If you are a Marvel movie fan than you know about Doctor Strange. You know, the rich neurosurgeon
whose quest to heal his injured hands after a car crash led him to study esoteric powers? And by
being able to use these powers he became a superhero of the Marvel Cinematic Universe.
One of the keys to Doctor Strange’s amazing powers is the Eye of Agamotto, a mystical
amulet made by the sorcerer Agamotto. It houses a glowing green gem called the Time Stone. It
gives whoever possess it the ability to alter and manipulate time. In the movie, Doctor Strange uses
it to save the Earth from destruction by the demon Dormammu, by trapping him in an endless time loop.
It’s thanks to the Time Stone that the stories of the Marvel Universe can follow all kinds of
convoluted timelines. This powerful gem is one of the six Infinity Stones around which
much of the action in the movie franchise revolves.
But, but this is all just far-fetched fantasy, right? Well,
yes… and no. As with many Hollywood sci-fi movies, what you see on screen in the Marvel
franchise might seem like pure invention but in fact draws on a surprising amount of real
science – pushed to the limits of plausibility perhaps, but nevertheless based in proper physics.
So how is this based in real science? Well, the idea is that the Time Stone is in fact an example
of an object that physicists have recently dreamed up and now even made for real. A real time stone?
HOW DOES THIS WORK – THAT’S COMING UP RIGHT NOW!
Before we get into TIME STONES and how they work,
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One of the scientific advisers for the Marvel series is Spiros Michalakis,
a mathematical physicist at CalTech. He has worked not only on movies like Dr. Strange,
but also Ant-Man, which showed the hero shrinking and entering the quantum realm. He has explained
that the Time Stone, as magical as it sounds, is actually based on an object that has been
exciting many physicists recently, and which has now been created inside a quantum computer.
It goes by a name that already sounds straight out of the Marvel Universe: a time crystal.
So what is a time crystal? We all know about ordinary crystals – like
this salt crystal. The atoms in them are all lined up in an orderly pattern,
as if each sits on a square of a three-dimensional checkerboard, which scientists call a lattice.
If you were the size of the quantum Ant-Man standing on one of these atoms,
and you moved in some direction through space, you’d encounter other, identical atoms at regular,
periodic intervals. The atomic structure of an ordinary crystal repeats again and again
in space – it’s symmetrical, so that if
you viewed any parts of it, you would see the same repeating pattern throughout.
The reason that atoms or molecules form crystals is because this puts the structure in its lowest
energy state, which all systems in the universe tend towards.
In 2012, the theoretical physicist Frank Wilczek, who won the 2004 Nobel prize in physics for his
work on the structure of subatomic particles, asked whether it might be possible to make
crystals that are symmetrical not in space, but in time. What this means is that the particles
it contains are constantly rearranging themselves into different configurations. But at
regular intervals in time, they return to exactly the same configuration.
It would be a bit like a team of American football players who are moving
all around after the snap but who, every few plays, find themselves
back in the same formation. Wilczek said that behavior like this would
be like the “spontaneous emergence of a clock” within the system of particles,
ticking at a rate it sets for itself.
That’s why making time crystals isn’t just an intellectual exercise for physicists – it
could be useful too. They would be natural timekeepers beating to a pulse of their
own choosing. Some researchers think time crystals might help us make better atomic
clocks – currently the most accurate timekeepers, used for example in GPS navigation satellites.
Others have suggested that time crystals made from quantum particles could be components for building
quantum computers, which can be much more powerful than today’s classical machines.
But these applications are speculative right now.
The regular, periodic behaviour that Wilczek described looks a lot like the pendulum in a
clock – an old grandfather clock. The pendulum swings back and forth, and at the end of each
to-and-fro swing, the bob or all the atoms it contains – returns to the same position.
But no ordinary pendulum can swing forever no matter how well
it’s made. Friction at the pivot point will make it slowly lose energy until it stops swinging.
Wilczek wondered if there was some way of making a collection of quantum particles
that, like a pendulum, will keep moving,
but will periodically return to the same positions – and whether they could do
this without pumping energy into the system to keep the motion going.
His idea got other physicists thinking. Wilczek admitted that a time crystal sounded dangerously
like a perpetual motion machine, which is forbidden by the laws of thermodynamics.
But he argued that it isn’t really, because it neither consumes nor produces energy.
However, three years later, other physicists proved that actually a quantum time crystal
can’t avoid the same problem as a pendulum. It will gradually dissipate
the energy it starts with, so that the oscillations will slowly die away.
This did not put an end to the story though, because just as you can keep
a pendulum swinging as long as you give it a little push every so often, so too can
a time crystal be kept oscillating by feeding energy into it with some kind of driving force.
This should not be a big deal because we see this happening all the time,
for example in children’s playgrounds, as someone can keep a swing going by pushing it.
But there happens to be a big difference: When you push a child on a swing,
the oscillations happen at the same frequency as the pushing. But physicists realized that,
for the kind of quantum systems that Wilczek had studied, something odd happens when you
produce oscillations by such a periodic driving force. The period of the oscillations – that is,
the length of time it takes for the particles to return to their original configuration – is
not the same as the period of the pushing. It can be twice as long, or three times,
as long, or any whole-number multiple. It’s as if the particles are saying “Thanks for
the push – but we’re going to vibrate at the frequency we choose, not the one you choose.”
So it turns out that this kind of behavior is genuine time-crystal behavior,
because the periodicity arises from the interactions of the particles within the
crystal and not from the pushing. All the pushing does is it stops the time crystal
from running out of energy. Because the periodicity is some whole-number or
“discrete” multiple of the driving period, they are called discrete time crystals.
This concept of the periodicity of time crystals emerging
from within the crystal itself rather than from any external source,
was the inspiration for the idea of time manipulation in the Dr. Strange Marvel movies.
Now, I want you to understand that no legitimate scientist
really thinks we can manipulate time using time crystals, at least nothing like that yet. But
there’s some logic to the Marvel madness, and it goes like this.
The curious thing about time crystals is that they dance to the beat of their own drum. They
take in energy from their surroundings but their periodic ticking rate is their own. So the idea
of the science advisers for the movie was that the Time Stone is a quantum time crystal that somehow
seals off a part of space and time and imposes its own internal clock on the flow of time there.
So how does this actually affect real events inside that zone? Here the advisers used another,
highly speculative idea from the forefront of physics, called the holographic universe.
It roughly says that the total amount of information inside a volume of space
can be encoded on the boundary of that volume. Relating this to our universe,
it means that all the information contained in our universe, including time, could be encoded on
its boundary infinitely far away. You can imagine this like a 3D hologram created on a 2D surface.
Now you might ask, "Is that what our real world is like?" – a kind of quantum projection on the boundary of the
universe? The problem is no one knows for sure because it's mathematically identical. But
this idea of the Marvel scientists is not as crazy as it might sound.
It has its roots in real science, and that’s the idea the Marvel advsiers ran with.
What it would mean is that all of reality, everything that happens,
is basically a kind of quantum computation taking place in that quantum boundry realm.
In this picture, you could say that everything including us is made of quantum code.
So the Time Stone, being a quantum time crystal, can take a patch of that quantum code
a bit of reality,
whether past, present or future – and rewire it to transform the way time moves within it.
The Time Stone, taking in energy from its surroundings, imposes its own pulse on the way
time flows inside the bit of the universe that it controls. Spiros Michalakis explains it this way:
“The Eye of Agamotto is a time crystal [that] can generate its own quantum dynamics
despite being driven by the [external] environment at whatever frequency.”
Is this confusing and Far-fetched? sure. But it’s not all total fantasy,
because time crystals are real. And we’ve made them, by controlling quantum matter.
How did we do this?
One of the ways to make a quantum time crystal is to take a row of atoms that act
like little magnets; they have a spin, which can point in one direction or the other – up or down.
In the time-crystal state, the spins would keep flipping back and forth along the row like a
stadium wave. They would do this with some kind of period – making the structure a time crystal.
You would need to keep adding energy in order to sustain this wave, and then also figure
out a way to dissipate this energy so that the system does not become too hot and fall apart.
In 2017, two teams reported that they had made discrete quantum time
crystals experimentally in chains of spins, for example by suspending a row
of charged atoms in an electromagnetic trap. Still, though, they couldn’t entirely prevent
these systems from absorbing too much energy. It wasn’t until 2021 that two teams of scientists
independently made a discrete quantum time crystal that could in theory keep oscillating forever.
They made them actually inside quantum computers.
Quantum computers do their calculations using quantum bits, or Qbits,
which are like particles with spin that can point up or down. And these up or down states encode the
1s and 0s of binary information. These bits are manipulated using the rules of quantum mechanics,
which allow quantum computers to do things that aren’t possible in normal classical computers.
In these experiments, the oscillations died away after only about a hundred cycles.
But that’s because the quantum bits in any of today’s quantum computers
become scrambled in just a second or less as they interact with all the stuff around them,
in a process called quantum decoherence. But it wasn’t due to any failure of the time crystal
itself. I made a video on decoherence if you want to learn more about that process.
Now the question can be raised, was this a simulation of a time crystal conducted on
a quantum computer – or did they create a real time crystal from the computer’s quantum bits?
The funny thing is
no one knows for sure, but there may not be any difference.
It was a time crystal made from the actual quantum objects that make up the computer’s quantum bits.
And it works, pulsing away for as long as the computer can keep its bits in their collective
quantum state. So we can now say that quantum time crystals do indeed really exist in the world.
But so far, the idea of these time crystals being able to create some kind of isolated
holographic quantum realm where time can exist differently and out of phase with the real world
is still only a Hollywood fantasy, but you have to give the movie makers some credit because
it is at least connected to the ideas in real science, which you don’t see in every movie.
And if you have a question or comment for me or other viewers, please leave it in the comments section,
because I try to look at all of them. I’ll see you in the next video my friend.