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So, I heard that all speed is relative. And that nothing can travel faster than light.
Then I guess it is OK for a spaceship to leave Earth at 0.6c constant speed. And what if an other spaceship were to leave Earth at 0.6c in the opposite spacial direction.
Then the relative speed between the two ships would be 1.2c, which is greater than c. How would that work out? Maybe something with time dilation?