5 ms·

Move clocks at the exact same speed and acceleration in opposite directions, so they stay synchronized.

by drran 6y ago

andrewbarba 6y ago
I don’t think this works either because you can’t meaningfully agree on when light was emitted from one of the clocks. The only solution should involve a single clock but then you are always measuring 2 way and not 1 way speed.
- klodolph 6y ago
  > I don’t think this works either because you can’t meaningfully agree on when light was emitted from one of the clocks. You can in fact meaningfully agree. You put the clocks in similar reference frames (like “standing on the surface of the Earth”), and accept some small but non-zero margin for error. The fact that a spaceship traveling around the earth does not measure light pulses emitted by these clocks as simultaneous is irrelevant—because we know that the notion of simultaneity relies on reference frame. What we do get is that anyone standing on the Earth’s surface can measure the pulses as simultaneous, within the specified margin of error. This error must necessarily account for the the fact that time progresses differently at different altitudes and latitudes, if your clocks are accurate enough. Because General Relativity is an extremely accurate theory and we have accurate measurements of the relevant physical constants & the mass of the Earth, we can account for the different reference frames and run the clocks at the correct rates so they continue to be synchronized even when they are free running (again, with the appropriate margin of error). If you are using ordinary quartz clocks, then the clocks probably have enough error that you can ignore relativistic effects. I’m assuming we want atomic clocks if we’re series about chronometry, especially considering how cheap they are these days. The idea that synchronizing clocks is somehow impossible stems from an unrealistic idea of how people measure time in the first place.
jerf 6y ago
Veritasium just had a good video which discusses this: https://www.youtube.com/watch?v=pTn6Ewhb27k https://www.youtube.com/watch?v=pTn6Ewhb27k It turns out there's some circularity in your definitions of "Move clocks at the exact same speed and acceleration in opposite directions" and "synchronized"; that's basically the definition of "synchronized", which is fine from a certain point of view, but from the point of view of examining the nature of space and time themselves, not adequate.
- TheCraiggers 6y ago
  That was a very neat video, and I learned some stuff too! Thanks for posting that.
  - jerf 6y ago
    He clickbaited me but good on that one, but it delivered the goods.
    - eins1234 6y ago
      Long time Veritasium subscriber here. He actually made a great video a while ago explaining why professional Youtubers don't have much of a choice when it comes to clickbaiting with titles and thumbnails, because it's the only way to reliably get lots of impressions and views and grow their channel: https://www.youtube.com/watch?v=fHsa9DqmId8 https://www.youtube.com/watch?v=fHsa9DqmId8 It made me gain a bit of empathy for creators using these tactics on Youtube and tolerate it as long as it's not being used to promote content that's devoid of any substance, which is pretty much never the case for Veritasium videos or any of the other educational channels I subscribe to.
      - jerf 6y ago
        Yes, I understand and agree. It makes me sad as well but I've made my peace with it. Nevertheless, I commented about this one in particular because when I saw the title card, I legitimately thought, even having seen many of his videos, that he couldn't possibly deliver on that. He got me; he did. I was impressed.

Move clocks at the exact same speed and acceleration in opposite directions, so they stay synchronized.

by drran 6y ago

Move clocks at the exact same speed and acceleration in opposite directions, so they stay synchronized.

I don’t think this works either because you can’t meaningfully agree on when light was emitted from one of the clocks. The only solution should involve a single clock but then you are always measuring 2 way and not 1 way speed.

klodolph 6y ago
> I don’t think this works either because you can’t meaningfully agree on when light was emitted from one of the clocks. You can in fact meaningfully agree. You put the clocks in similar reference frames (like “standing on the surface of the Earth”), and accept some small but non-zero margin for error. The fact that a spaceship traveling around the earth does not measure light pulses emitted by these clocks as simultaneous is irrelevant—because we know that the notion of simultaneity relies on reference frame. What we do get is that anyone standing on the Earth’s surface can measure the pulses as simultaneous, within the specified margin of error. This error must necessarily account for the the fact that time progresses differently at different altitudes and latitudes, if your clocks are accurate enough. Because General Relativity is an extremely accurate theory and we have accurate measurements of the relevant physical constants & the mass of the Earth, we can account for the different reference frames and run the clocks at the correct rates so they continue to be synchronized even when they are free running (again, with the appropriate margin of error). If you are using ordinary quartz clocks, then the clocks probably have enough error that you can ignore relativistic effects. I’m assuming we want atomic clocks if we’re series about chronometry, especially considering how cheap they are these days. The idea that synchronizing clocks is somehow impossible stems from an unrealistic idea of how people measure time in the first place.

jerf 6y ago

Veritasium just had a good video which discusses this: https://www.youtube.com/watch?v=pTn6Ewhb27k https://www.youtube.com/watch?v=pTn6Ewhb27k It turns out there's some circularity in your definitions of "Move clocks at the exact same speed and acceleration in opposite directions" and "synchronized"; that's basically the definition of "synchronized", which is fine from a certain point of view, but from the point of view of examining the nature of space and time themselves, not adequate.

TheCraiggers 6y ago
That was a very neat video, and I learned some stuff too! Thanks for posting that.
- jerf 6y ago
  He clickbaited me but good on that one, but it delivered the goods.
  - eins1234 6y ago
    Long time Veritasium subscriber here. He actually made a great video a while ago explaining why professional Youtubers don't have much of a choice when it comes to clickbaiting with titles and thumbnails, because it's the only way to reliably get lots of impressions and views and grow their channel: https://www.youtube.com/watch?v=fHsa9DqmId8 https://www.youtube.com/watch?v=fHsa9DqmId8 It made me gain a bit of empathy for creators using these tactics on Youtube and tolerate it as long as it's not being used to promote content that's devoid of any substance, which is pretty much never the case for Veritasium videos or any of the other educational channels I subscribe to.
    - jerf 6y ago
      Yes, I understand and agree. It makes me sad as well but I've made my peace with it. Nevertheless, I commented about this one in particular because when I saw the title card, I legitimately thought, even having seen many of his videos, that he couldn't possibly deliver on that. He got me; he did. I was impressed.