- #76

DevilsAvocado

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Thanks!

Amen

Amen

- Thread starter physicsnoob12
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- #76

DevilsAvocado

Gold Member

- 751

- 91

Thanks!

Amen

Amen

- #77

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But I can't get it to work. If you take three fundamental constants, electron mass (m), Planck constant (h) and speed of light (c), you can form a fundamental mass (m), a fundamental length (L=h/mc) which is the Compton wavelength, and a fundamental time (T=h/mc^2) which is 1 over the Compton frequency. If you go to a new universe, where the speed of light is c' (as measured by our present universe meter sticks and clocks) but all the dimensionless constants remain the same, then some or all of the fundamental constants will have to change their values in order to keep the dimensionless constants the same. That means that the Compton wavelength may change by some unknown factor due to the change in the speed of light, and the possible corresponding changes in the Planck constant and the mass of the electron required to keep the dimensionless constants the same. Suppose the values of h and m in the new universe are h' and m' as measured by our clocks and meter sticks. Then the new Compton wavelength will be L'=h'/m'c' and the new Compton time will be T'=h'/m'c'^2. The new speed of light will be measured as L'/T'=c', not c!. For example, if, in the new universe, the speed of light were cut in half, and h and m remained the same, and the dimensionless constants were kept constant by changing the vacuum permittivity and the gravitational constants, then all lengths would double in the new universe, but all times would quadruple. A meter stick would be twice as long, but a clock would click 4 times more slowly, and the numerical value of c would be half of what it is in our universe. It appears that the speed of light is something that must have its particular value in order for the universe to be what it is, and it is a valid question to ask why it has the value it does. Either that or I missed something...

- #78

PhanthomJay

Science Advisor

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Thanks for the response! The most popular responses to the question regarding why the speed of light is what it is are:It appears that the speed of light is something that must have its particular value in order for the universe to be what it is, and it is a valid question to ask why it has the value it does. Either that or I missed something...

1.) "It just is", and

2.) "Its the way we define the meter and second"

Neither one of these satisfies me.....I think it's got something to do with Feynman's sum of histories...but what do I know about the quantum world....and If I read Hawking correctly, he's on his knees worshipping Gravity................:surprised

Thanks again.

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