# Speed of a tachyon increases as its energy decreases

1. May 3, 2013

### Astro-Anouar

I Found This in Wikipedia ''the speed of a tachyon increases as its energy decreases. In particular, approaches zero when approaches infinity'' and My question is How can be this Possible ?! First I know ,When the speed of a particle increase, his Energy will increase Too , No ? Second How Can The speed Be Infinity ?! and Finally Why we create The Tachyon , Einstein said that the Photon is the Fastest ,so what the purpose of Tachyon why we create it ?!

2. May 3, 2013

### phinds

The tachyon is a mathematical construct that is not believed to exist in the real world.

3. May 3, 2013

### Staff: Mentor

Exercise: find the (relativistic) formula that gives a particle's speed v in terms of its energy E and mass m. You will find that it contains an m2.

Tachyons, if they exist, have imaginary mass: m = iμ where μ is a real number. (iμ)2 = -μ2. In the formula that you get in the exercise above, this changes a sign, which in turn produces the behavior of v with respect to E as described in Wikipedia.