This explains some things

As Slashdot reported, the bad news is that there is no travel through time.

The good news is that distance is "an illusion" and we'll be able to travel anywhere, instantly. I don't pretend to understand all of it, but I'm OK with trading time travel for distance travel.

So, to explain why this explains some things: The aliens are here; they have been here a long time. Getting from, say ... Alpha Omega Epsilon Delta IV (or any other star system) ... is not a problem. It's just one we haven't solved. Yet. And the reason there are no really old examples of certain radioactive isotopes that couldn't (shouldn't?) exist before the Atomic Age, is that no one has ever traveled back in time to put them there. Ever. (I owe that last to a PhD friend (nuclear physics) who asserted that as proof of no time travel. You go argue with him; he's lots smarter than I am.)

I guess he was saying that if time travel were possible, then we would have isotopic proof of it, because it would be impossible not to take these decaying buggers back with us, if we went. No funky isotopes, ergo, no funky time travel.

But we can fold space, though. Cool.