Either it would have negative mass and imaginary energy, or it has negative energy and imaginary mass - <a href="http:&#x2F;&#x2F;math.ucr.edu&#x2F;home&#x2F;baez&#x2F;physics&#x2F;ParticleAndNuclear&#x2F;tachyons.html" rel="nofollow">http:&#x2F;&#x2F;math.ucr.edu&#x2F;home&#x2F;baez&#x2F;physics&#x2F;ParticleAndNuclear&#x2F;tac...</a>