Symbolism, Imagery, Allegory
Tachyons are hypothetical particles that can travel faster than light. Now, according to the theory of relativity as conceived by Albert Einstein—maybe you've heard of him—nothing can travel faster than light. The speed of light is, in a sense, the universal speed limit. In fact, nothing with mass can travel at even the speed of light, leaving massless particles as the true speed demons in the universal grand prix.
Then in the 1960s, tachyons were proposed as particles that could not only move at the speed of light but also contained mass. If these particles could be found, their discovery would basically throw out special relativity, a.k.a. the playbook for the known laws of physics. However, no compelling experimental data has been found for their existence. If you're interested in learning more about these hypothetical faster-than-light particles, you can find an explanation with a bunch of math here or a more public-friendly discussion here.
If you're thinking that's all more than a little bit confusing, well, you're not alone. It's a complex issue that has had people with advanced degrees in theoretical physics scratching their heads for decades.
But we aren't here to talk about whether or not tachyons really exist for a couple reasons. For starters, we in the land of literature learning guides lack those advanced science degrees. But more importantly, their reality isn't the point when dealing with tachyons in Timescape. When questioning the importance of these particles in regards to the novel, we should be asking ourselves not whether they exist, but what they symbolize. And thankfully, we can answer this question without any fancy lab equipment.
The Trouble with Tachyons
In the world of the novel, these particles are used by Renfrew to send messages back in time to warn the world of the impending ecological disasters. He does this by striking high-energy ions against an indium antimonide sample—the force gives off tachyons, and then he hides his message in these tachyons in the form of Morse code (1.65). Since tachyons travel faster than light, they can break through the barriers of the physical universe and travel back in time. That's the short and simple version at least.
The problem Renfrew and Markham come across is that they can't fully grasp the consequences of their time-altering antics. They know that tachyons exist and that messages can be sent back in time, but they don't know what this means for humanity's understanding of reality. This leads us to the symbolic nature of tachyons in the novel: Tachyons represent scientific discovery and its ability to change our perception of reality. As Gordon notes:
He had taken up the idea with Wong, the particle physicist, and got the conventional reply: they violated special relativity, […] gliding across the universe in less time than Gordon's eye took to absorb a photon of the pale, watery laboratory light—these things went against reason. (39.43)
But a lot of scientific discoveries have gone against the reason of their day and proven to be true. From at least as far back as the Classical Greeks, people thought that the Earth was the center of the universe, a belief called the geocentric model. For the Earth-bound observer, the sun and stars appear to travel around the Earth, so the belief makes a certain amount of sense.
Then along came Copernicus, who noted that, actually, the sun is at the center of the universe. He was followed by the likes of William Herschel and Edwin Hubble, both of whom helped us realize that the sun was only the center of the solar system, which was housed in the suburbs of the Milky Way.
The point is that with each scientific step, Earth got farther and father away from the center of the universe. With the Earth, humanity itself also got farther and farther away from the center of creation. This forced humanity to reconsider truths that it had held to be self-evident for hundreds, if not thousands, of years.
And science forces us to reconsider these truths all the time. The theory of evolution required us to reconsider the origins of our species. The theory of relativity had us question how everything interacts in time and space. Heck, the entire field of geology forced us to reevaluate just how long our planet has been spinning through space. With each of these paradigm shifts, humans had to reconsider themselves, their place in the universe, and the truths they hold.
Think Again
Tachyons act as a symbol for these paradigm shifts within the novel. With the discovery and manipulation of tachyons, Markham and Renfrew have to reconsider the very concept of time. And we're not talking some jet lag or daylight savings type adjustments either—we mean fundamental, cutting-to-the-core changes to how to consider time.
Markham can no longer consider time in the everyday sense: past, present, and future all existing in a straight line and heading in one direction. Instead, Markham notes:
There's no way around it. The equations of physics are all time-symmetric. That's one of the riddles of modern physics. How is it that we perceive time passing, and yet all the equations of physics say that time can run either way, forward or backward? (9.108)
We never receive any straight up answers to those questions, but maybe that's the point of tachyons as a symbol, too. They aren't meant to show us how science will always come up with answers to our new understanding of the world; they are meant to represent the ways in which science forces us to reconsider what we know to be true about, well, everything. In some cases, even the concept of truth itself.