[chris (OP)]

What are tachyons, how are they made and what is their nature?

[JohnDuffield]

What are tachyons, how are they made and what is their nature?

Tachyons are hypothetical particles that travel faster than light. They were proposed nearly fifty years ago, they have not been detected, and they remain hypothetical. There is no known way in which they can be made, and their nature is not known. Note however the speed section from the Wikipedia article:

"One curious effect is that, unlike ordinary particles, the speed of a tachyon increases as its energy decreases. In particular, E approaches zero when v approaches infinity".

This is not in accord with known physics, and suggests to me that the tachyon is a mathematical abstraction only. A "negative carpet". That's where you need a 16m² carpet for a room. So you say that a carpet measuring -4m by -4m will do the job nicely.

[chris (OP)]

Thank you; now I know why I didn't know about them...

[PmbPhy]

Thank you; now I know why I didn't know about them...

You should know that a tachyon is not the name of a particular particle but the name for a particular ype of particle. That is to say that any particle that can move faster than the speed of light is called a tachyon.

For example see Faster-than-light speeds, tachyons, and the possibility of tachyonic neutrinos by Robert Ehrlich, Am. J. Phys. 71, 1109 (2003)

Faster-than-light speeds and hypothetical FTL particles known as tachyons are exciting subjects for students, given their speculative and controversial nature. This article presents an overview of these subjects and their role in special relativity and examines the possibility that one or more of the three neutrinos is a tachyon. The paper also describes several low tech demonstrations useful for teaching about faster-than-light speeds and tachyons in intermediate and advanced introductory college-level physics courses.

See http://physicsbuzz.physicscentral.com/2011/09/physicists-report-evidence-of-quicker.html

I have no idea if that's true or not. I just stumbled upon it as I was searching.

[evan_au]

In theory, it takes an infinite amount of energy to accelerate something from below the speed of light up to the speed of light. So you can't make a tachyon by accelerating normal matter.

The possibility of tachyons pops out of the mathematics of relativity (in a similar way that Dirac saw the possibility of the positron in the mathematics of the electron). The difference is that positrons were rapidly found, while tachyons have not to date, despite several experiments looking for them.

In relativity, there are multiple places like time & length with factors like 1/√(1-v²/c²). This approaches infinity as v→c.
It becomes "imaginary" if v>c, which leads to the possibility that it is not a realistic solution.

However (in my primitive understanding), despite the unreal nature of time and space for such particles, the equation for energy comes out as a real value, which has held out the tantalising possibility that these may be real particles.

How you could create or detect them is unknown, but that doesn't stop people from trying...

[Bill S]

Because, theoretically, a tachyon travels backwards in time, searching for it would involve searching for some sort of tachyon precursor: an event that would indicate that a tachyon was about to be formed.  Therefore the tachyon would have to be observed before it was formed. 

A crystal ball might be an advantage here.