Imagine you have a powerful torch - a flashlight if you prefer - and you switch it on, and point it at a wall 200 metres away. Now take a pencil, and move it quickly across the path of the beam, just in front of the lens.

Let's say the tip of the pencil is moving at 15 metres per second. I think that's highly doable. The shadow of the pencil on the wall will cover (let's say) 60 metres in the time it takes the pencil to move 3cm, so it moves at 2000 times the speed of the pencil.

Now imagine that you fix the torch to a tripod, then attach the pencil to a mechanism that's capable of propelling the pencil across the beam extremely fast - at the speed of 300km / second. So the pencil tip will travel that 3cm distance in 1/10000000 seconds.

Granted you aren't going to find the sort of equipment that will allow you to do this on Amazon but it is theoretically possible in principle.

But in that same 1/10000000 of a second, the pencil's shadow on the wall will have travelled 60 metres. That's a speed of 600000 km / second, which is a little more than twice the speed of light.

What's the catch?