I'm reminded of the first book about not-exactly-time-travel that I read, which made an incredible impression on me. It was Gregory Benford's Timescape from 1980. The story is set in 1998, which of course was the future from 1980's point of view, and the Earth is on the brink of an ecological collapse. What has happened is that a certain strain of ocean-living bacteria has mutated so that it can live on a certain kind of toxins that humanity has dumped in the ocean. The bacteria thrive and spread exponentially, making the oceans erupt in huge 'bubbles' of rust-colored bacteria infestation, forming yellow clouds in the sky as ocean water evaporates, and raining down onto the earth as bacterial precipitation.
Desperate scientists try to save the Earth. They conclude that it is too late to combat the bacteria and save the oceans. Instead, their only hope is to actually try to send a message to the past and try to persuade the people of the past not to dump so many toxins in the oceans, thereby changing the course of history.
The scientists have sort-of-tamed Albert Einstein's hypothetical particles, the tachyons. Tachyons move faster than light, and they can never slow down below the speed of light. Therefore the tachyons might actually carry a message into the past, since it is hypothesized that we would actually travel to the past if we could move faster than light.
One extremely memorable one-liner from Gregory Benford's book was this. One person wondered why, if scientists could control tachyons, they could not build a spaceship of tachyons that could carry humanity to safety in the past. The scientist answered, 'How do you propose to get on a spaceship that is flying past you faster than light?' How indeed?
So the scientists were going to send a message, Morse code-like, into the past, with the help of tachyons. Another extremely memorable one-liner from the book was when the scientists were trying to aim their tachyon message beam at the right place. They were actually aiming it into the sky, otherwise it wouldn't reach the Earth's past! One astounded civil servant asked the scientists, 'You mean the past is in the sky somewhere?' And you know, the answer is yes. The past is in the sky. The reason for that is that the Earth, along with the rest of the solar system, is continually moving through space. We are not in the same place in space now as we were thirty years ago. If we want to send a message to the Earth thirty years ago, we will have to send that message into the the part of the sky where we were at that time. (Which means, by the way, that there is more to time travel than meets the eye, and you would actually have to travel in space as well as in time, if you want to visit the Earth of the past.)
Back to Gregory Benford's book. The scientists are successful. They do manage to send their message to the past, and the people of the past heed the warning and save the Earth. But guess what? This doesn't save the people of the future, those who sent the warning to the past. Instead the timeline splits in two, one timeline where the Earth is saved, and one where it plunges, unstoppable, into ecological collapse.
And it really makes excellent sense that the timeline would split in two. If the situation in the future was not absolutely desperate, the people of the future would not be desperate enough to try to send a message to the past. So if the people of the past receive a message from the future, then the situation in that future has spiralled out of control. And if the people of the past heed the warning from the future and save themselves, then the people of the future are nevertheless doomed, otherwise they wouldn't have made it possible for the people of the past to save themselves... it makes your head hurt, no?
So I wonder how many timelines we are going to end up with here, Carol!
Ann
