Believers Beware

[Neddy Bate]

Hello MacM,

Excellent post Neddy. I'll let Pete answer since you asked him the questions but I just wanted to emphasize the believes aspect of SR. This is where my argument has been for many years now.

"Relative Velocity" only causes the perception of slower ticking. The "Actual Velocity" by the accelerated clock "Actually" loses accmulated time.

And you are correct this FTL aspect of SR in the real world physics is generally ignored and even denied by most relativists.

Thanks MacM. Everyone is free to reply, I was just saying hi to Pete before I quoted his post.

MacM, I have read your ideas for a long time, and I know you have been vary consistant in pointing out that only the accelerated (F=ma) clock shows any change in accumulated time. Now Pete seems to be saying that only the accelerated (F=ma) frame experiences length contraction. I have never heard of that before, so I hope someone can elaborate further.

Also, I noted above that the accelerated (F=ma) frame experiences a disagreement of simultaneaty even among clocks at rest in its own frame. It seems like there is more to explore there, too, in terms of the strangeness of the resulting consequences.

Good thread by the way!

 

[MacM]

Nedd Bate,

Hello MacM,

MacM, I have read your ideas for a long time, and I know you have been vary consistant in pointing out that only the accelerated (F=ma) clock shows any change in accumulated time. Now Pete seems to be saying that only the accelerated (F=ma) frame experiences length contraction. I have never heard of that before, so I hope someone can elaborate further.

Keep in mind that in SR under inertial conditions is where they claim reciprocity. That is each frame claims the rest condition and that it is the other that has motion.

Also that accordingly SR claims that the physical affect of relative motion is time dilation of the moving frame and from the moving frame the affect is spatial contraction.

The thing people need to understand here is that those conditions are not from the respective frames vantage point. That is both frames consider themselves as at rest and it is the other that is time dilated.

Neither frame "Sees" length contraction. Spatial contraction is a condition imposed on the other frame mathematically. That is the "Resting Frame" CLAIMS the moving frame sees less distance but there is NEVER a moving frame view since both claim to be at rest.

NOW acceleration breaks that symmetry and reciprocity vanishes. Now you have the situation where one frame really has motion (the frame accelerating and feeling F=ma) and the other experiences only relative motion; hence either the moving clock ticks slow or travels less distance to account for the loss of accumulated time BUT IT CAN BE BOTH PHYSICALLY - MY POINT).

Also, I noted above that the accelerated (F=ma) frame experiences a disagreement of simultaneaty even among clocks at rest in its own frame. It seems like there is more to explore there, too, in terms of the strangeness of the resulting consequences.

I think "Strangeness" is a very polite adjective - ha.

Good thread by the way!

Thanks. Very few here appreciate it I'm afraid.

 

[Pete]

Hi Neddy,

This is news to me. I have never seen this mentioned in any of the basic SR lessons, or twin paradox resolutions. If it is an accurate statement, I sure wish someone would have told me this sooner. It might have helped me make sense of what is really supposed to be going on in SR.
It would seem to me that, in the Chevy's reference frame, the FTL (faster than light) velocity of the cosmic object is the result of length contraction of the entire reference frame of the cosmic object. This change in distance takes place during the time that the Chevy is accelerating, which can be an arbitrarily brief period of time.

That's right.
Have you heard or read descriptions of how you could travel 26000 light years to the center of the galaxy in only 12 years subjective time if you have a constant acceleration of 1 gravity? This is much the same thing.

Am I to understand that there is no length contraction of the Chevy's reference frame as realized from the cosmic object's reference frame, simply because the cosmic object does not accelerate by F=ma (to borrow MacM's terminology for real acceleration)?

No, that's not correct. The length of the Chevy in the cosmic object's frame would change by the same proportion as the distance from Earth to the cosmic object in the chevy's frame changes.


I think you're at the stage where you'll need to draw, interpret, and manipulate space-time diagrams to follow what's going on. This particular thought experiment is confusing because we're dealing with the chevy over a small space-time interval, but we're dealing with the object over a very long interval - the object that is simultaneous with the chevy in its new reference frame is an older object (older in proper time) than the object that was simultaneous with the chevy before it accelerated.

To see the symmetry, you'd have to consider a chevy that had been cruising at 60mph for thousands or millions of years.

I have been trying to understand this age puzzle by considering that, in the accelerated reference frame, the formerly-synchronized clocks throughout that frame begin to run at different rates (depending on their height in the pseudo-gravitational well caused by the acceleration) and that this is true in all reference frames including the accelerated one. This would mean that, after the acceleration is over, the clocks would have to be re-synchronized before we could re-establish this inertial frame as being on "equal footing" to the unaccelerated frame (in that clocks are synchronized in their own frame, at least). Only then can we say that each of the two inertial frames are just as valid, and eachj believes the other frame to have the slower ticking clocks, etc.

Yes, you can artificially privilege a particular frame by synchronizing clocks in it before you begin.

 

[Neddy Bate]

The length of the Chevy in the cosmic object's frame would change by the same proportion as the distance from Earth to the cosmic object in the chevy's frame changes.

We can replace the car in the opening post with an extremely long train -- one that extends all the way from the Chevy to the celestial object. The acceleration could be achieved by applying an even distribution of force along the entire length of the train, for example, an array of rockets timed to occur simultaneoulsy in its own frame.

The SR theory seems to predict that the entire train would become length-contracted (just as the Chevy did), in the celestial object's frame of reference.

SR prohibits FTL travel in inertial frames in flat space.

If the train is extremely long, and it is contracting in length, the theory seems to suggest that some components of the train would exceed c in the inertial & flatspace frame of the celestial object. I think this might have been what the opening post was meant to bring to our attention. Cheers.

 

[Pete]

We can replace the car in the opening post with an extremely long train -- one that extends all the way from the Chevy to the celestial object. The acceleration could be achieved by applying an even distribution of force along the entire length of the train, for example, an array of rockets timed to occur simultaneoulsy in its own frame.

The SR theory seems to predict that the entire train would become length-contracted (just as the Chevy did), in the celestial object's frame of reference.

Hi Ned,
Yes, in the celestial object's frame, the acceleration along the train's length wouldn't be uniform (except for the first instant).

If the train is extremely long, and it is contracting in length, the theory seems to suggest that some components of the train would exceed c in the inertial & flatspace frame of the celestial object.

That's a better way to address symmetry - thanks.

I can see how this appears to imply FTL motion in the inertial frame, but it doesn't work out that way on analysis.

Here's why:
In the celestial object's frame, the front of the train accelerates much more slowly than the rear end. In fact, while the rear end takes only 60 seconds to get up to 60mph, the front end takes thousands of years to reach that speed.

I think this might have been what the opening post was meant to bring to our attention. Cheers.

Maybe, but I really doubt Mac thought that far.

 

[MacM]

Maybe, but I really doubt Mac thought that far.

Hmmmmm. Now I wonder why you would ever say that since I spend more time actually thinking about the consequences of SR than most here. .