# Lorentz Factor - Help!

1. Apr 30, 2007

### Santural

I looked up Twin Paradox, and I understand the concept of time in SR, and also understand the Einstein synchronization convention concept, but now there is just something I don't get here:
I looked at twin paradoxes and apparently you must use the Lorentz factor (or it's inverse, anyway) to figure out the time a specific journey would take on the earth rest frame (or along the lines. Can't put it in words.)
So, the only thing is, what does each letter stand for in :
$$\displaystyle\epsilon=\sqrt{1-v^2/c^2}$$?

Which I believe is the inverse of the lorentz factor.

Santural : Below the average layman.

Last edited: Apr 30, 2007
2. Apr 30, 2007

### Staff: Mentor

Are asking what v and c stand for? v = speed of the traveling twin (or moving frame); c = speed of light.

3. Apr 30, 2007

### Santural

Right! Thats part of what I need. However:
Wikipedia says:
(I added the bold).
What is that epsilon? Where is 0.5 derived from?

4. Apr 30, 2007

### Staff: Mentor

By plugging numbers into that formula:

$$\epsilon = \sqrt {1 - \frac{v^2}{c^2}} = \sqrt {1 - \frac{(0.866c)^2}{c^2}} = \sqrt {1 - 0.866^2} = 0.5$$

Or have I misunderstood your question?

5. Apr 30, 2007

### Santural

......:uhh: hehe...um...:tongue: ....really, just um....hehe...my bad.....

I guess I was being a LITTLE dumb there, sorry.