Shadows Can "Move" Across A Surface Faster Than The Speed Of Light

Traveling faster than the speed of light in a vacuum is impossible, according to Einstein's theory of special relativity.

Particles without mass must travel at the speed of light, while any other object cursed with mass finds that it cannot approach 299,792,458 meters per second (983,571,056 feet per second) without expending infinite amounts of energy . Physicists and sci-fi writers have tried to get around this, with concepts like the warp drive . But likely these will turn out to be forbidden by those pesky laws of physics, given that any faster-than-light travel can lead to universe-breaking paradoxes .

However, there is something in the room with you right now that can break the speed of light, assuming you are not sat in a dark room. Shadows are able to exceed the speed of light – and absolutely smash it, in fact.

You may have questions, such as "what the hell are you talking about?". Imagine you have a torch powerful enough to light up the moon to some extent. Pass a finger across the front of the torch quickly, and the shadow your finger cast can move across the lunar surface at speeds far in excess of the speed of light.

The same sort of idea can be achieved by simply waving a laser across the night sky. If you imagine a giant dome placed (to pick a number) 100 light-years across surrounding you, when this laser hits it 100 years in the future the points will whizz across the dome at speeds far exceeding that of light.

But both these examples are just illusions.

"Just the image of the beam as it races across the night sky is moving faster than light, but there is no message, no net information, no material object that actually moves along this image,” astrophysicist Michio Kaku explained in the Big Think .

The laser point is not really moving per se – what you are seeing is the photons hitting the dome, shortly followed by different photons hitting a different part of the dome after you moved your laser 100 years in the past.

Nothing really moved faster than light, and no information was transferred, leaving the universe and physics intact.