My admittedly tenuous grasp of (astro?)physics prompts me to ask;
Is the Big Bang still banging, and is space expanding locally?
As I understand it,the “big bang” was not a sudden explosion outward in space from some point, but rather an expansion of space itself. I have been told “there was no ‘where’ before” - I.E. the Big Bang was the creation of space.
Also, I further understand that the universe appears to be not contracting but actually expanding, with such expansion attributed in part at least to “dark energy”.
So, is the “expanion of space itself” from the Big Bang considered to also be part of the present expansion of the universe? I.E. is the Big Bang still going on?
If so would that be applying “locally” - not just on an intergalactic scale, but even at a “human” scale? Is any one attempting to measure that and if so how would you even do it?
IANA astrophysicist, but my understanding is the same as yours: that the Big Bang did not happen in space, but it created Space as we know it.
Since space is still expanding, one could say that the ‘explosion’ is still happening. But in my non-AP opinion, the Big Bang was an event that happened at the instant time started and the expansion is ‘The Expansion of the Universe After the Big Bang’.
The inflationary epoch ended some time ago across the observable universe.
Rather than exponential, faster than light expansion, everything we can now see is subject to Hubble’s law.
Whether inflation is still occuring outside the observable universe is unknowable to us.
A couple of misconceptions, there: First, Hubble’s law applies to any epoch of the Universe, including inflation (though the interpretation of it can differ somewhat in different epochs). Ultimately, all you need to derive Hubble’s law is that the scale factor of the Universe is changing, and that the Universe be homogeneous and isotropic. And in any era, Hubble’s law will mean that there is some horizon distance beyond which things are receding at greater than c.
Second, we are currently in an epoch of exponential expansion, due to the dark energy (whatever the heck that is). The current timescale for that expansion is much longer (i.e., slower) than it was during inflation, but it’s still exponential, and so far as we can tell qualitatively no different from inflation.
Nowdays the constant runs about 77 (km/s)/Mpc or about 2.5×10[sup]−18[/sup] s[sup]−1[/sup].
Back in the inflationary epoch it ran about 4×10[sup]35[/sup] s[sup]−1[/sup].*
Obviously that means that the constant changed at some point in time, yet in all 26 billion odd lightyears of the currently observable universe, and as far as anyone has been able to determine, Hubble’s constant is indeed a constant.
We are far enough past the time of superluminal expansion that we can no longer see evidence of a changing Hubble value. For my money, that tells me that the big bang is over, at least in our local part of the universe.
No, we can see pretty clearly that it changes, and in fact it’d be a surprise if it didn’t. The Hubble parameter is roughly the reciprocal of the age of the Universe, so (in the simpler models, at least) it’ll decrease as time goes on.