Then, as shown at left, the natural reading would be that the tachyon propagates backwards in time. We could equally well draw the figures so that C's worldline is vertical. That the figure showing observer A looks more natural is just an accident of the way the figures have been drawn. C's reporting of the tachyon traveling backwards in time is as good as A's reporting of the tachyon traveling forwards in time. The principle of relativity assures us that the reports of all of the observersĪre equally good. So it is easy to fall into the trap of imagining that the figure with observer A shows what is really happening: that the tachyon is really propagating forwards in time and that the other two figures represent distorted reporting from observers B and C in motion. That means that the tachyon is traveling backwards in time.Īll three figures above are drawn with the tachyon moving up the page. It arrives at the earlier hypersurface that collects events from an earlier time before it was created. The tachyon is created on the "now" hypersurface of simultaneity and propagates towards the "earlier" hypersurface of simultaneity. That is, for B, the tachyon has infinite speed-it covers distance in no time-and it has disappeared to spatial infinity in the same instant "now."įinally observer C, who moves even faster in the same direction, judges the tachyon to be traveling into the past.
So the tachyon exists only "now" for observer B. Indeed the "now" hypersurface contains all the events in the tachyon's history. Observer B finds the tachyon to lie fully within one of B's hypersurfaces of simultaneity, the "now" hypersurface that contains the event of the tachyon's creation. Observer B moves in the direction of propagation of the tachyon. Observer A judges the tachyon to be movingįorward in time from its creation at the instant marked "now." It propagates from the "now" hypersurface of simultaneity towards the "later" hypersurface of simultaneity. The figures below show a tachyon being created and propagating into space and how three different observers would judge the same process of tachyon creation. With the spacetime representation of the relativity of simultaneity, it is now easy to see how this comes about.
While bradyons are familiar and include protons, electrons and neutrons, tachyons have never been observed.įor present purposes, the interesting fact is a curious property: for some observers tachyons travel backwards in time.
They are distinguished from "bradyons," particles that travel at less than the speed of light. They are hypothetical particles that travel faster than light. One of the most intriguing entities in relativity theory are tachyons. Once we have the notion of spacetime and the simple picture it brings of the relativity of simultaneity, we find that other processes and effects in special relativity become much easier to understand.
0 kommentar(er)
