Retroreflection occurs when light rays hit a surface and reflect radiation back to the source. Different to reflection, where the light scatters; retroreflection is precise, focused. Worn by tradies, cyclists, technical wear fashion heads—for safety in low light and for style. It’s used on the moon, too, where humans have placed retroreflectors on the surface. Scientists started shooting laser beams at the retroreflectors to calculate the distance between the moon and Earth. They still do it, sending out beams of light and having them bounce back to us.

My dad would always complain about cyclists not wearing high vis gear at night—so dangerous, you can’t even see them! When I was seventeen I sat in McDonald’s and it was a bright hot day and there was a loud crash outside. A cyclist hit by a truck. They carried him away in the middle of the day and the sun was shining and you could see everything.