Tackling Inflation

[Brian O]

Faster than light inflation at the birth of the universe has always been a great problem.

What if the universe began as a sea of entangled particles in a single quantised state which was only stable at a limited number of sizes?

The universe would be infinitesimal and large at the same time but would stay like that forever until something happened to collapse the alternative states.

It might be that two or more fluctuations took place at the same time and/or in the same space and only one stable size was compatible between them.

Thus, a jump between a small point and a finite sized universe could occur before time as we understand it existed without the need for a faster than light expansion .

Any thoughts?

[saac]

I always thought, that the physics of the universe at the period of inflation were not those we experience now. The fundamental forces were not yet discrete (still unified) - not 100% sure so I may be wrong here. The faster than speed of light restriction is a restriction on mass, stuff in the universe, and not space itself, leaving the universe free to inflate faster than light as it saw fit. Exactly how physicists can predict what conditions were like during such incomprehensible timescales is always a source of amazement to me !

Jim 

Edited March 14 by saac

[JeremyS]

Tackling inflation? I thought politics weren’t allowed on here 🤔

[Franklin]

I don't understand politics or cosmology, but inflation is what I do to my tyers.

Edited March 14 by Franklin

[andrew s]

The simple answer is we don't know. There are several theories covering the proposed period of inflation. 

It is still an active area of research but unless we get a quantum theory of gravity it is all very speculative. 

As @saac points out all the forces were unified. Particles only condensed out after inflation so our normal ideas of entanglement etc. don't apply.

Regards Andrew 

Edited March 14 by andrew s

[Franklin]

1 hour ago, saac said:

Exactly how physicists can predict what conditions were like during such incomprehensible timescales is always a source of amazement to me !

Mind blown!

As a "Stargazer" I love looking at the night sky, it's massive and beautiful and not of this world, but practically everything I see up there is in our own galaxy, the Milky Way. 

The Universe is full of countless other "Milky Ways" and I find trying to make sense of all this impossible. This is a subject which is undoubtably scientific, but because of it's very nature can't help merging with other not so scientific ideas. I'm no scientist but when I talk to my friends about these things they always come back to me with the same questions, "What happened before the Big Bang?", "How can that be possible?", "Something must have existed before existence began?". 

All I can come up with is "Hats off to whoever solves the puzzle"😁.

[saac]

22 hours ago, Franklin said:

I'm no scientist but when I talk to my friends about these things they always come back to me with the same questions, "What happened before the Big Bang?", "How can that be possible?", "Something must have existed before existence began?". 

All I can come up with is "Hats off to whoever solves the puzzle"😁.

The way I reconcile this is -  because we (our intellect) are part of existence (ourselves products of the "after the big bang") we are constrained only to know that existence or reality. The common answer is that anything prior to that is not a legitimate question as prior is a measure of time and time appears to be a property of existence (part of the fabric of our universe).  That leads to the entirely unsatisfactory "time",  and hence "prior", did not exist before the big bang.  That's so difficult for us to conceive because we don't experience time like that so our thinking is constrained.  

But as you say "hats off to them" - it's one thing to read about it, another to come up with it from first principles. They are genuinely gifted people. 

Jim 

Edited March 15 by saac

[Albir phil]

On 15/03/2024 at 22:17, saac said:

The way I reconcile this is -  because we (our intellect) are part of existence (ourselves products of the "after the big bang") we are constrained only to know that existence or reality. The common answer is that anything prior to that is not a legitimate question as prior is a measure of time and time appears to be a property of existence (part of the fabric of our universe).  That leads to the entirely unsatisfactory "time",  and hence "prior", did not exist before the big bang.  That's so difficult for us to conceive because we don't experience time like that so our thinking is constrained.  

But as you say "hats off to them" - it's one thing to read about it, another to come up with it from first principles. They are genuinely gifted people. 

Jim 

Time is a measurement created by we humans,it is our way of understanding and explaining things around us including distance,if we were not here time would go on but unmeasurable 

 

 

 

[saac]

7 hours ago, Albir phil said:

Time is a measurement created by we humans,it is our way of understanding and explaining things around us including distance,if we were not here time would go on but unmeasurable 

 

 

 

The way we experience time definitely makes it difficult to understand its true nature but time does appear to be an intrinsic (potentially emergent) property of our universe. 

Jim

Edited March 18 by saac

[andrew s]

Time has many faces. We have our experience of it passing, our psychological time, and its rate can slow and speed-up with our moods. 

In physics time is a parameter in a space-time geometry that we find effectively underpins our best theories. 

There is no requirement for them to be the same.

Regards Andrew 

[Brian O]

So I can see that inflation is an expansion of space rather than any matter within it.

But even if the embryonic universe consisted exclusively of energy, each photon would be moving away from its neighbours at more than the speed of light.

Maybe we are dealing with a pure form of energy without a mass equivalent, perhaps in a phase of matter somewhat more energetic than a plasma.

Can anyone help me out here, please?

[andrew s]

11 minutes ago, Brian O said:

Can anyone help me out here, please?

This may help you. Regards Andrew 

[saac]

28 minutes ago, Brian O said:

So I can see that inflation is an expansion of space rather than any matter within it.

But even if the embryonic universe consisted exclusively of energy, each photon would be moving away from its neighbours at more than the speed of light.

Maybe we are dealing with a pure form of energy without a mass equivalent, perhaps in a phase of matter somewhat more energetic than a plasma.

Can anyone help me out here, please?

Not sure what you mean by pure energy.  I don't think separating the energy/matter equivalence makes sense either. 

Jim 

[Ratlet]

I quite like the idea that inflation came first before the matter.

The energy of the universe drove expansion of space at ridiculous speeds and then when it eventually 'stretched' enough and the energy density got to a certain point there was a phase change and the energy driving expansion got dumped into the universe as matter and light.  New idea to me but it makes much more sense that way round rather than matter/energy first they inflation mysteriously happening (which I think was the preferred explanation in the 80's/90's/00's).

I'm getting a bit more excited about advanced physics than I have done in years (at my popular science level understanding).  For ages it felt like there were gaps in our understanding and we knew they were there but didn't know the shape of them.  Feels like now they're getting a much tighter head on where the theories breakdown.  Lots of arguments and intensity and it kind of feels like there is a shift coming.

[Zermelo]

On 13/03/2024 at 17:06, Brian O said:

Faster than light inflation at the birth of the universe has always been a great problem.

The constraint of the speed of light applies to inertial frames of reference within the theory of special relativity. The expansion of space itself is described in the theory of general relativity, and is not constrained in the same way.

[robin_astro]

On 13/03/2024 at 17:06, Brian O said:

Faster than light inflation at the birth of the universe has always been a great problem.

What caused inflation is an open subject but why specifically is "faster than light inflation" during the inflationary period seen as a problem any more than it is now with the current rate of expansion which, depending on the coordinate system used, also implies "faster than light velocities". 

According to the description in the link posted by Andrew, inflation took place under conditions where "normal", (though extreme) physics holds.  Isn't the question of "faster than light velocities" at both early and late times therefore resolved within the framework of general relativity as Zermelo points out without the need of new physics?

Robin

[jjohnson3803]

I'm a heretic.  I accept that inflation theory explains a good many things, but there is something about it that whispers, "Epicycles!" to me.

I have doubts about dark matter as well and I frankly don't think it will be found anytime soon.  Kind of like Supersymmetry in the Standard Model.

But I acknowledge that I'm often wrong, at least according to my wife, so I'll leave debates to others and keep trying to decipher cosmology preprints on arxiv.org.

 

 

[andrew s]

2 hours ago, robin_astro said:

What caused inflation is an open subject but why specifically is "faster than light inflation" during the inflationary period seen as a problem any more than it is now with the current rate of expansion which, depending on the coordinate system used, also implies "faster than light velocities". 

According to the description in the link posted by Andrew, inflation took place under conditions where "normal", (though extreme) physics holds.  Isn't the question of "faster than light velocities" at both early and late times therefore resolved within the framework of general relativity as Zermelo points out without the need of new physics?

Robin

You are Zermelo are quite right.

In the curved space time of GR comparing velocities of separated objects is generally impossible. However,  locally the speed of light is always measured to be the same i.e. c.

To see the issue of comparing velocities. Take two cars on opposite side of the equator heading north at a velocity v. Initially,  their relative velocity is zero. But, by the time they get to the pole they are heading for a collision at relative velocity 2v.

Regards Andrew 

[iantaylor2uk]

As I understand it, inflation occurred very early after the big bang. According to Wikipedia, inflation occurred at times from 10^-36 to about 10^-32 seconds after the big bang.

However, particles (neutrinos, electrons, quarks etc.) are not thought to have formed until 10^-12 to 10^-6 seconds (https://www.astronomy.com/science/how-did-the-first-element-form-after-the-big-bang/) and protons, neutrons, atoms, didn't form until a few minutes had past. 

I don't believe there were any photons around at the time of inflation, so the "speed of light" as such didn't exist when inflation occurred, so I don't really see what the problem is. 

[andrew s]

The speed of light isn't really (or just) the speed of light! It's is a shorthand for the upper speed limit to the propagation of information in a spacetime governed by GR. That's partly why we need inflation to explain the amazing uniformity of the CMB as otherwise it could not be in the near perfect thermal equilibrium we observe. Without it, regions of space would get too far apart to "communicate" about their temperatures. Inflation stops them from getting out of equilibrium as the expansion is too fast to allow it.

Regards Andrew 

Edited March 21 by andrew s

[iantaylor2uk]

The only way time is measured in relativity is by using photons - think of special relativity where Einstein uses mirrors and photons to explain the change of length with speed. 

If there aren't any photons, there is no way of measuring time, and so I doubt that special and general relativity apply in an era before photons. 

[andrew s]

Just now, iantaylor2uk said:

The only way time is measured in relativity is by using photons - think of special relativity where Einstein uses mirrors and photons to explain the change of length with speed. 

If there aren't any photons, there is no way of measuring time, and so I doubt that special and general relativity apply in an era before photons. 

In GR spacetime is just geometry with a well defined metric. Add an equation of state of the contents and you're away.

To provide experimental data to test such a mathematical model you don't just need photons you need to build both clocks and measuring sticks and an intelligence to use them. 

Once you are reasonably happy with the models predictions v your observations you can extrapolate to the time before clocks (or photons) as time like space is just a parameter in the model. The tricky bit is having an equation of state not the geometry. 

Regards Andrew 

[Brian O]

On 20/03/2024 at 21:36, saac said:

Not sure what you mean by pure energy.  I don't think separating the energy/matter equivalence makes sense either. 

Jim 

Sorry for the tentative terminology.

I'm trying to get my head around a time without matter as we know it.

On further reading, I find that inflation most likely occurred before the existence of Higgs Bosuns and mass.

Maybe before the existence of photons.

So if there were no point particles or photons at the time, where can we start any measurements and what form of energy existed?

[andrew s]

19 minutes ago, Brian O said:

where can we start any measurements and what form of energy existed?

Currently,  the earliest data we can get is from the CMB. We may potentially be able to get information from before that from primordial gravitational waves but don't hold your breath. 

The infered initial ratio of H to He & Li also give information on the first nuclear synthesis and hence the conditions at that time.

Regards Andrew 

Edited March 22 by andrew s