If light is a wave, then why does it travel in a vacuum too?

Also there is a density of space-time. This density would be very light for matter but it has. Now generally it is called as Higgs Field. So thus, light travel in space-time (your vacuum) as a particle or a wave, doesn't matter. read more

Field waves are essentially vibrations of fields like electric, magnetic and gravitational fields. Field waves require no material medium to travel. Light is an electromagnetic wave and hence can travel through vacuum. read more

Light is an electromagnetic wave, while sound is an mechanical wave. To travel from one point to another sound requires something that exists materially between those 2 points. read more