[Please excuse accidental publishing of this post earlier this afternoon with only a couple sentences completed. I'm still in recuperation mode and doped to the gills. Wheee! Sorry, that just slipped out.]
I found the time traveler at my own kitchen table. He didn't look well. I asked, "What's wrong?"
TT: I've been ill lately, recuperating on a diet of vegetables, mainly.
Geo.: So I see. What sort of illness?
TT: Oh, the kind timetravelers get when they stop any where or any when and try to settle down.
Geo.: How long have you been traveling?
TT: 68 years, all forward.
Geo.: No Backward?
TT: Oooh I wish. You need superluminal speed to send anything back in time and I'm just not up to it.
Geo.: What about positrons?
TT: Antiparticles of electrons?
Geo: Or electrons going back in time. I've never heard a firm answer. Both descriptions work in physical calculations.
Geo.: We send electrons as modulated electromagnetic waves into the future all the time --radio, tv etc. Why not generate positrons, modulate their wavelength and send them into the past?
TT: Because, in the grace and cruelty of time, there are some things we're not meant to do.
Geo: That's absurd, we could repair so much past damage!
TT: Typical thought of a backwoods hick! What was your zip code in your home town, Geo.?
Geo.: Uh, e-i-e-i-o.
TT: And what is your current occupation?
Geo.: Teaching applied hornet-dodging at our south door.
TT: And what are your most ancient ancestors?
Geo.: Fossil remains on primordial plains.
TT: And if you could send a message to them --perhaps to improve their hygiene. What would that be?
Geo.: Uh, lavatories?
TT: These are people who have only mineral content now. If you were similarly fossilized, what would you expel in a lavatory?
TT: Excuse me, I must be vegetating on now.