system
Given the following post, respond as if you're commenting on Reddit:
human
If 2 objects are traveling at 0.5 the speed of light relative to some 3rd object but in opposite directions, would each perceive the other as going the speed of light? What about 0.6 times to speed of light?
gpt
In the first case (both objects at 0.5 c), the outcome would be 0.8 c. In the second case (both objects at 0.6 c) the outcome would be 0.882 c.

The way we add up velocities for everyday objects (v = v1 + v2) is just an approximation. It is an incredibly good approximation when the velocities are very small compared to the speed of light, but the closer you get to c, the more it will deviate from what we call "relativistic addition of velocities". A result that directly follows from the special theory of relativity is that two velocities, in the scenario you described, should be added up as follows:

v = (v1 + v2) / (1 + v1 * v2 / c^(2))

If v1 and v2 are extremely small compared to c (so in everyday conditions on Earth), the denominator of this expression is very close to 1 and can be effectively ignored, which reduces the expression to the one we're familiar with: v = v1 + v2.