# Question about the speed of light [duplicate]

The speed of light is constant as long as you are measuring it from a reference frame moving at a constant velocity, such as earth

What do we have to measure it from a reference frame moving at a constant velocity ? Isn't the speed of light always constant?

Also sorry if this question seems dumb, im a 10th grader..

• Possible duplicate: Does the speed of light vary in noninertial frames? Sep 17 '16 at 8:58
• This question is not dumb at all! (Unlike the answer to this question, the one with a bazillion downvotes). It all depends on how to define velocity in accelerated frames. +1 for the duplicate. Sep 17 '16 at 15:05