Does Time Really Exist?
from Through the Wormhole; For most of us, time was a set of numbers we use to gauge our days. Is time a real thing built into the Universe? Or is it just an abstraction, something we humans created to keep our civilizations running? For the answer, we have to ask a deceptively simple question what is time? Think about it. Try to define it. It's not easy. Time is what keeps everything from happening all at once, and so time is that part of the world that orders events in a certain way so they happen sequentially, from beginning to end. What we're realizing in neuroscience is that time is not what we thought it was. Time just does not exist. What exists is these distributions of everything in the world, these what I call "Nows." That's the real thing. What I enjoy about time is the recording of it. To Roger Smith, time is money. His custom-made watches sell for hundreds of thousands of dollars. In 1884, a world conference decided that the meridian line that passes through the observatory at Greenwich was to be the Initial Meridian the master time for planet Earth. Greenwich Mean Time is our best approximation of time as described by Sir Isaac Newton a steady beat pounding behind the scenes of the Universe. Lee Smolin is a theoretical physicist trying to solve the mysteries of time. Newton's concept of time was that it was absolute. The problem with this is that it's actually impossible for any of us to detect absolute time. We don't detect absolute time. We detect time as relationships between things that happen, and we can illustrate this by asking the musicians to start up the music. One, two, three, four. And they start to play, and they develop time between themselves, a relational time completely built from the relationships between the notes they're playing, the events they're creating. That's what time is really like. Sean Carroll is a physicist at the California Institute of Technology. In fact, time and space are one thing called space-time, which is four-dimensional. That's what we live in. That's what we move in and live our lives through. Einstein furthermore realized that gravity is a manifestation of the curvature of space-time. You have stuff in the Universe you know, a planet or a black hole or some kind of mass or energy it warps the space and time around it, and that's what we see as gravity. And it really is the space-time that gets warped. It's time as well as space. So, if you travel close to a strong gravitational field, you feel the flow of time differently than in outer space. The relativity of time causes a lot of strange effects, such as time running faster for astronauts than people on Earth. But Einstein's solution to the mystery of time opens up an even more challenging notion. If we look around, we see that all of space exists right here, right now. So, doesn't it follow that all of time past, present, and future already exists, as well? Could it be that the future is already here? Physics says that all the moments of time are equally real, and that tempts us into saying that they all exist simultaneously, they all exist now, but that's not what it's like. Different moments of time are really like different places in space. They're not here. They exist, but they're somewhere else. David Eagleman of the Baylor College of Medicine has spent much of his career puzzling out how humans perceive time. He's found that our perception of time is governed by biological and psychological states. This is another case of memory warping time. What happens during a really high-intensity event is you have an emergency control center in your brain that kicks into gear and lays down very dense memories during that event. When you snap your fingers, it looks like it's simultaneous. It looks like the sight and the sound are happening at the same time. But in fact, what's happening is your auditory system is able to take information coming in through the ears and process that very quickly, whereas your visual system is much slower. So, what happens is your brain hears the sound, and then it sees the sight, and somehow it has to take both of those and stitch them together and serve up a single story, which is that they were simultaneous, even though the signals are arriving at the brain at different times. This whole thing is really smeared out in time, and yet it doesn't feel that way to us. Time seems to vary from person to person, and the elastic nature of our subjective time has caused David to wonder whether time is, in fact, real. I think that time might be the most stubborn psychological filter that we have, and that when we start really reaching down below that, when we start really figuring out how time is constructed by the brain, we're going to have to go back to physics and rejig all of the equations there. Is it possible to eliminate the human factor and pull time completely out of our physical description of the Universe? This man says "yes." He's rejigged Einstein's equations, and he's found that time may not exist at all. Declaring that time is an illusion may sound radical, but the denial of time is an old idea 2,500 years old. In 500 B.C., the philosopher Parmenides declared that motion is impossible because for an object to move any distance, it would have to pass through an infinite series of fractional steps to get from one place to another, and no one can take infinite steps. And if motion is impossible, then change is also impossible. So, therefore, time must be an illusion. No one knew quite what to make of this. Surely, motion is real. Things do change and time does pass, right? Maybe not. In an ancient village in the English countryside, this man thinks that the laws of quantum physics prove that Parmenides was right. His name is Julian Barbour. Decades ago, he began carefully laying out a mathematical case that the Universe doesn't need time, which is a bit odd, as he's surrounded by the past. We're standing in the town, which is a very ancient street, and behind me is my home, built 1659. Newton was 17 then, just seriously beginning to think about time and motion. If time doesn't exist, what's all this? To Julian, everything we see is an archaeological dig. Things are there first, and time is deduced from it afterwards. He believes this 1,000-year-old church and these 14th-century wall paintings are proof that the whole of time exists in slices of space. Our past is just another world, or it's another possible configuration of the Universe. It's another now. And this is literally true. The instant is not in time. Time is in the instant. Julian's radical view of time grows out of the Wheeler-Dewitt Equation, a mathematical exercise from the 1960s that sought to reconcile Einstein's Relativity with quantum mechanics. A strange thing happens when you do this. You're left with an equation that has no "T" for time. Since this runs counter to observable reality, most saw the equation as further proof that quantum physics and relativity theory don't play well together. But to Julian, it was a revelation. There is no unique history in quantum mechanics. And if the evidence from the attempts to combine quantum mechanics with Einstein's General Relativity is right, there is no time at all. So at the deepest level of reality, time doesn't exist. What matters is how objects relate to each other in freeze frames of space. My view of the Universe it's just like a huge collection of snapshots which are immensely, richly structured. They're not in any communication with each other. They're worlds unto themselves. But each world is so rich that it's, so to speak, part of this world. It's snapshots within snapshots. This is really what our life is about. According to Julian, all of these snapshots of the Universe exist simultaneously. Time really is real. The idea that time is an illusion has ignited a civil war in physics a war that pits friend against friend. Is time an illusion we create to make sense of the Universe? Neurologists and physicists say it might be so. But there's another camp that says we can't ignore what our senses and observations tell us, that time really does exist. In this view, we experience the world as a flow of moments because that's the way nature is. Passage of time is a basic truth and, in fact, may be the one true thing in the Universe. Tim Maudlin is a philosopher of physics at Rutgers University. To say that the passage of time is really an illusion suggests that it's not really, really the case that I'm getting older all the time, that I should be worried that my death is, every day, one day closer to me and so on. But I just can't believe that. As hard as I try, I can't believe it, and it doesn't fit with the world I live in. For Tim, it is just common sense that time exists. So, why do some physicists deny it? Tim thinks it's an occupational hazard of working with math. Our representations in physics are all mathematical, and mathematical objects are not in time. Mathematical objects don't change. So, if you work too much with numbers and numbers don't change and you're using that to represent the world, it might seem hard to see how the world itself can really be changing. People seem to be stuck on the idea that the world has the features of the mathematics that they use to represent it. That allowed people to get carried away with their mathematics and lose sight of the physical world. Julian Barbour believes space is all there is and time is an illusion. Tim says Julian has got it all wrong. We need time, but we don't need space. We can make space not fundamental, but time remains fundamental. There doesn't have to be anything more than time, and you can't do it the other way around. You have to start with space and then get time. So, time is at the very bottom level. I think even this is what the physics is telling us, although we haven't been paying enough attention to it. Did space come first... Or did time come first? This argument leads all the way back to the explosive birth of our Universe the Big Bang. Physicists agree that the Big Bang created space. They don't agree on whether it also created time. There's a lot of people in physics and philosophy who think that time is an illusion, that what's really true at the deepest, deepest level is timeless, is outside of time. And I don't believe that. I used to believe that, but I've come to believe that time is really, really real. Lee Smolin believes that time is older than the Universe it was here before the Big Bang, and it will be here after the Universe ends. And he thinks he can prove it by looking closely at how particles of light behave over long distances. In theory, physics doesn't seem to need time, and yet we feel ourselves moving through it. If time wasn't born in our minds, then where did it come from? Sean Carroll thinks he knows. Sean is a theoretical physicist at the California Institute of Technology. Time is real. We use it every day. The evidence is all around us. But as scientists, the more we think about what time really means, the more mysterious it becomes. Sean accepts the common-sense idea that time moves forward from the past to the future, like an arrow. But why does time have a direction? Sean believes the answer is closely tied to something called entropy. Our Universe seems to be out of balance. The far, far future is going to be a very, very disorganized place, but the far, far past was highly organized. As physicists, this kind of imbalance really bugs us.
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