When the Weird Unit is the Perfect Unit
“Light years”. It is one of those highly misleading units in science. It suggests we are talking about time: light years . Instead, it is a unit for distance: the distance light would travel in those years . Why come up with such misleading names, right? Except in one scenario, where it is the perfect unit, as I discovered while reading Cixin Liu’s sci-fi novel, The Dark Forest where mankind makes contact with an alien civilization. But it is not human-to-alien contact, but radio contact (radio signals sent into space). Now the distance between the human and alien is stated in (what else?) light years. The aliens then decide to come to earth. But of course, they can’t travel at the speed of light, which means it would take them centuries to get here. See why it is the perfect unit now? All we want to know is how long it will take them to get here. After all, if the aliens are hostile, surely having centuries to prepare for their arrival is a good thing, right? And if they’...