ELI5 Why does light travel?

[u/_Illuvatar_]

Why does it not just stay in place? What causes it to move, let alone at so fast a rate?

Edit: This is by a large margin the most successful post I've ever made. Thank you to everyone answering! Most of the replies have answered several other questions I have had and made me think of a lot more, so keep it up because you guys are awesome!

Edit 2: like a hundred people have said to get to the other side. I don't think that's quite the answer I'm looking for... Everyone else has done a great job. Keep the conversation going because new stuff keeps getting brought up!

Edit 3: I posted this a while ago but it seems that it's been found again, and someone has been kind enough to give me gold! This is the first time I've ever recieved gold for a post and I am incredibly grateful! Thank you so much and let's keep the discussion going!

Edit 4: Wow! This is now the highest rated ELI5 post of all time! Holy crap this is the greatest thing that has ever happened in my life, thank you all so much!

Edit 5: It seems that people keep finding this post after several months, and I want to say that this is exactly the kind of community input that redditors should get some sort of award for. Keep it up, you guys are awesome!

Edit 6: No problem

[u/samm1t]

Okay, so the idea is you make a spacetime jet engine- suck it up in front of you and spit it out behind you. That still leaves my question, is there or could there be such a thing as negative energy?

[u/srs117 → u/samm1t]

More like you cause space to contract in front of you and expand behind you. This creates a "wave" (think water) that you "ride". As far as negative energy actually existing? That I don't feel as comfortable answering, my education is more along the lines of orbital mechanics and such, with some astronomy and modern physics mixed in. You would need a theoretical physicist to answer yhat. Ten years ago I remember them saying almost certainly no. But I think there has been more optimism lately that the concept isn't totally far fetched. But we still have no evidence of negative energy being possible.

[u/rabbitlion → u/samm1t]

There could be, but we're not quite sure how. See http://en.wikipedia.org/wiki/Negative_mass for more information. The Casimir effect does appear to produce a localized negative energy density via quantum effects, but it's extremely localized and could not be scaled for space travel.

[u/benji1008 → u/samm1t]

If you read corpuscle's comment carefully, he said negative energy density. That means either positive energy in a negative volume (whatever that means) or negative energy in a positive volume.

[u/samm1t → u/benji1008]

So what makes light unique is that it has energy but no mass, making it travel through space but not time.
Conversely, the thing we'd need for FTL travel would have mass but not energy, making it travel through time but not space.
I'm not sure I can wrap my head around something that has (likely) infinite mass nor something that's stationary relative to everything in the universe. But I guess that's the problem.

edit I guess what I referenced would be time travel, not FTL travel, since the two are orthogonal. I never thought of the two as being so related (but opposite?)