10 October 2011
by Amanda Gefter
Read more: “About time: Adventures in the fourth dimension”
TAKE a few steps forward, turn around and walk back. No problem. Now let a few seconds pass, then turn around and head back a few seconds in time. No luck? Of course not. As we know only too well, time, unlike space, has only one direction – it flows from past to future, and never the other way round.
That all sounds like the natural order of things, but if you look closely enough at nature, you will find that it isn’t. A thorough search of the laws of physics turns up no such arrow of time. For example, you can use Newton’s laws of motion to work out where a ball was thrown from in the past just as well as where it will land in the future. And when it comes to particles, the laws and forces …