According to you, what's the most realistic portrayal of time travel? The one of "Harry Potter 3" by J. K. Rowling, or that of the TV series "Lost"?

The last mission in the Iconian War story arc in the game “Star Trek Online”.

Lost. (and I love me some HP)

I prefer the Lost type of time travel where changing the past is impossible because “whatever happened happened”. Meaning that if you travel back in time to 1977, it’s your present but it’s the past for everyone else. So you could theoretically find a photo from 1977 with the present you in it from that time you traveled back there. If you had seen that photo before you traveled, it wouldn’t matter because there’d be nothing you could do to stop the traveling from happening—the photo is proof that it always happened. That makes more sense to me than the “change the past” model seen in HP.