system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: Tachyons

Saw someone mentioning it in a thread. Read about it on Wiki and watched some Youtube videos. Still have absolutely no idea what this thing is or any of the concepts about it.
gpt
They're ipothetical particles which travel faster than light. They would achieve that having imaginary (negative squared) mass. This would mean their velocity would INCREASE with the decrease of their energy, unlike the other particles, with positive mass, that do just the opposite.

Many scientists don't believe in their existance because they would be in conflict with the known laws of physics.