5 ms·

Why can't it spin faster?

chrisseaton 7y ago
I'm sure it can spin a bit faster. Why can't it spin so fast that the final wheel visibly turns? Well the first wheels would melt from friction or be torn apart before then, and where are you going to get that much energy to turn them so fast? At some point there's the speed of light as a limit as well.
- owenmarshall 7y ago
  There are 10^80 electrons in the universe, Eddington thinks. Even if you managed to make a contraption that turned one electron into one rotation of the first wheel, and you fed the entire universe to your contraption... you’re coming up a few dozens order of magnitude short to make that full turn :^)
  - chrisseaton 7y ago
    That's what I already said > where are you going to get that much energy to turn them so fast?
    - owenmarshall 7y ago
      I guess you just have to make a machine that manages two turns per electron. (I know you did - but any chance to introduce Eddington’s number is fun)
      - chrisseaton 7y ago
        > I guess you just have to make a machine that manages two turns per electron. But that just isn't going to be tractable.
  - klyrs 7y ago
    What's 80 orders of magnitude between friends? https://en.wikipedia.org/wiki/One-electron_universe https://en.wikipedia.org/wiki/One-electron_universe
- mkagenius 7y ago
  > At some point there's the speed of light as a limit as well. Why not put it in a dark room before starting up
  - chrisseaton 7y ago
    The speed of light as a limit applies to matter like these cogs as well.
klyrs 7y ago
After an hour, the 10th gear hasn't perceptibly moved. If you went 10x faster, the 11th gear wouldn't have perceptibly moved. At 100x faster, and you still won't see motion in the 12th gear. For every gear you want to see move, you'll need to spin the first gear exponentially faster!
thedance 7y ago
Even if the first gear's teeth were moving at supersonic speeds, there still would not be any perceptible motion of the last 90 gears or so. If the first gear's teeth were moving at relativistic speeds, there would still be no apparent motion in about 80 of the gears. The speed of light is only about a million times higher than the speed of sound, and this contraption loses a factor of a million after six gears.
- perl4ever 7y ago
  I did not know this, but according to what I was just reading, pretty much any physical material must rupture when it spins close to the speed of sound in that material. If you imagine a relativistic spinning disk anyway, then it gets interesting because due to length contraction, the circumference changes relative to the diameter. I'm not up to the math, but it seems like it might change the effective gear ratio depending on your perspective and the closeness of the speed to C. https://en.wikipedia.org/wiki/Ehrenfest_paradox https://en.wikipedia.org/wiki/Ehrenfest_paradox
6nf 7y ago
It will just wear out faster

I'm sure it can spin a bit faster. Why can't it spin so fast that the final wheel visibly turns? Well the first wheels would melt from friction or be torn apart before then, and where are you going to get that much energy to turn them so fast? At some point there's the speed of light as a limit as well.

owenmarshall 7y ago
There are 10^80 electrons in the universe, Eddington thinks. Even if you managed to make a contraption that turned one electron into one rotation of the first wheel, and you fed the entire universe to your contraption... you’re coming up a few dozens order of magnitude short to make that full turn :^)
- chrisseaton 7y ago
  That's what I already said > where are you going to get that much energy to turn them so fast?
  - owenmarshall 7y ago
    I guess you just have to make a machine that manages two turns per electron. (I know you did - but any chance to introduce Eddington’s number is fun)
    - chrisseaton 7y ago
      > I guess you just have to make a machine that manages two turns per electron. But that just isn't going to be tractable.
- klyrs 7y ago
  What's 80 orders of magnitude between friends? https://en.wikipedia.org/wiki/One-electron_universe https://en.wikipedia.org/wiki/One-electron_universe
mkagenius 7y ago
> At some point there's the speed of light as a limit as well. Why not put it in a dark room before starting up
- chrisseaton 7y ago
  The speed of light as a limit applies to matter like these cogs as well.

klyrs 7y ago

After an hour, the 10th gear hasn't perceptibly moved. If you went 10x faster, the 11th gear wouldn't have perceptibly moved. At 100x faster, and you still won't see motion in the 12th gear. For every gear you want to see move, you'll need to spin the first gear exponentially faster!

thedance 7y ago

Even if the first gear's teeth were moving at supersonic speeds, there still would not be any perceptible motion of the last 90 gears or so. If the first gear's teeth were moving at relativistic speeds, there would still be no apparent motion in about 80 of the gears. The speed of light is only about a million times higher than the speed of sound, and this contraption loses a factor of a million after six gears.

perl4ever 7y ago
I did not know this, but according to what I was just reading, pretty much any physical material must rupture when it spins close to the speed of sound in that material. If you imagine a relativistic spinning disk anyway, then it gets interesting because due to length contraction, the circumference changes relative to the diameter. I'm not up to the math, but it seems like it might change the effective gear ratio depending on your perspective and the closeness of the speed to C. https://en.wikipedia.org/wiki/Ehrenfest_paradox https://en.wikipedia.org/wiki/Ehrenfest_paradox

6nf 7y ago

It will just wear out faster