The Nobel Prize for Physics in 2022 made for some pretty big headlines because it acknowledged that the universe is not “locally real.” But that phrase doesn’t necessarily mean what a lot of people think it does. Here’s what it actually means, and why it is worthy of the biggest prize in physics.

TRANSCRIPT:

A few months back in October of 2022, the Nobel Prize for Physics was awarded to John Clauser, Alain (Ah-lawn) Aspect, and Anton Zeilinger (Zigh-ling-er). And you probably saw some headlines about it.

A few months back in October of 2022, the Nobel Prize for Physics was awarded to John Clauser, Alain (Ah-lawn) Aspect, and Anton Zeilinger (Zigh-ling-er). And you probably saw some headlines about it.
Nobel Prizes usually make headlines but these were a bit more bombastic than most. Claiming that they won it for proving that the universe… isn’t real.
And you thought this channel gives you an existential crisis.
But in this case, we’ve got a rare switcheroo, where the news headlines will make you question the nature of reality and I’m here to say… Eh.
When did I become a debunking channel?
The fact that this was awarded the Nobel Prize is really more of a confirmation of theories that have already been widely accepted by the science community – I’ve even talked about it here before.

But, it is interesting stuff. And it does reinforce that the universe is way weirder than we can possibly imagine. On the smallest scales anyway.
So let me do my amateur best at breaking this down. No, the universe is not locally real. But here’s what that actually means.
So on this channel, I get corrected a lot. Like… A lot. I’m sure many of you are warming up your fingers to straighten me out in the comments already.

One thing and this is super pedantic but hey, we’re talking about internet comments here, is whenever I use the word “theory” in the casual, general audience way.
Like if I said I have a theory about why butts have cracks, people will be quick to point out that it’s not actually a theory… it’s a hypothesis. And then ask if I’m okay.
And yes, in a scientific sense, my buttcrack idea is a hypothesis to be tested and not a theory to serve as a basis for knowledge.

But the word “theory” does have a more casual use that laypeople use in the everyday world that doesn’t mean the exact same thing as a research scientist would use it.
And this is kind-of the same thing, when physicists say, “The universe is not locally real,” there’s a different scientific meaning to those words than the layperson might hear.

Luckily for science communicators and nerdy websites, that layperson meaning is pretty clickbaity.

So let’s break this down, what does it mean that the “universe is not locally real?”

Also keep in mind I’m not an actual scientist. But I’ll do my best. Now… let’s go back in time.

Whoa… too far. Let’s jump ahead a little.

All right this works. So ever since scientists and philosophers existed, they have pondered the nature of light. Because some experiments seemed to show it behaving like a wave, some like a particle.
This was a problem that vexed the greatest thinkers of their day like Thomas Young and Sir Isaac Newton.
Flash forward to 1905, Albert Einstein built on the work of Max Planck to show light can be divided into discrete quantities, called photons. In other words, he showed that light was a particle. And there was much rejoicing.

The problem is… they only acted like particles when they were emitted and absorbed. When they were moving through space, they acted like waves. Which was an annoying thing that all quantum objects seemed to do.

Or, according to Max Born, the German-Polish mathematician and grandfather to Olivia-Newton John… No, really. As he said about his work with quantum collisions,  “One does not get an answer to the question, ‘What is the state after collision?’ but only to the question, ‘How probable is a given effect of the collision?’  From the standpoint of our quantum mechanics, there is no quantity which causally fixes the effect of a collision in an individual event.”

The Realist Debate

What Born was advocating for, here, is called the statistical approach to quantum mechanics, or QM.
And to translate that for all us non-grandfathers of Olivia Newton John, it basically means that until a quantum particle is measured, it has no definite values. It only exists as a statistical probability.
It’s like saying that when an archer fires an arrow, from the moment it leaves the bow until it hits the target, it only exists as a cloud of probabilities.

Obviously with a macro object like an arrow or a baseball or a cow (Monty Python), that’s totally absurd, but in the quantum world, that’s how things work. And that was proven true in experiment after experiment after experiment.

And that’s QM, quantum mechanics, many of you already know about this, but it was a radical new science at the time, promoted by Niels Bohr, Werner Heisenberg, and Max Born, they’re considered the founding fathers of QM.
Does that make quantum mechanics Olivia Newton-John’s father…? I’ll stop now.

One person who wasn’t on board with statistical QM was Einstein. Einstein HATED this idea. In fact, he wrote in a letter to Max Born in 1947: “I cannot seriously believe in it because the theory cannot be reconciled with the idea that physics should represent a reality in time and space, free from spooky action at a distance.”
Stick a pin in “spooky action at a distance.”

We’ll get back to that.

Einstein and those like him became known as “realists” because they believed that a particle was a particle was a particle was a particle, it was a real thing from start to finish. The whole idea that a tiny piece of physical matter could become a math equation was ridiculous.(meme of Einstein with caption, “Get Real”)

Likewise, statistical thinkers like Born, Heisenberg, are Bohr became known as non-realists. Because they believed that’s exactly what happens.
I should point out that individual theories vary, and there are probably as many nuances as there are people who take each side.

So, to go back to our original statement, “The universe is not locally real,” the “real” part of that refers to that argument, whether or not unmeasured particles exist as a physical particle or a statistical probability.
In other words… Einstein was wrong. But he didn’t go down without a fight.

There was a famous conference that happened right in the middle of this melee called the Fifth Solvay Conference where Einstein and Bohr had it out in a big debate, and Einstein challenged other realists to prove the non-realists wrong, which led to a whole slew of thought experiments, the most famous of which is Schrödinger’s cat.

Schrödinger’s Cat 

Apparently Erwin Schrödinger had a great aunt who was a crazy cat lady, so it was only natural that he imagined shutting one of them in a box.
Most of you are probably familiar with Schrödinger’s Cat, the idea being that you put a cat in a box with a vial of poison that would break or not break according to the behavior of a quantum particle, the argument being that if unmeasured particles are just probabilities, then until you look in the box, the cat is both alive and dead at the same time, which is obviously ridiculous.
Which…  I always thought that Schrödinger’s Cat was meant to explain quantum mechanics, like it was an educational tool, but he was actually arguing against it.

I think a lot of people get that confused, I know I did.
Something else that a lot of people don’t know is that in that same paper where he outlined this thought experiment, he also first coined the term “entanglement.”
This was actually inspired by another paper that year from Einstein and two other physicists, Boris Podolsky and Nathan Rosen.
In this paper, they tried to prove the realist case using the concept of entanglement, but it was so new, it didn’t have a name yet.  It was actually Schrödinger who named it in his cat paper.

Quantum Entanglement

So, entanglement, what is that exactly? Simply put, it’s when the value of a property in one quantum object implies the value of the matching property in another.  (beat) Simpler put, it’s when the properties of two particles are linked.

Electrons, for example, have a property called spin.  It’s possible to entangle two electrons so their spin will measure as opposites. So if you measure the spin of one electron as clockwise, you know the entangled electron spins counter-clockwise.
Although… electron spin is not the same as like the spin of a basketball, it’s a different thing based on angular momentum but for both our sanities, let’s save that for another time.
But still, even if particles are entangled, you only know that after measurement. Before that, values of both particles only exist as statistical probabilities.

The EPR Paradox

So Einstein, Podolsky and Rosen asked what happens when entangled objects are separated, and you measure the values of one of them. Does the other one snap out of statistical probability? And if so, how does it know to do that?
This is the “spooky action at a distance” that I was talking about earlier, also known as the EPR Paradox. Named after Einstein, Podolsky and Rosen.

In the paper, they argued that there must be something else going on here, you can’t just have two particles communicate with each other across space and time, that just makes no sense.
They suggested that if you can predict a quantum object’s properties, something has to make those predictions come true.  They named that “something” hidden variables.

Non-realists say hidden variables don’t exist.  Physics is pure statistics.  There’s nothing but math all the way down. Which is the most hellish version of reality I can think of…
In the years after the EPR paper was published, there were several different hypotheses put forth with different takes on hidden variables, the problem was the technology hadn’t progressed to the point that this could actually be tested.
Einstein spent the last years of his life trying to solve this problem, and never quite got there. In fact it would be nine years after he died before someone figured out a way to test if the universe is real.

Locality and Realism

That test had to do with the “local” part of the headline.
In physics, locality means no two objects can influence each other faster than the speed of light.  Einstein believed in locality.  It was a big part of his special theory of relativity.
So “local” doesn’t necessarily mean close to each other – light from Alpha Centauri is “local” – it just takes 4.3 years to get here.
So to Einstein, a complete theory of physics would explain particles as real and their influences as local.  In other words, “locally real.”
But some in the realist camp aren’t so picky.

Bohm’s EPR and the Universe According to Bell

Take Pilot Wave Theory. I did a video about this a while back, it was proposed by David Bohm, anyway, with pilot wave theory, the  universe is real, but not local.

And in the paper where he proposed Pilot Wave, Bohm and his academic advisor Yakir Aharonov outlined a theoretical experiment to test the paradox using our old friend particle spin.
“Theoretical” is the key word here. They didn’t actually know how to pull it off.

Aharonov is still alive, and his niece is a quantum computer scientist mentions different ways of changing axes, which is why I gloss over the detail

But in 1964, the Irish physicist John Bell read the paper and was inspired to figure out the spin experiment.

Yes, so far in this video, I have talked about Born, Bohr, Bohm, and Bell.

Anyway, what Bell did was he came up with two formulas, one that would reflect a universe with locally-real hidden variables, and one that reflected non-realist QM.
And long explanation mercifully truncated, when Bell ran the formulas, he found they disagreed. The outcomes were fundamentally different in the universe with hidden variables from in the one without.

And his big takeaway from all that razzmatazz is that local hidden variables and quantum mechanics don’t mix, an idea now called Bell’s Theorem. Or, Bell’s Inequality.
In mathematics, an inequality is any formula where the two sides are not equal so like 1 + 2 = 3 is an equality but 2 + 2 > 3 is an inequality. In Bell’s example, QM does not equal hidden variables. So there you go.

But to prove this theorem requires more than fancy math, you’ve gotta do an experiment, which he proposed and called it the Bell Test, because he liked putting his name on things.
But once again, the technology to perform the test didn’t exist yet.
Coming up with runnable Bell tests, and using the results to shed light on physics is how John Clauser, Alain Aspect, and Anton Zeilinger won the Nobel Prize.  And I mean “shed light” literally.

John Clauser

Because they used photons to test the Bell inequality.  Photons act differently than the particles Bohm and Aharonov proposed checking for spin.
In 1969, John Clauser teamed up with physicists Abner Shimony and Michael Horne, and physics student Richard Holt, to work out how to use them in a Bell test.

By the way, I know I’m throwing a LOT of names out there right now, you don’t need to know exactly who all these people are, but I’m saying their names because they are reflected in some terms that you might have heard before, so it’s just context, bear with me.

Anyway, they broke from the initial idea that Bell had because Bell imagined measuring the spin of particles as perfectly up or perfectly down. Which is incredibly hard with photons.
So Clauser and his colleagues just… relaxed that rule

The result was an experimental setup that uses light to test the Bell inequality while accounting for imperfect results. And in 1969, it was named the CHSH Inequality. And now you know why I said all those names earlier.
And you’re going to have to forgive me for being intentionally vague for the purposes of this video, this is literally stuff that Einstein couldn’t come up with. I know my limits.
But simply put, any experiment that violates the CHSH inequality disproves hidden variables and is considered proof of statistical quantum mechanics.

Still with me? All right.

Three years later (1972), Clauser and his colleague, Stuart Freedman, ran the first successful Bell test.  And their results violated the CHSH inequality.
And somewhere in the afterlife, Einstein cried.

Actually Clauser was also disappointed.  He later admitted he wanted to “shake the world” with a hidden variable win.  But he’ll just have to settle for a Nobel Prize.
But, he shared this prize with two other people, because there were still some loopholes in the theory and they helped close them.
So let’s talk about Alain Aspect real quick.

Alain Aspect

First of all, the year after Clauser’s big experiment, so 1973, Richard Holt ran a separate test.
Holt if you remember was one of the H’s in CHSH. I… don’t know which one.
But his test actually satisfied the CHSH inequality.  So maybe hidden variables were a thing!

But his hidden variable acted like a ghost in the machine.  It was kinda determined by how the measurement was done.
But Alain Aspect broke the tie by introducing a random element to his measurements so that the measuring devices couldn’t influence each other.
Specifically, he changed the polarization of photons while they were on the way to a filter.  The filter would either block photons or let them through, depending on the polarization.

This randomness let Aspect prove his measuring devices weren’t pre-determining the outcome.  Anyway, this was a big hit in the physics community, and it continually violated the CHSH inequality in multiple runs in labs all over the world.
This was another nail in the coffin to the hidden variables theory, and a big win for the non-realists.

Anton Zeilinger

But the theory still wasn’t 100%. There were still a couple objections and loopholes that the realists would point out, and that’s when Anton Zeilinger stepped in and said, “Hold my Pan Galactic Gargle Blaster.” Apparently he’s a huge Hitchhiker’s Guide to the Galaxy fan.
So Zeilinger did his test in 1998, but long before that, he had worked with entangled particles.  There’s actually a type of entanglement called the GHZ state.  The Z stands for Zeilinger.

His experiment addressed one of the objections to Aspect’s test, which was that his method of polarization was “predictable into the future.”  In other words, his randomization wasn’t random enough.(on screen: In collaboration with Gregor Weihs, Thomas Jennewein, Christoph Simon, and Harald Weinfurte)https://arxiv.org/pdf/quant-ph/9810080.pdf — dated 2008 on the PDF; I think this is a revision, as the submission date to arxiv is in 1998

So what they did was they used a “physical random number generator” that took the form of a light-emitting diode and a beam-splitter.
The light from the diode was nonpolarized, so the chance of its exiting the splitter in one of two directions was as random as anything science can get.

They also placed their measuring devices so far apart, they could  eliminate any chance of communication.
And, as you may have guessed, it worked. It closed the last loopholes and objections to the Bell test and to date anyway, no result has seriously challenged the completeness of statistical quantum mechanics.

In other words… the “non-realists” were right. Einstein and the realists were wrong. Quantum mechanics is super weird.

You Still Gotta Work

So, none of this is anything you haven’t already heard. We all know the quantum world is weird, hell, it’s a major plot point in the Marvel Cinematic Universe.
This year’s Nobel Prize simply honors the physicists whose work proved this theory beyond a shadow of a doubt. And rightfully so.
But because of the language used in the announcement, there were all these headlines saying “the universe isn’t real” like they proved simulation theory or something, which… No.

Frankly, I take offense to this because it’s MY job to give people existential dread, buddy.
So no, this doesn’t change anything about the world you live in, you still have to go to work tomorrow. Sorry.

Quantum Computing

On the upside, the more we understand about quantum mechanics, the better our future quantum computers can be.
Anton Zeilinger in particular has built a career on using entanglement to push the boundaries of quantum computing.
Maybe someday there will be a Nobel Prize for quantum computing and the headlines will say, “God is found in cheese.” Somehow.

So listen, when it comes to quantum physics.. I’m a filmmaker.
There’s some details that I totally left out in this video because as I said before, I know my limits, but I’m putting links to everything in the description. Lots of links.
I just thought I’d talk about this because I did get a lot of requests about it. It took me a while to get this out so hopefully it maybe filled some gaps in what you’ve already seen. Because I know a lot of other people have covered it.