Tachyons are more like metaphysical particles with imaginary mass and speed that’s faster than light. This particle got the name from Greek word tachys which means swift particle and was coined by Gerald Feinberg in 1967. Here’s the thought experiment: A certain Science lab on Pluto has an emitter and a detector, and so does an identical lab on Earth. Earth is supposed to fire a tachyon to Pluto at 11:55am and Pluto, after receiving it will send another one back to Earth at about 12:00am.
But, the scientist on Earth however receives the tachyon at 11:50am, ten minutes before they actually transmit the first tachyon. He was so startled by it that he destroys his lab equipments, making it impossible for himself to send a signal to Pluto to emit a tachyon. So where did the tachyon at 11:50 come from? The only possible answer is another universe, a universe where the lab on Earth wasn’t destroyed. Due to its speed, it can never really be observed even if it was real. Because one moment it’s not there, and the other moment, it’s gone.
When you’re looking through a hole, whenever something moves in front of you, you’ll see it approaching and departing. But Tachyons, which are faster than light, cannot be observed approaching. The “present” is such a short time that it really doesn’t exist. Tachyons are believed to have imaginary mass, existing in imaginary time. The word “imaginary” here, has a mathematical meaning, not a colloquial one. For example, the square root of -25 is an imaginary number. Well, not completely an imaginary number necessarily, but a real number multiplied by the imaginary term i. For example i2=-1. So tachyons do have mass and it theoretically does exist at a time, but those cannot be specifically defined using Grade 11 Physics and Mathematics. There was this possible method of detecting a tachyon, where instead of observing a tachyon, we would need to be on the same time slide as a tachyon. But unfortunately, we can’t measure inconceivably small time fragments. The last time we’ve been able to measure a time fragment, it was a hundred septillion longer than it was supposed to be.
While detection might still be possible in a universe with granular time, due to mathematical and unknown theoretical reasons, the moment you detect a tachyon, you’ll emit one too. You’d just turn on your detector and be flooded with random tachyon noise, never knowing if you are detecting a bunch of them or only emitting a bunch of them, or somewhere in between. It’s all random noise from the foamy levels of the Planck-scale universe. This means you’ll never be able to encode a message in tachyons to communicate with the past – tachyons cannot carry information from their superluminal world into our subluminal one.