What Is Thing-ness?

[spino...@aol.com]

The Origin of Matter and Time | Space Time | PBS Digital Studios

 

 

https://www.youtube.com/watch?v=fHRqibyNMpw

 

[Brent Meeker]

Neat!  But I didn't like his explanation of the twin paradox.  Special relativity works just fine for accelerated world lines.  It's just that non-geodesic world lines are shorter than geodesic ones.

Brent

On 8/1/2019 5:57 PM, spinozalens via Atoms and the Void wrote:

The Origin of Matter and Time | Space Time | PBS Digital Studios

 

 

https://www.youtube.com/watch?v=fHRqibyNMpw

 

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[spino...@aol.com]

-----Original Message-----
From: 'Brent Meeker' via Atoms and the Void <atv...@googlegroups.com>
To: atvoid <atv...@googlegroups.com>
Sent: Fri, Aug 2, 2019 1:20 am
Subject: Re: What Is Thing-ness?

Neat!  But I didn't like his explanation of the twin paradox.  Special relativity works just fine for accelerated world lines.  It's just that non-geodesic world lines are shorter than geodesic ones.

Brent

You're right, BUT in some sense you can still invoke acceleration if you think about it carefully. Feynman invokes acceleration in his essay on the twins paradox,  so this can't be too crazy. The standard refutation of  acceleration as an explanation  is the three clock scenario , an example where no physical clock experiences any acceleration.at all. However, this still involves a change of frame for an "effective" clock which is the clock with less duration.  A frame change can't be had without acceleration.   So the accelerated  effective clock ages slower. The effective clock must end up in the same frame as the clock that truly experienced no frame change , hence no acceleration. In SR time is a "personal" parameter. It makes no sense to compare the "time rate" of clocks in different frames to get any objective measure of duration.

Bob Zannelli 

On 8/1/2019 5:57 PM, spinozalens via Atoms and the Void wrote:

The Origin of Matter and Time | Space Time | PBS Digital Studios

 

 

https://www.youtube.com/watch?v=fHRqibyNMpw

 

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[Brent Meeker]

On 8/2/2019 2:00 AM, spinozalens via Atoms and the Void wrote:

-----Original Message-----
From: 'Brent Meeker' via Atoms and the Void <atv...@googlegroups.com>
To: atvoid <atv...@googlegroups.com>
Sent: Fri, Aug 2, 2019 1:20 am
Subject: Re: What Is Thing-ness?

Neat!  But I didn't like his explanation of the twin paradox.  Special relativity works just fine for accelerated world lines.  It's just that non-geodesic world lines are shorter than geodesic ones.

Brent

You're right, BUT in some sense you can still invoke acceleration if you think about it carefully.

Acceleration is just deviation from a geodesic path...which makes it shorter.

Feynman invokes acceleration in his essay on the twins paradox,  so this can't be too crazy. The standard refutation of  acceleration as an explanation  is the three clock scenario , an example where no physical clock experiences any acceleration.at all. However, this still involves a change of frame for an "effective" clock which is the clock with less duration.  A frame change can't be had without acceleration.  

Sure it can.  That's the three clock example.  The elapsed time measure is just "handed off" to a different inertial frame.

So the accelerated  effective clock ages slower.

That's what confuses people.  They think the clock runs slower.  It doesn't.  All the clocks in these thought experiments are ideal clocks that always run the same.  The clock doesn't age slower, it takes a shorter path that has less elapsed time.
If drive up the coast from L.A. to S.F. and you drive from L.A. to S.F. via Las Vegas, when we get to S.F. my odometer will show less elapsed distance.  But it doesn't mean my odometer "ran slow".

Bewnr

The effective clock must end up in the same frame as the clock that truly experienced no frame change , hence no acceleration. In SR time is a "personal" parameter. It makes no sense to compare the "time rate" of clocks in different frames to get any objective measure of duration.

Bob Zannelli 

On 8/1/2019 5:57 PM, spinozalens via Atoms and the Void wrote:

The Origin of Matter and Time | Space Time | PBS Digital Studios

 

 

https://www.youtube.com/watch?v=fHRqibyNMpw

 

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[spino...@aol.com]

-----Original Message-----
From: 'Brent Meeker' via Atoms and the Void <atv...@googlegroups.com>
To: atvoid <atv...@googlegroups.com>
Sent: Fri, Aug 2, 2019 12:25 pm
Subject: Re: What Is Thing-ness?

On 8/2/2019 2:00 AM, spinozalens via Atoms and the Void wrote:

-----Original Message-----
From: 'Brent Meeker' via Atoms and the Void <atv...@googlegroups.com>
To: atvoid <atv...@googlegroups.com>
Sent: Fri, Aug 2, 2019 1:20 am
Subject: Re: What Is Thing-ness?

Neat!  But I didn't like his explanation of the twin paradox.  Special relativity works just fine for accelerated world lines.  It's just that non-geodesic world lines are shorter than geodesic ones.

Brent

You're right, BUT in some sense you can still invoke acceleration if you think about it carefully.

Acceleration is just deviation from a geodesic path...which makes it shorter.

Feynman invokes acceleration in his essay on the twins paradox,  so this can't be too crazy. The standard refutation of  acceleration as an explanation  is the three clock scenario , an example where no physical clock experiences any acceleration.at all. However, this still involves a change of frame for an "effective" clock which is the clock with less duration.  A frame change can't be had without acceleration.  

Sure it can.  That's the three clock example.  The elapsed time measure is just "handed off" to a different inertial frame.

But that's the point. You can't "hand it off" without a frame change. How it handed off? One rocket sends am EM signal in frame 1 to be observed in frame 2. The EM signal involves acceleration.  You have an effective clock that changes frame. 

So the accelerated  effective clock ages slower.

That's what confuses people.  They think the clock runs slower.  It doesn't.  All the clocks in these thought experiments are ideal clocks that always run the same.  The clock doesn't age slower, it takes a shorter path that has less elapsed time.

Absolutely right of course. But the needed mechanism for an observer too see an objective duration of both clocks compared involves a frame change for the clock that shows less duration. But I take your point about the confusion. I am not suggesting that we don't view this in terms of spacetime paths. 

If drive up the coast from L.A. to S.F. and you drive from L.A. to S.F. via Las Vegas, when we get to S.F. my odometer will show less elapsed distance.  But it doesn't mean my odometer "ran slow".

This is not an exact analogy because in the twins scenario we have a different record of the ratio of the path length through time and space for the two clocks

Bob Zannelli  

Bewnr

The effective clock must end up in the same frame as the clock that truly experienced no frame change , hence no acceleration. In SR time is a "personal" parameter. It makes no sense to compare the "time rate" of clocks in different frames to get any objective measure of duration.

Bob Zannelli 

On 8/1/2019 5:57 PM, spinozalens via Atoms and the Void wrote:

The Origin of Matter and Time | Space Time | PBS Digital Studios

 

 

https://www.youtube.com/watch?v=fHRqibyNMpw

 

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[Brent Meeker]

On 8/2/2019 10:00 AM, spinozalens via Atoms and the Void wrote:

Feynman invokes acceleration in his essay on the twins paradox,  so this can't be too crazy. The standard refutation of  acceleration as an explanation  is the three clock scenario , an example where no physical clock experiences any acceleration.at all. However, this still involves a change of frame for an "effective" clock which is the clock with less duration.  A frame change can't be had without acceleration.  

Sure it can.  That's the three clock example.  The elapsed time measure is just "handed off" to a different inertial frame.

But that's the point. You can't "hand it off" without a frame change. How it handed off? One rocket sends am EM signal in frame 1 to be observed in frame 2. The EM signal involves acceleration.  You have an effective clock that changes frame. 

The outgoing rocket passes the ingoing rocket and the ingoing rockets clock is set to match that of the outgoing clock as they pass.  They are at the same place at that moment (B on the diagram).



I don't see that any acceleration is involved.  The only thing that must change frames is information.  Of course information is physically embodied, but that's true when the sender and receiver are relatively stationary too.  We don't think of that as involving acceleration.

Brent

[spino...@aol.com]

-----Original Message-----
From: 'Brent Meeker' via Atoms and the Void <atv...@googlegroups.com>
To: atvoid <atv...@googlegroups.com>
Sent: Fri, Aug 2, 2019 2:00 pm
Subject: Re: What Is Thing-ness?

This is not the three rocket example you need to show different duration of clocks. These clocks were never synchronized to start. What they read for time is irrelevant

Bob Zannelli   

[spino...@aol.com]

Sorry I didn't notice the stationary state. However, notice that the "effective "  clock at point B has changed frame. to be able to get back to the same ( approx) spacetime point at the stationary state to compare clocks. 

Bob Zannelli 

-- 

[Brent Meeker]

On 8/2/2019 11:35 AM, spinozalens via Atoms and the Void wrote:

-----Original Message-----
From: 'Brent Meeker' via Atoms and the Void <atv...@googlegroups.com>
To: atvoid <atv...@googlegroups.com>
Sent: Fri, Aug 2, 2019 2:00 pm
Subject: Re: What Is Thing-ness?

On 8/2/2019 10:00 AM, spinozalens via Atoms and the Void wrote:

Feynman invokes acceleration in his essay on the twins paradox,  so this can't be too crazy. The standard refutation of  acceleration as an explanation  is the three clock scenario , an example where no physical clock experiences any acceleration.at all. However, this still involves a change of frame for an "effective" clock which is the clock with less duration.  A frame change can't be had without acceleration.  

Sure it can.  That's the three clock example.  The elapsed time measure is just "handed off" to a different inertial frame.

But that's the point. You can't "hand it off" without a frame change. How it handed off? One rocket sends am EM signal in frame 1 to be observed in frame 2. The EM signal involves acceleration.  You have an effective clock that changes frame. 

The outgoing rocket passes the ingoing rocket and the ingoing rockets clock is set to match that of the outgoing clock as they pass.  They are at the same place at that moment (B on the diagram).

I don't see that any acceleration is involved.  The only thing that must change frames is information.  Of course information is physically embodied, but that's true when the sender and receiver are relatively stationary too.  We don't think of that as involving acceleration.

Brent

This is not the three rocket example you need to show different duration of clocks. These clocks were never synchronized to start. What they read for time is irrelevant

Bob Zannelli  

??  I don't understand that remark.  I thought it would go without saying that the red rocket and Earth clocks are identical and they are set together at A.  The grey rocket also has an identical clock which is set to agree with the red rocket clock as they pass one another at B (set to 2011).   Then when the grey rocket passes Earth, its clock reads 2015 while the Earth clock reads 2017.  Why is that irrelevant?  It's the twin paradox, but without any acceleration.



Brent

[spino...@aol.com]

-----Original Message-----
From: 'Brent Meeker' via Atoms and the Void <atv...@googlegroups.com>
To: atvoid <atv...@googlegroups.com>
Sent: Fri, Aug 2, 2019 3:17 pm
Subject: Re: What Is Thing-ness?

Brent

This is not the three rocket example you need to show different duration of clocks. These clocks were never synchronized to start. What they read for time is irrelevant

Bob Zannelli  

??  I don't understand that remark.  I thought it would go without saying that the red rocket and Earth clocks are identical and they are set together at A.  The grey rocket also has an identical clock which is set to agree with the red rocket clock as they pass one another at B (set to 2011).   Then when the grey rocket passes Earth, its clock reads 2015 while the Earth clock reads 2017.  Why is that irrelevant?  It's the twin paradox, but without any acceleration.

Brent I quickly corrected my comment in a second post

Here it is again

Sorry I didn't notice the stationary state. However, notice that the "effective "  clock at point B has changed frame. to be able to get back to the same ( approx) spacetime point at the stationary state to compare clocks. 

Bob Zannelli 

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Brent

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[Brent Meeker]

On 8/2/2019 1:12 PM, spinozalens via Atoms and the Void wrote:

-----Original Message-----
From: 'Brent Meeker' via Atoms and the Void <atv...@googlegroups.com>
To: atvoid <atv...@googlegroups.com>
Sent: Fri, Aug 2, 2019 3:17 pm
Subject: Re: What Is Thing-ness?

Brent

This is not the three rocket example you need to show different duration of clocks. These clocks were never synchronized to start. What they read for time is irrelevant

Bob Zannelli  

??  I don't understand that remark.  I thought it would go without saying that the red rocket and Earth clocks are identical and they are set together at A.  The grey rocket also has an identical clock which is set to agree with the red rocket clock as they pass one another at B (set to 2011).   Then when the grey rocket passes Earth, its clock reads 2015 while the Earth clock reads 2017.  Why is that irrelevant?  It's the twin paradox, but without any acceleration.

Brent I quickly corrected my comment in a second post

Here it is again

Sorry I didn't notice the stationary state. However, notice that the "effective "  clock at point B has changed frame. to be able to get back to the same ( approx) spacetime point at the stationary state to compare clocks. 

Bob Zannelli

Understood.  I posted the reply before I read your correction.

Brent