“…It’s what I call the Law of Conservation of Time,” said Professor Blisham, pointing to a forest of algebraic formulas on the chalkboard. “Time that is past has not vanished; time that is future already exists. You see, I simply refuse to believe that the universe possesses one anomalous fundamental property. When we burn a stick of wood, the matter and energy in the wood is not subtracted from the universal total. When we traverse space, the space we came from does not cease to exist. Space is relativistically curved, yes, and multidimensional, but it is nevertheless there, it is not a figment of our perception. Time as we perceive it is a nothingness: past and future are nonexistent, and the present is an infinitesimal dot, with no more duration than a point in space has extent. We feel ourselves to be running along a track that vanishes as soon as we pass and that does not come into existence until we arrive. Isn’t it more sensible to assume that the track is permanent?”
“That’s right, Prof,” said a strangely familiar voice, as the laboratory door pushed open to reveal someone who looked exactly like Professor Blisham, but a bit stouter, a bit grayer, and wearing a suit and tie of startlingly narrow cut. “Time travel is possible – technically, though not pragmatically – and here I am to prove it.”
“Why, it’s me!” cried Professor Blisham.
“Crazy, man, huh?” said the new, older Blisham, looking around in nostalgic amusement. “Wow, look at this cool pad you had here. It’s bringing back, like, memories. What a swinging time this was.” He strode up and shook the old, younger Blisham warmly by the hand. “Man, it’s wild to see you after all these years.”
Blisham moved back in horror. “But – but if I meet myself – if we meet ourselves – won’t the universe implode because of the paradox? Aren’t you breaking the laws of conservation of matter and energy by entering this timeframe?””
The later, more sophisticated Blisham laughed indulgently. “Cool it, man, when did a paradox ever blow anything up? Paradoxes are for digging. As for laws, who passed those laws? What jail do you go to for breaking them? A law of nature is just a description of what’s happened in the past, daddio. If you break it, well, there are ways to get away with it.”
The more innocent Blisham sank into a chair and wiped his brow. “But – but – I still feel I’m myself. My consciousness resides inside this brain in this cranium. We can’t have two consciousness, can we? What, then, is inside your brain?”
More laughter, like that of a parent at a child’s cuteness. “Man, you are too much. Continuous personal identity is an illusion, man, like didn’t you know that? It’s just narrative point of view. A so-called individual is just a first-person POV, that’s all, and there are countless numbers of them but each of them thinks it’s the only one. Baby, you still got your POV and I got mine, and that’s how it goes, right?”
“Oh, my,” said the sweat-bathed antecedent Blisham in a fluttery tone. “Well, I suppose it could – “
“Yeah, well, it’s been swinging talking to you, babe, but I gotta split, you know? Before the whole thing does. The whole show, know what I mean? The whole –“
“Universe?” the pale and trembling Blisham finished in alarm.
The visitor snapped his fingers. “That’s the word I was looking for. Thanks, man. Yeah, like, time travel is theoretically possible but it’s not downright advisable, know what I mean? Look, let me give it to you straight. Every traveler who goes back into the past upsets the chain of causation that would have been established. I come back here, I know stuff you don’t, see? And by acting on it, talking about it, for chrissake even thinking about it for all I know, we undo the links and cause new links to have to be formed. Like, I know who’s gonna win the election next month, Dewey or Truman. But if I go blabbing about it, and thousands and then millions of people hear it, don’t you think that might swing the election? So then we’ve gotta have two universes, one with Old Man D. as the prez and one with Old Man T. Well, multiply that by all the things I know from your future. And multiply that by the number of time travelers there would be if this thing ever really got into production. (I’m just sneaking here from my lab before I let anyone else know, ya dig?) It’s like” – he pressed his fingers to his brow with a Brando-esque grimace of anguished thought – “it’s like if a car comes to a fork in the road, you know? Ya gotta go one way or the other, buddy, you can’t swing both ways, if you know what I mean, ha ha. But with this time travel gig, that doesn’t work: the car tries to go on umpteen roads at once, and what happens? The car splits up into tiny parts, one axle going on this road, the carburetor rolling down another – crazy, huh? Presto, man: no more car! A universe full of time-travel action wouldn’t stay in one piece long, you catch my drift?”
“I say, I fear I do,” the host Blisham murmured in distress.
“That’s why travel into the future’s like safer than into the past. The past, you like screw around with the very chains of causation. The future, you’re just tinkering with things that haven’t happened yet, so causation isn’t broken – you’re just leaving someone a hell of a mess to clean up. I gotta tell you, man, this thing makes the butterfly effect look like a slight change of breeze. Hey, you don’t know what the butterfly effect is, do you, ‘cause like Ray Bradbury hasn’t written ‘A Sound of Thunder’ yet. Ooh, man, that’s another piece of like top-secret info I just let slip. Two in one visit, that’s like pushing it, you know? Man, if I don’t watch out, the whole thing could like melt into jello while I’m standing here.”
Summoning up a burst of energy, the pre-time-travel Blishman stood up, pointing a sweating finger at his antagonist. “Do you mean to say that by traveling here you have endangered the very fabric of – “
“Well, it’s not that bad, at least I don’t think. Theoretically, just one visit may not be enough to do it. It’s like – the universe isn’t exactly like a house of cards where one card pulled out brings the whole thing down. It’s more like one of those games where you build a tower of sticks, and then you take away one stick at a time and see who makes the tower fall. Or, like, here’s another cool way to look at it: if one cat drops in to your pad for dinner, that doesn’t mess up your plans much, does it? But if a thousand cats dropped in, you’d probably have to move, you know? Or at least throw them out.”
“And that is precisely what I’m about to do with you, sir,” said the younger and more prudent Blisham, grabbing his guest by the inch-wide lapels. “You can go back to your time machine, or whatever it is you use, right now, and take your…consciousness, if you call it that… with you.”
“Cool, baby, I dig what you’re saying, but” – the traveler looked at his wristwatch – “oh man, you know? I’m always doing this. Like losing track of time. I start blowing and I forget where I’m supposed to be. I hope I haven’t overstayed, man, really. Because I had it like all calibrated and all that jazz, but – I mean, look how much you know already about cool threads and hip jive that you never knew before. That’s messing up the program, dad, that’s adding more forks to the road. Now I gotta split, you know? ‘Cause if we’re not careful, I could be standing here shooting the breeze with you, man, and the whole thing could just disap–“