Sir, – Margaret Moore (September 29th) asks what word will be used to describe faster than the speed of light. Superphotic would do nicely. However, there are already theoretical faster-than-light particles known as tachyons. Accepting the existence of tachyons means that the speed of light is a barrier rather than a limit, ie sub-light-speed particles cannot travel faster than the speed of light and tachyons cannot travel slower than the speed of light. – Yours, etc,