Cycling is a healthy exercise. As a speed lover, have you ever wondered what will happen if the speed of a bicycle approaches the speed of light, say 90% of the speed of light, which is about 970 million kilometres per hour?

Of course, in the real world, it is impossible to ride so fast. But scientists did use Einstein's theory of relativity to study the scenario of a "Relativity Bicycle" (a bicycle that travels almost as fast as light). Recently, British physicists, Evan Cryer-Jenkins and Paul Stevenson, have put forward some new insights about relativity bicycle and come up with the following scenario (ignoring the interaction between air molecules and the bicycle).

When the bicycle is speeding towards you, the light from the bicycle and the cyclist is blue-shifted to become invisible ultraviolet rays as a result of the Doppler effect. Being no longer visible, the bicycle and the cyclist appear in the surrounding landscape as a fast-approaching black silhouette. On the other hand, when the bicycle and the cyclist are moving away from you, the light is red-shifted to become invisible infrared rays. Once again they appear as a receding black silhouette and eventually disappear in the distance. The most intriguing thing happens at the instant the bicycle and the cyclist pass by your side when light shifts from blue to red, a blast of pulsating rainbow tones will suddenly burst out!

If you want to know more, you can refer to this paper: https://arxiv.org/abs/1906.11642

Finally, as a friendly reminder from the editor, please ride at a safe speed.