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Darius Macab
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I was talking with my friend and the best answer i could come up with is "It does." But, i could not explain why. Could you guys help me out?
Thanks
DM
Thanks
DM
phinds said:WHOA HERE ... unless I have this totally wrong, time does NOT slow down for you when you get near the speed of light. It APPEARS to other inertial frames of reference to have slowed down but to YOU it doesn't seem to slow down at all. To you it seems like things in the OTHER frames of reference have slowed down (and of course, they would disagree).
Pengwuino said:the observer moving relative to the guy initially at rest will experience a slower time change.
phinds said:Hm ... I wonder if that's really the right way to say it. As I understand it, the guy moving will not EXPERIENCE a slower time change but he will have UNDERGONE a slower time change even though not experiencing it. I think this is more than semantic nitpicking.
The guy who travels off at 99.99% of the speed of light (forget about getting squashed by initial G force in this thought experiment) and travels in a huge arc back to the starting point will feel that he has been traveling through time at a perfectly normal rate, but when he gets back he'll see that a clock on the ground that was synchronized with his to start with is now far into the future of his clock even though he EXPERIENCED time as normal.
feihong47 said:well, I was wondering how you'd solve that numerically. Say I went 99% of C for 100 s, assuming C is 3x10^8 m/s. How much time would have elapsed on my stopwatch?
phinds said:WHOA HERE ... unless I have this totally wrong, time does NOT slow down for you when you get near the speed of light. It APPEARS to other inertial frames of reference to have slowed down but to YOU it doesn't seem to slow down at all. To you it seems like things in the OTHER frames of reference have slowed down (and of course, they would disagree).
GarryS said:Then why does one person age more than the other?
phinds said:Hm ... I wonder if that's really the right way to say it. As I understand it, the guy moving will not EXPERIENCE a slower time change but he will have UNDERGONE a slower time change even though not experiencing it. I think this is more than semantic nitpicking.
The guy who travels off at 99.99% of the speed of light (forget about getting squashed by initial G force in this thought experiment) and travels in a huge arc back to the starting point will feel that he has been traveling through time at a perfectly normal rate, but when he gets back he'll see that a clock on the ground that was synchronized with his to start with is now far into the future of his clock even though he EXPERIENCED time as normal.
No, it doesn't matter his direction, his speed is what counts relative to some frame, in this case the stationary clock. So the traveling clock always experiences the same time dilation throughout the entire journey.akshayxyz said:Hi,
I am out of touch in physics for more than a decade, so please excuse my obsolete and corrupt memory/understanding of the concepts...
As per my understanding velocity is a vector quantity, and if the traveler indeed comes back to the starting point - while travelling in the arc - the velocity vector relative to the stationary clock will not always be 0.9999c, half of the journey time should dilate, and the other half, it would be other wise... so when he does comes back and stops, there should not be any time difference.
You are correct, each observer will read the other one's clock as ticking slower by exactly the same amount but here we are not talking about time dilation, we are talking about Relativistic Doppler which is what each observer actually sees of the other one's clock. The amount of slowdown that they see is not the amount of time dilation.akshayxyz said:The time dilation effect should come into picture, when the person traveling at 99.99%c, tries to read the stationary clock - since that information from stationary clock can at best be sent at c... so the 1 second ticks sent by stationary clock to the person traveling at 99.99% c, will not be 1 second ticks read as per the clock with the traveling man... and vice versa ( if the stationary person tries to read the clock traveling at 99.99%c)
What happens when the traveler makes the U-turn, is that he immediately sees the stationary clock speed up. This the Relativistic Doppler in the other direction, exactly the inverse factor, but time dilation is still going on.akshayxyz said:So, if the traveller continue traveling at 99.99%c, in the direction away from the stationary clock - the time ticks sent by stationary clock when read on traveller's clock will appear dilated - relatively.
However, I am not sure what happens, when the traveller takes a U-turn and approaches the stationary clock... and if it must come to rest to read the clock, there would be a process of deceleration also - and it would no more be non-accelerating frames of observation...the traveller must read the stationary clock, while maintaining the constant speed.
Because the frequency of an oscillator is directly related to the speed at which the oscillator is moving. This includes the atoms that constitute the biological oscillators of an organism. So, the faster you move, the less you age.GarryS said:Then why does one person age more than the other?
While the mainstream geometrical interpretation (Minkowski) of SR is quantitatively correct, there's no detailed mechanistic understanding of differential aging yet -- though the quantitatively equivalent Lorentz ether theory is a step in that direction.
So you're saying that the person that accelerated to 0.5c is accumulating less age than the person at rest because of the time duration that he spends at that speed? And this is better explained by LET than SR? And that if he increases his speed, his clock slows down and if he decreases his speed, his clock speeds up? It sure sounds like you are promoting an absolute state of rest. Can you explain further, because I'm afraid that Garry will get a wrong impression?ThomasT said:Because the frequency of an oscillator is directly related to the speed at which the oscillator is moving. This includes the atoms that constitute the biological oscillators of an organism. So, the faster you move, the less you age.GarryS said:Then why does one person age more than the other?
While the mainstream geometrical interpretation (Minkowski) of SR is quantitatively correct, there's no detailed mechanistic understanding of differential aging yet -- though the quantitatively equivalent Lorentz ether theory is a step in that direction.
As others have noted, nobody will feel like they're aging any differently as their speed increases or decreases, and their own clocks won't appear to them to be slowing down or speeding up. But they will feel something if their speed increases or decreases, and it's during these intervals of changing speeds that the changes in biological oscillators, as well as the, say, crystal oscillator that's the basis of a reference clock, are occurring.
But this shouldn't be confused with what's actually determining the accumulated difference in age between, say, a person at rest on Earth and a person moving at an average of, say, .5 c in a spaceship. This accumulated difference is solely determined by the duration of intervals wrt which there are differences in speed between the two.
The difference in time (or age) that the (earthbound and travelling) biological oscillators accumulate during an interval is due to their difference in speed during that interval. A traveller moving at an average of, say, .5c for a roundtrip interval of, say, 30 years (earth time) will have aged noticeably less than the earthbound person (by an amount given by the Lorentz transformation).ghwellsjr said:So you're saying that the person that accelerated to 0.5c is accumulating less age than the person at rest because of the time duration that he spends at that speed?
Yes.ghwellsjr said:And that if he increases his speed, his clock slows down and if he decreases his speed, his clock speeds up?
Not necessarily. They're quantitatively equivalent. But to even begin to have a mechanistic understanding of why an oscillator's frequency decreases as the oscillator's speed increases, and vice versa, then you'd have to have the oscillator interacting with something.ghwellsjr said:And this is better explained by LET than SR?
I don't know what that might refer to. Relativity says that the laws of physics don't depend on states of motion, and, so far, that seems to be the case.ghwellsjr said:It sure sounds like you are promoting an absolute state of rest.
What I suggested is that the frequency of an oscillator is directly related to the speed at which the oscillator is moving, and that there's currently no detailed mechanical explanation of how a change in the speed of an oscillator produces a change in the frequency of the oscillator.ghwellsjr said:Can you explain further, because I'm afraid that Garry will get a wrong impression?
His specific question was prompted by the statement that time dilation is reciprocal.ThomasT said:What other impression might he get from anything I've said?
Your posts state that it all is a result of one person having a speed while the other one is at rest. You seem to be stating the opposite of what phinds was saying. Can't you incorporate the reciprocal nature of time dilation into your discussion and explain why the "person at rest on earth" could be the one with the slowed down "biological oscillators" just as validly as the person moving at 0.5c in a spaceship?GarryS said:Then why does one person age more than the other?phinds said:WHOA HERE ... unless I have this totally wrong, time does NOT slow down for you when you get near the speed of light. It APPEARS to other inertial frames of reference to have slowed down but to YOU it doesn't seem to slow down at all. To you it seems like things in the OTHER frames of reference have slowed down (and of course, they would disagree).
Ok, but his question was about differential aging not time dilation. Time dilation is symmetric, and is due to the SR conventions applied by observers in relative motion wrt each other in a relativistic universe (ie., apparently our universe, wherein the speed of light is constant and the same for all observers regardless of their state of motion).ghwellsjr said:His specific question was prompted by the statement that time dilation is reciprocal.
That's just one scenario, that is, where one person and his clock move about at relativistic speeds wrt the Earth while the other person and his clock remain at rest wrt the earth.ghwellsjr said:Your posts state that it all is a result of one person having a speed while the other one is at rest.
phinds said (I'm paraphrasing) that each observer would see the other's clock as slowing down, and that each observer would see his own clock as not slowing down. And I said that, "As others have noted, nobody will feel like they're aging any differently as their speed increases or decreases, and their own clocks won't appear to them to be slowing down or speeding up". Which doesn't contradict what phinds said.ghwellsjr said:You seem to be stating the opposite of what phinds was saying.
No, because SR predicts, and analogous experiments support the expectation, that the person moving at 0.5c in a spaceship would be the one who actually aged less, and with that the inference that the traveller's biological and reference clock oscillators' periods actually physically dilated.ghwellsjr said:Can't you incorporate the reciprocal nature of time dilation into your discussion and explain why the "person at rest on earth" could be the one with the slowed down "biological oscillators" just as validly as the person moving at 0.5c in a spaceship?
You can say precisely what each twin will see of the other one's clock, but there is no neutral perspective from which you can identify an instant that applies to both of them.akshayxyz said:@ghwellsjr
thanks for the response.
I still have doubts about the 'twin paradox'.
Lets take the example of stationary A and moving B (lets say at .9999c).
As you also agreed - "You are correct, each observer will read the other one's clock as ticking slower by exactly the same amount".
Lets say at some instant B sends message/tick to A, that he is 10 y/o as per B's clock. A would get this message let's say when A is 20 y/o (as per A's clock). and vice-versa.
Now at that instant (when at receives that message), would B also not have aged to 20? Even though A would not know about it.
So, essentially both should age at same rate (from neutral perspective), and it should just be the time gap in knowledge of their ages with each other.
You specified that A is stationary and B is moving at .9999c, which means that B is aging and his clock is accumulating time slower than A by a factor of 70.7.akshayxyz said:I still have doubts about the 'twin paradox'.
Lets take the example of stationary A and moving B (lets say at .9999c).
Lets say at some instant B sends message/tick to A, that he is 10 y/o as per B's clock. A would get this message let's say when A is 20 y/o (as per A's clock). and vice-versa.
Now at that instant (when at receives that message), would B also not have aged to 20?
By "neutral perspective" I assume you mean some common referent. Like say A is on Earth, so he's stationary wrt the Earth, and B is moving at .9999c wrt A and the Earth. Ok, so when the Earth-Sun system marks 10 years, then A will have aged 10 years and A's clock will have accumulated 10 years, but B will have aged (and B's clock will have accumulated) only about 51 days and 15 hours.akshayxyz said:So, essentially both should age at same rate (from neutral perspective) ...
But, assuming that you did the calculation correctly, you could also say that from a reference frame in which B is at rest, A and the Earth-Sun system are moving away at 0.9999c and when B will have aged 10 years, A's clock will have accumulated only about 51 days and 15 hours and the Earth will have only progressed about 1/7 of a revolution around the Sun.ThomasT said:By "neutral perspective" I assume you mean some common referent. Like say A is on Earth, so he's stationary wrt the Earth, and B is moving at .9999c wrt A and the Earth. Ok, so when the Earth-Sun system marks 10 years, then A will have aged 10 years and A's clock will have accumulated 10 years, but B will have aged (and B's clock will have accumulated) only about 51 days and 15 hours.
I assume you're talking about what B would see and not what actually is the case, because if B is moving away from the Earth-Sun system and A at .9999c, then during the interval that B's clock goes from 0 to 10 years, then the Earth would have gone around the sun 707 times. But yes I understand that B would see the Earth as only having progressed about 1/7 of a revolution around the Sun when he (B) marks that his clock has accumulated 10 years.ghwellsjr said:But, assuming that you did the calculation correctly, you could also say that from a reference frame in which B is at rest, A and the Earth-Sun system are moving away at 0.9999c and when B will have aged 10 years, A's clock will have accumulated only about 51 days and 15 hours and the Earth will have only progressed about 1/7 of a revolution around the Sun.
Because it wouldn't illustrate differential aging, which is what akshayxyz seemed to me to be concerned about, and which I take to be the basic theme of this thread (ie., a discussion about the relationship between speed and timekeeping/aging).ghwellsjr said:Or you could pick a Frame of Reference midway between A and B such that both of them are traveling at exactly the same speed in opposite directions and in which they both age at the same rate. Why wouldn't this FoR be a better "neutral perspective" than one in which either A or B was at rest?
Yes, point taken. So I just specified a common referent, the Earth. I thought it would then be clear(er) to akshayxyz that as long as A was at rest wrt the Earth and B was moving at .9999c wrt the Earth, then B would be aging, and his clock accumulating time, slower than A by a factor 70.7ghwellsjr said:And there are a gazillion other Frames of Reference that establish totally different accumulated times on A's and B's clocks, none of which can be called a "neutral perspective".
Maybe that's how some people use the term "neutral perspective" in these sorts of discussions. I don't know. But, as I mentioned above, I don't think that "preferred reference frame" was what akshayxyz was referring to wrt his use of the term "neutral perspective".ghwellsjr said:That's just a euphemism for "preferred reference frame" of which there are none.
Ignea_unda said:This whole discussion about "preferred reference frames" not existing seems a moot point after the Hafele-Keating Experiment. Please correct me if I'm wrong but according to http://hyperphysics.phy-astr.gsu.edu/hbase/relativ/airtim.html" , a clock moving easterly "gained" time while the clock going westerly "lost" time. IF there was no "preferred" reference frame, then we could look at both clocks and see relatively the same time. Moreover, both clocks' reference frame could be chosen as "correct" and all the clocks timing would line up, eventually. However, we see that since one clock gained time and the other lost time, there must be some absolute to which everything is measured to. I'm NOT comparing them to the Earth fixed reference frame, but rather the net change. Again, please point out the flaw in my logic if it is there and show how it is wrong.
phinds said:I may be misreading you but it seems you believe the experiment DOES show that there is a preferred frame of reference when it fact it shows the opposite.
You seem to be leaving out the middle clock. There were three clocks and their motion was relative to each other and the results were compared relative to each other and were consistent with relativity. There was no measurement against anything "absolute". Each of the 3 would see the other two exactly as predicted by relativity (within the margin of error of the measurement).