Debates about the nature of time are, well, timeless. What is time? Where does it come from? And why does it only seem to move in one direction, like an arrow shot from a bow?
Depending on who you ask, this "arrow of time" can be considered as something fundamentally hard-coded into the fabric of reality, or a mere product of our limited perceptions, or an emergent property of thermodynamics—to name just a few ideas. To add to the confusion, there's the vexing fact that the equations we use to explain the universe work perfectly well if time's arrow flies in reverse.
Imagine a world in which time really could flow backwards. Among other things, there'd be some use in crying over spilled milk, since maybe the dairy drips could end up back in their cup. And, if nothing else, people might have fewer regrets about past mistakes, because they could just rewind the clock to make better choices. So the idea certainly has appeal, save for the fact that, based on our everyday experience, time's reversal should be utterly impossible.
Some researchers have postulated, however, that such "time-reversal symmetry" might break down at subatomic scales, and that our intuition toward time's one-way flow may arise from some quirk of the quantum realm. But, as our top story by news intern Gayoung Lee details, a new study of this gnarly problem suggests that, nope, time-reversal symmetry holds there, too. And so the mystery of time's arrow persists, and our timeless questions remain.
I'm, ahem, short on time, so will leave further explanation to the story itself, which I hope you'll read and enjoy. Until next time! —Lee Billings
