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I would like to remind you that if the universe is infinite, then by definition its age must be infinite.

Why the same process (which formed SMBH) can't form less massive black hole seeds?

A theory is ...like a family tree of COVID-19

Quote from: Dave Lev on 14/05/2022 14:59:48I would like to remind you that if the universe is infinite, then by definition its age must be infinite.Not so. If the Universe started off with an infinite size, then it would presumably still be infinite in size even if its age is finite. Let's not confuse the total Universe with the observable Universe. The observable Universe can have a finite size while the Universe as a whole can potentially have (and always have had) an infinite size.

Perhaps he should get a chance to explain why he thinks that because we don't know the size and shape of the universe, we can't use this maths

The observable Universe can have a finite size while the Universe as a whole can potentially have (and always have had) an infinite size.

The really tiny black holes won't be around today, because they would have evaporated long ago by Hawking radiation.

Why shouldn't I lock this topic?

Just tell me to stop the discussion in this topic - and I would stop.

Quote from: Halc on 14/05/2022 17:13:08 Why shouldn't I lock this topic?Perhaps he should get a chance to explain why he thinks that because we don't know the size and shape of the universe, we can't use this mathsQuote from: Dave Lev on 14/05/2022 14:59:48"the time it has taken for the galaxies to reach their current separations is t=D/v .But, from Hubble's Law, we know that v=H0D .So, t=D/v=D/(H0×D)=1/H0 .So, you can take 1/H0 as an estimate for the age of the Universe."which doesn't mention the size and shape of the universe.I have to say I'm really quite curious about that.

"the time it has taken for the galaxies to reach their current separations is t=D/v .But, from Hubble's Law, we know that v=H0D .So, t=D/v=D/(H0×D)=1/H0 .So, you can take 1/H0 as an estimate for the age of the Universe."

Why do you think that normal BH (with mass bigger 1 M☉) shouldn't evaporate?

Based on the BBT the Universe started from "Planck epoch".

Quote from: wiki"All matter and energy of the entire visible universe is contained in a hot, dense point (gravitational singularity), a billionth the size of a nuclear particle."So, how that "gravitational singularity, a billionth the size of a nuclear particle" could suddenly be considered as Infinite space without breaking the BBT theory?

"All matter and energy of the entire visible universe is contained in a hot, dense point (gravitational singularity), a billionth the size of a nuclear particle."

Therefore, if the Universe started off with an infinite size

"the theory describes an increasingly concentrated cosmos preceded by a singularity in which space and time lose meaning (typically named "the Big Bang singularity")."If you start the Bang when the Universe is already infinite

So, how can we claim about concentrated cosmos while this cosmos is already infinite?

If you start the Big Bang from "Planck epoch", and you claim that the early universe was compact, then by definition due to the expansion rate there is a limit for the maximal size of the Universe.

Let's assume that the maximal size of the universe after the inflation is X.

We know that the expansion rate is based on Hubble constant (about 70 (km/s)/Mpc).

Therefore, after 13.8 BY with that kind of expansion rate - there must be a maximal size for the Universe.

If the real universe is bigger than this maximal estimated size, then there must be an error in the BBT.

If you claim that the BBT didn't start from "Planck epoch"

then our puzzled scientists

So, how could it be that after observing that quasar for quite long time, we didn't observe even one tinny star as it falls inwards with amazing fireworks?

You're going on again claiming nothing falling into black holes, even the ones that are visibly doing so at the highest rates

So, how that "gravitational singularity, a billionth the size of a nuclear particle" could suddenly be considered as Infinite space without breaking the BBT theory?We also know that there is no empty space with no energy. Therefore, if the Universe started off with an infinite size then by definition it should have some sort of energy.

To help you understand, consider looking at it backwards through time. You start off with a universe of infinite size, with roughly the same (low) density everywhere.

Our observable Universe is a sphere of limited size within this larger Universe

As you go further back in time, the density of all matter increases and the "bubble" that represents our observable Universe gets smaller.

However, the Universe as a whole is still remains infinitely large because no degree of shrinkage can change that. So as you go further and further back in time, our observable Universe continues to shrink until it shrinks to zero (or close to zero) size at the moment of the Big Bang.

The total Universe is still infinitely-large at this point, however. It's just that the density everywhere is infinite (or at least very, very high)

That is incorrect as the density of matter in our real infinite universe is fixed over time.

This could be correct ONLY if you shrink the observable Universe while there is no change in all infinite universe outside that observable universe.

So, how we prove that only the Observable Universe shrinks?

Now do you think that as we go further and further back in time, the Universe M could shrink to zero (or close to zero) in just 13.8 BY?

If not, then as the total Universe is infinitely-large at this point, it would still be infinite even if we shrink it by go back 13.8BY in time.

Quote from: Dave Lev on 16/05/2022 14:52:43Just tell me to stop the discussion in this topic - and I would stop.I'd like you to actually start a discussion.A discussion is where you actually answer the points out to you>Ones like thisQuote from: Bored chemist on 14/05/2022 17:58:43Quote from: Halc on 14/05/2022 17:13:08 Why shouldn't I lock this topic?Perhaps he should get a chance to explain why he thinks that because we don't know the size and shape of the universe, we can't use this mathsQuote from: Dave Lev on 14/05/2022 14:59:48"the time it has taken for the galaxies to reach their current separations is t=D/v .But, from Hubble's Law, we know that v=H0D .So, t=D/v=D/(H0×D)=1/H0 .So, you can take 1/H0 as an estimate for the age of the Universe."which doesn't mention the size and shape of the universe.I have to say I'm really quite curious about that.

The visible universe was perhaps the size of a grapefruit immediately after inflation. Estimates vary considerably.

That was my entire point. It demonstrates how the Universe as a whole can be infinitely large at the moment of the Big Bang even though our observable Universe was still incredibly tiny.

QuoteQuoteWe know that the expansion rate is based on Hubble constant (about 70 (km/s)/Mpc).No, the Hubble constant is based on the current measured expansion rate. It isn't a constant, and it only tells you approximately how old the universe is since it is in units of t-1.

QuoteWe know that the expansion rate is based on Hubble constant (about 70 (km/s)/Mpc).

QuoteQuote from: Dave Lev on 14/05/2022 14:59:48"the time it has taken for the galaxies to reach their current separations is t=D/v .But, from Hubble's Law, we know that v=H0D .So, t=D/v=D/(H0×D)=1/H0 .So, you can take 1/H0 as an estimate for the age of the Universe."which doesn't mention the size and shape of the universe.

Quote from: Dave Lev on 14/05/2022 14:59:48"the time it has taken for the galaxies to reach their current separations is t=D/v .But, from Hubble's Law, we know that v=H0D .So, t=D/v=D/(H0×D)=1/H0 .So, you can take 1/H0 as an estimate for the age of the Universe."

So how can you claim that a theory for a universe that starts as a grapefruit size after the bang and the inflation, could perfectly work while at the big bang moment it is already infinite?

I assume that only if we set the Hubble constant as infinite value there is a possibility to get infinite Universe in a finite time.

You don't "set" it, you measure it.

Making up numbers- particularly infinite ones- is not science.

The size and shape of the universe do not occur in this equation.QuoteQuote from: Dave Lev on Yesterday at 17:43:02"the time it has taken for the galaxies to reach their current separations is t=D/v .But, from Hubble's Law, we know that v=H0D .So, t=D/v=D/(H0×D)=1/H0 .So, you can take 1/H0 as an estimate for the age of the Universe."So any change to the size and shape of the universe would not affect that equation.So we do not need to know what the size and shape of the universe are, in order to calculate that equation.

Quote from: Dave Lev on Yesterday at 17:43:02"the time it has taken for the galaxies to reach their current separations is t=D/v .But, from Hubble's Law, we know that v=H0D .So, t=D/v=D/(H0×D)=1/H0 .So, you can take 1/H0 as an estimate for the age of the Universe."

So please don't make up numbers- particularly not Hubble constant

just to fit it into the BBT theory.

OK, lest stop being silly.You are still trying to say that we can't use thisQuote from: Dave Lev on 18/05/2022 17:43:02"the time it has taken for the galaxies to reach their current separations is t=D/v .But, from Hubble's Law, we know that v=H0D .So, t=D/v=D/(H0×D)=1/H0 .So, you can take 1/H0 as an estimate for the age of the Universe."because we don't know the size of the universe.Lets try a few different sizes for the universe and see what difference it makes.The Universe is small enough to fit in my pocket say 0.01 metres1/H0 is about 14 billion years.Now let's say the universe is a trillion light years across1/H0 is still about 14 billion years.Did you notice that 1/ H0 does not actually change?

1/H0 is about 14 billion years.Now let's say the universe is a trillion light years across1/H0 is still about 14 billion years.

QuoteQuote from: Dave Lev on Today at 17:35:46just to fit it into the BBT theory.Technically, there's quite a big range of values that would more or less work.

Quote from: Dave Lev on Today at 17:35:46just to fit it into the BBT theory.

If the speed of expansion was infinity times the distance away then my monitor which is about a metre away would be receding at a rate of 1 times infinity ie infinity metres per second.Well that's plainly wrong.

You chose one of the values it can't have- infinity.