# What's the secret behind v < c

#### topsquark

Forum Staff
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.

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

#### neila9876

@dragon:
".. worried about speed of light not becoming infinite?"
I can't find this sentence in my post.

#### topsquark

Forum Staff
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