Is change real?

[swansont]

1 minute ago, tim.tdj said:

The fact that we can be either moving or stationary relative to something as fundamental as the CMB seems to suggest to me that a preferred frame does exist. Is there something I am not understanding here? If yes, I would be very grateful if you could explain it to me.

We can always measure a speed with respect to another frame. What we can't do is tell which one is at rest. Are we moving and that frame is at rest, or is it the other way around.

A preferred frame is one where the physics tells you that you are definitely at rest. We can do this with accelerations — you can tell if you are accelerating. But not with velocity. 

[StringJunky]

16 minutes ago, swansont said:

It means that they can happen in an order that would not be possible classically, but we have plenty of examples of classically impossible things in QM (e.g. tunneling). The example I recall (vaguely; it was >20 years ago) is a multi-photon excitation, where the photon for an excited transition arrives first, and the transition still happens, even though the transitions have different energy.

Right. Cheers.

[tim.tdj]

1 minute ago, swansont said:

We can always measure a speed with respect to another frame. What we can't do is tell which one is at rest. Are we moving and that frame is at rest, or is it the other way around.

A preferred frame is one where the physics tells you that you are definitely at rest. We can do this with accelerations — you can tell if you are accelerating. But not with velocity. 

I already fully understand what you have said here and that that it applies if there is no external indicator telling you whether or not you are at rest. However, it seems to me (perhaps wrongly) that the CMB can be used as an external indicator because I am theorising that you are absolutely at rest if you can't detect a cosmic dipole. Can you explain why I might be wrong?

[swansont]

1 hour ago, tim.tdj said:

I already fully understand what you have said here and that that it applies if there is no external indicator telling you whether or not you are at rest. However, it seems to me (perhaps wrongly) that the CMB can be used as an external indicator because I am theorising that you are absolutely at rest if you can't detect a cosmic dipole. Can you explain why I might be wrong?

That tells you if you are at rest with respect to the CMB. You can do that for any two frames of reference. It will not tell you if that rest is absolute. That would require that physics itself behave differently in that one frame. Doppler shifts still follow the same formula, so they are not evidence of an absolute frame.

[StringJunky]

 

2 minutes ago, swansont said:

That tells you if you are at rest with respect to the CMB. You can do that for any two frames of reference. It will not tell you if that rest is absolute. That would require that physics itself behave differently in that one frame. Doppler shifts still follow the same formula, so they are not evidence of an absolute frame.

What would be the acid test for finding a preferred frame: different physics in general or some difference in particular?

[swansont]

7 minutes ago, StringJunky said:

What would be the acid test for finding a preferred frame: different physics in general or some difference in particular?

Physics working differently in that frame vs all of the others. I don't think it would be a particular difference, since that might artificially narrow the testing.

But consider that there are numerous ways you can tell if you are in an inertial frame, where Newtonian physics works vs an accelerating frame, where F = ma no long holds without adding in pseudo-forces. It doesn't matter what the pseudo-force is, as long as you can find evidence of it.

One major difference, though, is we know you can be in an accelerating frame. We have really good evidence that you can't be in a preferred frame.

[StringJunky]

37 minutes ago, swansont said:

Physics working differently in that frame vs all of the others. I don't think it would be a particular difference, since that might artificially narrow the testing.

But consider that there are numerous ways you can tell if you are in an inertial frame, where Newtonian physics works vs an accelerating frame, where F = ma no long holds without adding in pseudo-forces. It doesn't matter what the pseudo-force is, as long as you can find evidence of it.

One major difference, though, is we know you can be in an accelerating frame. We have really good evidence that you can't be in a preferred frame.

Right.  Cheers.

[tim.tdj]

57 minutes ago, swansont said:

That tells you if you are at rest with respect to the CMB. You can do that for any two frames of reference. It will not tell you if that rest is absolute. That would require that physics itself behave differently in that one frame. Doppler shifts still follow the same formula, so they are not evidence of an absolute frame.

Hi Swansont

Thank you very much. You have made it somewhat clearer. What you seem to be implying (correct me if I am wrong) is that the CMB is not as much of a fundamental entity as I am thinking it may be. (I expect that you can probably see why it is very tempting to view the CMB as being the basis for a preferred reference frame.)

I think that we basically need to wait until more laws of physics are discovered and then run tests on the newly-discovered laws of physics to see if a preferred reference frame emerges. I am guessing there is not much else we can do to answer this question until then.

[studiot]

6 hours ago, tim.tdj said:

Hi Studiot

Thank you very much for your reply.

Very interesting question.

I think I define change to be any alteration whatsoever (however small) of the relationship between at least two subatomic particles.

In your example, the man and his clothing are all large macroscopic objects consisting of gazillions of subatomic particles. So each shirt or each tie may look the same but they each consist of a unique pattern of subatomic particles. Also, the processes of washing and changing them entails a huge amount of change.

 

Well that's easy then.

Consider two c- existent sub atomic particles, one with a significantly longer life than the other.

When the shorter lived one expires, the relationship of co-existence ceases.

 

[tim.tdj]

10 minutes ago, studiot said:

 

Well that's easy then.

Consider two c- existent sub atomic particles, one with a significantly longer life than the other.

When the shorter lived one expires, the relationship of co-existence ceases.

 

Hi Studiot

Very interesting reply.

From the perspective outside of time (I am being a devil's advocate here because I don't actually believe in such a perspective), this can be seen as two time lines (one for each particle) where one line is shorter than the other. From the perspective outside of time, these lines do not change.

[studiot]

55 minutes ago, tim.tdj said:

From the perspective outside of time (I am being a devil's advocate here because I don't actually believe in such a perspective), this can be seen as two time lines (one for each particle) where one line is shorter than the other. From the perspective outside of time, these lines do not change.

How is a timeline 'outside time' ?

 

What I am saying is that there is a state or situation in which you could (in principle) hold both particles in your hand together.

And there is another state where you could only hold one of them.

And since you could observe both states

1) Change exists

2) What we call Time must exist to permit this.

Edited March 5, 2019 by studiot

[tim.tdj]

12 minutes ago, studiot said:

How is a timeline 'outside time' ? 

Hi Studiot

The timelines themselves are not outside time. The hypothetical perspective i mentioned from which we are viewing it is outside time. It is like looking at a piece of paper with a graph with an x axis and a t (time) axis. By looking at the piece of paper, we are outside the time represented by the t axis because we can see the whole of the graph at once.

12 minutes ago, studiot said:

What I am saying is that there is a state or situation in which you could (in principle) hold both particles in your hand together.

And there is another state where you could only hold one of them.

And since you could observe both states

1) Change exists

2) What we call Time must exist to permit this. 

Your two particles would be represented by two lines of different lengths drawn on the piece of paper I mentioned above which represent the different lifespans of the two particles. This drawing does not change.

The debate the scientific philosophers are having is whether the Universe at the most fundamental level is like the unchanging piece of paper with unchanging timelines predrawn on it or the Universe is as we perceive it (we perceive it changing).

[studiot]

4 minutes ago, tim.tdj said:

Your two particles would be represented by two lines of different lengths drawn on the piece of paper I mentioned above which represent the different lifespans of the two particles. This drawing does not change.

This is a representation not the reality.

(You said it yourself)

5 minutes ago, tim.tdj said:

The debate the scientific philosophers are having is whether the Universe at the most fundamental level is like the unchanging piece of paper with unchanging timelines predrawn on it or the Universe is as we perceive it (we perceive it changing).

If they were 'predrawn' then they have a separate existence from what they are drawn on.

Predrawn also implies something rather radical.

[tim.tdj]

4 minutes ago, studiot said:

This is a representation not the reality.

What we perceive might be misleading . "Reality" at the most fundamental level might be be much closer to the representation I mentioned than what we perceive.

5 minutes ago, studiot said:

 

     If they were 'predrawn' then they have a separate existence from what they are drawn on.

 

I don't know if the analogy of ink on paper can be extended this far. The events prewritten into the SpaceTime Block (if that is really what the Universe is) would be an integral part of the SpaceTime Block, they would  not be separate from it.

15 minutes ago, studiot said:

Predrawn also implies something rather radical.

I agree that the SpaceTime Block is a pretty radical idea.

[studiot]

Quote

tim.tdj

24 minutes ago, studiot said:

Predrawn also implies something rather radical.

I agree that the SpaceTime Block is a pretty radical idea.

No I didn't say the spacetime block was radical, I said the idea of pre drawing something on it or in it was radical.

I even empahsised the 'pre'.

Pre means 'before.', usually in time but also in other contexts such as sequence.

[tim.tdj]

12 minutes ago, studiot said:

No I didn't say the spacetime block was radical, I said the idea of pre drawing something on it or in it was radical.

I even empahsised the 'pre'.

Pre means 'before.', usually in time but also in other contexts such as sequence.

Sorry, I misunderstood. Yeah, I agree with you that the idea of everything that we have ever experienced being prewritten into the Universe is a very radical idea because it is all so complicated and intricate. It might be the result of mathematics which are way more complicated than the mathematics that produces the Mandelbrot Set. It implies we are living inside mathematics. Anyway, remember that as I mentioned previously, I am being a devil's advocate about the SpaceTime Block concept as I don't personally believe in it. I might be wrong though.

[swansont]

14 hours ago, tim.tdj said:

Hi Swansont

Thank you very much. You have made it somewhat clearer. What you seem to be implying (correct me if I am wrong) is that the CMB is not as much of a fundamental entity as I am thinking it may be. (I expect that you can probably see why it is very tempting to view the CMB as being the basis for a preferred reference frame.)

I think that we basically need to wait until more laws of physics are discovered and then run tests on the newly-discovered laws of physics to see if a preferred reference frame emerges. I am guessing there is not much else we can do to answer this question until then.

Yes, I can see that. But it is still A reference frame, not THE reference frame. One of convenience, not necessity.

There are many situations where one reference frame is convenient to use, but it doesn't mean you have to use it. 

[tim.tdj]

28 minutes ago, swansont said:

Yes, I can see that. But it is still A reference frame, not THE reference frame. One of convenience, not necessity.

There are many situations where one reference frame is convenient to use, but it doesn't mean you have to use it. 

Hi Swansont

Thank you very much for the clarification.

[Mans]

We can call this world, the world of change!

Everything in this world is included the change rule. The only thing that never is changed is the system (rules) of the world. 

Edited April 5, 2019 by Mans