Today we know biological factors of aging like DNA methylation increases & chromosome telomere shortens, that is we have an intrinsic clock. But Einstein suggests time stops at light speed & so should do aging. Question is on which clock, on our watch or body clock? Who has shown DNA methylation stops at high speeds? Why would this happen at all?
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4$\begingroup$ Question is on which clock Why do you think that various kinds of clocks aren’t all measuring the same elapsed time? Do you think that there is some preferred kind of clock and only it tells the correct time? If so, what clock would that be? And why? $\endgroup$– G. SmithNov 11, 2020 at 18:53
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$\begingroup$ The rate of mutations (Molecular clock of evolution), the methylation (which characterizes aging), and the circadian clock are all grounded in physical and chemical processes - that is these processes are affected by relativity in the same way as a conventional clock (except that the latter is likely more precise). In other words, the confusion here is between the time and the processes that one may use to measure time. $\endgroup$– Roger V.Apr 27, 2021 at 13:33
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2 Answers
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If you are traveling near the speed of light relative to another observer, then according to that other observer you are moving through time much slower than he is. But according to you, everything appears normal - your world doesn't become one of slow motion. It's the same for your watch and your body clock. It doesn't depend on the mechanism of time measurement - it's not that moving fast is affecting the gears or circuits in your watch. It's time itself that is slower compared to the other observer.
answered Nov 11, 2020 at 18:57
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1$\begingroup$ But it's believe the guy moving at speed of light for several years when he returns to earth he would find everyone much older. It means dna methylation for him occurred at a lower rate! Who has shown that? Why should that even happen? How is speed affecting methyl group binding DNA? $\endgroup$– MCHNov 12, 2020 at 19:34
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$\begingroup$ @MCH: specific, biological experiements have not been run, but there is strong evidence that ALL physical processes are slowed. For instance, radioactive decay of particles proceeds more slowly for a moving particle, at a slower rate completely consistent with the one predicted by Einstein. $\endgroup$ Jul 16, 2021 at 15:33
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$\begingroup$ It's not speed affecting the process, it's "the underlying time in the reference frame is changed relative to the outside" $\endgroup$ Jul 16, 2021 at 15:33
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I think you have a basic misconception here.
Einstein suggests time stops at light speed & so should do aging.
No. This is not what Einstein says and not what time slowing down means.
What time slowing down means is that an observer who sees you traveling at some velocity $v$ sees your time slowing down relative to their own.
However you don't see your own time slow down. Time is completely normal for you. What you see is the observer (who you see moving at velocity $-v$ relative to you) seems to have their time slowed down. Yes, it works both ways !
Both of you see time in your own frame of reference pass normally and the other person's time slow down relative to yours.
Question is on which clock, on our watch or body clock? Who has shown DNA methylation stops at high speeds? Why would this happen at all?
OK, it should be clear that this does not happen at all, but there is another misconception in your question.
It's the "at the speed of light" part.
Objects with a non-zero mass cannot reach the speed of light.
The only things which can reach the speed of light must have zero mass and what's more there is no valid frame of reference for such an object. You cannot describe the passage of time for such an object in the way you would for a massive object. These massless particles always travel at the speed of light and are seen to do so by all observers.
answered Nov 11, 2020 at 19:01
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1$\begingroup$ Yup. Subjective time is only affected by how interesting your surroundings are. Department meetings, for instance, take a lot longer than the same amount of calendar time spent doing something interesting in the lab. $\endgroup$ Nov 11, 2020 at 19:13
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$\begingroup$ But it's believe the guy moving at speed of light for several years when he returns to earth he would find everyone much older. It means dna methylation for him occurred at a lower rate! Who has shown that? Why should that even happen? How is speed affecting methyl group binding DNA? $\endgroup$– MCHNov 12, 2020 at 19:34
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$\begingroup$ It's not just DNA methylation, it's time itself relative to the other observer. I'm not aware of any experimental test of the twin paradox which involves a round trip, but there are ample examples of time dilation e.g. muon decay. These are created in the upper atmosphere and have a short half-life (in their rest frame) such that they should not reach the surface of the earth. But because of time dilation, they do. $\endgroup$ Nov 12, 2020 at 22:47