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Decoding the Universe: Quantum | Full Documentary
When we look at the world at the tiniest scales in the subatomic realm, things get weird – very weird. Welcome to the quantum universe, where particles can spin in two directions at once, observing something changes it, and something on one side of the galaxy can instantly affect something on the other, as if the space between them didn’t exist. Buckle up for a wild ride through the discoveries that proved all of this to be true and paved the way for the digital technologies we enjoy today – and the powerful quantum sensors and computers of tomorrow.
The following NOVA program contains scenes of quantum physics, which is known to cause confusion, anxiety, and even heartbreak. Please see your physicist if symptoms persist. Quantum physics, it’s the science of the very small, but it punches far above its weight.
Quantum physics has not just been important, it’s been revolutionary. It’s the most successful scientific theory of the last 100 years. Quantum mechanics already permeates everything we do.
Everything from your computer or cell phone to how we keep time depends on our understanding of the quantum world. We could say now that we live in a quantum age. And it’s behind one of the greatest discoveries in the history of science.
Gravitational waves. Tiny ripples in the fabric of spacetime itself. Gravitational waves give us a whole new way to look at the universe.
And yet, beyond the mathematics, quantum physics makes a shocking claim that at its deepest level, reality plays like a game of chance. Probabilities are not a measure of what we don’t know. They’re just intrinsic to the quantum theory.
With mind-boggling behaviors like superposition and entanglement. This is weird. It’s strange.
What quantum physics really means remains deeply mysterious. But it’s created the world we live in today. Quantum physics actually governs everything around us.
There’s not some weird outpost of physics that’s far away. It’s completely changed the way we used to live into the way we live now. Decoding the universe.
Quantum. Right now on NOVA. As an American-based supplier to the construction industry, Carlisle is committed to developing a diverse workplace that supports our employees’ advancement into the next generation of leaders.
From the manufacturing floor to the front office, learn more at carlisle.com. December 12th, 1970. NASA launches a Scout B rocket from a former oil drilling platform off Kenya’s coast. Its payload is a small satellite named Uhuru, a Swahili word meaning freedom.
Uhuru is the first space telescope dedicated to observing x-rays, high-energy light waves invisible to our eyes. Powerful sources of x-rays constantly bombard Earth, but our atmosphere blocks them. With this groundbreaking telescope, a new vista for exploration opens.
But buried in the data collected from Uhuru is something ominous. In 1971, scientists revealed that the constellation Cygnus, the swan, contains what until then was more of a mythical mathematical beast. A black hole.
Black holes are the most mysterious objects in the universe. Also the most violent. Even Einstein didn’t think nature would allow such a crazy object.
Black holes are fearsome monsters capable of devouring whole planets, whole stars, each other. A black hole is created when gravitational forces bring together enough mass to put a rip into the fabric of spacetime. Some of them are genuinely monstrous.
I mean, millions, billions, maybe even 10 billion times the mass of our own sun. We don’t actually have a lot of physics to predict what’s going to happen to us when we go in. Hopefully none of us will experience it anytime soon.
In the decades since the first sighting, science has learned a lot about these menacing and mysterious objects of destruction. They aren’t that rare. Supermassive black holes sit at the center of most large galaxies.
We have one in ours. But it turns out these cosmic behemoths also may have an Achilles heel. First predicted by Stephen Hawking in 1974.
Scientists thought of a black hole as a one-way trip to oblivion that past its event horizon, nothing could escape. But Hawking disagreed. He theorized something did escape from these mighty giants.
Radiation. Ironically, the end result of physics at the tiniest of scales. Quantum physics.
Clifford Johnson is a nonfiction graphic author and also a theoretical physicist. One of the key things that was discovered in quantum physics is that empty space itself is not empty. It’s seething with possibility.
Instead of having empty space here, a particle and its antiparticle can appear, dance around a little bit, and then annihilate back into empty space. Now imagine that happening near a black hole horizon, which we’re told is a one-way door. What if one of those particles falls in? And now the partner doesn’t have anything to annihilate with, so it will actually fly off.
And a distant observer will see that particle as radiation coming from the black hole. Without consuming more matter, if it emits radiation, it will gradually shrink in size. The black hole actually begins to evaporate.
Now this is a completely stunning revelation. Known as Hawking radiation, its existence is still only a theory, but perhaps given enough time, and it is a very, very, very long time. For many black holes longer than the current age of the universe.
Even a supermassive black hole, like the one at the heart of the Milky Way, may evaporate and disappear. Vanquished by the quantum world and the physics of the very small. The quantum world is often cast as weird, and it sure can look that way in the movies.
You’re sending a signal down to the quantum realm. Where are we? But what is quantum physics? It arose as the solution to a problem. Science during the 19th century had investigated smaller and smaller amounts of matter and energy.
But by the first two decades of the 20th century, the existing line between the physics of particles and the physics of waves had grown murky. Especially when trying to understand the fundamental nature of light. Sometimes it really is important to describe light as a wave, as an extended object that sort of waves in space and travels over time, analogously to an ocean wave in the water.
Other times, as people like Albert Einstein and others began to find, they really, really had to describe aspects of light as if it was a collection of particles. It traveled almost like miniature billiard balls. Ultimately, the answer was a new kind of physics, quantum mechanics, which included an amalgam of ideas about both particles and waves.
Its earliest formulation dates back roughly 100 years. This 1927 conference in Brussels is where the world’s leading physicists met to discuss the newly formed theory. And there was a lot to discuss, because quantum mechanics represented a radical departure from the previous paradigm of physics, what we call today classical physics.
In classical physics, handed down by Newton, we had determinism. We had the clockwork universe. So if you throw a ball that’s a classical object with the same force, the same speed, the same angle, it’s always going to go to the same place, right? In principle, if you knew exactly the state of the whole world all at once, and you knew the laws of physics, you could exactly predict what everything was going to do, arbitrarily far in the future and into the past.
In classical physics, even events that we think of as random aren’t really. There are things that appear random in our everyday lives, like rolling dice. It looks random, right? But actually, it’s a deterministic set of events, which leads to whatever outcome the dice shows.
If I told you exactly how I was going to roll the dice. You could predict, based on that initial throw, what the final outcome is going to be. It’s a very hard mathematical problem, but it’s not intractable.
Quantum mechanically, that’s not the case. Quantum mechanics tossed out the certainty of the classical clockwork universe, for one that only allowed for probabilistic predictions about potential observations. Probability in quantum physics is different, because even if we have the most complete description that the laws of physics will allow us to have, typically, we’re unable to predict precisely what we’ll see when we observe a quantum system.
Quantum mechanics says we can know everything there is to know about the setup right now. And still, when we want to make a measurement of it in the future, the best we can do is say, there’s a 50% chance of getting this outcome, 30% chance of that, 20% chance of that. In the quantum theory, probabilities are not a measure of what we don’t know.
They’re just intrinsic to the quantum theory. We cannot get around them. That is impossible.
Some physicists raised on determinism had trouble accepting this new probabilistic view. Albert Einstein famously said that he didn’t believe God plays dice with the universe. But there is another related, even stranger aspect to quantum mechanics.
In classical physics, external reality is independent of the observer. Looking at the moon doesn’t change the moon. And if you look away, the deterministic laws of physics continue to guide the moon on its path.
But in quantum mechanics, things are weirder. The basic idea of quantum mechanics, the thing that we really struggle with to get our heads around, even as professional physicists, is that, unlike any other version of physics, quantum mechanics separates what happens in a system when we’re not observing it from what we see when we measure it. A few rare exceptions aside, quantum mechanics says that we can’t know the position of a particle like an electron when we’re not observing it.
At best, it can only be described mathematically as a wave, its exact position given in probabilities. But at the moment that the particle is observed, the probabilistic wave function collapses to one specific location. To the observer, who never sees this wave-like quality, it is like the particle was a particle all along.
That opens up a whole world of questions. You know, what happens to the observational outcomes that are not observed? What picks out which outcome is going to happen? This is still what we’re thinking about today. During that mysterious period, when the particle is considered neither here nor there, it is said to be in superposition.
In a sense, a combination of all the possible outcomes. But what does that really mean? Is the electron everywhere at the same time? Is it nowhere at all? Is it at one place and we just don’t know? All of those questions are actually outside of what quantum theory itself actually can answer. It’s not part of the theory at all.
So if you ask me, your guess is as good as mine. Unfortunately, that’s the best I can do. For most people, quantum mechanics remains deeply unintuitive.
And yet it has proven itself again and again by making predictions with uncanny accuracy. In practical terms, it is the most successful theory science has ever produced. And it has shaped our modern life.
Quantum physics has not just been important, it’s been revolutionary. It’s completely changed the way we used to live into the way we live now. Take our sense of time.
Perhaps there is no better illustration of our intimate relationship with it than music and dance. The underlying movement of tango is reliant on the beat, which is reliant on timing, which creates synchronization. To create a truly smooth dance, it’s not enough to just be synchronized on the beat.
It’s also the synchronicity. Between the beats, that’s important. That’s the real beauty in it, in finding that connection through stretching out that second.
Tara Fortier is a tango professional. And a physicist deeply involved in the science of time. So we have a number of systems in this lab.
She works here. These systems are used to characterize atomic clocks and also compare atomic clocks. At the Boulder, Colorado laboratories of the National Institute of Standards and Technology, or NIST.
Home to some of the atomic clocks that help set the official time for the country. Over the centuries, we’ve tracked time a variety of ways. By the sun’s movement, the swing of pendulums, the oscillations of springs, and in the 20th century, the vibrations of quartz crystals.
But since the 1960s, time has been officially determined using atomic clocks and the quantum characteristics of atoms. And the idea is that the laws of physics aren’t changing. Unlike something like the rotation of the earth, the rotation of the earth itself can change because of plate tectonics.
Because the moon is moving away from the earth, its physics is not truly fundamental. The reason why we love atomic clock, it’s a universally defined time. No matter who does the experiment, no matter where you do the experiment, in principle, once you correct it for all the systematic effects, it should produce the same time no matter where.
The consistency of atomic clocks arises from the very nature of atoms. Atomic clocks depend crucially on the quantum physics of atoms. You have a nucleus around which there are electrons in certain energy levels.
And these energy levels are possible energy states that the electron can have inside the atom. Since an electron can only be at certain energy levels and not in between, to get to a higher level, it needs to encounter a very specific helping hand, such as a particular photon. So if it were to absorb an incoming photon, it would have to be of just the right energy to jump from one level to a higher level.
That special relationship between the electrons of a particular atom and a photon of a specific energy level is a unique signature for that atom. It’s called a resonant frequency. So this characteristic signature of this atom gives us a very specific frequency standard that we can use to build a timekeeping device.
Atomic clocks work in different ways, but they all use a specific type of atom or molecule as a reference to lock in the frequency of an electromagnetic wave, whose oscillations provide the ticking of the clock. Today, a second is officially defined by counting the oscillations of the primary resonant frequency of a cesium-133 atom. That’s over 9 billion oscillations per second.
And you interact with that time reference more than you might think. For example, through the Global Positioning System, GPS. Turn right.
I think that GPS is actually kind of crazy when you think about it. How do we do anything before GPS? The U.S.-based GPS system uses over 30 dedicated orbiting satellites, each with multiple atomic clocks. When you use the GPS on your cell phone, its receiver checks the signals from four or more satellites.
The signal contains information about the satellite’s position and the time it sent the signal. That timestamp is critical. Your phone uses it to calculate how long it took to receive the signal, and from that, knows the distance to the satellite.
With that information from multiple satellites, it is possible to triangulate the phone’s position within a few yards. But the whole system depends on knowing the time. In the end, I find it amazing how strongly we’re committed and tied to atomic clocks, and how much we take it for granted.
Even though I build atomic clocks, but when I’m driving, being guided by this GPS service, you don’t really become aware of how much atomic clock technology has permeated everywhere in modern life. Have you had a chance to look at more systematically varying the VZ? Jun Yi is a physicist with joint appointments with NIST, the University of Colorado Boulder, and their joint institute, JILA. What if you lock the exacting on top of each other and see whether that peak disappears completely? He works on the new generation of atomic clocks known as optical atomic clocks.
While cesium clocks use microwaves, optical clocks use lasers, which run at higher frequencies. That also means using a different atom. Instead of cesium, Jun’s work mostly uses strontium atoms, along with a laser carefully tuned to one of strontium’s resonant frequencies.
It puts one of the strontium electrons into superposition. So it is both excited and unexcited at the same time, creating what Jun calls a quantum pendulum. This pendulum is swinging at a speed of nearly one million billion cycles per second.
It’s going back and forth, back and forth. And this superposition creates this quantum pendulum. And when it comes to accuracy, more swings or higher frequency equals more precision.
If you think of swings as marks on a ruler, the more marks you have, the more exactly you can measure. So compared to a cesium clock, Jun’s strontium clock is around 100,000 times more precise. And that much sensitivity makes all the more apparent some of the stranger aspects of time, including one first predicted by Einstein, gravitational time dilation.
In the movie Interstellar, part of the crew of a spaceship descends in a shuttle to a planet, orbiting a supermassive black hole. And when the shuttle returns, those on the mission feel they’ve only been gone for three hours, but not the crew member who remained in orbit. I’ve waited years, 23 years, four months, eight days.
The difference in time is another effect of the black hole’s warping of the fabric of space time. The warping not only means gravity gets stronger closer to the black hole, but time gets slower too. And you don’t need a black hole to be able to measure it.
Even on Earth, gravity varies. And so does time, based on the distance from the planet’s center. So a person at the top of the Empire State Building experiences weaker gravity and time going faster than a person at street level where gravity is stronger.
But all that happens imperceptibly. Our wristwatches just aren’t accurate enough to show the difference. But June’s optical clocks are so accurate that even a small difference in elevation between two clocks will reveal a discrepancy in the passage of time.
When the clock changes elevation by a few hundred microns, basically the size of a human hair, you will start to be able to see the time is actually running differently. With that much accuracy, a clock transforms into something more than a timepiece. It becomes a new window into the nature of the universe.
Making a clock is much more than just a piece to keep time. It is a sensor to explore fundamental physics, to expand our curiosity, to build new technologies that can connect to quantum computing, quantum information processing, and communication. Central to making June’s precision atomic clocks work are ultra-stable lasers, which themselves are also a quantum technology.
They date back to the 1960s. You are looking at an industrial laser which emits an extraordinary light, not to be found in nature. I will show you.
This scene from 1964’s Goldfinger is said to be one of the first popular depictions of this new cutting-edge tech. I think you’ve made your point, Goldfinger. Thank you for the demonstration.
Today, lasers are everywhere. There are medical lasers to correct vision, lasers at the checkout counter, lasers for cutting, communicating, entertaining cats, and, of course, for light shows, which encourage us all to trip the light fantastic. Which may be why experimental physicist Rana Athikari is laser-focused on lasers.
When I talk about how beautiful a laser is as an instrument, I don’t want to gush about it too much. Like, I’m in love with lasers. I don’t know.
I feel like a weirdo fanatic or something like that. But there’s something about them. To understand what makes laser light so special, it makes sense to look at an ordinary light bulb.
The old-fashioned kind, with a tungsten filament. It produces light through thermal radiation. An electric current passing through the filament heats it up.
