I suppose, but you read one conspiracy theory thread on the Dope, you’ve kind of read them all. It’s all the same playbook; all the same observations about human psychology you made.
That said, it was an entertaining read for about half the thread, and I did learn a cool analogy with the rulers.
I just burned time I’ll never get back having a look at that thread.
Lordy what a trainwreck.
Agree, it is interesting working through the misconceptions and some of the weird arguments, but it does just get to be repetitive. It isn’t a lot different to moon landing hoax CTers. I grow weary of conspiracy theories. Perhaps there was a time they were a bit of fun, but now we are beset on all sides. Eventually it comes down to some form of received truth. You can’t have a useful discussion with that.
There comes a point where the conversation isn’t really useful as a means of learning anything either.
What I find interesting is that the OP had trouble with relativity, and though they were a bit wedded to the thought experiments they’d already cobbled together on their own they were genuinely open to learn … probably … they did eventually disappear after receiving an explanation that made sense to them on the surface and saying they’d “have to think about that”.
Tom on the other hand is here as a preacher. Trying to establish where his thinking goes wrong and coming up with novel thought experiments and models to help him or others get out of the dead end they’re in might help out some other reader, but never Tom, as he’s not genuinely engaging with the answers, he believes he already knows what they will be and what the faith says the counter arguments are. He’s like a Chinese room, but only for discussions about relativity.
Francis, you are talking about points of view, which is simply appearances, whereas Einstein was talking reality, or fact, call it what you will. Now you have used the relativists favourite ploy, ignore the question asked, and ask one of your own.
You said :- “But SR doesn’t predict either of these. What it does predict is (depending on the exact manner in which the clocks are brought together) that the two clocks will be running at the same speed when measured side by side (boring) but also that one clock will be behind the other in displayed time (not boring).”
That sentence does try to answer, but fails. The question still stands - which clock is the slower [will be behind the other] and why that one?
Tom.
The one that is further away from the other.
Question to you: If clock A and B accelerate away from each other at relativistic speeds, then clock A turns around, catches up with clock B, and then matches its velocity, will one have ticked more ticks? If so, which one?
Hey, thanks for the plug Naita.
You forgot to name it and link it. Here it is :- http://problemswithrelativity.com/
There is some speculation in there, but there is also some good hard science.
Thanks,
Tom Hollings
I think we’re back to talking about points of view, simply appearances.
No matter how many times you ask the question, the answer remains the same. They will each appear to run slower to the other as has been demonstrated in real world experiments. Not only doesn’t represent a challenge to the theory of relativity, it is a strong supporting pillar confirming the theory.
Is it the words ‘appear’ and ‘seem’ that are creating some false impression here?
Each clock will be observed to run slower, from the reference frame viewpoint of the other. It won’t ‘seem as though it is’ - as in the illusory sense of seeming, but not being.
There’s no illusion - it will appear as it really is. It will seem as it is.
The problem with the page is that in between any hard science and speculation there is a lack of basic understanding of relativity.
Since I did open this line of discussion by mentioning your previous website plug in the thread I’ll spare everyone the labor and show an example of where you go wrong and pick apart the first obvious error that stands out to me, I’m sure it will not surprise anyone in this thread that it has to do with not grasping the concept of reference frames.
Einstein uses lightning strikes at two places on the railway track, and says that although they can be said to be simultaneous as judged from the embankment at a vantage point exactly equidistant from them, when judged from the moving train, they are not. He uses this as an argument for there being a different time in moving frames of rerefence.
I have difficulty in accepting this argument for the following reasons. In judging whether the lightning strikes are simultaneous, he uses light itself as a medium for carrying the information to the observer, without making any correction for the known finite velocity of light. Any number of other observers on the embankment, who are positioned so as not to be equidistant from the two lightning strikes, see the same two lightning strikes, but do not observe them to be simultaneous, and indeed, observe the timing difference between them to vary depending on where on the frame they are. This leads us to the conclusion that there can be an infinite number of time scales within one frame of reference - a conclusion which is not in accord with reality.
In Einstein’s thought experiment the finite velocity of light is very much an essential part of the observations. The observer on the embankment is placed equidistant from the lightning strikes to eliminate the travel time of the light from the equations, but any observer stationary with respect to the embankment will agree the lightning strikes were simultaneous, if the travel time of the light is taken into account.
The same applies to the observer on the train. The position equidistant from the strikes is chosen to eliminate travel time, but we could easily use any other position and add in travel time for the light.
For those unfamiliar with the rest of the though experiment Einstein points out that the observer on the embankment will see the light from the strikes hit the observer on the train at different times (we’re ignoring that the practical time difference would be negligible for a human observer, you can imagine a cosmically long train if you want). This is all well and good in our familiar Newtonian universe where Earth can regularly and to great benefit be chosen as a preferred reference frame in most instances, but experiments from Michelson-Morely on have shown that the Earth isn’t a preferred reference frame for the travel of light. In fact there are no preferred reference frames at all. So if the passenger who is equidistant from the two lightning strikes hitting the train sees them at different times, first the one forward of the observer and then the one behind, then in that reference frame, which is just as valid as that of the observer on the embankment, the two lightning strikes didn’t happen at the same time.
Tom doesn’t grasp this, because he doesn’t grasp the basic and very essential concept of all inertial reference frames being equal, instead he brings up a completely irrelevant issue of how we define simultaneity in one single inertial frame.
Maybe this is the one single place where Tom’s completely wrong. If so that’s unfortunate, since everything else in relativity requires understanding and accepting this elementary finding. I’m not reading the rest of it to find out.
It might help to realize that the two clocks are not both measuring the same quantity. Just like rulers at an angle are measuring lengths in two different directions, so too the two clocks are measuring time in two different directions.
To simplify the issue without even invoking timey-wimey stuff…
Two people are sitting opposite each other at a table; one person has a green apple, the other has a red apple. They both place their apples in front of them near the middle of the table, so the two apples are nearly touching.
Person 1 says “the red apple is behind the green apple”
Person 2 says “the green apple is behind the red apple”
Clearly these two statements are contradictory, so at most, one of them must be true.
Which apple is really behind which other apple?
“Behind is an absolute! One of them must be right!”
I disagree that this is a fruitful approach (pun intended). The train thought experiment has the benefit of actually being about special relativity. People (obviously) grasp the idea of the relativity of position without grasping the required elements of inertial reference frames in SRT.
Fair enough - I don’t want to take anything away from the reality of the lightning strike example; I’m trying to highlight that how things seem can be exactly how things really are and yet, can be different (indeed, contradictory) for different observers.
I don’t see Tom accepting the train thought experiment, simply because it’s too easy to accidentally impose some imaginary absolute frame of reference on the whole scenario.
I’m going to engage with you here again despite vowing not to, for two reasons. The first is to point out that, whether you realize it or not, this is a completely different question from your original one. The original question simply described two clocks A and B in constant relative motion, stated that relativity theory holds that A is running slower than B, but that B is also running slower than A, and flatly states since this is an obvious contradiction, relativity theory must be false. The problem with this, as has been explained to you more than a dozen times in many different ways, is that the “contradictory” assertion is made without any frame of reference, implicitly assuming that there is such a thing as absolute time, which is not true. The rhetorical question you ask in an effort to “disprove” relativity therefore doesn’t even make sense; it’s just incoherent.
This second question actually does make sense, and accordingly, it does have an answer. In order to be brought together into the same reference frame, one or both of the clocks must cease to be in an intertial reference frame and must experience acceleration. For the sake of simplicity, let’s put ourselves into the reference frame of clock A, which remains inertial. From this frame, we see that clock B undergoes acceleration and a change of direction. This introduces an asymmetry such that when they come together, clock B is observed to have an earlier time than A, though now both are ticking at the same rate.
The conceptual explanation is sometimes attributed to B having undergone the necessary acceleration to come into A’s reference frame, or alternatively that B’s reference frame has changed direction, although they’re mathematically equivalent. This is the essence of the twin paradox, which is considered a “paradox” because of confusion between the equivalence of inertial frames and the non-equivalence of non-inertial ones.
Sometimes, yes. But what is being illustrated here is just logical incoherence. Look at post #32, for example. Here, in order to show that he “uses math”, Tom tries to apply the Lorentz transformation to “prove” that “there is no theoretical upper limit to the velocity of the rocket”. But he inexplicably applies the transformation to the reference frame of the rocket exhaust, which is accelerating along with the rocket, and at any given time is always at a constant speed of 3000 m/s relative to the rocket. This not only tells us nothing about relativity, it doesn’t even tell us anything about the rocket’s speed in Newtonian terms.
So he’s taking a fundamental concept of special relativity – the Lorentz transformation – and by applying it to a comically inappropriate reference frame, is trying to show that a fundamental concept of relativity theory disproves relativity! Just as an aside, his formula for the Lorentz factor is wrong, too, not that it matters.
The other thing here is that if one accepts the Lorentz transformation as valid, which Tom apparently does (since he uses it, albeit incorrectly) one can easily see that as v approaches c, the divisor in the Lorentz factor reciprocal approaches zero, so as v tends to c, the Lorentz factor describing relativistic effects like time dilation and kinetic energy approaches infinity.
The argument about the two clocks is, if anything, even more incoherent, although I suppose we can blame Herbert Dingle for originating that one.
For some people, it can be helpful to explicitly have three characters, A (on Earth), Ba (heading away from Earth) and Br (returning to Earth). Ba and Br cross paths at some point, and Br sets his watch to the same time at Ba has at the moment of the crossing (allowable - “crossing” is a single event occurring at a particular place). When Br and A cross paths, Br and A have different values on their clocks, because A is measuring time in one reference frame, while Br is measuring the time from the moment Ba and A separated to the time when Br and A join - in two different reference frames. This eliminates the need for the brief period of acceleration otherwise required.
I thought the question posed was: “Time goes differently for those on the ‘spaceship’ then on earth. For the people on the spaceship would it be possible to travel let’s say 10 light years in less than 10 years ‘ship time’ if traveling near the SoL?”
As a casual observer, I am really enjoying the various in-depth descriptions, analogies and arguments for SRT. Thanks Francis_Vaughan, Wolfpup, Mangetout, Chronos, Asympotically_fat and everyone that I missed. This is a Classic Dope thread!
We have yet another informal analogy right here in this thread.
Some posts up, TH and FV each agreed with the other that this is getting “tedious”. But each of them sees the other as getting tedious. So which is it? Is TH getting tedious, or is it FV who is getting tedious?
There is another paradox in the universe that is illustrated by this thread. We have evidence here that at least one person in the universe (and probably many more) does not understand relativity, or at least has a very different concept of it. And yet, the universe continues to function. The whole universe does not come crashing down (as we all thought it would when Y2K hit, but it didn’t).
This leads us to the highly counter-intuitive conclusion: It is not necessary for everyone to understand relativity in order for the universe to function! Paradoxical as it seems, it is possible for one (or many) people to have no understanding of relativity, and yet nothing bad happens! How can this be?