This means that even the most run-down, old car has the potential to travel faster than light. When a beam of light is shone through the sodium condensate, the speed of light decreases to just 15 miles per hour.

In doing so, this condensate becomes the coldest substance on planet Earth. Itâ€™s these lasers which force the atoms to slow, stopping them from vibrating. The gas is made of elemental sodium first vaporised in an oven, then when the atoms are released theyâ€™re blasted with a laser beam. She accomplished this by creating whatâ€™s known as a â€œBose-Einstein condensate,â€ a cloud of gaseous atoms chilled to absolute zero. One physicist working at Harvard University, Lene Hau, has even successfully managed to stop light dead in its tracks - almost. While light naturally slows down, through natural bodies like diamond and water, there are also ways to artificially slow it. But what if the universal constant of â€œCâ€ actually did slow down, not just through other bodies but also in the vacuum of space? What would that mean for mankind, if anything at all? Sending light through certain transparent objects has already proven to slow it down significantly from that magic 186,000 miles per second figure â€“ which only applies when light is travelling through a vacuum â€“ and in fact, through diamond, the speed of light more than halves, to just 77,000 miles per second. Light may not be a constant after allâ€¦ it may have once been much faster and we might be able to artificially slow it down. The speed of light, 186,000 miles per second, is the unchanging foundation of modern physics â€“ but now some scientists are thinking that Einstein could have been wrong, or at least not totally right. Einstein was only in his 20s when he came up with the ground-breaking theory of relativity, which put a figure to the speed of light and denoted it from that point onwards as â€œCâ€, for â€œconstantâ€.

Lightspeed to warp speed calculator