Why can light travel through space but sound cannot?

sound is produced by vibration, i.e. when any thing start vibration then it produces sound. for example when a tunnig fork is hit on rubber pad its prongs starts vibration with difinit frequency ad hence produce sound. similarly when the strings of a gittar is dirturbed its starts vibration and hence produces sound. sound required a material medium for their journey, sound can not pass through vaccume because sound waves are mechanical waves.