Big Bang and preferred frames (split from What is time? (Again))

[geordief]

5 hours ago, Markus Hanke said:

 

The lack of a preferred frame means that no law of physics can vary if you go from one frame to another ('preferred' would need to mean that something about it is different compared to other frames), and that includes Maxwell's equations. 

I have heard that the Big Bang was not an explosion but that everything separated from all other objects (a bit like anti -gravity on steroids?)

 

Could  this be  an explanation for why there is actually  no preferred frame of reference? Every point at the initiation of that expansion period can equally be considered to be the starting point.....

 

Suppose that  there had in fact occurred an explosion  and that all bodies had receded from a single area radially  ,would such a fictitious scenario lead to some preferred frame of reference whereby the site of that explosion could be considered as "ground zero"(and a preferred frame of reference  if only on that one occasion)?

 

And would that scenario allow  for any invariance in c ?

Edited September 9, 2020 by geordief

[MigL]

"Would having a preferred frame imply the existence of preferred frames ?"

Seems painfully obvious.

[swansont]

!

Moderator Note

It's great that you want to ask question, but what's not so great is that you continue to hijack threads to ask them. 

If you have a direction not directed to the OP, or about the topic, you need to start a new thread.

 

 

You need to identify what would allow you to identify the preferred frame, and that will identify the part of physics you've broken that would give you a preferred frame. The thing is, you can't really describe that with accepted physics, since accepted physics doesn't have a preferred frame.

 

Also, what does " any invariance in c" mean? It's either invariant or it isn't. "Some invariance" is like being a little pregnant.

[geordief]

20 minutes ago, MigL said:

"Would having a preferred frame imply the existence of preferred frames ?"

Seems painfully obvious.

I wasn't sure my fictitious  point of explosion would count as a frame of reference but you seem to be saying that it would.

 

Would you say that such a fictitious universe with  its fictitious preferred  frame of reference implies that c might not be invariant  in that fictitious universe?

 

 

  

[swansont]

14 minutes ago, geordief said:

I wasn't sure my fictitious  point of explosion would count as a frame of reference but you seem to be saying that it would.

 

Would you say that such a fictitious universe with  its fictitious preferred  frame of reference implies that c might not be invariant  in that fictitious universe?  

Once you've decided to break the laws of physics, you can't rely on physics to tell you what happens. All bets are off.

Like I said in my last post, you have to explain how it's a preferred frame. Then you can possibly figure out which parts of physics you have broken. 

 

 

[zapatos]

1 hour ago, swansont said:

You need to identify what would allow you to identify the preferred frame, and that will identify the part of physics you've broken that would give you a preferred frame. The thing is, you can't really describe that with accepted physics, since accepted physics doesn't have a preferred frame.

Would you mind expanding a bit on how physics could be broken by having a preferred frame? Are you saying that losing then assumption of 'no preferred frame' means that certain calculations would no longer work? Or is it more of a case that we would have to rethink our explanation of what the universe looks like.

For example, when we discovered that our galaxy wasn't the entire universe, afaik that didn't mean any of our calculations no longer worked, only that we had to change our understanding of the universe and how it worked.

 

[MigL]

A 'preferred frame' implies that you can hang a co-ordinate system onto an event, and that origin point is at rest with respect to everything else in the universe. That is what the fictitious centralized Big Bang scenario does.
Essentially, it breaks relativity.
( and not just Einsteinian relativity, but all the way back to Galileo's time and earlier )

Edited September 9, 2020 by MigL

[zapatos]

2 minutes ago, MigL said:

Essentially, it breaks relativity.

Does it mean that GPS quits working? If not, what does quit working? Or is it more the case that Relativity will still work fine, but something else will be needed to account for the preferred frame. Similar to how Newtonian physics didn't quit working when Relativity came along and addressed new situations that Newtonian physics didn't address.

 

[swansont]

44 minutes ago, zapatos said:

Would you mind expanding a bit on how physics could be broken by having a preferred frame? Are you saying that losing then assumption of 'no preferred frame' means that certain calculations would no longer work? Or is it more of a case that we would have to rethink our explanation of what the universe looks like.

An example might be an inertial frame vs. a rotating frame. We know that an inertial frame is "preferred" (though there is no particular one that is) and you can tell whether or not you are in that frame because F=ma works in an inertial frame, but you need to add a fictitious centrifugal force to that equation in a rotating frame.

IOW, F=ma no longer works

 

If you lose the invariance of c — the speed of light only has that value in one particular frame — special relativity no longer works. 

These problems ripple through physics. In the case of a non-invariant c, Maxwells equations fail, too. One can't assume one impossible thing but assume everything else works just fine.

 

44 minutes ago, zapatos said:

For example, when we discovered that our galaxy wasn't the entire universe, afaik that didn't mean any of our calculations no longer worked, only that we had to change our understanding of the universe and how it worked.

Physics got a whole lot simpler when we realized we weren't at the center, though. We didn't need epicycles that had no physical basis. You could make the math work (it's Fourier analysis), but the physics was different. And that's the change in our understanding. (F=ma and gravity) vs something that was not  

 

 

 

[zapatos]

47 minutes ago, swansont said:

An example might be an inertial frame vs. a rotating frame. We know that an inertial frame is "preferred" (though there is no particular one that is) and you can tell whether or not you are in that frame because F=ma works in an inertial frame, but you need to add a fictitious centrifugal force to that equation in a rotating frame.

IOW, F=ma no longer works

 

If you lose the invariance of c — the speed of light only has that value in one particular frame — special relativity no longer works. 

These problems ripple through physics. In the case of a non-invariant c, Maxwells equations fail, too. One can't assume one impossible thing but assume everything else works just fine.

 

Physics got a whole lot simpler when we realized we weren't at the center, though. We didn't need epicycles that had no physical basis. You could make the math work (it's Fourier analysis), but the physics was different. And that's the change in our understanding. (F=ma and gravity) vs something that was not  

That was very helpful. Thanks!

[MigL]

Sorry for not being very clear Zap.

Relativity doesn't just refer to Einstein's theories; the majority of our measurements are relative to something else.
For example, the speed of a ball I throw at you is measured with respect to me and you; based on that you can calculate the kinetic energy, and the force with which it will hit you. But if you measure the speed of the ball with respect to the Earth' orbit about the Sun, it may be moving backwards. Or if measured with respect to geordief's absolute frame at the centre of the universe, it may be moving close to the SoL, making calculations of the type mentioned non-sensical.

Don't get me wrong, there are things that are absolute, but we do have ways to deal with it.
In physics we distinguish measurements made on an absolute frame or scale. Think of the temperature scale.
When we measure relative to something else on the same scale, we call it 'gauge'.. Think of your body being at 100V potential, touching a live wire, and feeling only a 20V shock.

Edited September 9, 2020 by MigL

[zapatos]

4 minutes ago, MigL said:

Relativity doesn't just refer to Einstein's theories; the majority of our measurements are relative to something else.
For example, the speed of a ball I throw at you is measured with respect to me and you; based on that you can calculate the kinetic energy, and the force with which it will hit you. But if you measure the speed of the ball with respect to the Earth' orbit about the Sun, it may be moving backwards. Or if measured with respect to geordief's absolute frame at the centre of the universe, it may be moving close to the SoL, making calculations of the type mentioned non-sensical.

In physics we distinguish measurements made on an absolute frame or scale. Think of the temperature scale.
When we measure relative to something else on the same scale, we call it 'gauge'.. Think of your body being at 100V potential, touching a live wire, and feeling only a 20V shock.

Ah yes, relativity vs Relativity. Sometimes I'm slow on the uptake.

Thanks for the further explanation. 😁

[Markus Hanke]

13 hours ago, geordief said:

Could  this be  an explanation for why there is actually  no preferred frame of reference?

It's rather the other way around - relativity being valid is a prerequisite for the evolution of the universe to occur in the first place. If there were preferred frames, and relativity did not hold, then the universe would either not exist at all, or it would look very different. After all, the expanding universe is a consequence of the laws of gravity, which are intrinsically relativistic.

 

[geordief]

6 hours ago, Markus Hanke said:

It's rather the other way around - relativity being valid is a prerequisite for the evolution of the universe to occur in the first place. If there were preferred frames, and relativity did not hold, then the universe would either not exist at all, or it would look very different. After all, the expanding universe is a consequence of the laws of gravity, which are intrinsically relativistic.

 

Isn't the expanding universe a result of more than the laws of gravity?

 

There was the initial inflation and also dark energy....might gravity be a "bit player" ** in the overall scheme?

 

** a very big "bit player"

[Eise]

7 hours ago, Markus Hanke said:

It's rather the other way around - relativity being valid is a prerequisite for the evolution of the universe to occur in the first place. If there were preferred frames, and relativity did not hold, then the universe would either not exist at all, or it would look very different. After all, the expanding universe is a consequence of the laws of gravity, which are intrinsically relativistic.

Hmmm. I thought that a 'Newtonian universe' would also be unstable, i.e. it must also expand or collapse. No doubt it would be a different kind of universe, but at least it would expand (or collapse).

[Markus Hanke]

2 hours ago, Eise said:

Hmmm. I thought that a 'Newtonian universe' would also be unstable, i.e. it must also expand or collapse. No doubt it would be a different kind of universe, but at least it would expand (or collapse).

A Newtonian universe would have a fixed spacetime background with Euclidean geometry - there is no basis there for any dynamics in the metric. 

[Eise]

On 9/10/2020 at 4:23 PM, Markus Hanke said:

A Newtonian universe would have a fixed spacetime background with Euclidean geometry - there is no basis there for any dynamics in the metric. 

But aren't you taking general relativity for granted here? My point is only that even if we would live in a Newtonian universe, it would be dynamic because of gravity. Even if the universe would be infinite. If we would start with a 'magically created' homogeneous distribution of static mass, the universe would 'collapse', i.e in a Newtonian framework, all masses would be moving to each other. The only other option would be that all masses would have gotten an initial velocity large enough to move away from each other. Now this would look like a kind of explosion in space (not of space) I think many lay people still imagine the big bang like that.

[Markus Hanke]

14 minutes ago, Eise said:

My point is only that even if we would live in a Newtonian universe, it would be dynamic because of gravity. Even if the universe would be infinite. If we would start with a 'magically created' homogeneous distribution of static mass, the universe would 'collapse', i.e in a Newtonian framework, all masses would be moving to each other. The only other option would be that all masses would have gotten an initial velocity large enough to move away from each other. Now this would look like a kind of explosion in space (not of space) I think many lay people still imagine the big bang like that.

So you mean there would be dynamics of the mass distribution within such a universe, but not of the universe (i.e. spacetime) itself. That is indeed true, at least in principle - but it isn't what we observe in the real world.