are these locked in theories with a high level of certainty, or modern creation myths, dressed up as science

can it be proved there ever was a singularity, an infinitely dense super hot whatever, and of the apparent observed, or inferred expansion of the universe, are there other explanations

transition said:

are these locked in theories with a high level of certainty

Yes. It’s beyond doubt that the Big Bang occurred.

can it be proved there ever was a singularity, an infinitely dense super hot whatever, and of the apparent observed, or inferred expansion of the universe, are there other explanations

No. It’s fair to say that the extremely early universe can’t even be modelled using physics that we know at this point.

dv said:

transition said:

are these locked in theories with a high level of certainty

Yes. It’s beyond doubt that the Big Bang occurred.

I wouldn’t go that far. It seems to me that it’s possible that all the evidence that suggests a Big Bang could be due to some other phenomenon.

dv said:

can it be proved there ever was a singularity, an infinitely dense super hot whatever, and of the apparent observed, or inferred expansion of the universe, are there other explanations

No. It’s fair to say that the extremely early universe can’t even be modelled using physics that we know at this point.

In fact I’d say that the idea that the initial state of the Big Bang was a singularity with infinite density is not even the scientific consensus view.

“I wouldn’t go that far. It seems to me that it’s possible that all the evidence that suggests a Big Bang could be due to some other phenomenon.”

Explain

dv said:

“I wouldn’t go that far. It seems to me that it’s possible that all the evidence that suggests a Big Bang could be due to some other phenomenon.”

Explain

We have no idea what is going on outside our limits of observation, so it seems possible that something may be going on that makes what we can see look like a big bang, when it isn’t really.

The Rev Dodgson said:

dv said:

“I wouldn’t go that far. It seems to me that it’s possible that all the evidence that suggests a Big Bang could be due to some other phenomenon.”

Explain

We have no idea what is going on outside our limits of observation, so it seems possible that something may be going on that makes what we can see look like a big bang, when it isn’t really.

Also I have never seen any convincing evidence to prove that what looks like expansion is not a result of shrinking rulers, rather than expanding space.

The Rev Dodgson said:

dv said:

“I wouldn’t go that far. It seems to me that it’s possible that all the evidence that suggests a Big Bang could be due to some other phenomenon.”

Explain

We have no idea what is going on outside our limits of observation, so it seems possible that something may be going on that makes what we can see look like a big bang, when it isn’t really.

Vague. You could say that about evolution or gravity or anything. Given what we know, it’s not reasonable to doubt that there was a period of rapid expansion and early time before baryons could exist.

Before that it is up for grabs. We don’t know nothing.

dv said:

The Rev Dodgson said:

dv said:

“I wouldn’t go that far. It seems to me that it’s possible that all the evidence that suggests a Big Bang could be due to some other phenomenon.”

Explain

We have no idea what is going on outside our limits of observation, so it seems possible that something may be going on that makes what we can see look like a big bang, when it isn’t really.

Vague. You could say that about evolution or gravity or anything. Given what we know, it’s not reasonable to doubt that there was a period of rapid expansion and early time before baryons could exist.

Before that it is up for grabs. We don’t know nothing.

I’d put it on a different level to doubt about evolution. Evolution theory just assumes stuff behaved the same a few billion years ago as it does now.

Big bang theory excludes the possibility that what happened on a large scale outside our scale of observation made what we can see look like it was expanding from a very dense state, which seems to me to be a much higher level assumption.

dv said:

The Rev Dodgson said:

dv said:

“I wouldn’t go that far. It seems to me that it’s possible that all the evidence that suggests a Big Bang could be due to some other phenomenon.”

Explain

We have no idea what is going on outside our limits of observation, so it seems possible that something may be going on that makes what we can see look like a big bang, when it isn’t really.

Vague. You could say that about evolution or gravity or anything. Given what we know, it’s not reasonable to doubt that there was a period of rapid expansion and early time before baryons could exist.

Before that it is up for grabs. We don’t know nothing.

SBS had an interesting doco where it was suggested (by Astrologists) that there are parallel universes connected by blackholes and that our universe originated from the back end of one of them. In other words blackholes create other universes and ours is just one of them. To be it sounded more convincing than everything emanating from something the size of a pinhead

PermeateFree said:

dv said:

The Rev Dodgson said:

We have no idea what is going on outside our limits of observation, so it seems possible that something may be going on that makes what we can see look like a big bang, when it isn’t really.

Vague. You could say that about evolution or gravity or anything. Given what we know, it’s not reasonable to doubt that there was a period of rapid expansion and early time before baryons could exist.

Before that it is up for grabs. We don’t know nothing.

SBS had an interesting doco where it was suggested (by Astrologists) that there are parallel universes connected by blackholes and that our universe originated from the back end of one of them. In other words blackholes create other universes and ours is just one of them. To be it sounded more convincing than everything emanating from something the size of a pinhead

be = me

maybe models are just tools

and yes some of them really are

PermeateFree said:

dv said:

The Rev Dodgson said:

We have no idea what is going on outside our limits of observation, so it seems possible that something may be going on that makes what we can see look like a big bang, when it isn’t really.

Vague. You could say that about evolution or gravity or anything. Given what we know, it’s not reasonable to doubt that there was a period of rapid expansion and early time before baryons could exist.

Before that it is up for grabs. We don’t know nothing.

SBS had an interesting doco where it was suggested (by Astrologists) that there are parallel universes connected by blackholes and that our universe originated from the back end of one of them. In other words blackholes create other universes and ours is just one of them. To be it sounded more convincing than everything emanating from something the size of a pinhead

Astronomers not Astrologists :))

PermeateFree said:

dv said:

The Rev Dodgson said:

We have no idea what is going on outside our limits of observation, so it seems possible that something may be going on that makes what we can see look like a big bang, when it isn’t really.

Vague. You could say that about evolution or gravity or anything. Given what we know, it’s not reasonable to doubt that there was a period of rapid expansion and early time before baryons could exist.

Before that it is up for grabs. We don’t know nothing.

SBS had an interesting doco where it was suggested (by Astrologists) that there are parallel universes connected by blackholes and that our universe originated from the back end of one of them. In other words blackholes create other universes and ours is just one of them. To be it sounded more convincing than everything emanating from something the size of a pinhead

I vaguely recall Carl Sagan talking about that. I know the novel Contact was based around wormholes and multiverses.

SCIENCE said:

maybe models are just tools

and yes some of them really are

I’d say models are more than that. They are our best guess of how things really work.

It’s possible that they have it totally wrong, but there is no reason to assume that is the case.

PermeateFree said:

dv said:

The Rev Dodgson said:

We have no idea what is going on outside our limits of observation, so it seems possible that something may be going on that makes what we can see look like a big bang, when it isn’t really.

Vague. You could say that about evolution or gravity or anything. Given what we know, it’s not reasonable to doubt that there was a period of rapid expansion and early time before baryons could exist.

Before that it is up for grabs. We don’t know nothing.

SBS had an interesting doco where it was suggested (by Astrologists) that there are parallel universes connected by blackholes and that our universe originated from the back end of one of them. In other words blackholes create other universes and ours is just one of them. To be it sounded more convincing than everything emanating from something the size of a pinhead

Astrologists?

dv said:

PermeateFree said:

dv said:

Vague. You could say that about evolution or gravity or anything. Given what we know, it’s not reasonable to doubt that there was a period of rapid expansion and early time before baryons could exist.

Before that it is up for grabs. We don’t know nothing.

SBS had an interesting doco where it was suggested (by Astrologists) that there are parallel universes connected by blackholes and that our universe originated from the back end of one of them. In other words blackholes create other universes and ours is just one of them. To be it sounded more convincing than everything emanating from something the size of a pinhead

Astrologists?

Read on, has already been corrected.

dv said:

PermeateFree said:

dv said:

Vague. You could say that about evolution or gravity or anything. Given what we know, it’s not reasonable to doubt that there was a period of rapid expansion and early time before baryons could exist.

Before that it is up for grabs. We don’t know nothing.

SBS had an interesting doco where it was suggested (by Astrologists) that there are parallel universes connected by blackholes and that our universe originated from the back end of one of them. In other words blackholes create other universes and ours is just one of them. To be it sounded more convincing than everything emanating from something the size of a pinhead

Astrologists?

Cusp.

“We also know there are known unknowns; that is to say we know there are some things we do not know. But there are also unknown unknowns—the ones we don’t know we don’t know.”

Theoretical physicist Donald Rumsfeld

Ian said:

“We also know there are known unknowns; that is to say we know there are some things we do not know. But there are also unknown unknowns—the ones we don’t know we don’t know.”

Theoretical physicist Donald Rumsfeld

chuckle

Wind back the history of what we* can see, and eventually we reach extreme conditions that can’t be satisfactorily modelled with physics that work well the conditions prevailing later.

Cosmology has been stuck like that for quite some time now, but they may find some way forward (or backwards :)) eventually.

*“we” meaning fully equipped, qualified astrophysicists, not us lot.

Bubblecar said:

Wind back the history of what we* can see, and eventually we reach extreme conditions that can’t be satisfactorily modelled with physics that work well the conditions prevailing later.

Cosmology has been stuck like that for quite some time now, but they may find some way forward (or backwards :)) eventually.

*“we” meaning fully equipped, qualified astrophysicists, not us lot.

You never know, they could be sitting around discussing how it all began and one of them will say, “someone sent me a copy of a forum post in Australia and it struck me that we might all be wrong.”

dv said:

transition said:

are these locked in theories with a high level of certainty

Yes. It’s beyond doubt that the Big Bang occurred.

can it be proved there ever was a singularity, an infinitely dense super hot whatever, and of the apparent observed, or inferred expansion of the universe, are there other explanations

No. It’s fair to say that the extremely early universe can’t even be modelled using physics that we know at this point.

Need to get terms sorted out here. Which “Big Bang” and which “Expansion”?

The expanding universe – 100% confirmed.

The “big bang” in the sense of the first 4 seconds of the universe where elementary particles were synthesised – 100% confirmed.

The “big bang” in the sense of cosmic inflation in the first millisecond of the universe – close to 100% confirmed.

The “big bang” in the sense of an infinitely dense infinitely hot state at time zero – not confirmed, only supported by Occam’s razor.

> can it be proved there ever was a singularity.

Nothing can be proved, ever. “I couldn’t trust the thinking of a man who takes the Universe – if there is one – for granted.”, Douglas Adams.

mollwollfumble said:

The “big bang” in the sense of an infinitely dense infinitely hot state at time zero – not confirmed, only supported by Occam’s razor.

Occam’s razor is (in my opinion) highly over rated.

There is no evidence (and can be no evidence) that the Universe started as a singularity with infinite density, and many good reasons to think that it didn’t.

The Rev Dodgson said:

mollwollfumble said:

The “big bang” in the sense of an infinitely dense infinitely hot state at time zero – not confirmed, only supported by Occam’s razor.

Occam’s razor is (in my opinion) highly over rated.

There is no evidence (and can be no evidence) that the Universe started as a singularity with infinite density, and many good reasons to think that it didn’t.

Expansion is usually a result of compression?

roughbarked said:

The Rev Dodgson said:

mollwollfumble said:

The “big bang” in the sense of an infinitely dense infinitely hot state at time zero – not confirmed, only supported by Occam’s razor.

Occam’s razor is (in my opinion) highly over rated.

There is no evidence (and can be no evidence) that the Universe started as a singularity with infinite density, and many good reasons to think that it didn’t.

Expansion is usually a result of compression?

Possibly I’m missing your point, but I’d say the opposite was true.

The Rev Dodgson said:

roughbarked said:

The Rev Dodgson said:

Occam’s razor is (in my opinion) highly over rated.

There is no evidence (and can be no evidence) that the Universe started as a singularity with infinite density, and many good reasons to think that it didn’t.

Expansion is usually a result of compression?

Possibly I’m missing your point, but I’d say the opposite was true.

I don’t mind. ;)

roughbarked said:

The Rev Dodgson said:

roughbarked said:

Expansion is usually a result of compression?

Possibly I’m missing your point, but I’d say the opposite was true.

I don’t mind. ;)

I understood you, rb ;)

https://en.wikipedia.org/wiki/Balloon_modelling

transition said:

roughbarked said:

The Rev Dodgson said:

Possibly I’m missing your point, but I’d say the opposite was true.

I don’t mind. ;)

I understood you, rb ;)

https://en.wikipedia.org/wiki/Balloon_modelling

Well the balloon expands because of tension, and the gas inside is shrunk, not expanded.

The Rev Dodgson said:

mollwollfumble said:

The “big bang” in the sense of an infinitely dense infinitely hot state at time zero – not confirmed, only supported by Occam’s razor.

Occam’s razor is (in my opinion) highly over rated.

There is no evidence (and can be no evidence) that the Universe started as a singularity with infinite density, and many good reasons to think that it didn’t.

> Occam’s razor is (in my opinion) highly over rated.

It’s both highly overrated (as a theoretical tool) and highly underrated (as a practical tool).
For example, the existence of “time” can’t be proved without Occam’s razor.
I once saw a derivation of general relativity that does not make the assumption that time exists.

> many good reasons to think that it didn’t.

I can’t think of any. Any that you can think of?

mollwollfumble said:

The Rev Dodgson said:

mollwollfumble said:

The “big bang” in the sense of an infinitely dense infinitely hot state at time zero – not confirmed, only supported by Occam’s razor.

Occam’s razor is (in my opinion) highly over rated.

There is no evidence (and can be no evidence) that the Universe started as a singularity with infinite density, and many good reasons to think that it didn’t.

> Occam’s razor is (in my opinion) highly over rated.

It’s both highly overrated (as a theoretical tool) and highly underrated (as a practical tool).
For example, the existence of “time” can’t be proved without Occam’s razor.
I once saw a derivation of general relativity that does not make the assumption that time exists.

> many good reasons to think that it didn’t.

I can’t think of any. Any that you can think of?

He’ll get back to you later.

mollwollfumble said:

The Rev Dodgson said:

mollwollfumble said:

The “big bang” in the sense of an infinitely dense infinitely hot state at time zero – not confirmed, only supported by Occam’s razor.

Occam’s razor is (in my opinion) highly over rated.

There is no evidence (and can be no evidence) that the Universe started as a singularity with infinite density, and many good reasons to think that it didn’t.

> Occam’s razor is (in my opinion) highly over rated.

It’s both highly overrated (as a theoretical tool) and highly underrated (as a practical tool).
For example, the existence of “time” can’t be proved without Occam’s razor.
I once saw a derivation of general relativity that does not make the assumption that time exists.

> many good reasons to think that it didn’t.

I can’t think of any. Any that you can think of?

Every time in the past when theories have been extrapolated beyond the scale where evidence was available, the extrapolation has been found to be wrong.

Why would it be any different in this case?

Quite apart from infinite density being incompatible with quantum mechanics.

As for the existence of time, I’m not sure what sort of time you are talking about, but for the standard meaning time is simply an observation.

Peak Warming Man said:

mollwollfumble said:

The Rev Dodgson said:

Occam’s razor is (in my opinion) highly over rated.

There is no evidence (and can be no evidence) that the Universe started as a singularity with infinite density, and many good reasons to think that it didn’t.

> Occam’s razor is (in my opinion) highly over rated.

It’s both highly overrated (as a theoretical tool) and highly underrated (as a practical tool).
For example, the existence of “time” can’t be proved without Occam’s razor.
I once saw a derivation of general relativity that does not make the assumption that time exists.

> many good reasons to think that it didn’t.

I can’t think of any. Any that you can think of?

He’ll get back to you later.

ISWYDT

(At least it occurred to me after a short time)

mollwollfumble said:

I once saw a derivation of general relativity that does not make the assumption that time exists.

So how is velocity defined in the absence of time?

The Rev Dodgson said:

mollwollfumble said:

The Rev Dodgson said:

Occam’s razor is (in my opinion) highly over rated.

There is no evidence (and can be no evidence) that the Universe started as a singularity with infinite density, and many good reasons to think that it didn’t.

> Occam’s razor is (in my opinion) highly over rated.

It’s both highly overrated (as a theoretical tool) and highly underrated (as a practical tool).
For example, the existence of “time” can’t be proved without Occam’s razor.
I once saw a derivation of general relativity that does not make the assumption that time exists.

> many good reasons to think that it didn’t.

I can’t think of any. Any that you can think of?

Every time in the past when theories have been extrapolated beyond the scale where evidence was available, the extrapolation has been found to be wrong.

Why would it be any different in this case?

Quite apart from infinite density being incompatible with quantum mechanics.

As for the existence of time, I’m not sure what sort of time you are talking about, but for the standard meaning time is simply an observation.

> Every time in the past when theories have been extrapolated beyond the scale where evidence was available, the extrapolation has been found to be wrong.

Fair enough.

> Quite apart from infinite density being incompatible with quantum mechanics.

Actually, stretching my theoretical knowledge to the limit and perhaps beyond, the opposite is true. Classical mechanics says that the electron has a classical radius that does not agree with observations. Quantum mechanics says that the radius of the electron is exactly zero, giving it infinite density. Electrons and a lot of other subatomic particles are point-like. (I’m hedging a bit here, an electron has zero radius if its momentum is completely unknown).

> time is simply an observation

No. How do you observe time?

The mathematical process for generating a general relativity without either a continuous or quantised time coordinate is known as Schild’s ladder, also called parallel transport. https://en.wikipedia.org/wiki/Schild%27s_ladder

mollwollfumble said:

The Rev Dodgson said:

mollwollfumble said:

> Occam’s razor is (in my opinion) highly over rated.

It’s both highly overrated (as a theoretical tool) and highly underrated (as a practical tool).
For example, the existence of “time” can’t be proved without Occam’s razor.
I once saw a derivation of general relativity that does not make the assumption that time exists.

> many good reasons to think that it didn’t.

I can’t think of any. Any that you can think of?

Every time in the past when theories have been extrapolated beyond the scale where evidence was available, the extrapolation has been found to be wrong.

Why would it be any different in this case?

Quite apart from infinite density being incompatible with quantum mechanics.

As for the existence of time, I’m not sure what sort of time you are talking about, but for the standard meaning time is simply an observation.

> Every time in the past when theories have been extrapolated beyond the scale where evidence was available, the extrapolation has been found to be wrong.

Fair enough.

> Quite apart from infinite density being incompatible with quantum mechanics.

Actually, stretching my theoretical knowledge to the limit and perhaps beyond, the opposite is true. Classical mechanics says that the electron has a classical radius that does not agree with observations. Quantum mechanics says that the radius of the electron is exactly zero, giving it infinite density. Electrons and a lot of other subatomic particles are point-like. (I’m hedging a bit here, an electron has zero radius if its momentum is completely unknown).

> time is simply an observation

No. How do you observe time?

The mathematical process for generating a general relativity without either a continuous or quantised time coordinate is known as Schild’s ladder, also called parallel transport. https://en.wikipedia.org/wiki/Schild%27s_ladder

You observe time by watching something move, or by watching some other property change (colour for instance).

I hadn’t heard of Schild’s ladder, but from a quick read how it provides a time-free relativity is totally unobvious to me.

The Rev Dodgson said:

mollwollfumble said:

The Rev Dodgson said:

Every time in the past when theories have been extrapolated beyond the scale where evidence was available, the extrapolation has been found to be wrong.

Why would it be any different in this case?

Quite apart from infinite density being incompatible with quantum mechanics.

As for the existence of time, I’m not sure what sort of time you are talking about, but for the standard meaning time is simply an observation.

> Every time in the past when theories have been extrapolated beyond the scale where evidence was available, the extrapolation has been found to be wrong.

Fair enough.

> Quite apart from infinite density being incompatible with quantum mechanics.

Actually, stretching my theoretical knowledge to the limit and perhaps beyond, the opposite is true. Classical mechanics says that the electron has a classical radius that does not agree with observations. Quantum mechanics says that the radius of the electron is exactly zero, giving it infinite density. Electrons and a lot of other subatomic particles are point-like. (I’m hedging a bit here, an electron has zero radius if its momentum is completely unknown).

> time is simply an observation

No. How do you observe time?

The mathematical process for generating a general relativity without either a continuous or quantised time coordinate is known as Schild’s ladder, also called parallel transport. https://en.wikipedia.org/wiki/Schild%27s_ladder

You observe time by watching something move, or by watching some other property change (colour for instance).

I hadn’t heard of Schild’s ladder, but from a quick read how it provides a time-free relativity is totally unobvious to me.

I’d heard of it before but only because I read the book by Greg Egan.

https://en.wikipedia.org/wiki/Schild%27s_Ladder

sibeen said:

The Rev Dodgson said:

mollwollfumble said:

> Every time in the past when theories have been extrapolated beyond the scale where evidence was available, the extrapolation has been found to be wrong.

Fair enough.

> Quite apart from infinite density being incompatible with quantum mechanics.

Actually, stretching my theoretical knowledge to the limit and perhaps beyond, the opposite is true. Classical mechanics says that the electron has a classical radius that does not agree with observations. Quantum mechanics says that the radius of the electron is exactly zero, giving it infinite density. Electrons and a lot of other subatomic particles are point-like. (I’m hedging a bit here, an electron has zero radius if its momentum is completely unknown).

> time is simply an observation

No. How do you observe time?

The mathematical process for generating a general relativity without either a continuous or quantised time coordinate is known as Schild’s ladder, also called parallel transport. https://en.wikipedia.org/wiki/Schild%27s_ladder

You observe time by watching something move, or by watching some other property change (colour for instance).

I hadn’t heard of Schild’s ladder, but from a quick read how it provides a time-free relativity is totally unobvious to me.

I’d heard of it before but only because I read the book by Greg Egan.

https://en.wikipedia.org/wiki/Schild%27s_Ladder

Unfortunately, the book has nothing to do with its title.

I’ve only seen it done once, and right now I’m not even sure if it was in Misner, Thorne and Wheeler (perhaps in Chapter 11) or in a journal article. The concept of a geodesic, path travelled by any object, is fundamental (Occam’s razor), as is the notion of causality (Occam’s razor) and a constant speed for light (Occam’s razor). You create spacetime by measuring the 4-D distance between parallel geodesics. But spacetime itself doesn’t automatically separate into space and time.

To measure time, you can only do it by counting a number of periods of an event assumed to be periodic (assumption from Occam’s razor) or by using a distance (assumed to by constant by Occam’s razor) divided by the speed of light or other speed assumed to be constant.

The Rev Dodgson said:

transition said:

roughbarked said:

I don’t mind. ;)

I understood you, rb ;)

https://en.wikipedia.org/wiki/Balloon_modelling

Well the balloon expands because of tension, and the gas inside is shrunk, not expanded.

I get this too.

mollwollfumble said:

sibeen said:

The Rev Dodgson said:

You observe time by watching something move, or by watching some other property change (colour for instance).

I hadn’t heard of Schild’s ladder, but from a quick read how it provides a time-free relativity is totally unobvious to me.

I’d heard of it before but only because I read the book by Greg Egan.

https://en.wikipedia.org/wiki/Schild%27s_Ladder

Unfortunately, the book has nothing to do with its title.

I’ve only seen it done once, and right now I’m not even sure if it was in Misner, Thorne and Wheeler (perhaps in Chapter 11) or in a journal article. The concept of a geodesic, path travelled by any object, is fundamental (Occam’s razor), as is the notion of causality (Occam’s razor) and a constant speed for light (Occam’s razor). You create spacetime by measuring the 4-D distance between parallel geodesics. But spacetime itself doesn’t automatically separate into space and time.

To measure time, you can only do it by counting a number of periods of an event assumed to be periodic (assumption from Occam’s razor) or by using a distance (assumed to by constant by Occam’s razor) divided by the speed of light or other speed assumed to be constant.

Ah, so you are talking about measuring time, rather than just observing it?

In that case I agree there are a number of assumptions that quite possibly are based on Occam’s razor (and quite possibly are invalid).

Ah, so you are talking about measuring time, rather than just observing it?

—
Can’t you do both with a light clock?