If I shoot a marshmallow at you at high speed, there will be a measurable delay between the time I fire and the the time it bops you on the head.

The faster the marshmallow goes, the less time between the firing and the bopping.

At the speed of light, the delay is comparatively minimal. (If we're only a few yards apart it's teeniest fraction of a second. If we're billions of miles apart, it's really noticeable, even at the speed of light.

Current physics seems to show that light speed is the top speed possible under normal conditions in the physical universe.

Now, what if my marshmallow were zipping along FTL? In theory, if it were going fast enough, the firing and the bopping would take place at precisely the same instant. And faster than that (this is the point), the sugary confection would hit *even before* it was fired. Looking back on the whole event, it would seem to us that the 'mallow had traveled backwards in time. We'd remember that you'd uttered an otherwise inexplicable "Ouch!" even before the marshmallow was fired.

The effect would have preceded the cause. Voila! A marshmallow that traveled backwards in time!

Of, course how it might have seemed to the marshmallow (which I've just endowed with human consciousness)is another story. It probably wouldn't be much like the movies. SF takes the abstract notion of "going backwards" and adds adventures. That's why it's called science *fiction.*

This was all explained to me when I was a lad by a guy with a huge cranium and skinny arms, wearing a long silvery cape. I never saw him again.