The numerical value is determined empirically, and as far as I know it is simply a result of our historical choice of length and time units.
The fact that there is a definite speed of light is also a property of nature but there is some "explanation". We know that space and time mix. When you speak of an event you need to state both position and time. When you speak about two events, you need to tell their relative position and time difference as well as a reference frame (by indicating its velocity). This separation of events in space and time will be different for different observers, if they are moving at different speeds. The way you transform this quantity includes a constant. When you write the equations governing the electromagnetic phenomena and require that the results obey these transformation rules, it turns out that this constant is the speed of the electromagnetic waves, which is of course light.
The event separation transformation rule dictates that no information can be transferred faster than this constant, the speed of light. Otherwise you can have two events A & B, where the A can influence B in one reference frame and B can influence A in another reference frame. This would lead to a contradiction.
These are explained much better in standard relativity texts. I'd recommend Rindler's "Essential Relativity" and Thorne's "Time Warps and Black Holes"'s first few chapters.
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.
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.
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.
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.
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.
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?"
You might find this paper interesting: A Derivation of Special Relativity
from Causal Sets--http://arxiv.org/abs/1005.4172
It doesn't answer why c is the value of c, but it's an interesting way to show that there must be an invariant bounding speed limit. It doesn't assume the "existence of space
or time, motion, constancy of the speed of light, or the principle of relativity."
“Although this result isn’t as exciting as some would have liked,” said Bertolucci, “it is what we all expected deep down. The story captured the public imagination, and has given people the opportunity to see the scientific method in action – an unexpected result was put up for scrutiny, thoroughly investigated and resolved in part thanks to collaboration between normally competing experiments. That’s how science moves forward.”
Couldn't agree more. Whilst there has been a lot of criticism from the science community it was wonderful to experience a bit of drama and excitement.
God knows everyone is looking for something/anything hopeful to distract from the endless bad news.
Really? Has there been that much criticism from the science community? I though everyone with respectable opinions thought it was handled exactly like proper scientists should have handled it.
OPERA had unexpected results contradicting the status quo of our understanding of fundamental physics. They did everything they could to determine and correct and calibrate possible errors. They published the results and methodology in hopes that their peers could either help them understand what went wrong, or confirm it. An they did (the former).
I saw it as the science community at its finest. Sure, there was a lot of skepticism and disbelief in the accuracy/correctness, but that is part of the game. You don't take things at face value, and you don't ignore unexpected results.
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So, I don't have any objection to what you wrote, but, is my impression wrong?
There has been enough criticism from scientific community at large and more importantly from within the OPERA collaboration that their spokespeople resigned from their position.
Not much of that criticism coming from respectable scientists made it to mainstream media, though. I presume that is because they did not want to show a "holier than thou" attitude openly. But internally a lot of people thought "they must have done something wrong" and after they found the error "what were they thinking?".
I think your impression is wrong, but very understandable unless you interacted with people offering criticism directly or semi-directly through one or two persons.
While I don't disagree with your characterization of the criticism, it was more complex than just "people within the scientific community were critical and people outside thought they did the right thing in opening up the data and methodology to criticism when they could not identify a problem in the initial troubleshooting."
A large part of the community took a "wait and see" approach that was (obviously) skeptical of the results.
Because of the hype associated with the event, it's not surprising that people would end up resigning whether or not they really did anything wrong. I can't say that I have enough of a background to know if they should have resigned or not, but I certainly wouldn't use the fact that they resigned as conclusive proof that whatever was done wrong was handled incorrectly as opposed to a reasonable error.
> I though everyone with respectable opinions thought it was handled exactly like proper scientists should have handled it.
Not all criticism towards science comes from people with respectable opinions. In fact, most criticism towards the scientific community comes from people who have nothing but the most tenuous grasp on what science actually is and, more often than not, to defend a specific agenda.
In an ideal universe I think they did everything right. On the other hand, knowing what we know about the state of the popular press and the imagination of the internet it might have been worth being a little more careful to make it clearer that this is probably just an experimental error.
