Comment by hartror | Hacker News Reader

Comment by hartror | Hacker News Reader

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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_a...

As does: http://en.wikipedia.org/wiki/Fundamental_physical_constant

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.

>like Pi is always 3.14159265, to us or to hypothetical aliens.

Unless you're counting in base Pi, then Pi is 10.

Pi is only 3.14... in base 10. Just like the c is ~2.99 * 10^ 6 m/s because we define a meter that way.

Wonder what the (inverse of )the diameter of a circle of unit 1 in base Pi is in base Pi?

You are confusing units and numeral systems. Pi is always Pi no matter how you count whereas c is dependent on how you measure time and space.

Even a theory without any experimentally derived values is still an experimentally derived theory.

Unless all the results are theoretically, too. E.g. group theory.

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