ISF Logo   IS Forum
Forum Index Register Members List Events Mark Forums Read Help

Go Back   International Skeptics Forum » General Topics » Science, Mathematics, Medicine, and Technology
 


Welcome to the International Skeptics Forum, where we discuss skepticism, critical thinking, the paranormal and science in a friendly but lively way. You are currently viewing the forum as a guest, which means you are missing out on discussing matters that are of interest to you. Please consider registering so you can gain full use of the forum features and interact with other Members. Registration is simple, fast and free! Click here to register today.
Tags Allais Effect , Dark Flow , relativity , Theory of Relativity

Reply
Old Yesterday, 02:57 PM   #1161
Reality Check
Penultimate Amazing
 
Join Date: Mar 2008
Location: New Zealand
Posts: 25,505
Thumbs down Usual abysmal ignorance of SR (time dilation)

Originally Posted by SDG View Post
How can we be sure there is a time dilation in SR then?
21 October 2019 SDG: Usual abysmal ignorance of SR (time dilation)

We can be sure there is a time dilation in SR because time dilation has been textbook physics in SR for 114 years .

We can be sure there is a time dilation in SR because we have measured time dilation matching SR in experiments for most of those 114 years .

We can be confident there is a time dilation in SR because the use of SR in GPS is part of what gives the accuracy of GPS (GPS receivers apply SR).
Reality Check is offline   Quote this post in a PM   Nominate this post for this month's language award Copy a direct link to this post Reply With Quote Back to Top
Old Yesterday, 02:59 PM   #1162
Reality Check
Penultimate Amazing
 
Join Date: Mar 2008
Location: New Zealand
Posts: 25,505
18 posts of ignorance, fantasies and a few lies from 30 August to 27 September 2019 (and growing!)
  1. 27 September 2019 SDG: Back to "textbook example" idiocy that cannot show any problem with SR!
  2. 30 September 2019 SDG: A rather dumb question when a post is about all of SDG's posts!
  3. 30 September 2019 SDG: A "By your logic nobody should have a look at Einstein's ideas" fantasy.
  4. 30 September 2019 SDG: Still has not learned the definition of proper time!
  5. 30 September 2019 SDG: An obvious error that posts showing knowledge about SR show no knowledge.
  6. 1 October 2019 SDG: Repeats his "relativity has two time interval options for the train frame" error but at least dropped the blatant error of proper time (time inside the frame).
  7. 1 October 2019 SDG: Persisting with the "two different train time intervals for one platform time interval" error
  8. 17 October 2019 SDG: Usual time interval lie, same abysmally ignorant questions and a persistent delusion.
  9. 21 October 2019 SDG: Usual abysmal ignorance of SR (proper time)
  10. 21 October 2019 SDG: Some "define time dilation with the blue arrow" gibberish
  11. 21 October 2019 SDG: Usual abysmal ignorance of SR (time dilation)
  12. 21 October 2019 SDG: We still complain about weeks of persistent ignorance of basic SR (Lorentz transformation and proper time).

Last edited by Reality Check; Yesterday at 03:09 PM.
Reality Check is offline   Quote this post in a PM   Nominate this post for this month's language award Copy a direct link to this post Reply With Quote Back to Top
Old Yesterday, 03:08 PM   #1163
Reality Check
Penultimate Amazing
 
Join Date: Mar 2008
Location: New Zealand
Posts: 25,505
Thumbs down We still complain about weeks of persistent ignorance of basic SR

Originally Posted by SDG View Post
I gave you two clocks with the same proper time interval within one reference frame and I showed you how the grid of inertial observers in the other frame will get two different proper time intervals for one proper time interval in the first frame considering c is constant and you still complain?
21 October 2019 SDG: We still complain about weeks of persistent ignorance of basic SR (Lorentz transformation and proper time).

SDG has been told several times that the Lorentz transformation is 1 to 1. Any time interval in frame A transforms to 1 and only 1 time interval in frame B.
SDG has been told several times that proper time is the time measured by a clock moving along a world line. That is the time that an observer reads on their own clock. A proper time interval is a time interval on the observer's own clock.
Reality Check is offline   Quote this post in a PM   Nominate this post for this month's language award Copy a direct link to this post Reply With Quote Back to Top
Old Yesterday, 03:21 PM   #1164
Robin
Penultimate Amazing
 
Join Date: Apr 2004
Posts: 10,702
Originally Posted by SDG View Post
Yes, I added half-mirrors because it appears to me you do not see the problem.
Probably because you are not telling us what the alleged problem is.
Quote:
Remember, the one way blue arrow and the round-trip arrow measure the same time within the same reference frame.
No they don't. The one-way light beams and the reflected light only take the same time in the platform frame.
__________________
The non-theoretical character of metaphysics would not be in itself a defect; all arts have this non-theoretical character without thereby losing their high value for personal as well as for social life. The danger lies in the deceptive character of metaphysics; it gives the illusion of knowledge without actually giving any knowledge. This is the reason why we reject it. - Rudolf Carnap "Philosophy and Logical Syntax"

Last edited by Robin; Yesterday at 03:41 PM.
Robin is online now   Quote this post in a PM   Nominate this post for this month's language award Copy a direct link to this post Reply With Quote Back to Top
Old Yesterday, 07:49 PM   #1165
Robin
Penultimate Amazing
 
Join Date: Apr 2004
Posts: 10,702
SDG,

Here is what I think is a crucial question. Below is your setup, a plan view of the platform frame, the arrows representing beams of light in two directions.

Is the proper time of the interval AC 2 seconds, or something else?

__________________
The non-theoretical character of metaphysics would not be in itself a defect; all arts have this non-theoretical character without thereby losing their high value for personal as well as for social life. The danger lies in the deceptive character of metaphysics; it gives the illusion of knowledge without actually giving any knowledge. This is the reason why we reject it. - Rudolf Carnap "Philosophy and Logical Syntax"

Last edited by Robin; Yesterday at 07:54 PM.
Robin is online now   Quote this post in a PM   Nominate this post for this month's language award Copy a direct link to this post Reply With Quote Back to Top
Old Yesterday, 07:52 PM   #1166
Roboramma
Penultimate Amazing
 
Roboramma's Avatar
 
Join Date: Feb 2005
Location: Shanghai
Posts: 12,922
Hold on. Isn't the proper time along a light ray always equal to zero?
__________________
"... when people thought the Earth was flat, they were wrong. When people thought the Earth was spherical they were wrong. But if you think that thinking the Earth is spherical is just as wrong as thinking the Earth is flat, then your view is wronger than both of them put together."
Isaac Asimov
Roboramma is offline   Quote this post in a PM   Nominate this post for this month's language award Copy a direct link to this post Reply With Quote Back to Top
Old Yesterday, 07:56 PM   #1167
Robin
Penultimate Amazing
 
Join Date: Apr 2004
Posts: 10,702
Originally Posted by Roboramma View Post
Hold on. Isn't the proper time along a light ray always equal to zero?
I am, as I have said, only a beginner. Yes, you are probably right, that makes sense. In which case I have been using the term wrongly as well.

Edit: Yes, (delta t)^2 - (delta x)^2 - (delta y)^2 - (delta z)^2 should be zero for a light ray, so the square root of that would be zero.
__________________
The non-theoretical character of metaphysics would not be in itself a defect; all arts have this non-theoretical character without thereby losing their high value for personal as well as for social life. The danger lies in the deceptive character of metaphysics; it gives the illusion of knowledge without actually giving any knowledge. This is the reason why we reject it. - Rudolf Carnap "Philosophy and Logical Syntax"

Last edited by Robin; Yesterday at 08:02 PM.
Robin is online now   Quote this post in a PM   Nominate this post for this month's language award Copy a direct link to this post Reply With Quote Back to Top
Old Yesterday, 08:11 PM   #1168
Robin
Penultimate Amazing
 
Join Date: Apr 2004
Posts: 10,702
However the proper time of the interval AB can be considered as something different from the proper time of the light ray, I think.

Edit: No, because the proper time calculation comes out the same, so scratch that too.
__________________
The non-theoretical character of metaphysics would not be in itself a defect; all arts have this non-theoretical character without thereby losing their high value for personal as well as for social life. The danger lies in the deceptive character of metaphysics; it gives the illusion of knowledge without actually giving any knowledge. This is the reason why we reject it. - Rudolf Carnap "Philosophy and Logical Syntax"

Last edited by Robin; Yesterday at 08:17 PM.
Robin is online now   Quote this post in a PM   Nominate this post for this month's language award Copy a direct link to this post Reply With Quote Back to Top
Old Today, 07:55 AM   #1169
SDG
Critical Thinker
 
Join Date: Jul 2018
Posts: 417


Gentlemen,
what is the length of the red dotted line in the train frame?
Go ahead, consider the length contraction.
Now remember that the half of the blue line is 1cs, the time 1s.
What is 3.6055 number?
How is this related to gamma=2?
SDG
SDG is online now   Quote this post in a PM   Nominate this post for this month's language award Copy a direct link to this post Reply With Quote Back to Top
Old Today, 08:27 AM   #1170
Myriad
Hyperthetical
 
Myriad's Avatar
 
Join Date: Nov 2006
Location: A pocket paradise between the sewage treatment plant and the railroad
Posts: 15,461
Originally Posted by SDG View Post


Gentlemen,
what is the length of the red dotted line in the train frame?

On my screen, it's about 36 mm long.

If you want a better answer than that, please define the parameters of the red line more clearly. Such as, "It depicts the path taken by _____ when it moves from from _______ to _______ ."

Quote:
Go ahead, consider the length contraction.

What length contraction? Your diagram depicts a Newtonian relativity in which SR does not apply and the speed of light is not constant. Why would there be length contraction?

Please address the answers you've been given to your previous questions before jumping on to new ones.
__________________
A zÝmbie once bit my sister...
Myriad is offline   Quote this post in a PM   Nominate this post for this month's language award Copy a direct link to this post Reply With Quote Back to Top
Old Today, 09:03 AM   #1171
SDG
Critical Thinker
 
Join Date: Jul 2018
Posts: 417
Originally Posted by Myriad View Post
On my screen, it's about 36 mm long.

If you want a better answer than that, please define the parameters of the red line more clearly. Such as, "It depicts the path taken by _____ when it moves from from _______ to _______ ."




What length contraction? Your diagram depicts a Newtonian relativity in which SR does not apply and the speed of light is not constant. Why would there be length contraction?

Please address the answers you've been given to your previous questions before jumping on to new ones.
Myriad,
What is wrong with Newtonian relativity?
SDG


Last edited by SDG; Today at 09:25 AM.
SDG is online now   Quote this post in a PM   Nominate this post for this month's language award Copy a direct link to this post Reply With Quote Back to Top
Old Today, 10:58 AM   #1172
Myriad
Hyperthetical
 
Myriad's Avatar
 
Join Date: Nov 2006
Location: A pocket paradise between the sewage treatment plant and the railroad
Posts: 15,461
Originally Posted by SDG View Post
Myriad,
What is wrong with Newtonian relativity?
SDG

https://i.imgur.com/fb9LCXN.png

It predicts observations that turn out to be wrong when measurements are made upon fast-moving objects in the real world, including observations of the speed of light between relatively moving objects and observations of elapsed time on moving clocks and of the lifetimes of unstable moving particles.

If you want to claim SR is unnecessary to model reality, finding mathematically-proven-impossible "contradictions" in SR is not actually useful even if you could do it, which you can't and haven't. You must instead explain the actual real-world observations with some other model.
__________________
A zÝmbie once bit my sister...
Myriad is offline   Quote this post in a PM   Nominate this post for this month's language award Copy a direct link to this post Reply With Quote Back to Top
Old Today, 11:09 AM   #1173
halleyscomet
Philosopher
 
halleyscomet's Avatar
 
Join Date: Dec 2012
Posts: 9,870
Originally Posted by SDG View Post
Myriad,
What is wrong with Newtonian relativity?
SDG

https://i.imgur.com/fb9LCXN.png
To start, it completely fails to explain the orbit of Mercury:
https://physics.stackexchange.com/qu...-about-mercury

The attempts to explain the orbit of Mercury using Newton's equations were a catastrophic failure that spanned generations. Multiple literal geniuses who did things like use Newton's equations to discover entire planets were unable to account for Mercury. Then Einstein came along. The very first proof he offered of General Relativity was using to to accurately predict the next position of Mercury at the next Solar eclipse.

The whole affair is a fascinating chain of research, egos, triumph and defeat. It's chronicled at the layman level in the excellent book, The Hunt for Vulcan: . . . And How Albert Einstein Destroyed a Planet, Discovered Relativity, and Deciphered the Universe.
__________________
Look what I found! There's this whole web site full of skeptics that spun off from the James Randy Education Foundation!
halleyscomet is offline   Quote this post in a PM   Nominate this post for this month's language award Copy a direct link to this post Reply With Quote Back to Top
Old Today, 01:09 PM   #1174
SDG
Critical Thinker
 
Join Date: Jul 2018
Posts: 417
Originally Posted by Robin View Post
Let me see if I can phrase this better.

The proper time of an interval is the time measured by a clock which passes through both intervals.

So the proper time of an interval is only the same as the co-ordinate time of a frame if it is measured by a stationary clock in that frame.

Only one of those intervals is measured by a stationary clock on the platform.
Robin,
both blue arrows are stationary in the platform frame.
What is the problem?

There is a proper time interval along a world line.
Then there are clocks that can measure the proper time interval.
Where did you the idea that direction of the light clock is defining factor?
Please, a book quotation.
Thanks,
SDG
SDG is online now   Quote this post in a PM   Nominate this post for this month's language award Copy a direct link to this post Reply With Quote Back to Top
Old Today, 01:44 PM   #1175
Reality Check
Penultimate Amazing
 
Join Date: Mar 2008
Location: New Zealand
Posts: 25,505
Thumbs down An abysmally ignorant "Newtonian relativity" question

Originally Posted by SDG View Post
What is wrong with Newtonian relativity?
22 October 2019 SDG: An abysmally ignorant "Newtonian relativity" question.

SR is the fix for "Newtonian relativity" failing for relativistic speeds as anyone who learns any physics knows.

22 October 2019 SDG: Stupidity of a diagram showing he knew what time dilation was before he asked about it !

21 October 2019 SDG: Usual abysmal ignorance of SR (time dilation)
Reality Check is offline   Quote this post in a PM   Nominate this post for this month's language award Copy a direct link to this post Reply With Quote Back to Top
Old Today, 01:49 PM   #1176
Reality Check
Penultimate Amazing
 
Join Date: Mar 2008
Location: New Zealand
Posts: 25,505
Exclamation "both blue arrows are stationary in the platform frame" gibberish

Originally Posted by SDG View Post
both blue arrows are stationary in the platform frame.
22 October 2019 SDG: "both blue arrows are stationary in the platform frame" gibberish

All of the arrows are arrows in a diagram and are all stationary !

What stationary means in physics and especially the train thought experiment is not moving according to an observer. A brick on the platform is stationary according to the platform observer. A rivet on the train is stationary according to the train observer.
Reality Check is offline   Quote this post in a PM   Nominate this post for this month's language award Copy a direct link to this post Reply With Quote Back to Top
Old Today, 02:43 PM   #1177
Robin
Penultimate Amazing
 
Join Date: Apr 2004
Posts: 10,702
Originally Posted by SDG View Post
Where did you the idea that direction of the light clock is defining factor?
Please, a book quotation.
Thanks,
SDG
Here from A First Course in General Relativity, Bernard F. Schutz, chapter 1 "Special Relativity"


Please reciprocate and post the definition of proper time that you are using.

Thanks,
Robin
__________________
The non-theoretical character of metaphysics would not be in itself a defect; all arts have this non-theoretical character without thereby losing their high value for personal as well as for social life. The danger lies in the deceptive character of metaphysics; it gives the illusion of knowledge without actually giving any knowledge. This is the reason why we reject it. - Rudolf Carnap "Philosophy and Logical Syntax"
Robin is online now   Quote this post in a PM   Nominate this post for this month's language award Copy a direct link to this post Reply With Quote Back to Top
Old Today, 02:49 PM   #1178
The Man
Unbanned zombie poster
 
The Man's Avatar
 
Join Date: Jun 2007
Location: Poughkeepsie, NY
Posts: 14,072
Originally Posted by Reality Check View Post
22 October 2019 SDG: "both blue arrows are stationary in the platform frame" gibberish

All of the arrows are arrows in a diagram and are all stationary !

What stationary means in physics and especially the train thought experiment is not moving according to an observer. A brick on the platform is stationary according to the platform observer. A rivet on the train is stationary according to the train observer.

That's why I've always preferred the phrase "co-moving" instead of "stationary". As "stationary" can still imply some absolute stationary reference frame. While "co-moving" exemplifies, as you note above, the relativity of being, well, "stationary".
__________________
BRAINZZZZZZZZ
The Man is offline   Quote this post in a PM   Nominate this post for this month's language award Copy a direct link to this post Reply With Quote Back to Top
Old Today, 02:51 PM   #1179
Robin
Penultimate Amazing
 
Join Date: Apr 2004
Posts: 10,702
Originally Posted by SDG View Post
There is a proper time interval along a world line.
The bigger issue is that, as Robborama has pointed out, the proper time along the world of a light ray is always zero.

It is clear from the definition of proper time that this must be the case:

delta tau=sqrt((delta t)^2-(delta x)^2-(delta y)^2-(delta z)^2)

Naturally for the speed of light, the space interval is going to be the same as the time interval.

And we can confirm it by calculation for your arrows:

Arrow 1:
delta t=2
delta x=0
delta y=2
delta z=0
delta tau = sqrt(2^2-0-2^2-0) = 0

Arrow 2:
delta t=2
delta x=sqrt(3)
delta y=1
delta z=0
delta tau=sqrt(2^2-sqrt(3)^2-1-0) = 0

So the proper time for both of your arrows is zero. If you disagree please post your alternative calculations using an accepted definition of proper time.
__________________
The non-theoretical character of metaphysics would not be in itself a defect; all arts have this non-theoretical character without thereby losing their high value for personal as well as for social life. The danger lies in the deceptive character of metaphysics; it gives the illusion of knowledge without actually giving any knowledge. This is the reason why we reject it. - Rudolf Carnap "Philosophy and Logical Syntax"

Last edited by Robin; Today at 03:55 PM.
Robin is online now   Quote this post in a PM   Nominate this post for this month's language award Copy a direct link to this post Reply With Quote Back to Top
Old Today, 03:14 PM   #1180
Robin
Penultimate Amazing
 
Join Date: Apr 2004
Posts: 10,702
As it happens I have the definition of proper time that SDG must be using, it comes straight after the thought experiment about the train that he keeps using:



It clearly says that if an interval has to be measured by more than one stationary clock in a frame then it is not a proper time for any if its clocks.

This is why the author has the pulse reflect back to its original location on the train.

Naturally we can say that a clock that has the same x value as the original clock will transform to the same time as the original when the motion is only in the x direction.

However the same cannot be said of the two clocks needed to measure the duration of the angled arrow.
__________________
The non-theoretical character of metaphysics would not be in itself a defect; all arts have this non-theoretical character without thereby losing their high value for personal as well as for social life. The danger lies in the deceptive character of metaphysics; it gives the illusion of knowledge without actually giving any knowledge. This is the reason why we reject it. - Rudolf Carnap "Philosophy and Logical Syntax"

Last edited by Robin; Today at 03:54 PM.
Robin is online now   Quote this post in a PM   Nominate this post for this month's language award Copy a direct link to this post Reply With Quote Back to Top
Old Today, 03:48 PM   #1181
Robin
Penultimate Amazing
 
Join Date: Apr 2004
Posts: 10,702
Originally Posted by Robin View Post
The bigger issue is that, as Robborama has pointed out, the proper time along the world of a light ray is always zero.

It is clear from the definition of proper time that this must be the case:

delta tau=sqrt((delta t)^2-(delta x)^2-(delta y)^2-(delta z)^2)

Naturally for the speed of light, the space interval is going to be the same as the time interval.

And we can confirm it by calculation for your arrows:

Arrow 1:
delta t=2
delta x=0
delta y=2
delta z=0
delta tau = sqrt(2^2-0-2^2-0) = 0

Arrow 2:
delta t=2
delta x=sqrt(3)
delta y=1
delta z=0
delta tau=sqrt(2^2-sqrt(3)^2-1-0) = 0

So the proper time for both of your arrows is zero. If you disagree please post your alternative calculations using an accepted definition of proper time.
Of course the same thing goes for the train frame:

Arrow 1:
delta t=4
delta x=-sqrt(12)
delta y=2
delta z=0
delta tau = sqrt(4^2-(-sqrt(12))^2-2^2-0) = 0

Arrow 2:
delta t=1
delta x=0
delta y=1
delta z=0
delta tau=sqrt(1^2-0-1^2-0) = 0
__________________
The non-theoretical character of metaphysics would not be in itself a defect; all arts have this non-theoretical character without thereby losing their high value for personal as well as for social life. The danger lies in the deceptive character of metaphysics; it gives the illusion of knowledge without actually giving any knowledge. This is the reason why we reject it. - Rudolf Carnap "Philosophy and Logical Syntax"

Last edited by Robin; Today at 03:55 PM.
Robin is online now   Quote this post in a PM   Nominate this post for this month's language award Copy a direct link to this post Reply With Quote Back to Top
Old Today, 04:09 PM   #1182
Robin
Penultimate Amazing
 
Join Date: Apr 2004
Posts: 10,702
Incidentally, from the textbook I quoted above, the author takes a little time to address the kind of misunderstanding SDG has of special relativity. It must have come up often enough in his lectures for him to have included it in his text book;

__________________
The non-theoretical character of metaphysics would not be in itself a defect; all arts have this non-theoretical character without thereby losing their high value for personal as well as for social life. The danger lies in the deceptive character of metaphysics; it gives the illusion of knowledge without actually giving any knowledge. This is the reason why we reject it. - Rudolf Carnap "Philosophy and Logical Syntax"

Last edited by Robin; Today at 04:17 PM.
Robin is online now   Quote this post in a PM   Nominate this post for this month's language award Copy a direct link to this post Reply With Quote Back to Top
Old Today, 04:32 PM   #1183
The Man
Unbanned zombie poster
 
The Man's Avatar
 
Join Date: Jun 2007
Location: Poughkeepsie, NY
Posts: 14,072
Originally Posted by Robin View Post
Incidentally, from the textbook I quoted above, the author takes a little time to address the kind of misunderstanding SDG has of special relativity. It must have come up often enough in his lectures for him to have included it in his text book;

https://robinsrevision.files.wordpre...e-14.png?w=528

One of the first questions I asked SDG here. If his quandary was about some apparent lack of symmetry in SR. Also it may be why he apparently prefers Newtonian or Galilean relativity, having an absolute reference frame and thus lacking said symmetry.

eta:

https://en.wikipedia.org/wiki/Time_dilation#Reciprocity
__________________
BRAINZZZZZZZZ

Last edited by The Man; Today at 04:42 PM.
The Man is offline   Quote this post in a PM   Nominate this post for this month's language award Copy a direct link to this post Reply With Quote Back to Top
Old Today, 05:39 PM   #1184
SDG
Critical Thinker
 
Join Date: Jul 2018
Posts: 417
Originally Posted by Robin View Post
Probably because you are not telling us what the alleged problem is.

No they don't. The one-way light beams and the reflected light only take the same time in the platform frame.
Robin,
I hope this will help:



As the question is posted: Are the green lines going to have the the same length and the same direction in the train frame?
SDG
SDG is online now   Quote this post in a PM   Nominate this post for this month's language award Copy a direct link to this post Reply With Quote Back to Top
Old Today, 05:44 PM   #1185
Roboramma
Penultimate Amazing
 
Roboramma's Avatar
 
Join Date: Feb 2005
Location: Shanghai
Posts: 12,922
Originally Posted by SDG View Post
Robin,
I hope this will help:

https://i.imgur.com/5TpEESG.png

As the question is posted: Are the green lines going to have the the same length and the same direction in the train frame?
SDG
Again, what does "length" mean? Are you still talking about proper time? Because it's an invariant quantity (the same in all frames), and along a light ray is always zero.

If you are actually asking about a length, then you're not asking about the green lines.
__________________
"... when people thought the Earth was flat, they were wrong. When people thought the Earth was spherical they were wrong. But if you think that thinking the Earth is spherical is just as wrong as thinking the Earth is flat, then your view is wronger than both of them put together."
Isaac Asimov
Roboramma is offline   Quote this post in a PM   Nominate this post for this month's language award Copy a direct link to this post Reply With Quote Back to Top
Old Today, 05:45 PM   #1186
Robin
Penultimate Amazing
 
Join Date: Apr 2004
Posts: 10,702
OK, two can play at this game.

Castor is the stationmaster, Pollux the conductor. They each have a light clock which has photon bouncing up and down perpendicular to the track at a distance of 0.1 cs.

Pollux is on a train moving at the velocity of 0.2c. Initially they are both at x=x'=t=t'=0 and their light clocks begin with the photon at the bottom.

When Pollux sees 1 s on the platform clock he leaps onto another train travelling at the same speed the opposite direction, until he returns to Castor.

Castor had his army arrayed along the platform plotting the position of the photon in Pollux's light clock.

Similarly Pollux had his army arrayed along both trains, plotting the position of the photon in Castor's light clock. The train 1 observers (who are behind Pollux) start to plot data when they see the platform clock show 0s and keep plotting until the platform clock shows 1s.

The train 2 observers (who are in front of Pollux) plot data starting when they see the platform clock register 1s and continue until Castor arrives back

Castor analyses the data and confirms that Pollux has aged more slowly based on the length of the path he plotted compared to the length of the path the photon would have taken in the two frames.

However Pollux also analyses the data that his army has returned and they also show that the path Castor's photon has taken is longer on the train compared with the path it would have taken on the platform frame. So from his data Castor should be the younger.

Who is right, and why?

Yay! I have broken SR

Nobel Committee: "Here, have a Nobel Prize"
Me: "No thanks, I am trying to give them up"
__________________
The non-theoretical character of metaphysics would not be in itself a defect; all arts have this non-theoretical character without thereby losing their high value for personal as well as for social life. The danger lies in the deceptive character of metaphysics; it gives the illusion of knowledge without actually giving any knowledge. This is the reason why we reject it. - Rudolf Carnap "Philosophy and Logical Syntax"

Last edited by Robin; Today at 05:46 PM.
Robin is online now   Quote this post in a PM   Nominate this post for this month's language award Copy a direct link to this post Reply With Quote Back to Top
Old Today, 05:47 PM   #1187
SDG
Critical Thinker
 
Join Date: Jul 2018
Posts: 417
Originally Posted by Robin View Post
SDG,

Here is what I think is a crucial question. Below is your setup, a plan view of the platform frame, the arrows representing beams of light in two directions.

Is the proper time of the interval AC 2 seconds, or something else?

Robin,
The AC is 2s of proper time in the platform frame.
The reason is every clock in the same frame has to measure the same time.
The AB is 2s and AC is 2s as well.
SDG
SDG is online now   Quote this post in a PM   Nominate this post for this month's language award Copy a direct link to this post Reply With Quote Back to Top
Old Today, 05:51 PM   #1188
Robin
Penultimate Amazing
 
Join Date: Apr 2004
Posts: 10,702
Originally Posted by SDG View Post
Robin,
I hope this will help:

https://i.imgur.com/5TpEESG.png

As the question is posted: Are the green lines going to have the the same length and the same direction in the train frame?
SDG
What would help is actually explaining what the problem is that you think you see.

Asking vague questions about undefined green arrows will obviously not help.
__________________
The non-theoretical character of metaphysics would not be in itself a defect; all arts have this non-theoretical character without thereby losing their high value for personal as well as for social life. The danger lies in the deceptive character of metaphysics; it gives the illusion of knowledge without actually giving any knowledge. This is the reason why we reject it. - Rudolf Carnap "Philosophy and Logical Syntax"
Robin is online now   Quote this post in a PM   Nominate this post for this month's language award Copy a direct link to this post Reply With Quote Back to Top
Old Today, 05:58 PM   #1189
Robin
Penultimate Amazing
 
Join Date: Apr 2004
Posts: 10,702
Originally Posted by SDG View Post
Robin,
The AC is 2s of proper time in the platform frame.
The reason is every clock in the same frame has to measure the same time.
The AB is 2s and AC is 2s as well.
SDG
You are talking about co-ordinate time, not platform time. Look at your own textbook, it can only be proper time if it can be measured by the same clock, not just a clock showing the same time.

You are assuming that if two clocks show the same time then they must be equivalent. That is a fallacy in SR, because two clocks that show the same time will not necessarily transform to the same time in another frame.

If you are claiming that an interval that has to be measured by two clocks in a frame then the proper time for that frame is not the proper time of any clock in the frame. The text book that you are citing says so.

So, before you can proceed, show me the textbook definition of proper time you are using and then show that your intervals have the same proper time using calculations.
__________________
The non-theoretical character of metaphysics would not be in itself a defect; all arts have this non-theoretical character without thereby losing their high value for personal as well as for social life. The danger lies in the deceptive character of metaphysics; it gives the illusion of knowledge without actually giving any knowledge. This is the reason why we reject it. - Rudolf Carnap "Philosophy and Logical Syntax"
Robin is online now   Quote this post in a PM   Nominate this post for this month's language award Copy a direct link to this post Reply With Quote Back to Top
Old Today, 06:29 PM   #1190
SDG
Critical Thinker
 
Join Date: Jul 2018
Posts: 417
Originally Posted by Robin View Post
Here from A First Course in General Relativity, Bernard F. Schutz, chapter 1 "Special Relativity"


Please reciprocate and post the definition of proper time that you are using.

Thanks,
Robin

Robin,
Please, have a look.
As I mentioned already. There is a proper time interval along a world line and there is a clock that measures the proper time.
We can have a 1mm cavity, let the light bounce inside and count bounces.
We can have a rod and let light fly along the rod.
If the clocks are in the same frame they will measure the same proper time interval.
'Locality' is important in general frames.
We are talking about a flat space-time in the thought experiment so the light second here and there is not a problem.
SDG






From:
SDG is online now   Quote this post in a PM   Nominate this post for this month's language award Copy a direct link to this post Reply With Quote Back to Top
Old Today, 06:32 PM   #1191
Robin
Penultimate Amazing
 
Join Date: Apr 2004
Posts: 10,702
I am assuming that Pollux, as a hero of ancient Rome, can take slamming into a train bulkhead at a few hundred million kilometres per hour in his stride.
__________________
The non-theoretical character of metaphysics would not be in itself a defect; all arts have this non-theoretical character without thereby losing their high value for personal as well as for social life. The danger lies in the deceptive character of metaphysics; it gives the illusion of knowledge without actually giving any knowledge. This is the reason why we reject it. - Rudolf Carnap "Philosophy and Logical Syntax"
Robin is online now   Quote this post in a PM   Nominate this post for this month's language award Copy a direct link to this post Reply With Quote Back to Top
Reply

International Skeptics Forum » General Topics » Science, Mathematics, Medicine, and Technology

Bookmarks

Thread Tools

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Forum Jump


All times are GMT -7. The time now is 06:32 PM.
Powered by vBulletin. Copyright ©2000 - 2019, Jelsoft Enterprises Ltd.

This forum began as part of the James Randi Education Foundation (JREF). However, the forum now exists as
an independent entity with no affiliation with or endorsement by the JREF, including the section in reference to "JREF" topics.

Disclaimer: Messages posted in the Forum are solely the opinion of their authors.