Light waves are transverse, they are independent of medium (they don't need a "substance" to travel through) which is why we can see light from the sun, travelling across 93 million miles of vacuum!


The speed of light has always fascinated scientists, and science fiction writers. The goal of "faster than light" travel (FTL) is still a future dream. When we talk about the speed of light (SOL) we refer to this "in a vacuum" as the speed of light varies depending on the medium it is passing through.


SOL (c) in a vacuum:



To put this into context, an object travelling at this speed would travel around the Earth's equatorial belt (40,075,017m) :