: : : If i have two light-source, A and B. : : : A send light C1 and B send light C2.

: : : B.....C2.....C1.....A

: : : What happens when light meets?

: : : B.......C3........A.

: : : C1+C2 join together, and result is C3.

: : : What is speed of C3?

: : what do you mean, what is the speed of C3?

: : If i understand what your asking, your saying : : that when two light beams are aimed at eachother : : and they meet; what is the speed at the meeting : : point?

: : i'm not sure what your asking.

: : the speed of two passing beams is irrelevant. : : however, it is more interesting to note that : : the observed velocity of light passing by, while : : traveling the opposite direction, (at or near the : : speed of light), will appear that the light : : passing by me is not the sum of my velocity : : and the light passing. But rather the light passing : : by would appear the normal velocity of lightspeed. : : This is relativity.

: Indeed-- u'=(u+v)/(1+uv/c2) {according to the STR) : Thus, as u=v=c, u'=(u+v)/2=c : ergo de facto-- both beams will go towards one : another at the speed of light -- c. : Einstein made his own conclusions due to this : numeric calculations on 1905-- the result was the Special Theory of Relativity... : A question worthwhile.