Romy asks, “What is time?”
Imagine this: One day, everything froze. People walking to meetings stopped mid-step, even if they were late. All TV shows and radio broadcasts paused, all predators quit chasing their prey, all birds and airplanes and divers hung suspended in midair. Imagine that neurons stopped firing, electron stopped spinning, raindrops stopped falling, planets locked into place, and the light traveling from the sun ground to a halt.
Then, an hour passed.
Finally, the Universe snapped back into action. Just as immediately as everything stopped, it all started back up again.
You’re not any older, since the aging process froze. You didn’t even notice, because your thought process froze. For all you know, this cosmic freeze happened just a few seconds ago. Hell, for all you know, it’s been a thousand years since you started reading this sentence!
Time is weird and confusing. And I’m sorry to say, knowing more about it will only make it more weird and confusing.
Confusing things are easier to understand with an analogy, and time is no exception. We tend to think of time as a road. This way, moving through time (which we don’t understand) is just like moving through space (which we do understand). Just look at how we talk about time: stuff can be in the “far” or “near” future, we look “forward” to things and put the past “behind” us, Friday is “approaching” and June “follows” May.
It wasn’t until this one pretty smart dude came along that we realized this was more than just analogy. Albert Einstein came up with the theory of relativity, which tells us that it doesn’t really make sense to think of space without time or time without space. We’re not moving through space and moving through time — we’re moving through spacetime.
What does that mean? Well, right now you’re moving through spacetime super-duper fast. It just happens that pretty much all of that movement is in the time direction. If you got in a spaceship and rocketed away at half the speed of light, you’d be going so fast in the space direction that you’d be slower in the time direction. When you made it back to Earth, you’d have aged less than the rest of us! (So, if you can’t wait to see who wins the 2018 World Cup, zoom around the galaxy at near-lightspeed for a couple weeks.)
You’re always moving at the same speed through spacetime, it’s just the direction that changes.
But wait a minute. Time is different than space, right? You can move right and left, no problem. But you can only move from the past toward the future, not back. Why?
Well, this is embarrassing. We’re not sure.
Believe it or not, the laws of physics work just as well backwards as they do forwards. The same way you can watch the world through a mirror and everything makes sense, you could watch the world in rewind and all the rules would still work.
Don’t buy it? Imagine throwing a ball up in the air and catching it. Now rewind. Still works. Imagine dribbling a ball. Now rewind. Still works! You could even drop a glass and shatter it and rewind that — if all those shards of glass were thrown together just right, they’d lock together and shoot up into your hand. (Just because it follows the rules doesn’t mean it’s particularly likely.)
It’s actually even crazier than that. We’ve run some experiments where things in the future seem to affect things in the past. We’ve even caught some tiny particles that seem to be traveling backwards in time. The one thing we know for sure only goes forward through time is this thing called “entropy” — but that’ll have to wait for another day.
So why are we hurtling uncontrollably towards the future? Why can we remember yesterday but not tomorrow? Why do causes usually happen before effects, and history textbooks only talk about the past?
One of the greatest mysteries of our Universe is this dumb-sounding question: Why does time go forwards and not backwards?
More on this: Stanford Encyclopedia of Philosophy, Time
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Originally published at milobeckman.com on February 19, 2015.
