Question

What is a tachyon (other than a subatomic particle - what is its function within the Universe)?

Answer 1

you could visit the following website...
http://starfields.org/what_is_tachyon_energy.htm

Answer 2

tachyons are hypothetical particles that travel faster than the speed of light. They have never been observed in nature, and hence only exist on teh pages of theoretical physics. Infact most physicists do not believe that they exist, as they could violate causality.

if they did exist some suggested properties is that they would be particles travelling slower than the speed of light, but backwards in time. In our direction for the time arrow, tachyons would not be able to slow down to the speed of light or below it, requiring an infinite amount of energy to do so. They would thus have the strange properties that the more energy you gave them, teh slower they would move.

Tachyons would only appear to be a fun exercise in theoretical physics, and the universe would not appear to make use of them, except for when it comes to saving the Star Ship enterprise from quantum singularities by aiming a tachyon burst toward it. In other words, it appears taht the use of teh tachyon in our universe is solely for the purpose of making a good sci fi story.