The Beginning of the Universe

[swansont]

4 minutes ago, Airbrush said:

What is the evidence that the big bang was not an explosion?

You’re asking for me to prove a negative. I didn’t say there was evidence it wasn’t an explosion, I said the evidence doesn’t support that hypothesis. You own the burden of proof here, if you want to claim that it was.

What does an explosion look like, and what evidence exists? An explosion in a vacuum would have matter expanding from the point of the explosion. There’s no evidence of that. What’s the temperature profile of an explosion? Is it a predominantly uniform temperature everywhere you look? No. 

 

[exchemist]

20 minutes ago, Airbrush said:

 

What is the evidence that the big bang was not an explosion?

What is the likelihood that the expansion we are able to see continues to infinity (assuming a flat universe)?  I propose that even scientists are not comfortable with very large numbers.  The number of Planck volumes in our observable universe is less than 10 to the power of 200.

Surely an explosion is a rapid expansion, in volume, of matter, isn’t it?

[Airbrush]

14 minutes ago, exchemist said:

Surely an explosion is a rapid expansion, in volume, of matter, isn’t it?

Yes, and the big bang was a rapid expansion of energy that cooled and condensed into matter.

On 1/25/2024 at 8:21 AM, Genady said:

Not necessarily. There are ways to have even infinite number of infinite universes in a multiverse. And if some of them are finite, they do not necessarily have a center, edges, etc.

Can you describe this more?  It is hard to imagine how more than one infinite universe could co-exist in a natural way.  We may arbitrarily divide an infinite universe into any number of sections, each section extends to infinity in one direction, but that is not natural.  How can a finite-sized universe not have a center or edges?

Edited March 10 by Airbrush

[Genady]

17 minutes ago, Airbrush said:

more than one infinite universe could co-exist in a natural way

As I have mentioned, there are many ways. One of them is that the multiverse's space is not necessarily three dimensional.

 

17 minutes ago, Airbrush said:

How can a finite universe not have a center or edges?

If its geometry is not Euclidean, for example.

Edited March 10 by Genady

[exchemist]

30 minutes ago, Airbrush said:

Yes, and the big bang was a rapid expansion of energy that cooled and condensed into matter.

Can you describe this more?  It is hard to imagine how more than one infinite universe could co-exist in a natural way.  We may arbitrarily divide an infinite universe into any number of sections, each section extends to infinity in one direction, but that is not natural.  How can a finite-sized universe not have a center or edges?

You can’t have an expansion of energy. Energy is a property, not an entity. Energy has to be the energy of something, a physical system of some kind.

[Moontanman]

2 minutes ago, exchemist said:

You can’t have an expansion of energy. Energy is a property, not an entity. Energy has to be the energy of something, a physical system of some kind.

I read it as the energy of expansion cooled into matter or at least that is how it was worded when I read it in several articles many years ago. The wording "expansion of energy" was "energy of expansion" is this significant? 

[exchemist]

3 hours ago, Moontanman said:

I read it as the energy of expansion cooled into matter or at least that is how it was worded when I read it in several articles many years ago. The wording "expansion of energy" was "energy of expansion" is this significant? 

I doubt it. Expansion is not a physical system. A physical system has to comprise matter, radiation or fields of some description, I think.

As I understand it, the Big Bang hypothesis suggests radiation and maybe (?) some elements of matter were present at a very early stage, but since the laws of physics break down as one extrapolates back towards the presumed singularity (if there was one), it's probably a bit meaningless to speculate too much.    

[MigL]

5 hours ago, Airbrush said:

What is the evidence that the big bang was not an explosion?

An explosion has a radial direction.
Parts of the 'exploding' material closer to the origin of the explosion would be moving towards the intermediate parts, while the furthest parts wouls be moving away from the intermediate parts.
We observe ALL parts moving away from us, no matter which direction we look ( and so do observers on the other parts )

Even if the explosion was a 'surface' effect so that all parts are equidistant from the origin, we would still see 'voids' when looking towards the origin, or away from it; we see neither of these.

IOW, the universe's 'explosion' is not consistent with observations, but expansion, as in increasing separations between parts of the universe, is.

( c'mon Airbrush, you've participated in enough of these discussions to know better about this, and some of your other claims )

[Airbrush]

On 3/10/2024 at 3:30 PM, MigL said:

An explosion has a radial direction.
Parts of the 'exploding' material closer to the origin of the explosion would be moving towards the intermediate parts, while the furthest parts wouls be moving away from the intermediate parts.
We observe ALL parts moving away from us, no matter which direction we look ( and so do observers on the other parts )

Even if the explosion was a 'surface' effect so that all parts are equidistant from the origin, we would still see 'voids' when looking towards the origin, or away from it; we see neither of these.

IOW, the universe's 'explosion' is not consistent with observations, but expansion, as in increasing separations between parts of the universe, is.

( c'mon Airbrush, you've participated in enough of these discussions to know better about this, and some of your other claims )

Thanks for your explanation.  But what if the "surface" or skin of the balloon, had a thickness of over 100 billion light years?  Then the expansion would resemble what we can see, no voids would be seen, and we would not know the direction of the expansion.

On 3/10/2024 at 11:22 AM, exchemist said:

You can’t have an expansion of energy. Energy is a property, not an entity. Energy has to be the energy of something, a physical system of some kind.

Are you suggesting that the big bang was not an expansion of energy?  First there is energy.  Much later, after it cools down, a huge amount of energy congeals into a small amount of matter, E = mc2, so E/c2 = m.

Edited March 18 by Airbrush

[exchemist]

23 minutes ago, Airbrush said:

Thanks for your explanation.  But what if the "surface" or skin of the balloon, had a thickness of over 100 billion light years?  Then the expansion would resemble what we can see, no voids would be seen, and we would not know the direction of the expansion.

Are you suggesting that the big bang was not an expansion of energy?  First there is energy.  Much later, after it cools down, a huge amount of energy congeals into a small amount of matter, E = mc2, so E/c2 = m.

Yup, that’s a (quite common) misconception. We can only speculate about what might have been first, but what’s for sure it wasn’t just “energy” somehow existing on its own. That would be as silly as claiming that what came first was “momentum”, without saying the momentum of what. You can’t have a jug of energy any more than you can a jug of momentum, or velocity. All these are properties, not entities.
 

Incidentally, “m” in Einstein’s equation does not stand for matter, it stands for mass, which, like energy, is a property of matter, not a free-standing entity. Another misconception is that the equation predicts “conversion” between energy and mass. What it actually says is that rest mass has energy. It’s not one or the other but both at once. The entities involved are radiation and matter. Energy and mass are properties.

In the early stages of the big bang model, there is thought to have been radiation, and sub-nuclear particles, I think. It will have been these entities that possessed the energy.

Edited March 18 by exchemist

[Airbrush]

16 minutes ago, exchemist said:

Yup, that’s a (quite common) misconception. We can only speculate about what might have been first, but what’s for sure it wasn’t just “energy” somehow existing on its own. That would be as silly as claiming that what came first was “momentum”, without saying the momentum of what. You can’t have a jug of energy any more than you can a jug of momentum, or velocity. All these are properties, not entities.
 

Incidentally, “m” in Einstein’s equation does not stand for matter, it stands for mass, which, like energy, is a property of matter, not a free-standing entity. Another misconception is that the equation predicts “conversion” between energy and mass. What it actually says is that rest mass has energy. It’s not one or the other but both at once. The entities involved are radiation and matter. Energy and mass are properties.

In the early stages of the big bang model, there is thought to have been radiation, and sub-nuclear particles, I think. It will have been these entities that possessed the energy.

Very interesting.  I like your explanation.  Then you said that "something" maybe some kind of sub-nuclear particles possessed the energy.  Let's work backwards.  Now we have matter.  Before that, matter was in the form of energy, sub-nuclear particles possessed energy, and we don't know what was between that and the start of the big bang.  Right?

[Luc Turpin]

I have been reading and re-reading this thread trying to understand what happened near the big-bang and still cannot wrap my head around it!

Can someone describe to me, based on observation and best model so far, what we think occurred at or near the big-bang?

Is there an analogy that can help explain what took place?

Desperately seeking understanding!

[exchemist]

40 minutes ago, Airbrush said:

Very interesting.  I like your explanation.  Then you said that "something" maybe some kind of sub-nuclear particles possessed the energy.  Let's work backwards.  Now we have matter.  Before that, matter was in the form of energy, sub-nuclear particles possessed energy, and we don't know what was between that and the start of the big bang.  Right?

No matter was not "in the form of energy". That is the same confusion as before. There would have been radiation and fields (radiation is a form of oscillating field) that possessed energy. The entity is the radiation, or the field. Energy is one of its properties, along with other properties like direction, phase, frequency, amplitude and so forth.

But my very limited understanding of this (I'm not even a physicist) is that when you try to extrapolate back you reach a limit at which our current theories of matter, radiation and fields etc break down. So we can't "see" any further back, even theoretically. Strictly, the big bang theory starts from the limit of credible extrapolation. All the stuff about singularities etc only has the status of conjecture, so far as I know. 

 

 

[Phi for All]

6 minutes ago, Luc Turpin said:

Is there an analogy that can help explain what took place?

Analogy doesn't help much with this. It confuses things further.

Very simply, so simply that it can't possibly be held to any degree of accuracy: the universe was extremely small, the matter in it was extremely dense and therefore extremely hot, and then the universe (which is everything there is) expanded rapidly (and the last point, working backwards, at which we can accurately measure it is what we call The Big Bang). At some point, the density of matter decreased enough to allow space between it to form, and the temperatures continued to fall.

It could be that all that matter squeezed so small is similar to what happens in a black hole, but black holes happen inside the universe, and particles that fall inside are measured relative to the black hole, and no velocity can change that. When the whole universe is inflating itself so rapidly though, everything is different because everything is moving and expanding, everything in the universe is participating in the event. 

And I've probably made it worse. 

[joigus]

On 11/12/2023 at 4:04 AM, Chris Sawatsky said:

A sphere exploded but did not expand in every possible direction simultaneously?

Picture an inflating balloon. Now suppress the space around and inside the balloon, as there is no such thing as "inside" or outside the balloon. There would be only whatever stuff makes up the balloon. Now make the balloon itself 3-dimensional, with time providing for the "history" aspect of it.

Spaces don't have to be embedded in higher-dimensional spaces. IOW, the only existing directions are those tangential to the balloon's rubber if you will.

Edited March 18 by joigus
minor correction

[Luc Turpin]

39 minutes ago, Phi for All said:

Analogy doesn't help much with this. It confuses things further.

Very simply, so simply that it can't possibly be held to any degree of accuracy: the universe was extremely small, the matter in it was extremely dense and therefore extremely hot, and then the universe (which is everything there is) expanded rapidly (and the last point, working backwards, at which we can accurately measure it is what we call The Big Bang). At some point, the density of matter decreased enough to allow space between it to form, and the temperatures continued to fall.

It could be that all that matter squeezed so small is similar to what happens in a black hole, but black holes happen inside the universe, and particles that fall inside are measured relative to the black hole, and no velocity can change that. When the whole universe is inflating itself so rapidly though, everything is different because everything is moving and expanding, everything in the universe is participating in the event. 

And I've probably made it worse. 

You have greatly contributed to my understanding of the big-bang; thanks

1 hour ago, exchemist said:

No matter was not "in the form of energy". That is the same confusion as before. There would have been radiation and fields (radiation is a form of oscillating field) that possessed energy. The entity is the radiation, or the field. Energy is one of its properties, along with other properties like direction, phase, frequency, amplitude and so forth.

But my very limited understanding of this (I'm not even a physicist) is that when you try to extrapolate back you reach a limit at which our current theories of matter, radiation and fields etc break down. So we can't "see" any further back, even theoretically. Strictly, the big bang theory starts from the limit of credible extrapolation. All the stuff about singularities etc only has the status of conjecture, so far as I know. 

 

 

+1

[MigL]

1 hour ago, Phi for All said:

the universe was extremely small, the matter in it was extremely dense and therefore extremely hot

Just to clarify.
The matter dominated era comes later; the first era was radiation dominated.

What later became matter, with mass, was originally all massless radiation ( possessing the property of energy ), because the Electroweak force had not decoupled yet for the Higgs mechanism to give mass to Fermions,
This would have been when the observable universe was in causal contact ( light/information has time to traverse it ) in order to establish an equilibrium that ensures isotropy and homogeneity, prior to a vacuum energy driven inflationary period that expanded that observable universe many many orders of magnitude.

See Alan Guth, Electroweak symmetry break, and Inflationary Theory.

 

[Mordred]

On 3/10/2024 at 11:21 AM, Airbrush said:

 

What is the evidence that the big bang was not an explosion?

What is the likelihood that the expansion we are able to see continues to infinity (assuming a flat universe)?  I propose that even scientists are not comfortable with very large numbers.  The number of Planck volumes in our observable universe is less than 10 to the power of 200.

An explosion has different dynamics that are measurable. You can easily confirm the difference yourself. Take a ruler from a central point at various different angles measure off 1 cm then 3 cm then 6 cm etc.  Now think of the ratio of change the result of radiating outward from the central point and measure the angles. You should notice angle changes as well as a preferred direction and location.

 

Now place dots on a balloon measure the angles prior to inflating (inflate just enough to get a sphere. Then inflate the balloon further. The angles do not change and the ratio of change in distance is identical between any two points. 

[KJW]

3 hours ago, Mordred said:

An explosion has different dynamics that are measurable. You can easily confirm the difference yourself. Take a ruler from a central point at various different angles measure off 1 cm then 3 cm then 6 cm etc.  Now think of the ratio of change the result of radiating outward from the central point and measure the angles. You should notice angle changes as well as a preferred direction and location.

 

Now place dots on a balloon measure the angles prior to inflating (inflate just enough to get a sphere. Then inflate the balloon further. The angles do not change and the ratio of change in distance is identical between any two points. 

For an explosion from a single point, every particle moving away from that point also moves away from each other at a speed that is proportional to the separation between the particles. Consider two arbitrary particles. Construct the triangle from the positions of the two particles and the origin of the explosion. This is the configuration at time=T. At time=2T, the configuration is a similar triangle of doubled lengths. This means that none of the angles have changed, the two particles are moving away from each other without any transverse motion.

 

 

[swansont]

1 hour ago, KJW said:

For an explosion from a single point, every particle moving away from that point also moves away from each other at a speed that is proportional to the separation between the particles

Two particles traveling in opposite directions, each at v wrt to the explosion, will separate at 2v (for v<<c) and this will not change with time, and therefor not change with separation.

For v to increase in such a scenario you’d violate both conservation of energy and Newton’s first law 

[KJW]

26 minutes ago, swansont said:

Two particles traveling in opposite directions, each at v wrt to the explosion, will separate at 2v (for v<<c) and this will not change with time, and therefor not change with separation.

For v to increase in such a scenario you’d violate both conservation of energy and Newton’s first law 

I didn't explicitly say it, but my description implied that the proportionality between speed and separation was for different pairs of particles at a particular instant in time. At different instants in time, the proportionality constant will be different such that the relative velocity between any particular pair of particles will be constant over time.

 

Edited March 25 by KJW

[swansont]

1 hour ago, KJW said:

I didn't explicitly say it, but my description implied that the proportionality between speed and separation was for different pairs of particles at a particular instant in time. At different instants in time, the proportionality constant will be different such that the relative velocity between any particular pair of particles will be constant over time.

 

The separation velocity of any two particles will be constant in time; absent any interaction, the velocity of each particles is constant. There’s nothing proportional with distance.

[KJW]

7 hours ago, swansont said:

There’s nothing proportional with distance.

At a given time=T, the velocity of any particle relative to a given particle is directly proportional to the displacement of the particle relative to the given particle. The proportionality constant is T^–1.

 

Edited March 26 by KJW

[swansont]

2 hours ago, KJW said:

At a given time=T, the velocity of any particle relative to a given particle is directly proportional to the displacement of the particle relative to the given particle. The proportionality constant is T^–1.

 

T isn’t a constant.

[KJW]

9 minutes ago, swansont said:

T isn’t a constant.

Time isn't a constant, but T is, by definition.

 

Edited March 26 by KJW