mega black
holes. Still later, these mega black holes all evaporate over a very long
epoch (10^60 years or something like that) via the process of Hawking
Radiation. Once this happens, there is nothing left in the universe except
radiation, and various short-lived "quantum vacuum" particles perhaps. Nothing
but a homogeneous soup of particles that are not even atoms. Penrose has
recently argued that this state could trigger another big bang, and start
another "cycle" but I don't know that that view is very much accepted
presently. The general thinking is that this final state of scattered
radiation is all the fat lady sings.

