BGV theorem

[lee_merrill]

Apparently even a succession of universes has to have a beginning!

Source: Cross Examined

The BGV Theorem pinpoints the need for the beginning of our physical universe. First, the theorem agrees that our universe had a beginning. Ideas of an eternal, self-existing universe is growing quickly out of favor in the scientific community at least at this stage. Our universe, the laws of physics found in our universe, and time itself had a beginning...

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Blessings,
Lee

[shunyadragon]

It is possible like our multi-verse have many if not infinite universes. There is the possibility of many multiverse.

I believe it is premature to to that anything 'has to have a beginning.'
To add I do not believe that the BGV Theorem is universally accepted by physicists.

[lee_merrill]

I believe it is premature to to that anything 'has to have a beginning.'

But doesn't the BGV Theorem say that any universe that on average, expands, has to have a beginning?

To add I do not believe that the BGV Theorem is universally accepted by physicists.

Well, it was peer-reviewed and published, and has not that I know of, been refuted.

Blessings,
Lee

[shunyadragon]

But doesn't the BGV Theorem say that any universe that on average, expands, has to have a beginning?

Well, it was peer-reviewed and published, and has not that I know of, been refuted.

Blessings,
Lee[/QUOTE]

In terms of universes beginning Virtually all cosmologists do not propose an absolute beginning. It is almost universally accepted that all possible universe began from something.

Being peer reviewed and published in this case does not justify the conclusion that universes nor possible multiverses 'have to have a beginning.' There are several different hypothesis concerning the nature of the origins of universe even a possible cyclic model that have not been refuted.

For the most part I consider these questions unresolved either way with a number of possibilities give the present hypothesis and models.

[lee_merrill]

Being peer reviewed and published in this case does not justify the conclusion that universes nor possible multiverses 'have to have a beginning.'

As I understand it, the theorem's conclusion is that universes that expand on average have an absolute beginning.

Source: Michael Strauss

In this paper, the authors show that any universe which is on average expanding has a timeline that cannot be infinite into the past, it must have had a beginning when it started to expand.

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There are several different hypothesis concerning the nature of the origins of universe even a possible cyclic model that have not been refuted.

There are ways to get around the BGV theorem, but these involve speculation.

Source: Michael Strauss

For instance, although the BGV theorem has very few assumptions, it is formulated in a classical space-time which may not give valid conclusions during the first 10^-35 seconds of the universe when quantum gravity would have been in effect...

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For the most part I consider these questions unresolved either way with a number of possibilities give the present hypothesis and models.

Source: Michael Strauss

But a good synopsis of how the BGV theorem has been received is given by Vilenkin himself when he says "The validity of the BGV theorem is not in question, but its interpretation has generated some controversy."

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Blessings,
Lee

[shunyadragon]

As I understand it, the theorem's conclusion is that universes that expand on average have an absolute beginning.

Source: Michael Strauss

In this paper, the authors show that any universe which is on average expanding has a timeline that cannot be infinite into the past, it must have had a beginning when it started to expand.

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I do not consider this an absolute beginning, because it is a beginning from preexisting energy.

There are ways to get around the BGV theorem, but these involve speculation.

Source: Michael Strauss

For instance, although the BGV theorem has very few assumptions, it is formulated in a classical space-time which may not give valid conclusions during the first 10^-35 seconds of the universe when quantum gravity would have been in effect...

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There is the possibility of a cyclic universe.

Source: Michael Strauss

But a good synopsis of how the BGV theorem has been received is given by Vilenkin himself when he says "The validity of the BGV theorem is not in question, but its interpretation has generated some controversy."

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I believe the interpretation of the BGV theorem does involve speculation. It is not the only game in town

[lee_merrill]

I do not consider this an absolute beginning, because it is a beginning from preexisting energy.

No, they show that the timeline cannot be infinite in the past.

There is the possibility of a cyclic universe.

This runs afoul of the second law of thermodynamics, which limits the number of cycles.

I believe the interpretation of the BGV theorem does involve speculation. It is not the only game in town

But the BGV theorem is not a model of the universe, rather it imposes a limit on models of the universe.

Blessings,
Lee

[Roy]

But doesn't the BGV Theorem say that any universe that on average, expands, has to have a beginning?

No. AIUI, the BGV theorem assumes the universe had a beginning, and shows that the period of expansion must have a beginning.

None of this is of any help to Xtian apologetics, even the 'we call this God' variety.

[lee_merrill]

No. AIUI, the BGV theorem assumes the universe had a beginning, and shows that the period of expansion must have a beginning.

Source: Alexander Vilenken

The BGV theorem says that if the universe is on average expanding along a given worldline, this worldline cannot be infinite to the past.

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So no assumption of a beginning.

Blessings,
Lee

[shunyadragon]

Source: Alexander Vilenken

The BGV theorem says that if the universe is on average expanding along a given worldline, this worldline cannot be infinite to the past.

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So no assumption of a beginning.

Blessings,
Lee

Yes an infinite assumption of beginnings, but not an absolute beginning to anything.

The view that the universe has a beginning from preexisting energy is almost universally accepted among physics and cosmology. The view that the multiverse must have a beginning is a matter of speculation and interpretation based on the BVG theorem, and NOT universally accepted.

[Roy]

Source: Alexander Vilenken

The BGV theorem says that if the universe is on average expanding along a given worldline, this worldline cannot be infinite to the past.

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So no assumption of a beginning.

Blessings,
Lee

You aren't quoting Vilenkin (whose name you misspelt).
You aren't even quoting Craig who's quoting Krauss who's quoting Vilenkin.
You're quoting Craig arguing that Krauss is not quoting Vilenkin.

You've been caught using misleading 'quotes' previously. So has Craig.

So there's no reason to believe Vilenkin actually wrote that.

[lee_merrill]

You're quoting Craig arguing that Krauss is not quoting Vilenkin.

No, I'm quoting Craig quoting Vilenkin, and the quote shows that the BGV theorem does not assume a beginning.

Blessings,
Lee

[shunyadragon]

No, I'm quoting Craig quoting Vilenkin, and the quote shows that the BGV theorem does not assume a beginning.

Blessings,
Lee

Whether the BGV theorem assumes a beginning or not is not an issue. It is best not to cite Craig in a science thread on the BGV theorem.

[Roy]

No, I'm quoting Craig quoting Vilenkin, ...

You've been caught using misleading 'quotes' previously. So has Craig.

So there's still no reason to believe Vilenkin actually wrote that.

and the quote shows that the BGV theorem does not assume a beginning.

No, it doesn't. It only shows it does not assume a beginning of the worldline of expansion.

Reading the surrounding context shows that even if Vilenkin did write the text Craig presents, he added possible exceptions and circumstances in which his theory wouldn't apply - which typically you have ignored.

[shunyadragon]

I believe that the view that the BGV theorem determines that the multiverse 'has to have a beginning' is flawed according to Guth who describes our universe being possibly in a pocket 'universe (pocket multiverse a possibly having a beginning).

Source: https://www.space.com/31465-is-our-universe-just-one-of-many-in-a-multiverse.html

Confronting the Multiverse: What 'Infinite Universes' Would Mean

How big is the multiverse?

One great question of existence is simply, how big is it? By "it" I mean everything that exists. All there is. What are the physical dimensions of all-there-is?

A place to start is the size of the universe in which we find ourselves. According to one of Guth's models, our pocket universe may be at least 10^23 times larger than our observable universe (because, in order to work, inflation requires at least 100 doublings of the size of the universe, 2^100 = roughly 10^30). This means that the pocket universe we call home would be 100 billion trillion times larger than everything we can see with our largest telescopes. (Models, no surprise, do jump around.)

Thus the vast expanse of our visible universe, Guth said, is but an insignificant speck within just our own inflating pocket universe. And this universe itself is only one pocket universe among an innumerable or even an infinite number of other pocket universes.

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This is an interesting article, because it cites different scientists and their perspective including some skeptics like Davies.