I should add for 2 and 3, that’s not to imply the time differences involved are necessarily large.
Each observer has an instantaneous velocity relative to the other, as I say if you argue that doesn’t count because they are moving around the same point, then you must surely believe that the instant an object fails to experience the centripetal acceleration (an object falls) it would be seen to experience a very different time rate suddenly. And what would you say if there was a counter-rotating turntable and train on the same axis above this other train, would you still not expect time dilation? (and yet this is still symmetrical and they can keep regular if intermittent track of each others time.
And if not, then you would have to conclude that there should not be any time dilation between 2 spaceships passing if each other if each one is moving perpendicular to a large mass that is curving their motion around it, such as the milkyway galaxy but, but the instant their paths straighten up massive time dilation.
Everyone is always completely and utterly ignoring my points about what then happens if time dilation does not occur in these instances.
You can’t just address half of te thought experiment, I already covered these objections, you can’t ignore them and at like you have achieved anything since there are paradoxes either way.
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It’s a symmetric situation, as is obvious from a third observer at rest in the center of the circle, and they have aged the same.
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Ok, so are you saying that there is time dilation occurring (from SR) on the train from the center perspective? So do the occupants on the train see time slowed for the researcher in the center?
If so then we have a paradox.
If not we have a different paradox, since you would expect that if a linear path was taken at the same velocity as the cabins, that this observer would be expected (I assume) to see the researcher at the centers time slowed since there is a large linear (and not just instantaneous) velocity difference, which means that we now have two observers who are in almost the same frame of motion (or are momentarily seeing different things of the rate of time of the researcher in the center.
However if the researcher in the center sees no time dilation for the occupants of the cabins on the turn table, but should for the linear path at the same instantaneous velocity, and this then should also be the view of those in the turn table too, so we back to the situation of no time dilation, and then the instant an object does not conform to this path it loses experiences massive time dilation, which still makes no sense.
And particles going around in a particle accelerator are believed to experience time dilation I am quite sure (muon life time).
Stop acting like you can take only a portion of the thought experiment, it must be complete.
How does the Doppler effect apparent time rate when they are not getting any closer or further away from each other???
Anyway you now would need to explain why if something momentarily (fallen or let go of), or continuously follows a linear path at the same velocity should immediately experience massive time dilation (seem frozen)! Such as a linearly moving train that passes by our turn table. Now we do not need to look across the turn table, we can observe these effects in our own cabin!
If you say time dilation still doesn’t occur, then that is tantamount to saying time dilation does not occur from relative motion.
Please stop acting like I am not mentioning this!
This is a part of the thought experiment.
Ok, if that is what you say, then you need to address the issue of linear motion occurring in these cabins, or with trains with equal linear velocity on a linear path.
There is a difference between something seeming contradictory, and something being contradictory, contradiction is impossible.
If there is no direct comparison of how time is progressing in the other time frame, then it seems contradictory, but maybe must maybe we can say that since (or if) there is no God’s eye view, and if we can’t have each experience the others time frame directly, but only in a highly distorted fashion…
Then it becomes a hard, but maybe possible pill to swallow.
As soon as you have this contradiction laid bare, in the same room so to speak. It can no longer be thought of as difficult to accept. It is now simply impossible.
SR works if you take it on faith, it is like someone who applies for a job that has all the credentials and qualifications, talks a good game, but is actually an incoherent coke head. If you really examine anything, it falls apart.
It looks ok on the surface, but don’t dig deeper or challenge it.
“Sure, it may work in practice, but it’ll never work in theory.”
The concept of closer and further do not stand up well in accelerated frames of reference, which (except in limited cases) cannot be spatially extended. However it can perhaps be seen that it is in someways useful to approximate the geometry of a rotating Born-rigid disk as that of the hyperbolic plane. Unfortunately trying to understand this without having at first a good understanding of the basics of special relativity is trying to run before you can walk.
I don’t know what you are trying to illustrate. The moment an observer on the disk ‘drops’ a clock that clock will still appear to run at the same rate as it will be, at that moment, co-moving with the observer who drops it. As the motion of the observer diverges from the movement of the clock, the rate they observe it to run will diverge from the own rate and it will appear slowed (I guess as I can’t be bothered to do any calculations for this rather pointless diversion), but so what?
I don’t understand you. Be more explicit.
I fail to see how the relativity of simultaneity accounts for different rates of time.
Rather it is an argument about being unable to say that 2 events in 2 different locations are simultaneous or not.
This has an effect on some efforts to set clocks in sync over distances and in different frames of reference, but seems not directly related to time dilation.
For all your complaining about people not reading your posts, it’s clear that you barely read mine, because I never said anything of the sort.
I said you would have to use General Relativity. You never addressed this. Apart from your quote of my post, you never said anything about General Relativity.
I pointed out that the two observers were not in inertial frames. Again, you never said anything about inertial frames in your reply.
No, because of the part of my post you ignored. You can’t ignore General Relativity, use non-inertial reference frames, and get consistent results. But since you are ignoring General Relativity, since you are looking at non-inertial reference frames, you get wrong results from your thought experiments.
Stop acting like you can take only a portion of physics (Special Relativity) and blindly apply it everywhere (in non-inertial frames).
To be consistent with what I have said: I disagree with this.
We’re not using Einstein’s field equations, the background is Minkowski spacetime. For me that is special relativity, not general relativity.
The reason it is relevant is that as a general rule, time dilation alone does not tell you how to transform the time difference between two events between two inertial frames. You also have to take into account the failure of simultaneity at distance. This is what you didn’t do in the first example you posted, it’s also a very common way people get confused about special relativity (i.e. by trying to examine changes in frames in terms of time dilation and length contraction only).
Sorry, my bad. I thought he was still talking about the frame of reference of either of the two observers rotating in the circle, where we’d have to describe the situation using GR.
Yes.
What you seem to be missing is that there are TWO different types of time dilation. One is caused by relative velocity. The other is caused by acceleration (or gravity – acceleration and gravity are equivalent.) Don’t take my word for it, go read the Wikipedia article on time dilation.
Your failure to grasp fundamentals like this is why your opinion on relativity is worthless.
No, it is not. Jesus, that’s the whole point. Both inertial and gravitational time dilation are what you are left with AFTER YOU CORRECT FOR THE DOPPLER EFFECT.
Sure you can. Your failure of imagination is not the universe’s problem.
I do not believe I meant to indicate you did, I was probably just covering one possible scenario, I try to cover all possible scenarios that I think the ‘reader’ may think of.
I did not understand what you meant, hence I did not address it.
My bad.
So what did you mean, if you want to tell me.
Same reason, I do not know what you mean by inertial fames, maybe I should, but I confess I don’t.
I assumed by inertial frames you meant something regarding straight line constant motion, now I think about it it sound like inertial frames is related to acceleration.
Since both observer accelerates as the turntable accelerated, expediences G-forces the whole time and then experiences deceleration, then I guess you can’t be referring to acceleration either. And I could other sources, but what I wouldn’t be use if what you mean is the same.
So if you want me to address inertial frames, please explain what this is, and why they aren’t.
Ok, MAYBE I now understand what you mean, you are saying that their experience is symmetrical, and therefore there is no time dilation, is that it?
I have many answers to that, but I will wait for you to confirm that that is what you mean.
Again, how am I ignoring GR? I have said that my understanding of GR is comparatively weak, and I am not even 100% certain I could draw an accurate dividing line between the 2 Relativities.
Ok, fine, let’s BOTH stop ignoring parts of the others argument ok?
You explain what you mean, and then we can continue.
BTW please consider that this is me against everyone else, I try to reply to everything, but I can’t, and maybe shouldn’t as that can be seen to be bad form too, and takes a lot of time, and increases the messages anyone following this has to read, which leads to very rough skimming which leads to more going in circles, conversationally that is.
I have mentioned the latter type of time dilation many times (4-5 minimum) in this thread.
That you say I am ignoring it goes to show that probably only a tiny amount of what I write is actually read.
Additionally it does not matter at all even if I did ignore it (which I didn’t) because i am setting up the thought experiment, I am asking others to tell me what should happen in it.
Now I also agree with Asympotically fat, it is a distraction that can be ignored, both because the diameter can be increased reducing this form of time dilation, and also these are not the droids, er time dilation you are looking for. (it is a paradox free kind since acceleration/gravity is not so much relative as it is absolute)
Your objections are worthless, I am simply setting up a thought experiment that can be tested, at least theoretically, and probably in reality.
There is nothing absolutely impossible about having motion, or motion in a circle.
Therefore it is only the results, and I am asking YOU what they should be.
And the whole scenario,with things assuming linear motion (or diverging from the expected arc) and or observers on a linear path that pass by the cabins at the same speed.
All these things are possible. The question is what will happen.
Ok, this is an interesting perspective, if I understand you correctly you are saying that at a constant velocity there is no ACTUAL time dilation, and the only ACTUAL time dilation is caused by GR with Inertial/gravitational equivalence. (huh, I can see you are, but I don’t believe my eyes)
Wow, now this I do agree is entirely paradox free, but is this what anyone else agrees with???
I am betting no, but hey you and I (If I understand you) have the same view on time dilation that can happen with Relativity!
One thing though is that your view, er our view, does not allow the classic twin paradox, at least not in the dramatic sense and not with very swift acceleration.
If one twin accelerated to 99.999999999% of the speed of light in our (earthen 1G) time frame in precisely 1 atto second, and then travels 30 light years distance and then stops just as quickly, turns around and then accelerates to 99.999999999% percent of the speed of light just as rapidly, and then as she gets to earth decelerates just as quickly…
Then her time dilation from all that moving at damn near the speed of light for 60 years and making 4 changes in velocity would be what? A dramatic dilation of that 1 earthen attosecond (x4)? Maybe in that atto second she experiences only a yocto second.
In other words we could probably not even measure the difference I suspect.
Oh and she would be dead from the G-forces we can’t magically remove incase that would remove the dilation as a result of said dampening. (well, I guess that depends on the method, some would be fine)
Sigh. An inertial frame is one that is NOT undergoing acceleration.
Let’s go through these points again, shall we?
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Time dilation is observed AFTER you correct for signal propagation. So bringing things like Doppler shift into your thought experiments often just confuses things.
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If you’re moving relative to another observer you see their clock ticking slower. This effect is reciprocal. If you’re in an INERTIAL REFERENCE FRAME – one that’s not accelerating – this is the only time dilation that comes into play.
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If you’re accelerating toward another observer you see their clock ticking faster. How much faster is a function of your distance from them. This effect adds to or subtracts from the time dilation causes by velocity difference.
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If you’re accelerating away from another observer you see their clock ticking slower. Again, how much is a function of distance. And it also adds to or subtracts from the time dilation caused by relative velocity.
Points 3 & 4 are not the product of a Doppler shift. You can observe their effects even if no signals are exchanged during the experiment and you just compare clocks at the end.
All of these effects come into play in the scenarios you’re describing, and until you understand what relativity actually says you’re bound to come to grief.
Stop talking about the train and rotating (non-inertial) frames. Just try to get your head around these points first.
Oh, okay, I’ll talk about the train.
You have a large velocity relative to someone in the opposite side of the train. You’re also experiencing a large acceleration toward them. The two time dilations cancel out.
This thread has gotten beyond my ability to contribute, but I’d like to thank Asympotically Fat, Zenbeam, and The Hamster King for continuing to plow through this and explain things in very accessible ways. This is why I love the Dope!
The objection isn’t that motion in a circle is impossible. The objection is that it’s a non-inertial frame of reference.
I do not ‘bring it in’, rather my experiments are designed so that there is zero, or negligible Doppler shift to make it clearer.
If you are ok with it, we could have simple linear motion and a means of SR violating instantaneous communication instead.
That sure makes things easier.
Ah ha, this is quite opposed to what you said earlier!
You said that once correction was made for the Doppler effect, the only sources of time dilation were gravitational/inertial.
I guess you must have meant in this example only.
Well that is fine, I accept that answer, BUT you have not answered the second part!
That if you say the only time dilation is essentially gravitational then it could have very very little time dilation…
So if you dropped a clock to fall with gravity/centrifugal force till it hits the floor/wall, it should now experience time dilation of travelling at almost the speed of light, even though the rate of fall need not be extraordinary (if the turn table is astronomically large).
Or the equivalent, another train in an inertial frame at the same velocity moving by.
Why wouldn’t these stationary but linear (inertial reference frame) parties experience time dilation?
WHAT!
That is Precisely what Doppler is!
3 and 4 obviously can NOT be observed without a signal, be it natural light, or radio, direct electrical signals etc… And obviously could not be observed with instantaneous communication.
I am not even sure what to say to such a thing.
Are you saying that this is an effect that causes the same effect as Doppler but in additional to Doppler?
Because what you said is essentially just that!
Also it would need to be a real effect, meaning we would have time dilation and time er compression, or time acceleration?!
AND you would have a paradox that an object could be experiencing time faster AND slower than 2 objects in the same inertial frame.
If Earth and Alpha Centuri kept track of each other’s rate of time and found they experienced time at the same rate then I travel to Alpha Centuri at high velocity I would be going though time faster than those in Alpha Centuri and slower than that of earth. Not just appearing to.
Now it would be hard to fully argue with this given SR issue with events in distant locating deciding on simultaneousness… but this would be quite odd indeed.
Are you saying that besides that of gravity, this is the only type of Time dilation/compression (or acceleration), or is normal time dilation in inertial frames an additional type?
Ok, in this event, if I move at .99c past a clock, I should see the clock to tick normally while I am not moving toward or away from it?
If anyone else agrees with this point of view (which mutes most of my objections since it is not just time dilation, and overall there is no net time rate difference between different frames when the frames are taken as a whole) I would be very interested to hear it.
But if so, WHY IS IT CALLED TIME DILATION!?!?!?!?
Why is it always about ships travelling very fast that are stuck in time relative to the rest of the galaxy and not about ships that experience massive acceleration of time?!?!?!?!?!
SciFi Novel in one sentence: An inventor develops a means of teleportation (or worm hole travel) and then has a generational ship of scientist travel toward earth at .999999c so that they may develop technology for thousands of years in their time only to arrive back at earth not long after the ship was sent into the wormhole.
Added bonus, the scientist cheaped out on the brakes, maybe he accelerated them to that speed with some astronomically fast (and lucky ) slingshot effect that means they must develop breaks before they get here, or else the will risk crash into the earth! (It might be hard to safely steer a spaceship at that speed)
In the initial example, I had 3 observers, OB1 (kenobi) at the station.
OB2 is moving away at a constant velocity from the station and at the moment in time we are inspecting right next to OB3 which is in the same inertial reference frame as OB1.
Soooo I would view that OB3 and OB2 must agree on rates of time, and should see in that moment that they both have the same time rate as each other.
Now I would have assumed that SR would however have the paradoxical situation of OB2 and OB3 both seeing the other guys clock as slower than theirs, but IF The Hampster King is correct, and if I am correct about what he is saying, SR would have OB2 and OB3 agree that they both experience time at the same rate.
Only OB1 would be left out of this agreement.
Before I say any more I want to see what the Hampster King and others say about this, is this accurately what SR predicts?