To explain why we cannot un-break an egg, we need to explain the arrow of time. To explain the arrow of time, we need to explain entropy. To explain why entropy explains the arrow of time, we need to explain the Big Bang. To explain the Big Bang… wait, now I am getting ahead of myself.
I’ve wanted to write about entropy on this blog before, but somehow it hasn’t come up yet. Similarly, the passing of time, a topic that has occupied me for years, also seemed just too all-encompassing, too complex to tackle in the short amount of time I have each day to set aside for this blog.
But I want to tell great stories, and sometimes it means handing the storytelling over to someone who has the time. Such as Adam Becker at BBC Earth’s Big Questions series, who has put together a compelling historical narrative on the science of the direction of time.
Amongst other things you will learn why a splash of milk spreads throughout your coffee cup without stirring, and what this has to do with the beginning of the universe, and finding a theory of everything.
There’s no fundamental law of nature that prevents us from un-breaking eggs. In fact, physics says that any event in our day-to-day lives could happen in reverse, at any time. So why can’t we un-break eggs, or un-burn matches, or even un-sprain an ankle? Why don’t things happen in reverse all the time? Why does the future look different from the past at all?
It sounds like a simple question. But to answer it, we’ve got to go back to the birth of the universe, down to the atomic realm, and out to the frontiers of physics…
Continue reading “Why does time always run forwards and never backwards?”