How does light “travel”faster than sound?



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Light is electromagnetic radiation. It requires no medium to travel through and can therefore propagate through both extremely sparse space, upper atmosphere and extremely dense plastics, water etc.

Sound however, requires sufficient medium to travel through. It is required to have the interaction of molecules of a medium, thus slowing it down.

Because sound is limited by the medium it travels through. As in, it can only go as fast as the stuff it’s made of. Light is not limited by that.

Light is an oscillating pair of electric and magnetic waves. Electric and magnetic waves can go as fast as anything can go, incidentally called the speed of light.

Because light is “it’s own thing” where as sound is an interaction between an atoms.

Think of light as a car. A car can travel pretty fast and sure things light hills and slopes can change how fast it goes but you can’t argue that a car can travel on its own pretty dang fast.

Sound is like a rumor. It requires people to hear it and then tell it someone else, if people are close together rumors can travel quickly, if they are far apart they travel slowly, but *without people there can be no rumors*. Because rumors only exist in being told, they aren’t a thing other than act of by shared between people.

That’s like light and sound in a nutshell. Light is a physical thing all by itself, and it just so turns out that this physical thing can travel insanely quickly. Sound isn’t a thing by itself, it’s an interaction between atoms. If the atoms are super close together it can travel quickly (less distance for the atoms to travel to interact), if they are far apart it travels slowly. But without atoms at all, there is no sound, but sound requires atoms. As a marketer for the Alien franchise once said – No one can hear you scream in space.

They’re 2 entirely different things. There’s no reason their speeds should be related in any way. Light is electromagnetic waves. It’s not really a physical thing that you can hold or touch. Electromagnetic waves don’t require any medium to propagate. For reasons beyond the scope of this question, all electromagnetic waves travel at the fastest anything in the universe can travel, which, in a vacuum, is just under 300,000 km/s.

Sound, on the other hand, is physical thing. It’s the vibrations that propagate through some physical medium, like air. It’s the actual molecules or atoms of that stuff vibrating. Sound can only travel as fast as those molecules or atoms can bump into each other.

Imagine you and I are sitting in a classroom on opposite ends of the room and I want to send a note to you. In order to get the note to you I have to hand it to the person sitting next to me, who hands it to the person sitting next to them, and so on and so forth until eventually the note reaches your desk. The more people in the room and the closer we sit together the faster the note will reach your desk, because there is less travel from person to person then if there were less people in the room spaced further apart.

In a sense this is how sound works. Molecules bumping into other molecules transmitting the energy (note) with them. The closer the molecules – like water or rock as opposed to air – the faster the wave of energy can travel. This is also why sound doesn’t travel in a vacuum like space – there is nothing else around to bump into.

Light is more like if I were to suddenly become infinitely lighter than a feather and sprint straight towards you. I don’t need anyone else around me to help pass the note and, in fact, the less people in the room the better because it’s less stuff in the way for me to get to you. Also, because I’m light and have no mass I don’t even need to ramp up my speed to get to a full sprint. Like I’d already be sprinting at full speed, as fast as the universe will let something sprint, the moment the note is created.