Daily Archives: January 19, 2011

Science Fiction Problems: Time Travel Part II

This is the second of two parts on the topic of time travel. To see part I, click here.

In this post:

  • Cosmic Strings, threadlike celestial bodies that stretch across galaxies, could be the super-dense super-highways we need to travel faster than light, and travel through time
  • Time Dilation is the slowing of time as objects approach the speed of light- scientists think that it might actually run backwards at speeds faster than light

Last week I covered a brief explanation of time as the 4th dimension and discussed the potential time-traveling properties of black holes and worm holes. This week, I’ll cover a few other means of time travel and some of the problems that occur when time-traveling. The first is another space-time trick that scientists think will allow the bending of time in a similar manner to black holes and wormholes, the cosmic string.

Cosmic Strings

This one’s a little more out there, but that’s the kind of thing that author’s can make work for them in their science fiction if they present it well.

cosmic strings network model

Space noodles.

Proposed by Princeton physicist J. Richard Gott in 1991, cosmic strings are theorized to be thread-like objects created in the early life of our universe. They are thought to spread across entire galaxies, crushed by immense pressures of millions of tons to a thickness smaller than an atom.

These strings would have a gravitational pull so great on objects passing near them that objects traveling along them would pretty well screw up Einstein’s model of relativity and travel at ridiculous speeds. With the way they distort space time, and the potential for faster-than-light travel along them (which will be discussed as another option in a moment), cosmic strings could be very useful for time travel. It may even be possible to drag two of these strings close to each other, or to pull one close to a black hole for even more effective results- although this is all, of course, very speculative, and very controversial in the scientific community.

Time Dilation

As far as time traveling methods go, this one’s far more limited than many of the others, but it has the advantage of experimentation that supports the theory very soundly, and is fairly well known in the science fiction community. As I discussed in my post Science Fiction Problems: Space Travel (FTL FTW?), the speed of light is the limiting factor in space travel, but in the case of time dilation, it is the limiting factor of time-travel as well. The idea is that as objects approach the speed of light, time for that object (“system time”) slows down. It has to do, again, with Einstein’s theory of relativity, where mass and velocity affect time, and at the speed of light, time stops- but more on that in a moment.

relativity diagram light clocks

This diagram actually uses light clocks, but it still illustrates that as the distance at speed between them increases, time slows

There have been several experiments done, resulting in what scientists call the “Twin Paradox”, where two identical clocks (usually atomic or otherwise designed so as not to be affected by changes in air pressure, heat, etc.) are synchronized and one is sent on a high-speed journey (plain, bullet-train, etc.) while the other is left still. When the traveling clock returns, it is slower than the stationary clock by an exact amount previously calculated by Einstein’s equations. What this means is that the traveling clock has actually recorded less time than the stationary one. This phenomenon has been recorded on the space shuttle missions and in many other examples, and the conclusion that scientists have come to is that, for these traveling objects, time has slowed down.

Now, the gained time is typically measured at seconds at most, but these are at speeds far closer to zero than the speed of light, so you can guess the implications. While we are nowhere near being able to make meaningful jumps into the future, it still seems like solid mechanics, and that doesn’t stop the science fiction community from running with the idea. Orson Scott Card’s Ender’s Game addresses time dilation with its space travel, and it has been used in countless other stories as travelers in ships stay young as their families on their home planet age far more quickly.

spaceballs ludicrous speed dark helmet

Ok, a little crass, but I liked the movie.

I mentioned earlier that time stops at exactly the speed of light… but the validity of that theory is the biggest hurtle to this method of time travel. We have future travel covered pretty well ( you wouldn’t have to actually reach the speed of light), but travel into the past is a bigger problem. Scientists theorize that beyond the speed of light, time might go backwards, but we don’t even have mathematical formulas to back this up. We simply don’t know, and obviously have no way to test it yet. In any case, for a story it’s not an unreasonable leap to make.

WELL, that covers all the different types of time travel I wanted to cover- see you next week for Part III where I’ll dig into some of the methods used in famous science fiction, and the problem of the time paradoxes that they usually ignore!

For now, what are some other methods you’ve seen or read, good or bad?