Relativistic Velocity: Can I Run Faster Than Light?

[profilexis]

I would have another question. If I travel at the speed of light (or 99.9999999999...% of the speed of light) in a spaceship and i begin to run from the back of the spaceship to the front in direction of the spaceship movement, will I be moving faster than the speed of light?

 

[arildno]

Nope.
As measured from the Earth frame (in which the spacecraft has the velocity indicated), you'd be measured to have a velocity strictly below c.

 

[RandallB]

You cannot just add velocities to get total velocity. Use:
w = (u + v)/ (1 + uv/c²)
If you define all the velocities in terms of light speed by dividing each one by “c” the formula is simpler and becomes:

w = (u + v)/ (1 + uv)

You’re more accustomed to living and working with speeds less than 0.0005
Where doubling that speed gives you
.001 / 1.00000025

You’ve just never needed the accuracy of dividing by such a small number at those small speeds. And just used the .001 part or (u + v).

But as one of the speeds becomes high, say above .25
Then using the whole formula and dividing becomes important.

 

[gyroverse]

http://galileo.phys.virginia.edu/classes/109N/lectures/adding_vels.html

 

[krab]

I would have another question. If I travel at the speed of light (or 99.9999999999...% of the speed of light) in a spaceship and i begin to run from the back of the spaceship to the front in direction of the spaceship movement, will I be moving faster than the speed of light?

The ... means the 9's go on forever? That means you are traveling exactly the speed of light. This is impossible, unless, like a photon, you have zero mass.