quote:
"The speed of light in a vacuum is defined to be exactly 299,792,458 metres per second (or 1,079,252,848.8 km/h, which is approximately 186,282.397 miles per second, or 670,616,629.4 miles per hour). This value is denoted by the letter c, reputedly from the Latin celeritas, "speed", and also known as Einstein's constant."
I'm aware that c is a constant. (This may not mean what you think it means. More below.) But because there is no perfect vacuum in this universe, light always travels through a medium. Every medium has an index of diffraction, n. The speed of light in any given observation is c/n. (Other mediating factors may include things like "group velocity.") Therefore, no photon has ever struck your eyeball at c. None. Ever. Thus the following statement is false:
quote:
Look at any scientific theory ever. Scientists have measured the speed of light a few, say, million times. It has always come up at a constant speed. They infer from these limited observations that the speed of light is unchanging, and it will always be this speed for EVERY observation.
Quite the opposite of true. So is this one, as far as I can tell:
I am not aware that this is the case. I asked you to say what scientists made what observations leading to this "wrong" inference, and when. Instead of answering, you gave me the definition of c.
Yes, c is a constant, not, as you allege, because "Scientists have measured the speed of light a few, say, million times. It has always come up at a constant speed. They infer from these limited observations that the speed of light is unchanging, and it will always be this speed for EVERY observation." Quite the opposite. If you ever measure a photon striking your apparatus at c, then something is very wrong.
No, c is always c for the same reason that one milliliter of water at 4 degrees C and one atmosphere of pressure will always have mass of 1 gram. Not because millions of observations have confirmed this, but by definition. Do you understand?
To say you observed a variance in c would be much like saying you had observed an hour with other than 60 minutes in it, or a dollar with other than 100 cents in it, or indeed a milliliter of water at 4 degrees C and one atmosphere pressure with a mass other than 1 gram. You see, c is operationally defined in meters per second. And how is the meter operationally defined? By the distance light would travel in a vacuum during a precise and tiny fraction of a second. In other words, c is defined in terms of the meter, and the meter is defined in terms of c. c cannot vary according to our yardstick because c is the yardstick. To propose a variable c borders on nonsense.
And yet, there is a serious though marginal line of thought that proposes exactly this-- that c has varied over cosmological time.
In any case, the facts, their meaning, and the basic logical process is quite the opposite of what you've asserted. I still await a real-life example of a scientific conclusion that resembles "no black swans exist because all the observed ones have been white."
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