Time Travel

So I just got done Watching tonight's episode of Lost. No spoilers if you didn't watch, but I will say it involved time travel. Lots of it. The more I watched the more I kept yelling "No. NO. That doesn't make any fucking sense, time doesn't work like that, you braindead plebs" at my tv. I know time travel is mostly theoretical, but can /sci/ explain time travel to me as best as they can? I'm sure you understand it better than Lost's writers do

You enter a tube and you crawl through it and come out the otherside as a Roman in a bathrobe