4 ms·

c is 299,792,458 m/s only because the meter is so defined; it makes just as much or more sense to say that the speed of light is 1, and this is where we get the

by Cushman 14y ago

c is 299,792,458 m/s only because the meter is so defined; it makes just as much or more sense to say that the speed of light is 1, and this is where we get the Planck units. From this perspective, it becomes obvious that the question, "Why is the speed of light one unit length per unit time?" is an absurd one. There is no other alternative.

benihana 14y ago
Seems tautological. I think what he's asking is, why is there to be a limit to how fast light can go, and he's looking for a better answer than "because there is one." I would love to know why there's an arbitrary speed limit to lights that (from our understanding) spacetime doesn't necessarily have to obey.
- Nogwater 14y ago
  Here's the best explanation that I've seen: http://www.reddit.com/tb/fjym4 http://www.reddit.com/tb/fjym4 And what do you mean "spacetime doesn't necessarily have to obey"?
- Cushman 14y ago
  Well, yeah, it is tautological. If there weren't a limit on the rate of information transfer, everything possible would happen instantaneously and there would be no way to really experience anything. Call it selection bias if you like. The speed of light is like the rate of time; it is because it can't not be in any meaningful way. This isn't to say that, given the tenets of simulationism, we can't hypothesize an "external time", and describe the rate of our universe as some amount of Tx/t. But the fact that that's an amount of time per time should also demonstrate why it's a meaningless concept in-universe.
- planetguy 14y ago
  Actually there's two questions here; the question I think he's asking and the question you think he's asking. The question you think he's asking is: why is there a limit to how fast light can go? For this we have a reasonably good explanation; it's more or less a consequence of basic geometry once you've understood relativity. The question I think he's asking is: given that we have a value of c why is it that value of c and not some other? For this we have no damn explanation, it's just an arbitrary constant that got baked into the universe for some reason. Perhaps one day we'll understand it in terms of something else, but perhaps it's just as in-principle unanswerable as "so why the fuck is there a universe in the first place?"
hartror 14y ago
The question isn't absurd from a lay persons point of view and the explanation falls short. What Cushman means is a number like Pi is always 3.14159265, to us or to hypothetical aliens. Whereas the speed of light can be just effectively represented as 299,792,458 or 1 depending on the units you use. What you are effectively asking about ck2 is calculation of dimensionless physical constants which are of ratios of like-dimensioned physical constants, for example the fine structure constant. These could in theory be calculated one day without using experimentally derived values . . . maybe. The wikipedia page on the physical constants has a good run down on this: http://en.wikipedia.org/wiki/Physical_constant#Dimensional_and_dimensionless_physical_constants http://en.wikipedia.org/wiki/Physical_constant#Dimensional_a... As does: http://en.wikipedia.org/wiki/Fundamental_physical_constant http://en.wikipedia.org/wiki/Fundamental_physical_constant
- gmaslov 14y ago
  Even a theory without any experimentally derived values is still an experimentally derived theory.
  - eru 14y ago
    Unless all the results are theoretically, too. E.g. group theory.
- Cushman 14y ago
  I think I'm saying something more fundamental than "the number isn't important", though it's true I was a bit terse. The thing a layman needs to know about c in order to understand this is that it isn't a measurement of speed as we're used to thinking about it, but a fundamental relationship between time and space in our universe. It does measure something we can quantify in units that make intuitive sense: it is the smallest possible distance per the smallest possible time. c is not arbitrarily that; it is the fact that ties those two dimensions into a single universe, without which they would not have anything to do with each other, and without which the concepts of time and distance individually wouldn't mean anything to us. Is that a little clearer? I'll agree it's not possible to really grok this stuff without at least doing a bunch of reading on Wikipedia.
archgoon 14y ago
It's an absurd one? Isn't this question essentially the Hierarchy Problem?

by Cushman 14y ago

benihana 14y ago

Seems tautological. I think what he's asking is, why is there to be a limit to how fast light can go, and he's looking for a better answer than "because there is one." I would love to know why there's an arbitrary speed limit to lights that (from our understanding) spacetime doesn't necessarily have to obey.

Nogwater 14y ago
Here's the best explanation that I've seen: http://www.reddit.com/tb/fjym4 http://www.reddit.com/tb/fjym4 And what do you mean "spacetime doesn't necessarily have to obey"?
Cushman 14y ago
Well, yeah, it is tautological. If there weren't a limit on the rate of information transfer, everything possible would happen instantaneously and there would be no way to really experience anything. Call it selection bias if you like. The speed of light is like the rate of time; it is because it can't not be in any meaningful way. This isn't to say that, given the tenets of simulationism, we can't hypothesize an "external time", and describe the rate of our universe as some amount of Tx/t. But the fact that that's an amount of time per time should also demonstrate why it's a meaningless concept in-universe.
planetguy 14y ago
Actually there's two questions here; the question I think he's asking and the question you think he's asking. The question you think he's asking is: why is there a limit to how fast light can go? For this we have a reasonably good explanation; it's more or less a consequence of basic geometry once you've understood relativity. The question I think he's asking is: given that we have a value of c why is it that value of c and not some other? For this we have no damn explanation, it's just an arbitrary constant that got baked into the universe for some reason. Perhaps one day we'll understand it in terms of something else, but perhaps it's just as in-principle unanswerable as "so why the fuck is there a universe in the first place?"

hartror 14y ago

The question isn't absurd from a lay persons point of view and the explanation falls short. What Cushman means is a number like Pi is always 3.14159265, to us or to hypothetical aliens. Whereas the speed of light can be just effectively represented as 299,792,458 or 1 depending on the units you use. What you are effectively asking about ck2 is calculation of dimensionless physical constants which are of ratios of like-dimensioned physical constants, for example the fine structure constant. These could in theory be calculated one day without using experimentally derived values . . . maybe. The wikipedia page on the physical constants has a good run down on this: http://en.wikipedia.org/wiki/Physical_constant#Dimensional_and_dimensionless_physical_constants http://en.wikipedia.org/wiki/Physical_constant#Dimensional_a... As does: http://en.wikipedia.org/wiki/Fundamental_physical_constant http://en.wikipedia.org/wiki/Fundamental_physical_constant

gmaslov 14y ago
Even a theory without any experimentally derived values is still an experimentally derived theory.
- eru 14y ago
  Unless all the results are theoretically, too. E.g. group theory.
Cushman 14y ago
I think I'm saying something more fundamental than "the number isn't important", though it's true I was a bit terse. The thing a layman needs to know about c in order to understand this is that it isn't a measurement of speed as we're used to thinking about it, but a fundamental relationship between time and space in our universe. It does measure something we can quantify in units that make intuitive sense: it is the smallest possible distance per the smallest possible time. c is not arbitrarily that; it is the fact that ties those two dimensions into a single universe, without which they would not have anything to do with each other, and without which the concepts of time and distance individually wouldn't mean anything to us. Is that a little clearer? I'll agree it's not possible to really grok this stuff without at least doing a bunch of reading on Wikipedia.

archgoon 14y ago

It's an absurd one? Isn't this question essentially the Hierarchy Problem?