There was a young lady named Bright,
A. H. Reginald Buller, 1923
Whose speed was far faster than light.
She went out one day,
In a relative way,
And returned the previous night!
Introduction
Tachyons often make an appearance in our favorite sci-fi shows as “beams” or “fields” that cause some form of “time disturbance.” What are tachyons anyway? Put simply, they are theoretical particles that travel faster than light. It’s important to note that most physicists don’t think they even exist. In fact, tachyons straddle the line somewhere between science and pseudo-science.
Special Relativity
First let’s quickly review special relativity. As you may recall, Einstein’s theory states that nothing can go faster than light. Nothing! Why? Because as an object approaches the speed of light, its mass increases towards infinity and the energy required to further accelerate the object also increases towards infinity. Finally, just before the speed of light is reached, infinite energy is required to go any faster, thus, the speed of light is forever out of reach.
Gerald Feinberg
In 1967 a physicist named Gerald Feinberg began tinkering with Einstein’s equations. He was dead set on finding a way for particles to go faster than light, while still satisfying the maths involved in special relativity and avoiding the inconvenience of infinite mass and energy.
He was inspired by a 1954 short story by James Blish titled Beep. It’s about a galactic empire that holds sway over the galaxy via a device called an ancel which is capable of instantaneous communication over vast distances. Feinberg thought this was a pretty cool concept and wanted to see if science could support it.
Feinberg found that if he gave a particle negative mass, the particle could travel faster than light and Einstein’s equations still worked out. What’s negative mass you might ask? Who knows? But it allows particles to go faster than light. He dubbed these particles tachyons, a riff on the Greek word tachus for “swift.”
Negative mass turns the rules of relativity upside down. Not only do tachyons travel faster than light, but they cannot possibly go slower than light.
Time Travel
Yet another consequence of approaching the speed of light is that time begins to slow down from the traveler’s point of view, until, at the speed of light, time completely stops. Stranger still, traveling faster than light causes time to actually move backwards.
Einstein and others played around with thought experiments involving faster than light particles before Gerald Feinberg, but only as a means of disproving the possibility that they exist.
Einstein laid out a thought experiment using faster than light particles as a means of communication. In it, person A sends a question to person B using faster than light particles, then person B responds, also using faster than light particles. The problem here is that person A would receive their response before they even asked a question. And that’s just scratching the surface. With backward time travel of any kind we find ourselves stuck in all kinds of paradoxes that cause the universe to break. I’m sure you can think of a few (it’s a great party game). For that reason alone, most physicists believe tachyons cannot possibly exist.
Tachyonic Fields
Interestingly, physicists at CERN have found evidence that the Higgs field is tachyonic in nature. However, the negative mass in this case does not mean that a particle interacting with the field is propelled backwards through time as Gerald Feinberg might have speculated. Rather, it only means that the field is in an unstable state. When the math starts returning negative mass, infinite values, or tachyons, it means something in the theory just broke.
Conclusion
Despite the fact that tachyons seem destined for the trash heap of scientific speculation, they continue to pop up from time to time in scientific research. For instance, in 2012 a team in Italy set the scientific community ablaze when they observed neutrinos traveling faster than light. However, their research was immediately debunked after faulty equipment was found as the cause. But this illustrates that physicists are still not absolutely sure about tachyons.
So who knows? Someday it may be possible to send a message to yourself with instructions not to go out on that horrible date in 2012… but then you wouldn’t have gone on that date and you wouldn’t need to tell yourself not to go on it, and…. oh never mind.
