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Thanks. Now getting the point.An accelerometer attached to B reads 0. Only A is accelerating according to attached accelerometers.
Because accelerometers show that it is not relative.
Thanks. Now getting the point.An accelerometer attached to B reads 0. Only A is accelerating according to attached accelerometers.
Because accelerometers show that it is not relative.
Thanks. A new thought for me.The key point to take away from the twin paradox is that the time difference is due to the moving twin's change of frame.
The acceleration is essentially irrelevant except for the fact that the moving twin must decelerate and accelerate so that they can change their frame.
You can easily set up a twin paradox without any accelerations. I use the values from above.
Set up a stationary observer on earth, another at the turning poiint and another at twice the distance of turning point. All three synchronise their clocks to read 0.
The moving twin_1 accelerates before the experiment starts in such a way that she is travelling at V when she passes earth, and she passes when the earth clock reads 0. She looks at the earth clock and sets her clock to 0.
A similarly moving twin_2 passes the point twice the turning point distance away, travelling at V towards earth.
The two moving travellers meet at the turning point. The stationary person's clock reads 5 but twin_1's clock reads only 4.5.
twin_2 sets her clock to be the same at twin_1, or 4.5. twin_2 continues to earth and arrives at earth when earth says it is 10. However, twin_2's clock reads 9, made up of the 4.5 which she set, plus the 4.5 for her journey time, totalling 9.
So, whereas the earth bound twin says 10 years have elapsed since twin_1 left, the total travel time measured by the two moving twins is only 9 years.
So, we have the same time difference but there have been no accelerations.
Acceleration has nothing to do with the twin paradox other than it is necessary for the moving twin to accelerate and decelerate to change her frame. The twin paradox is about changing frames.
Actually, Einstein, probably the biggest proponent of ‘motion is relative’, clearly and mathematically specified that if motion involving proper acceleration is compared to motion without, you need to include time dilation due to potential difference in the calculation. This means that the traveling twin must have a period where the stay at home twin’s clock runs faster due to being higher in a potential well.Thanks. Nice explanation of coordinate and proper acceleration. Now I am getting the point. The problem is, in most of the books dealing with SR or GR, that I have read, and as far as I remember, only the term acceleration is used, not proper acceleration. More so, doesn't it mean that, "motion is relative" this statement is not fully applicable in case of motion experiencing proper acceleration?
Thanks for your participation and making the debate so illuminating. But, as I told in the very beginning of the post, I am not a physicist. I am a biologist. Relativity and twin paradox is quite naive to me. And my main aim is to understand what is time itself. I am working on this very problem. The current dispute that whether it is just frame change, or acceleration that accounts for the twins gaining different ages can be better solved by you learned physicists itself, and I hope you will do it. I am just here to learn from you people.If, as in the twin paradox, the acceleration causes a change in speed then this does does affect the clock rate.
I think therefore your statement is both incorrect and very misleading.
99% of the explanations of the twin paradox say "It is caused by the fact that the travelling twin accelerates" but they never give a calculation showing how it comes about, nor provide an equation relating the age difference to the rate and duration of the acceleration experienced. I suggest the statement is therefore as meaningless as saying "It is caused by the fact that the travelling twin is wearing a bikini".
The twin paradox is explained by the fact that the moving twin changes their frame of reference. That is the essential kernel of the solution - everything else is second order. It is a simple application of the Lorentz transformation equations to get the resultant time difference.
Secondly, no-one citing acceleration as the cause ever shows how acceleration can account for the fact that both twins see each each other age more slowly than themselves during the entire time. This can only be resolved by invoking a frame change. It has nothing to do with acceleration.
Perhaps we could ask the original poster dayalanand roy , who has obviously worked on the subject, whether he found the change of frame explained things to him.
Thanks. But here, the potential difference and potential well are a bit new terms for me. Is the potential difference term used here conveys the same meaning as in case of any electric current?Actually, Einstein, probably the biggest proponent of ‘motion is relative’, clearly and mathematically specified that if motion involving proper acceleration is compared to motion without, you need to include time dilation due to potential difference in the calculation. This means that the traveling twin must have a period where the stay at home twin’s clock runs faster due to being higher in a potential well.
Similar. They both involve the notion of a mathematical object known as a "scalar field". Which pretty just means associating a number with every point in a space. They both have units of energy per unit charge. It is just that in one case the "charge" is the electrical charge on a test particle and in the other case the "charge" is the mass of the test particle.Thanks. But here, the potential difference and potential well are a bit new terms for me. Is the potential difference term used here conveys the same meaning as in case of any electric current?
More like gravitational potential. When a rocket is accelerating you effectively have a gravitational field in the frame of the rocket. Clocks at different potentials in that field run at different rates, even when they are not moving in that frame.Is the potential difference term used here conveys the same meaning as in case of any electric current?
No. While you can tell who accelerated ( changed velocities), you can't tell what velocity they began with or ended with, only that they differ by a certain amount. So for example, with two starting ships side by side, and one accelerates by 100 km/sec. There is no way to distinguish between both rockets starting "at rest" and one accelerating to 100 km/sec, and both rockets already moving at 100 km/sec and one accelerating to a stop while the other continues on.. More so, doesn't it mean that, "motion is relative" this statement is not fully applicable in case of motion experiencing proper acceleration?
Thanks. Now I am getting the point.No. While you can tell who accelerated ( changed velocities), you can't tell what velocity they began with or ended with, only that they differ by a certain amount. So for example, with two starting ships side by side, and one accelerates by 100 km/sec. There is no way to distinguish between both rockets starting "at rest" and one accelerating to 100 km/sec, and both rockets already moving at 100 km/sec and one accelerating to a stop while the other continues on.
Yes. Thanks for a simpler explanation.More like gravitational potential. When a rocket is accelerating you effectively have a gravitational field in the frame of the rocket. Clocks at different potentials in that field run at different rates, even when they are not moving in that frame.