These atomic physicists are about to create an exotic state of matter in space.
They’re sending commands to a special lab currently installed aboard the International
Space Station, that operates when the astronauts are asleep.
It’s engineered to trap gas atoms and cool them to temperatures just a hair’s edge
above absolute zero.
When it gets this cold, a curious state of matter called a Bose-Einstein condensate comes
into existence.
This isn’t your classic solid, liquid, or gas, but an ultracool state of matter - that
behaves like a wavy super atom.
Making them in space is an opportunity to hold a magnifying glass to the quantum world,
but only for a brief period of time.
It is incredibly challenging making something ultra cold, because there is nothing in the
natural world that wants to be ultra cold.
Something like this is so rare, so unnatural, so unlikely, that you're talking about the
coldest spots in the known universe.
The quest for colder temperatures has gone on for over a hundred years.
Scientists kind of steadily working to get colder and colder temperatures.
And by cold...
We're talking seriously chilling.
Nanokelvin is a billionth of a degree above absolute zero, and picokelvin is now a trillionth.
Strange and curious things happen when we get atoms to ultra-cold temperatures.
But to understand why colder regimes are an exciting playground for scientists, we have
to wade into some quantum mechanics: Quantum mechanics tells us that everything
has both a particle and a wave nature to it.
And so at normal temperatures atoms just act like little billiard balls.
As we cool a gas of atoms, we lower its momentum and each particle's wave nature starts to
become more and more pronounced.
And if you get cold enough...
These wavelengths get so large,
those atoms really start to blur together.
At that point, this strange new state of matter occurs called the Bose-Einstein condensate.
Bose is the person that really came up with the breakthrough to show that particles called
bosons behave in this collective way.
Einstein predicted that this state of matter would exist, but he thought it was at such
a ridiculously low temperature that you would never be able to actually observe it.
This was back in the 1920s when quantum mechanics was the new revolution on the scene.
They didn’t have the technology to wrangle atoms just yet.
But eventually...
Understanding quantum mechanics gave us lasers, semiconductors, transistors.
In the 1980s, people discovered ways to actually use lasers to cool atoms to incredibly cold
temperatures.
Most people's intuition is that you shine a bunch of lasers on something it makes it
hotter.
But by tuning a laser to a particular resonance frequency, scientists can slow down the motion
of an atom, which essentially cools it.
Then in the 90s, people started developing these techniques to move those atoms into
magnetic traps, and then use this other technique called evaporative cooling to get to still colder
temperatures.
Evaporation relies on losing atoms.
They need atoms to go away to get out of the trap and carry energy with them.
After decades of technical progress, teams finally made Bose-Einstein condensates in
the lab.
They last inside a trap for a glorious 15-20 seconds.
It was clear that gravity had a big effect on these systems, and it would be interesting
to do these types of things in space, even though it was totally crazy to even think
about that.
We were confining them with magnetic fields and the magnetic fields themselves are changing
and perturbing the atoms.
We would like to turn off the fields, and just study the atoms on their own, but of
course in gravity, they just kind of go plop.
And that’s why putting a lab in space offers a unique advantage.
You can shut the trap off and these matter waves remain floating.
We think we can get to a new regime of even colder temperatures for even longer amounts
of time, and make really sensitive measurements.
And that’s where this engineered quantum mechanics box comes in.
CAL is a multi-user cold atom lab within the International Space Station.
The heart of it is what we call the science module.
Then inside that there's a vacuum chamber.
There's computer to control everything, and to store the data.
There's electronics to drive magnetic field coils.
And then there is a whole suite of lasers.
We have two species that we're trying to trap: both Rubidium and Potassium.
The reason we like to cool those is because they've got one electron in their outer shell.
You want to be able to continually drive, excited state, ground state, excited state,
ground state, while you cool these atoms.
We have this little small vacuum that has this little atom chip on top of it, and then
that's mounted inside an assembly that steers all our laser beams.
For cold atom physicists who are used to tweaking their experiments, building a lab that could
operate remotely was a huge milestone.
We sometimes call that last phase of a mission the death march.
We had a number of issues that last few months, and things broke that we've been working with
in the lab for decades and never had one break.
This is sort of been my baby.
It's something I've been working on for 20 years pretty much.
And to finally see it all together, was just wow.
It was something that was amazing to go through.
And wonderful to go through and you don't want to do it again.
The instrument is placed near the center of mass of the ISS, that's important for the
gravitational measurements that we eventually want this kind of technology to be able to
do.
But it's right next to the astronauts exercise bike, and it's pretty ludicrous when you see
these videos of, you know, the shaking that's going on nearby.
So it runs during the crew sleep periods.
When these LED lights switch on...
We make the sample, and then we release it.
We snap off our magnetic fields, and the gas will start to expand.
You shine in a final laser pulse that blasts the cloud apart, and then you collect this
light that includes the shadow of the atoms on a CCD camera behind them.
Tens of microseconds later, you send in another pulse that's a reference image.
You subtract the two and you get a density profile of the atoms that were there.
We're always anxious to see as soon as possible the images coming down.
To detect that it is a Bose-Einstein condensation, there's certain signatures that you look for.
It's a very sharp transition.
Virtually every day we go down there and we turn it on, and we run a sequence to make
Bose-Einstein condensates.
We're sending up an upgrade up for CAL.
And the new capability is going to allow us to have something called an atom interferometer,
which is a really, amazingly sensitive sensor for things like accelerations, and gravity.
And this is probably in the long term, the most important thing to come out of using
cold atoms in space.
Interferometers use beams of light to make precision measurements of a given environment.
They’re great instruments to tackle some of the universe’s most stubborn mysteries.
Some of the teams are going to do studies of tests of Einstein's equivalence principle.
The Apollo astronauts did the first one of those in space, they dropped a hammer and
a feather and showed that on the moon, they fall at the same rate.That might not actually
be true.
We're going to drop a Rubidium atom and a Potassium atom.
We can read them out with laser beams using this atom interferometer technique to just
a fraction of wavelength of light.
As a general rule, you should never bet against Einstein but there is this fundamental conflict
between his theory, and what's called the standard model of quantum physics.
If there's a problem, that problem could be all the way back in the assumptions that that
theory was built on.
And Einstein’s equivalence is a fundamental tenet of general relativity.
You're testing this fundamental tenet of general relativity with quantum mechanics.
Another experiment that I really like is trying to study the quantum nature of collisions.
It gets to one of these I think one of the really profound questions in physics is that
the basic laws of physics are simple, that we have just a few fundamental particles and
they interact by these few simple rules.
And they also tell us that in this whole universe, the only thing that's happening, really the
only thing is, particles are coming together, they collide and they are bouncing off, sometimes
they change from one type to another.
Sometimes they just go off in different directions, but that's it.
And then how do we get this complicated universe that we see around us from that simple underlying
physics?
I think it's going to be a really important and again a kind of an iconic experiment, if we can pull it off.