Which apples are better, red ones or green ones? There is not much difference between the two - they are both good for you. But apples are somewhat overrated in their nutritional value. They are low in vitamin A and vitamin C.
Can anything travel faster than the speed of light? According to Albert Einstein's theory of relativity, no particle can be accelerated from below the speed of light to faster than the speed of light - 300,000 kilometres per second.
But since the 1960s physicists have been aware of the hypothetical existence of subatomic particles which always travel faster than light. These particles are called tachyons. The existence of tachyons is thought to be consistent with the theory of relativity.
Unlike particles which travel slower than light speed, tachyons could only exist at speeds faster than that of light.
While a particle travelling at less than light speed slows down as it loses energy, a tachyon would lose energy and accelerate until it had zero energy and was travelling at infinite speed.
Travelling at infinite speed and having zero energy, tachyons would be undetectable, which is also the case if they do not exist.