How do electromagnetic waves travel in space? I understand these types of waves are different than sound waves where matter acts as a medium. But how do these waves travel in space where there appears to be no medium? Is the space time continuum actually a physical substance although far different from matter, making it a medium for light? And why does light oscillate up and down anyway. Is it possible electromagnetic waves actually spiraled like it was falling kind of like water in a sink. At a side view it would look just like a regular wave if that was the case. I'm obviously no professional so don't laugh at this but I'm just throwing some thoughts I had out there.