Tachyons

Tachyons are hypothetical particles that travel faster than the speed of light. So far, they have never been detected, but the principle of relativity does not prohibit their existence. And an interesting type of symmetry would occur if they really did exist. In that case, all three types of conceivable particles would occur in nature – subluminal, luminal, and superluminal – rather than just two of the three. Therefore, a theoretical study of the possibility of tachyons is somewhat warranted.

In fact, the special theory of relativity places definite limitations on the properties of tachyons and how they might relate to other forms of matter. For example, you cannot create tachyons simply by accelerating normal matter to superluminal velocities. It would require more energy than is present in the entire universe to accelerate even one electron all the way to the speed of light. To exceed the speed of light with normal matter would be utterly impossible.

Subluminal, luminal, and superluminal particles constitute three distinct classifications. A particle belonging to one class can never exist in the other classes. For example, normal matter exists only in subluminal form. It can exist at rest or travel as fast as you like less than the speed of light, but it can never travel at the speed of light or go beyond. Photons (particles of light) exist in a vacuum only at the speed of light. They can never slow down or speed up. And tachyons can only exist in superluminal form. They can speed up to infinite speeds or go as slow as you like above the speed of light. But they can never slow down all the way to or below the speed of light.

Subluminal particles exist in time and are always at rest in their own proper frame. Luminal particles neither persist in time or space, but exist along the boundary between the two. They have no proper frame. Superluminal particles exist in space and always have an infinite velocity in their own proper frame.

And finally, even though no particle can change its type of classification, particles of each class can, at least in principle, be created and/or destroyed. Therefore, it is theoretically possible to convert particles of one type into particles of another type through the creation-annihilation process. For example, subluminal matter in the form of electrons and positrons can completely annihilate itself and create luminal matter in the form of high-energy photons.

For these reasons, some scientists believe that it may be possible some day to create and detect tachyons in the laboratory. If this ever becomes possible, then the theory of relativity predicts that faster than light communication will also become possible.

Questions:

Q1. According to special relativity, which of the following can travel with superluminal velocities? (A) the spot of glowing phosphor on the face of a CRT, oscilloscope, or television tube, (B) the appearance of objects approaching the observer at the speeds close to that of light (C) the collapse of quantum mechanical wave functions when a measurements are made (D) All of these. (E) None of these. Nothing can travel faster than the speed of light.
D 51532121

Q2. If tachyons exist, according to special relativity which are true? (A) As they pass through matter, they can slow down and stop. (B) They cannot pass through material bodies. (C) They can neither be created nor destroyed. (D) More than one of these. (E) None of these.
E 51532121

ModPhy1/Unit1/SpecialRelativity/RelativeView/Time/Simultaneity/Causality/Superluminal/