# Dark Matter and Velocity

If I was travelling 60% of light speed in one direction,
and you were travelling 60% of light speed in another direction
We would be invisible to eachother correct ?

Is that all that dark matter is? matter in which the distance between us is increasing faster than light speed?

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## Answers and Replies

Hootenanny
Staff Emeritus
Science Advisor
Gold Member
If I was travelling 60% of light speed in one direction,
and you were travelling 60% of light speed in another direction
We would be invisible to each other correct ?

Is that all that dark matter is? matter in which the distance between us is increasing faster than light speed?
No, the speed of light as viewed from any frame of reference has a definite speed c.

Janus
Staff Emeritus
Science Advisor
Gold Member
If I was travelling 60% of light speed in one direction,
and you were travelling 60% of light speed in another direction
We would be invisible to eachother correct ?
No, in fact, from each of our perpectives, the other would only be traveling at:

$$\frac{0.6c+0.6c}{1+\frac{0.6c(0.6c)}{c^2}} = 0.882c$$

relative to ourselves. This is how velocities add under Relativity.