- #1

- 270

- 28

## Summary:

- some idea in proper velocity i dont understand

## Main Question or Discussion Point

Hello :

as i read during quarantine introduction to elementary particles by griffth i encounter the following paragraph

"When we speak of the "velocity" of a particle (with respect to the labo-

ratory), we mean, of course, the distance it travels (measured in the lab frame)

divided by the time it takes (measured on the lab clock):

v = dx/dt

But in view of what has just been said, it is also useful to introduce the "proper" velocity, zeta, which is the distance traveled (again, measured in the lab frame)

divided by the proper time:

zeta = dx/d(tao) : d(tao) = dt/gamma*

According to equation (3.28), the two velocities are related by a factor of gamma:

zetta = gamma*v"

what i dont understand is how we can use two different quantities to describe velocity the distance is from the lab frame and the time is from particle frame

why zetta isnt written like this

zetta = dx'/d(tao)

as i read during quarantine introduction to elementary particles by griffth i encounter the following paragraph

"When we speak of the "velocity" of a particle (with respect to the labo-

ratory), we mean, of course, the distance it travels (measured in the lab frame)

divided by the time it takes (measured on the lab clock):

v = dx/dt

But in view of what has just been said, it is also useful to introduce the "proper" velocity, zeta, which is the distance traveled (again, measured in the lab frame)

divided by the proper time:

zeta = dx/d(tao) : d(tao) = dt/gamma*

According to equation (3.28), the two velocities are related by a factor of gamma:

zetta = gamma*v"

what i dont understand is how we can use two different quantities to describe velocity the distance is from the lab frame and the time is from particle frame

why zetta isnt written like this

zetta = dx'/d(tao)