Hi,
The speed of light in a vacuum (i.e., empty space), is a constant at a terrifically fast 186,282 miles per second (299,792 kilometers per second)! Generally scientist think of it as unchanging, but see this discussion here about the subject:
http://curious.astro.corn...niverse-intermediate

Light does move more slowly than that, though, when it is moving though materials of some sort rather than a vacuum.