#211 - Jim Al-Khalili - Reality Is An Illusion: Quantum Entanglement, Time & Dark Energy

Jim Al-Khalili (0:00)

Where all the mass of the star has now accumulated in a point of zero size.

How can that be, you know? Yeah, it doesn't make sense. But that's the thing, that's where physics breaks down. Basically, what they showed was Einstein was wrong. He couldn't restrict communication below the speed of light. These entangled particles really are communicating non-locally. The fact remains, quantum mechanics is non-local in conflict with Einstein's ideas. So, their view was nothing really exists until you measure it, right? All you can ever say about the quantum world is the results of measurement. You can't look behind the quantum curtain. She went completely against what astronomy had taught us. No one thought it would expand ever more quickly. So, she said, what's causing that?

Well, I don't know. Let's come up with a name. Call it dark energy. As a placeholder, we know something is causing the expansion of the space to accelerate.

Peter McCormack (1:00)

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Here we go, Jim. Nice to meet you.

Jim Al-Khalili (1:27)

Likewise.

Peter McCormack (1:27)

Very excited to talk to you because I look up at the sky and I'm trying to understand what's going on, why we're here, and I'm also quite introspective right now. I'm 47 I'm thinking a lot about time, an awful lot about time. I don't know how much I've got left.

But I was listening to your Mindscape podcast, and it struck me that there are probably multiple explanations of what time is. Most people think of time as a clock. That's our creation of time, but that is not time itself.

Jim Al-Khalili (1:59)

No. I mean, I think most people think, well, it's obvious. Time is that thing that clocks measure. Time is the seconds, minutes, and hours. No.

We invented clocks. We invented the units of time, the seconds, minutes, hours. Okay, we didn't invent the day and the year. That's about the Earth's spin and orbit around the Sun. But that isn't time itself. Time existed long before humans turned up.

What I find fascinating is this difference between what I call manifest time, which is our psychological experience of time, which seems so common sense. Then there's time in physics, in the laws of physics. The two are very different and they butt up against each other. What we think of as time is very different from the way it appears in the equations of physics that I study.

Peter McCormack (2:45)

Where are they kind of butting up against each other?

Jim Al-Khalili (2:47)

Well, for example, one of the most obvious things about time is that it flows. There's the flow of time. We move our now, our present moment moves towards the future all the time. Whether it's time flowing past us or we are moving through time doesn't really matter. But there's no notion of a flow of time in the laws of physics. Time just is.

There's no, even though there's change and things are changing all the time, there's no actually notion of something moving along what we call the time axis.

All times are just there. They exist.

Peter McCormack (3:23)

Is it that there is a requirement for an arrow of time?

Jim Al-Khalili (3:26)

Well, again, so there are three things. Does time flow and physics says no?

Is there an arrow of time, a direction of time? Again, so obvious. Clearly, the past comes before the future. It doesn't work the other way around.

There, there's a bit more meat to it and physics can get into it and say we can argue about whether or not there's an arrow of time, why there's an arrow of time, what gives time its direction, what makes time irreversible. Physics has something to say about that. Then the third thing is, what does now mean? What is the present moment?

I love it. Going all the way back to the ancient Greeks, there's been this debate about whether time is just an illusion. The future hasn't happened yet, so that doesn't exist yet. The past has happened, that no longer exists. All that's left is the present moment, the now. Yet now doesn't have a duration, it's just the dividing line between past and future. Ever-changing, but it doesn't exist in and of itself. If past, future and present all no longer exist, then time must be an illusion. A lot of philosophers have argued that. Obviously, people like Einstein come along and say the opposite, but no, actually all times exist. All times are equally real. That's the fascinating bit.