Hold your hands up. See that gap between them? That's a space, and you can see it’s there, even though you can't see the space itself. Now waggle those hands. That's motion, and you can see that’s there too. But can you see time? No. Can you see time flowing? No. Can you see any travelling through time? No. These phrases are just figures of speech. There’s no scientific evidence for time flowing or time travel. Time travel is Science fiction, and it’s going to stay that way forever because travelling back in time is impossible. It’s impossible because we don’t even travel forward in time, not really.

To understand this, think about a stasis box. That’s Science fiction too. It’s the ultimate refrigerator. No motion occurs inside the box, so when I put you inside one, electromagnetic phenomena don’t propagate. So you can’t see, you can’t hear, and you can’t even think. Hence when I open the door 5 years later, to you it’s like I opened the door just as soon as I closed it. And get this: you “travelled” to the future by not moving at all. Instead everything else did. And that motion wasn’t through time, and it wasn’t through spacetime, it was through space. Yes, the stasis box is fighting fire with fire, but don’t forget, we can freeze embryos now, so “in the future” maybe we’ll be able to freeze an adult. Then you could “travel” to the future by stepping into a freezer. But you aren’t really travelling. You aren’t moving. Everything else is.

That’s the size of it. Time is very simple, once you get it. But “getting it” is so very difficult. That’s because for most people, the current concept of time is so deeply ingrained, from childhood in a catch ‘em young way. They’re locked into a conviction that days pass, that time flows, and that a journey takes a length of time. It takes some steely rationality to break out of this, but it can be done. ( This post is quoted from phbpp physics discussion forum, I’m very interested in this post. I want to explore more of it. Anybody’s comment is welcome.)