Physics Help Forum What's the secret behind v < c
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Jul 23rd 2019, 07:28 PM   #51

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 Originally Posted by neila9876 Actually, it’s not necessary to care too much about if c is phase speed or group speed or the specific value of c in SR.
...But $\displaystyle v_g$ and $\displaystyle v_p$ are, in general, not equal. So we do have to make a distinction. However if you are interested only in one frequency, then yes, they are the same.

 Originally Posted by neila9876 Actually, c ≈ ****** m/s is a very small value in planet scale. For the motion elements such as mass, force, acceleration, momentum, kinematic energy, etc, their values can trend to infinite theoretically. Why cosmos / physics mistreat speed? This problem can be solved in 4D space SR.
What is it about speed that we are "mistreating?" I mean, any physical constant can never become infinite so why are you worried about the speed of light not becoming infinite?

-Dan
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 Jul 23rd 2019, 07:45 PM #52 Senior Member   Join Date: Mar 2019 Location: cosmos Posts: 495 @dragon: ".. worried about speed of light not becoming infinite?" I can't find this sentence in my post.
Jul 23rd 2019, 11:21 PM   #53

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 Originally Posted by neila9876 For the motion elements such as mass, force, acceleration, momentum, kinematic energy, etc, their values can trend to infinite theoretically. Why cosmos / physics mistreat speed?
The first sentence talks about properties that can tend to the infinite. Then you mention speed that Physics "mistreats." I had taken that to mean you thought that c ought to be able to tend to the infinite as well.

Sorry if I misunderstood. Can you please explain what you meant?

-Dan
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