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What If Time Moved in Two Directions? | Unveiled

VOICE OVER: Peter DeGiglio WRITTEN BY: Dylan Musselman
What if backwards time was possible? Join us... and find out!

Time's arrow moves in one direction, only - forwards! But, what would happen if it didn't? Physics actually allows for backwards time to exist, we just don't experience it in our universe... So, in this video, Unveiled looks at what the world might've been like had out temporal reality developed differently!
Transcript

What If Time Moved in Two Directions?


When you really think about it… everything is only a matter of time. We build our days, our weeks, our lives around how the clock continues to turn. Sometimes time drags and we may have time on our hands… but also it can feel as though time flies, we can find ourselves running out of time and before we know it… our time is up. In an alternate world, though, on another plain of existence, it needn’t be this way.

This is Unveiled and today we’re answering the extraordinary question; what if time moved in two directions?

Humans have been thinking about time for tens of thousands of years, but our progress toward truly understanding it has been… slow. The Ancient Greek philosopher Aristotle’s definition had until recently stood for millennia, with the great thinker describing time as “the calculable measure of motion with respect to before and afterness”. That line went mostly unchallenged for more than 2,000 years until one Albert Einstein came along, pitching various theories and developing our modern, more layered view of what time is. Still, we can at least say one thing; that time moves in a straight line. Or… can we?

Let’s scale it back. The time that we all use in our everyday lives - the measure of seconds, minutes, and hours - has its origins back with the Ancient Sumerians of Mesopotamia. They were the first to use sundials in an attempt to track time throughout the day. In general, we’ve used this or similar time keeping methods for thousands of years since, although we’ve obviously updated and improved them along the way. The modern measurement of a second, for example, is actually defined by the subatomic transitions of Caesium-133 atoms, which provide an extremely consistent and accurate period for what’s known as the Caesium Standard. The position of the sun in the sky really has very little to do with it.

Regardless of how we measure time, however, how we appreciate it has changed. For the great physicist Isaac Newton, time was absolute and no matter where you were in the universe it would run the same. But, of course, around three centuries after Newton, Einstein showed us that time is relative… that by simply moving through space faster, time is slowed for you relative to someone standing still. It was a major breakthrough. But still, irrespective of the relative speed at which it passes, it would seem as though time continues to move in one direction.

Most of the laws of physics have no objections to time moving in more than one direction, however. They work the same whether time moves forward or backward. And, indeed, there’s many an eye-catching theory - particularly regarding the possibilities of a multiverse - where time must move backwards. So why, from our perspective, is time an arrow? The most prominent theory refers to the second law of thermodynamics. It says that entropy, or chaos, is always rising in a closed system. So, since entropy can never be reversed, we might conclude that that’s why time never moves backwards.

But what would the world be like if it did? To understand this, let’s consider the dimensions we know, including time (the fourth dimension). Just as drawing a line between two dots creates the first dimension, drawing a line of progression from your birth to your death creates the fourth dimension. If you were able to live and move in this fourth dimension, you’d see your future and past stretched out before you something like a slinky, with each ring representing a different period in your life. Perhaps even a different moment. You’d be able to view, and maybe even visit, each of these moments, either before or after they had happened to you - moving through time much as you’d ordinarily move through three-dimensional space. Sounds exciting, doesn’t it?

In the real world (as we understand it), however, the downside is that living in the fourth dimension might not work for humans. After hundreds of thousands of years of evolution, we are by now so used to the arrow of time that our brains may be incapable of comprehending such a massive change as a world where time moves in more ways than one. In fact, the arrow of time remaining unchanged appears to be crucial to the existence of anything inside this universe, thanks again to entropy and the second law of thermodynamics. These are problems that have long been debated by scientists and philosophers, although the physicist Sean Carroll has particularly spoken at length, and in multiple interviews, about just how thorny and complicated the concept of time’s arrow can be.

But let’s now imagine that backwards time is possible, and that we can understand, use, and experience it. At this stage it would be as though we were all time travellers, although we’d all only be able to view our own lives. Time may have existed before you were here (and may continue to exist after you’re gone), but your gloriously, multi-directioned experience of time in the fourth dimension would still be limited by your own personal start and end point. Your own personal birth and death. You could revisit your first day on Earth or witness when your last will be, but you’d never be able to go back and see the dinosaurs. To do that, you’d have to rise through the dimensions to the fifth, sixth and, depending on the model you subscribe to, maybe beyond.

Time moving backwards seems impossible to us on our relatively simple plain of reality, but various physicists speculate that there are entire universes out there where time does move backwards with no issue. Julian Barbour, Flavio Mercati and Tim Koslowski are the three leading voices in favour of something called the Janus Point - a kind of theoretical space between universes, where the so-called arrow of time splits into two like a river does. In our reality, the Janus Point is effectively the Big Bang. Since then, we’ve existed on one side of the split, experiencing time as we do… but there was also a mirror universe born. One that’s totally out of our reach, where time moves backwards from our point of view.

So, finally, what would it be like were our universe and the proposed mirror universe to somehow fuse? It’s not something that any theory or model suggests could happen, but it would make for an interesting life. Were the future and past to mix, and should you still be able to move to any point in time yourself, then events would no longer follow any order at all. Now, the concept of cause and effect would no longer exist, so all moments in any life would be and feel random. On a small scale, you might find food reappearing on your plate after you ate it. More significantly, you could witness a car crash happening before either car was present, or even manufactured. Or long before even the driver was born… or long after they had already died.

Because most fundamental laws like gravity and quantum mechanics should all still work, there’d be no outright collapse… but it could still be torturous. It would be like moving off of a steady, one-way conveyor belt guided by time’s arrow, and moving into the drum of an infinite washing machine so that you’re thrown about the place forever more. Or, in one scenario, you could get caught between each of time’s directions, so that you end up living the same day, or the same time period, moving forwards and backwards again and again. At first glance, time moving in two directions should grant anything able to experience it with far greater freedom… but, in this case, you’d be horribly and completely trapped.

What’s key is that while this is a wholly hypothetical scenario, the question of time is one that we’re still far from answering. In Newton’s age, it was as though there was a master clock in the universe that never changed. Now we know that there’s no such thing, and that time is relative. Yet still, we so often think of time as moving in one direction only. But physics doesn’t demand that. The arrow of time, it seems, isn’t a prerequisite for life, the universe and everything. It’s just crucial for this universe and this life.

For as long as we humans remain lowly, three-dimensional creatures, we may never truly understand how time works. And if this particular alternate reality were to be suddenly thrust upon us, then it could well prove too much for our brains, perhaps even our universe, to handle. But that’s what would happen if time moved in two directions.
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