A century ago, the great polar explorers
were pushing further and further towards the coldest places on Earth:
the north and south poles.
The competition to reach these goals was matched
by a less publicised but equally daunting scientific endeavour:
the attempt to reach the coldest point in the universe:
absolute zero.
This mysterious barrier was a physical paradox
as tantalizing as the speed limit of light,
which can also never be exceeded.
It was a frontier so enticing
that rival physicists from all over Europe
begun a race towards this absolute limit of cold.
This is a story of showmanship,
setbacks,
rivalry and despair.
The stakes were high.
For the winner there was glory and the chance of the Nobel Prize.
For the loser, the prospect of being a forgotten foot soldier of science.
When explorers ventured into the Antarctic
they experienced some of the coldest temperatures on Earth,
reaching down to -80 °C.
But this was nothing compared to the ultimate limit of temperature,
absolute zero,
at around -273 degrees.
Only in a laboratory, by liquifying gases
could adventurers take the first steps
towards this Holy Grail,
a place utterly drained of all thermal energy.
Among the front-runners in the race towards absolute zero
was James Dewar, a professor at the Royal Institution in London.
"- It will be the greatest achievement of our age... "
In 1891, he gave one of his celebrated
Friday night public lectures
on the wonders of the super cold, to celebrate the centenary
of his great predecessor, Michael Faraday.
"... The descent to a temperature within 5 degrees of zero
would open up new vistas of scientific inquiry,
which would add immensely to our knowledge
of the properties of matter."
(Simon Schaffer) James Dewar is a canny and I think very ambitious,
practically-minded Scottish scientist.
He could really show, both his colleagues
and the fee-paying audiences
who came to this inmensely succesful brilliantly engineered lectures,
some of the secrets of nature.
Take this rubber ball...
It bounces well, I think you'll agree.
But let's see what happens
after a few seconds' immersion in liquid oxygen.
Dewar invented the vacuum flask to carry out his research,
and it's still called "a Dewar" to this day.
Now, let's see what happens.
(Kostas Gavroglu) This phantasmagoric aspect of science
always helped science to be accepted by the public.
Though it is a little mystifying, it did play a role
of having society, having the public accept
that these weird people in the laboratories
are doing truly interesting, if not magical things.
James Dewar's life was defined by the cold.
As a boy, he used to skate on a frozen pond in Scotland.
He claimed in later life that his most formative early experience
resulted from an accident on the ice.
(Tom Shachtman) After Dewar fell through the ice.
He was rescued
but when he got home they discovered that he had rheumatic fever,
which put him in bed for eight months.
And he was in danger of having his limbs atrophy, with pulsy
and so the village joiner set him tasks
to develop his limbs, and especially his hands,
and one of the tasks was to make a violin.
And he developed a great deal of mechanical aptitude
which stood him in very good stead in later years
when he had to create apparatuses for his uses.
Dewar's dream was to take on the mantle
of the Royal Institution's greatest scientist, Michael Faraday.
Seventy years earlier, Faraday had done experiments
showing that under pressure,
gases like chlorine and ammonia liquify.
And as this liquids evaporate, their temperature drops dramatically.
Faraday was curious to see if this method of pressurizing
gases into liquids could be used for all gases.
But some gases, what he called the "permanent" gases
would not liquify, no matter how much pressure he applied.
So he abandoned this line of research.
"Faraday's was a mind full of subtle powers,
of divination into nature's secrets...
and although unable to liquify the permanent gases,
he expressed faith in the potentialities
of experimental inquiry.
The lowest point of temperature attained by Faraday
was -130 degrees centigrade."
For over 30 years noone could reach a lower temperature than -130 °C.
Absolute zero remained an elusive and very distant goal.
Now, Michael Faraday, in the early to mid 19th century,
had left a kind of for-long frontier for physicists and chemists:
what he called the permanent gases (hydrogen, nitrogen, oxygen),
which no means whatsoever seemed to be able to liquify.
And this was a kind of "no man's land" which one could not cross.
And that was a standing challenge
for the scientists of the later 19th century:
"It must be possible to turn these gases into pure liquids."
It was not until 1873 that a Dutch theoretical physicist,
Van Der Waals, finally explained
why these gases were not liquifying.
By estimating the size of molecules and the forces between them,
he showed that to liquify these gases using pressure,
they each had to be cooled below a critical temperature.
At last, he had shown the way to liquify
the so-called permanent gases.
Oxygen was first, and then nitrogen,
reaching a new low temperature of almost -200 °C.
"Only the last of the permanent gases remains to be liquified:
hydrogen, in the vicinity of -250 °C.
It will be the greatest achievement of our age,
a triumph of science."
Dewar was determined to be the first to ascend
what he called "Mount Hydrogen".
But he was not alone.
The competitor Dewar feared most
was a brilliant Dutchman, Heike Kamerlingh Onnes.
Kamerlingh Onnes was younger than Dewar
and to a certain extent looked up to the Scotsman as his senior.
Dewar didn't have the same,
if you'll pardon the expression, "warm feelings,"
towards his rival in the race for cold.
Dewar recognized that Kamerlingh Onnes
had a new radical approach to science
and was planning an industrial scale lab.
(Dirk van Delft) When Onnes took over the physics laboratory in Leiden,
he was only 29 years old.
And, well, he gave his inaugural address
here in this lecture room,
the big lecture room of the Academy Building of Leiden University,
and it was all there.
He was explaining what to do in the next years,
and he was talking about liquifying gases,
making Dutch physics famous abroad, and well,
it was amazing how farsighted all those visions were.
Kamerlingh Onnes' lab was more like a factory.
He recruited instrument makers, glassblowers,
and a cadre of young assistants who became known
as "blue boys" because of their blue lab coats.
Later, he set up a technical training school,
which still exists to this day.
Dewar and Onnes could not have been more different.
Dewar was very secretive about his work,
hiding crucial bits of apparatus from public view
before his lectures.
Onnes on the other hand, openly shared his lab's
steady progress in a monthly journal.
Onnes was the tortoise to Dewar's hare.
In the case of Dewar, you had a brilliant experimenter,
a person who could actually build the instruments himself,
and a person who really believed in the brute force approach,
and that is, have your instruments,
set up your experiment, and try as hard as you can,
and then, you'll get the results you want to get.
In the case of Kamerlingh Onnes,
you have a totally different approach.
He's the beginning of what later on
was known as "big science".
Unlike Dewar, Onnes thought detailed calculations
based on theory were vital before embarking on experiments.
He was a disciple and close friend of Van Der Waals,
whose theory had helped solve the problem
of liquifying permanent gases.
Though their approaches were different,
Kamerlingh Onnes and Dewar
used a similar process in their attempts to liquify hydrogen.
Their idea was to go step-by-step down a cascade
using a series of different gases
that liquify at lower and lower temperatures.
By applying pressure on the first gas
and releasing it into a cooling coil submerged in a coolant,
it liquifies.
When this liquified gas enters the next vessel,
it becomes the coolant for the 2nd gas in the chain.
When the next gas is pressurized
and passes through the inner coil,
it liquifies and is at an even lower temperature.
The 2nd liquid goes on to cool the next gas and so on.
Step by step, the liquified gases become colder and colder.
Each one is used to lower the temperature of the next gas
sufficiently for it to liquify.
In the final stage, where hydrogen gas is cooled,
the idea was to put it under enormous pressure,
180 times atmospheric pressure,
and then suddenly release it through a valve.
This would trigger a massive drop in temperature,
sufficient to turn hydrogen gas into liquid hydrogen
at -252 degrees, just 21 degrees above absolute zero.
Here was the risky bit because his apparatus was
going down in temperature, getting very, very cold,
so very fragile, quite easy to fracture.
While at the same time,
the pressures he was working at were very, very high,
so the possibility of explosion.
He took the most amazing risks, both with himself
- he was a lion of a man in terms of courage -
and with those around him.
All the equipment he was working with
could have crumbled or blown up
and more than occasionally, it did.
Dewar had many explosions in his lab.
Several times, assistants lost their eyes
as shards of glass catapulted through the air.
In the notebook he actually writes,
jots down many details of what happened to the apparatus,
but not what happened to his assistants.
So somehow you get the impression that apparatus
is more important than the assistants.
(Frank James) Well, the assistants seemed to have been quite loyal to him
'cause he stayed working.
I mean, if you look at the picture of Dewar lecturing
there are two assistants.
There one of whom has lost his eye but the painter manages to portray him
with his lost eye facing the other way
so you don't actually see it in the picture.
So it clearly there was something going for Dewar with his assistants
in that he kept that sort of
loyalty in a way that would be almost inconceivable in the modern world.
Over in Leiden, Onnes was facing anxious city officials
who were so worried about the risk of explosions
that they ordered the lab to be shut down.
Dewar wrote a letter of protest on behalf of Onnes
but the Leiden lab remained closed for 2 years.
(Dirk van Delft) Onnes had to wait and to wait and to wait.
Dewar was already starting his liquifying hydrogen,
and Onnes had the apparatus to do so too,
but he just couldn't start,
so we had lost the battle before it was even begun.
The year is 1898.
Dewar has been working on trying to liquify hydrogen
for more than 20 years, and he's finally ready
to make the final assault on Mount Hydrogen.
By using liquid oxygen, they brought down the temperature
of the hydrogen gas to -200 °C.
They increased the pressure till the vessels were almost bursting
and then opened the last valve in the cascade.
(as James Dewar) "Shortly after starting, the nozzle plugged,
but it got free by good luck
and almost immediately drops of liquid began to fall
and soon accumulated 20 cubic centimeters."
Dewar had liquified hydrogen,
the last of the so-called permanent gases.
To prove it, he took a small tube of liquid oxygen
and plunged it into the new liquid.
Instantly, the liquid oxygen froze solid.
Now he was convinced.
He had produced the coldest liquid on Earth
and had come closer to absolute zero than anyone else.
(Tom Shachtman) Dewar thought that he had done
the most amazing feat of science in the world,
that he would be immediately celebrated for it
and get whatever prizes there were available.
And that didn't happen.
I think for Dewar, it was the ambition of a mountaineer.
You've climbed the highest mountain peak
that you can see in the range around you,
and just as you get to the top of the peak,
there's an even higher mountain just beyond.
That mountain was helium,
a recently discovered inert gas.
Van Der Waal's theory predicted helium would liquify
at an even lower temperature than hydrogen,
at around 5 degrees above absolute zero.
Now all Dewar had to do was obtain some.
It should not have been difficult.
The two chemists who had discovered the inert gases,
Lord Rayleigh and William Ramsay,
often worked together in the lab next door.
Unfortunately, Dewar had made enemies of both of them
by publicly criticizing their science and belittling their achievements,
so they had no desire to share their helium.
Kamerlingh Onnes was faced with the same problem as Dewar,
which was: Where can I get a supply of helium gas?
And he actually asked Dewar
to try and collaborate with him too, and Dewar said,
I'm having such a problem getting the gas by myself,
I can't possibly give you any. I'd like to, but I can't.
Eventually, each found a supply,
but Onnes' industrial approach paid dividends.
After 3 years, he had amassed
enough helium gas to begin experiments.
The tortoise was beginning to pull away from the hare.
The liquefaction of these gases
has become a matter of enormous pride and prestige for Dewar.
But pretty quickly he run out of resources.
He was reaching the limit of what the budget would bear
at the Royal Institution
and the helium supplies dried up.
One day, when they were in the mid of working with gas of helium
an assistant in Dewar's lab
turned the knob to the left instead of to the right,
the whole canister of the gas escaped into the air
and they had 6 months when they couldn't do any work whatsoever.
Dewar was furied.
(Kostas Gavroglu) At one point, Dewar writes to Kamerlingh Onnes
telling him that he is not in the race anymore.
He thinks that the problems for liquifying helium
are such that he's not able to complete the job.
The battlefields of science
are the centers of a perpetual warfare
in which there is no hope of a final victory.
To serve in the scientific army,
to have shown the initiative
is enough to satisfy the legitimate ambition
of every earnest student of nature.
Thank you.
In the summer of 1908, Onnes summoned
his chief assistant, Flim, from across the river.
They were finally ready to try to liquify helium.
At 5:45 on the morning of July the 10th,
he assembled his team at the lab.
They had rehearsed the drill many times before.
Leiden was a small university town
and the word quickly spread that this was the big day.
It took until lunchtime to make sure
the apparatus was purged of the last traces of air.
By 3 in the afternoon, work was so intense
that when his wife arrived with lunch,
he asked her to feed him so he didn't have to stop work.
This was a man obsessed.
At 6:30 in the evening,
the temperature began to drop below that of liquid hydrogen.
It's getting very late in the day
and the team is down to its last bottle of hydrogen
and if they can't liquify helium now
they're going to have to wait for months to try again
and the temperature gauge is stuck at five degrees above absolute zero.
And Onnes doesn't know why this is, and a colleague comes in
and he suggests that that means
maybe they've actually succeeded and they don't even know it yet.
So Onnes takes an electric lamp type thing and he goes
underneath the apparatus and looks, and sure enough,
there in the vial is this liquid sitting there quietly.
It's liquified helium.
They had reached -268 °C, just 5 degrees above absolute zero
and finally produced liquid helium.
This monumental achievement
eventually won Onnes the Nobel Prize.
When James Dewar heard
that he had lost the race to Kamerlingh Onnes,
it reignited a festering resentment.
Dewar berated his long-suffering assistant, Lennox,
for failing to provide enough helium.
Only this time, Lennox had had enough.
He walked out of the Royal Institution,
vowing never to return until Dewar was dead.
And he kept his word.
For Dewar, it was the end of his low temperature research.
He must've been incredibly irritated
and knowing Dewar he must...
one can imagine that sort of irritation he would've felt
when Onnes came in for the dutch to liquify helium
and even today Onnes' discovery of liquid helium
is seen as a much more significant discovery
than Dewar's work on liquifying hydrogen,
which is slightly unfair, 'cause it's all part of the process of
trying to achieve absolute zero.
It remained, that's very clear, a wound
in Dewar's soul that never really healed.
I think that Dewar emerges at the end of the story
as a rather tragic figure,
one of the very greatest late 19th century british scientists
who in the end is frustrated by a failure
which hardly anybody could have expected him to achieve.
James Dewar's dream of reaching absolute zero was over.
He spent the rest of his life
investigating other scientific problems,
such as the physics of soap bubbles.
He'd always been a loner.
Ultimately, his refusal to collaborate
costed him the glory he felt he deserved.
I think it's really impressive
how often scientists do seem to be driven
by the spirit of competition,
by the spirit of getting there first.
But what's really fascinating about these races,
the race for absolute zero,
is that the goalposts move as you're playing the game.
The race in science is not for a predetermined end,
and once you're there, the story's over,
the curtain comes down.
That's not at all what it's like.
Rather, it turns out you find things you didn't expect.
Nature is cunning, as Einstein would have said,
and she is constantly posing a new challenge,
unanticipated by those people who start out on the race.
Sometimes, an unexpected event
triggers a whole new area of research.
This happened in Leiden
as Onnes' team began to investigate how materials
conduct electricity at these very low temperatures.
They observed that at around 4 degrees above absolute zero,
all resistance to the flow of electricity abruptly vanished.
Electrical resistance dropped as if it had gone over a cliff.
It was going down and down and down and then disappeared
or all but disappeared.
Now, this was an astonishing thing.
Nobody ever had seen anything like this before.
There was nothing on Earth that had no electrical resistance.
Onnes later invented a new word to describe this bizarre phenomenon.
He called it "superconductivity."
(Allan Griffin) We have a circular ring of permanent magnets,
which are producing a magnetic field.
And now when we put a superconducting puck over it
and give it a little push,
the magnetic field repels the superconductor.
The magnetic field from the track
induces a current in the supercooled puck,
which in turn creates an opposite magnetic field
that makes the puck levitate.
It produces a magnetic field
like a north pole against north pole,
and that's why you have the repulsion.
As the puck warms up,
its superconducting properties vanish
along with its magnetically induced field.
For decades after its discovery in 1911,
the underlying cause of superconductivity
remained a mystery.
Every major physicist, every major theoretical physicist
had his own theory of superconductivity.
Everybody tried to solve it, but it was unsuccessful.
There were more surprises ahead.
In the 1930s, another strange phenomenon
was observed at even lower temperatures.
This rapidly evaporating liquid helium cools
until at 2 degrees above absolute zero,
a dramatic transformation takes place.
(Allan Griffin) Suddenly you see that the bubbling stops
and that the surface of the liquid helium
is completely still.
The temperature is actually being lowered
even further now, but nothing particularly is happening.
Well, this is really one of the great phenomenon
in 20th-century physics.
The liquid helium had turned into a superfluid,
which displays some really odd properties.
Here I have a beaker
with an unglazed ceramic bottom of ultrafine porosity.
Ordinarily, this container
with tiny pores can hold liquid helium,
but the moment the helium turns superfluid, it leaks through.
We call this kind of flow a "superflow."
Superfluid helium can do things
we might have believed impossible.
It appears to defy gravity.
A thin film can climb walls and escape its container.
This is because a superfluid has zero viscosity.
It can even produce a frictionless fountain,
one that never stops flowing.
Superfluidity and superconductivity
were baffling concepts for scientists.
New radical theories were needed to explain them.
In the 1920s, quantum theory was emerging as the best hope
of understanding these strange phenomena.
Its central idea was that atoms
do not always behave like individual particles.
Sometimes they merge together and behave like waves.
They can even be particles and waves at the same time.
This strange paradox was hard to accept,
even for great minds like Albert Einstein.
In 1925, a young Indian physicist, Satyendra Bose,
sent Einstein a paper he'd been unable to publish.
Bose had attempted to apply
the mathematics of how light particles behave to whole atoms.
Einstein realized the importance of this concept
and did some further calculations.
He predicted that on reaching extremely low temperatures,
just a hair above absolute zero, it might be possible
to produce a new state of matter that followed quantum rules.
It would not be a solid or liquid or gas.
It was given a name almost as strange as its properties:
a Bose-Einstein condensate.
For the next 70 years,
people could only dream about making such a condensate,
Matter can exist in various states.
Atoms at high temperature always form gases.
If you cool the gas, it becomes a liquid.
If you cool the liquid, it becomes a solid.
But under certain circumstances,
if you cool atoms far enough to extremely low temperatures,
they undergo a very strange transformation,
they undergo an identity crisis.
So let me show you what I mean by "an identity crisis."
When you go to low temperatures, the
quantum mechanical properties of the atoms become important.
These are very strange, very unfamiliar to us,
but in fact, each one of these atoms
starts to display wavelike properties.
So instead of points like that,
you have little wave packets, like that, moving around.
It's really difficult for me to explain just why that is,
but that's the way it is.
Now, as you go to very low temperatures,
the size of these packets gets longer and longer and longer.
And then suddenly, if you get them cold enough,
they start overlapping, and when they overlap,
the system behaves not like individual particles,
but particles which have lost their identity.
They all think they're everywhere.
This little wave packet over here can't tell
whether it's this one or that one or that one.
Or that one or that one or that one.
It's there, and it's there, and it's there.
They're all in one great big quantum state,
they're all overlapping.
They're all doing the same thing,
and what they're doing, to a good approximation is,
they're simply sitting at rest.
This Bose-Einstein condensate is
very difficult to imagine or to visualize.
I could imagine what it's like to be an atom
running around gaily, freely, bouncing into things,
sometimes going fast, sometimes going slow,
but in the Bose condensate, I'm everywhere at once.
I've lost my identity. I don't know who I am anymore.
I'm at rest, and all the other atoms around are at rest.
But there are not other atoms around.
We're all just one great big quantum system.
There's nothing else like that in physics
and certainly not in human experience.
So just to think about this causes me wonder and confusion.
Dan Kleppner's group, at MIT, began
to try to make a Bose-Einstein condensate in hydrogen.
(Dan Kleppner) As we started out the search for Bose-Einstein condensation,
our enthusiasm grew because hydrogen seemed
like such a wonderful atom to use.
It had everything going for it.
It had its light mass.
That means that the atoms will condense
at a higher temperature than other atoms would.
The atoms interact with each other very, very weakly.
All the signals seem to be pointing to the fact
that hydrogen was the atom
for getting to Bose-Einstein condensation.
Dan Kleppner's idea was to cool the hydrogen atoms
by making use of their magnetic poles.
He used a strong magnetic field
to create a cluster of atoms in a cold trap.
Unfortunately, sometimes one atom flipped another,
which triggered a release of energy that raised the temperature.
It was a frustrating time for us
because our methods were so complicated
we were having a hard time moving forwards.
It was time for the next generation to have a go.
Two scientists who trained in Kleppner's department
moved down west to Boulder, Colorado.
They came up with a different approach to the problem.
Rather than focusing on
the lighter atoms of the periodic table,
Eric Cornell and Carl Weiman hit upon the idea of using
much heavier metallic atoms, like rubidium and caesium.
But would using these giants enable them
to reach closer to absolute zero?
The idea in the field in those days was that
the light things like hydrogen and lithium would be easier,
and there are some good reasons for thinking that.
But we had other ideas.
Yeah, sort of gut intuition in some sense.
Their plan was to use a laser beam to cool the atoms,
a technique that had already been tried by their old lab at MIT.
Lasers are usually associated with making things hot,
but if they are tuned to the same frequency as atoms
traveling at a particular speed, they can make them cold.
When the stream of light particles from the laser
hits the selected atoms in the gas cloud,
the atoms slow down and hence become cold.
Laser cooling was a new tool that had the potential
to reduce the temperature of a gas
to within a few millionths of a degree of absolute zero.
But Cornell and Weiman were not
the only ones excited by this prospect.
A new scientist had arrived at MIT.
(Wolfgang Ketterle) It was in late '91 or early '92 that we had an idea,
an idea how a different arrangement of laser beams
would be able to cool atoms to higher density.
And it worked!
And this was really a trigger point.
I will never forget the excitement in those groups,
group meetings, when we discussed What do we next?
Because with higher density
there are many things you can do.
Could we now push to Bose-Einstein condensation?
I see, well, lots of cables and electronics...
Ketterle used used the full might of MIT's founding
to build a laser lab
to try to make a condensate in sodium atoms.
This is an atomic beam oven.
What is wrapped in tinfoil is a little vacuum chamber
where we heat up metallic sodium,
so the metallic sodium melts and evaporates,
and it's ultimately the sodium vapor,
the sodium atoms, which we tried to Bose-Einstein condense.
MIT, Boulder, and several other labs were chasing the same goal.
It had echoes of the race
to produce liquid helium almost a century earlier.
(Eric Cornell) As I tell my students today,
anything worth doing is worth doing quickly,
because science moves on and
we're all mortal and you want to do things.
While MIT was installing expensive industrial lasers,
Carl Weiman had a different approach.
I, throughout my experimental physics career,
always felt that
technology played the big part,
so if you could figure out a better technology for doing something
it was gonna pay off in the long run, in physics.
(Eric Cornell) In some cases, he was ripping open old fax machines
and taking out the little chip inside
that made the laser and showed that you could take these lasers
and put them into a home-built piece of apparatus,
stabilize the laser
and use them to do spectroscopy and laser cooling.
(Carl Weiman) This is actually our first,
what's called a "vapor cell optical trap."
You can see it's kind of this old cruddy thing
pulled together glass where we could send laser beams in
from all the different directions
and have just a little bit of the atoms we wanted to cool.
As well as bombarding the atoms with lasers,
they also trapped them in a strong magnetic field.
You can have all your magnetic trap coils
outside of the vacuum system
and then again, it's a lot easier, simpler, to do everything.
We would try this sort of magnetic trap,
that sort of magnetic trap, this sort of imaging,
that sort of imaging, that sort of cooling.
All those things we could do
without building a whole new chamber each time.
We tried literally 4 different magnetic traps in 4 years
instead of having a 3 or 4-year construction project for each one.
By being fast and flexible,
the Boulder group hoped to beat their old lab at MIT,
but MIT had its own plans.
This was a prize they felt should be theirs.
(Wolfgang Ketterle) There was a sense of competition,
but it was what I would call friendly competition.
I mean, can you imagine 2 athletes?
They are in the same training camps,
they help each other, they even give tips to each other,
but then when it comes to the race,
everybody wants to be the first.
The rival groups were all using
magnetic trapping and laser cooling to cool their atoms,
but for the final push towards absolute zero
to turn these atoms of gas
into the quantum state Einstein had predicted,
they needed one more cooling technique: evaporative cooling.
It's just like with this coffee; the steam coming off of the coffee
is the hottest of the coffee molecules
escaping and carrying away more than their fair share of energy.
In the case of the atoms, we keep the atoms in
a sort of magnetic bowl, and we confine the atoms there,
they zoom around inside the bowl, and then the hottest ones
have enough energy to roll up the side of the bowl
and fall over the edge, slop over the edge,
taking away with them much more than their fair share of energy.
And the atoms that remain have less and less energy,
which means they move slower and slower
and start to cluster near the bottom.
And as that happens,
we gradually lower the edges of the magnetic trap
and always so there's just a few atoms that can escape,
until finally the remaining atoms cluster
near the bottle of the bowl, huddle together,
they get colder and colder and denser and denser
and eventually in this way, evaporation forces
the Bose-Einstein condensation to occur.
One problem that we kept encountering
is that we had to keep the atoms isolated from the walls.
We had got a really good vacuum
and yet if the vacuum is perfect,
what is that you're actually working with,
we had had a little bit of rubidium gas in there,
a tiny bit rubidium gas that we could capture,
catch with our lasers and slow down.
So we had this wild idea of changing...
constantly changing the pressure in the chamber,
letting the pressure get higher and lower,
and we built a very elaborated chamber
with valves that open and close and a pump to turn on and off
and it didn't work for beams, I mean
we spent six months wasted, I might say six months on
valves opening, closing, pumps turning on and off.
The problem is the rubidium gas had a little bit of stickyness to it
and that meant when we were trying to *sucking sound*
get all the rubidium out of there,
that residual gas was heating up the atoms.
So eventually we had to give up on that idea.
By now the race to produce
a Bose-Einstein condensate was intensifying.
At every major meeting,
Eric Cornell and I gave talks or talked to each other.
We were keenly aware that we were
both working towards the same goal.
It's a mixed thing. On the one hand it's flattering
because they're using an approach which we had pioneered,
that we felt good about that.
On the other hand there was... maybe we were still little nervous
because... hmm... we want to advance knowledge,
but science is a competitive business.
and we felt that we wanted to do it first and...
and maybe that we were entitled to do it first.
Although even that's a mixed bag
because after all we had jumped into the game of the hydrogen people
who had shown us so many of the tricks over the years.
At one point, during that period I remember Carl Weiman
being quoted at an article saying that
he hopes that the MIT group gets there first
'cause they started there it all and so they'll get the Nobel Prize
and then the, the other group will do the interesting science.
Well, that was a very nice thought.
Didn't quite work out that way.
In June 1995, the Boulder group was working 'round the clock
knowing that several other labs
were also poised to produce the first condensate.
An official visit from a government-funding committee
was the last thing they needed.
The standard thing you do when important people come around
is you close down your lab and clean up everything
and put posters on the walls so they can see how productive you are.
Of course, that's the exact opposite of being productive.
We didn't want to close down the lab
or clean up our lab or put up posters.
We wanted to work very hard.
So the senior dignitaries in the 3-piece suits and so on
came in to the lab, and we left the lights off,
and everyone continued to work,
and I made them keep their voices down.
And talked to them rather in a hurried way
and then sort of shuffled them out the door,
and they all had a slightly puzzled look on their face
'cause it probably had never happened to them before
in their history of being a visiting committee,
that they were treated with as little... little pomp.
And later, I actually met one of the guys who said,
"I suspected something was up that day
because otherwise you never would've dared to do that".
June the 5th, 1995
turned out to be a big day in the history of physics.
They had finally made what Einstein had predicted 70 years before:
a Bose-Einstein condensate.
Our first reaction was wait, we gotta be careful here, you know.
Let's think of all the different knobs we can turn,
checks we can make and so on
to see if this really is Bose-Einstein condensation.
The condensate is sort of like a vampire.
If the sunlight even once falls on it, it's dead,
and so it... its realm is the realm of the dark.
But we can take pictures of them
because we strobe the laser light really fast,
and even as the condensate's dying, it casts a shadow,
and the shadow is frozen in the film.
Weiman and Cornell created the first Bose-Einstein condensate
in a cloud of just 3000 atoms of rubidium,
the first in the universe, as far as we know.
They had reached the temperature of
170 billionths of a degree above absolute zero.
One of the first things you need to understand
about Bose-Einstein condensation is how very, very cold it is.
Where we live, at room temperature,
is far above absolute zero in the scale.
Imagine that room temperature is represented by London,
thousands of kilometers from here.
Then on that scale, if we imagine right here
where I'm standing in Boulder is absolute zero,
the coldest possible temperature,
then how close are we to absolute zero?
If we think of London as being room temperature
and right where I am is absolute zero, then
Bose-Einstein condensation occurs
just the thickness of this pencil lead away from absolute zero.
Within weeks of the Boulder group's success,
Wolfgang Ketterle produced an even larger condensate
from ten million sodium atoms.
At last, quantum mechanics
was more than just theoretical mambo-jumbo.
It was something that could be seen with the naked eye.
Weiman, Cornell & Ketterle
shared the Nobel Prize for physics in 2001.
(Carl Weiman) One of the things Nobel Prize
means and the ceremony means is
that everybody remembers Eric's the person
who forgot to bow to the king!
There was a breakdown of protocol on my part.
There was no excuse because they actually drill us.
It's more like a... we have a series of rehearsals
practicing how to bow to the king, and I somehow managed
to bollocks it up at the last possible moment.
And I thought maybe, you know,
Carl who came after me would do this, make the same mistake,
and then no one would figure it out,
but no, he was perfect.
(Wolfgang Ketterle) I heard about the Nobel Prize when I was
woken up by a telephone call,
which was at, I think, 5:30 in the morning.
So you wake up, you go to the telephone,
and somebody tells you,
"Congratulations, you have won the Nobel Prize."
You're still tired, your brain is not fully functional,
but you realize this is big and...
and what you feel is, you know, pride,
pride for MIT, your collaborators, for yourself.
It's wonderful to see that your work gets recognized
and acknowledged in this way.
Like any great adventure,
the pursuit of science offers no guarantee of success.
But for the godfather of ultra cold atoms,
persistence eventually paid off.
After 20 years of struggling to obtain a condensate in hydrogen,
Dan Kleppner finally succeeded.
For a few fleeting moments, his dream came true.
(Daniel Kleppner) Of course, we were delighted,
and I think everyone was delighted
because we'd been working on it for so long.
It's kind of embarrassing to have this group,
which helped start the work and was working away there,
fruitlessly, while everyone was enjoying success.
When we got it, everyone was happy.
(Wolfgang Ketterle) To see that an effort, which lasted for 20 years,
which took so much patience, frustration and tenacity,
to see that succeed is just emotional. It's liberating.
I will never forget the standing ovation,
which Dan Kleppner received at the Verena Summer School
when he announced Bose-Einstein condensation in hydrogen.
Everybody just got up and gave...
it was sort of like an opera, where everybody just cheered,
and people were crying, and...
because everybody realized
that they had finished the race, but too late,
and it wasn't gonna work out,
but in some sense they had really stimulated the whole field.
So it was a very, very moving, very moving moment.
For the pioneers who had realized Einstein's dream
and created condensates, it was
the end of an extraordinary decade of physics.
Now, there was a new challenge:
to work out what to do with them.
At Harvard, a Danish scientist, Lene Hau,
had the idea of using a condensate to slow down light.
We all have this sense, you know, light is something that...
nothing goes faster than light, in vacuum,
and if somehow we could use this system
to get light down to, you know, to a human level,
I thought that was just absolutely fascinating.
It is actually very odd,
it's also extremely odd to a lot of my colleagues.
Lene Hau created a cigar-shaped Bose-Einstein condensate
to carry out her experiment.
She fired a light pulse into the cloud.
The speed of light is around a billion km/h,
but when the pulse hits the condensate,
it slows down to the speed of a bicycle.
(Lene Hau) So light pulse might start out
being 1 to 2 miles long in free space,
it goes into our medium,
and since the front edge enters first that will slow down.
The back end is still in free space, that'll catch up,
and that'll create that compression.
And it'll end up being compressed
from 1 to 2 miles down to 0.001 micron
or even smaller than that.
You could say well, gee, it's easy to stop light
because I could just send a laser beam into a wall
and I would stop it.
Well, the problem is, you lose the information
because it turns into heat.
You can never get that information back.
In our case, when we stop it, the information is not lost
because that's stored in the medium,
then we have time to revive it,
the system has all the information
to revive the light pulse, and it can move on.
One day, ultra cold atoms will probably be used
to process information
but quite how is hard to predict.
Sometimes the promised benefits from a scientific breakthrough
take a long time to emerge.
Many predicted that by this century
energy-saving superconducting power lines
and maglev bullet trains would be crisscrossing the continents.
Perhaps now, whilst world's energy supplies dwindle,
these technologies, once seen as uneconomic,
will start to take off.
Now it is the quantum nature of the cold frontier
that has captured imaginations.
Super cooled quantum devices
are mapping the magnetic activity of the brain
and cold atoms are being turned into quantum computers.
(Seth Lloyd) As a quantum mechanic, I engineer atoms.
To make a computer out of atoms, you have to somehow get atoms
to register information and then to process it.
Why build quantum computers?
Because they're cool, it's fun, and we can do it. Right?
I mean, we actually can take atoms
and if we ask them nicely, they'll compute.
That's a lot of fun. I mean, have you ever
talked to an atom recently and had it talk back? It's great!
You know? Learn to speak atom
and the atom speaks back. That's great.
Quantum world is, in the world of the very small,
is like an exotic wilderness that you've never been in before.
And things you're wondering and everything looks strange
and you see things that you've never seen
but if you really want to see what's going on
then you've got to be quiet.
So, if you go into the wilderness and you're going "blablabla"
then you're never going to see things
because all these exotic phenomena are going to know that you're there
and they're going to stay put and they're not going to come out.
So if you make a lot of noise that's bad.
Now, at the quantum level, at the microscopic level,
heat is noise.
So, if you want to see these strange and exotic effects
you have to be quiet.
Very quiet.
There can't be a lot of noise
and that means you have to cool things down.
Unlike ordinary computers where each decision is based
around a bit of information and is either a zero or a one,
in the quantum world, the rules change.
At first glance, a quantum computer
looks almost exactly the same.
But quantum mechanics is weird.
It's funky, okay? It's weird.
(Peter Shor) When you do quantum computing,
you want to make this weirdness work for you.
So now let's look at our quantum bit or Qbit.
The Qbit cannot only be a zero or a one, it can also both be...
- ...a zero and one...
- ...at the same time. - ...same time.
It's almost like a form of...
- And if you look at the mini worlds - ...parallel computation,
- ...interpretation of a quantum... - ...but in the parallel computer,...
- ...computer... - ...one processor does this,...
- ...what happens... - ...one processor does that.
- ..is that your... - So you've 2 processors...
- ...doing this and that.
- ...quantum computer is doing many... -
- ...quantum computer is doing many... - In a quantum computer, you've only...
- ...many computations... - ...one processor that's...
- ...all at the same time. - ...doing this and that...
- ...at the same time.
Within the giant Dewar Flask lies a prototype quantum computer
surrounded by its supercooled, superconducting magnet.
In the future, quantum computing could be used to predict
quantum interactions,
such as how a new drug acts on faulty biochemistry.
Or to solve complex encryption problems,
like decoding prime numbers
that are the key to Internet credit card security.
This weird quantum world is part of a new frontier
opened up by the descent towards absolute zero.
It's been a remarkable journey for scientists
into unknown territories
far beyond the narrow confines of Earth.
On the Kelvin temperature scale,
which begins at zero degrees for absolute zero,
the temperature of the Sun is around 5000 °K.
At 1000 °K, metals melt.
At 300 °K, we reach what we think of as room temperature.
Air liquifies at 100 °K,
hydrogen at 20 °K, helium at 4 °K.
The deepest outer space is 3 °K above absolute zero,
the coldest place outside the laboratory.
But the descent doesn't stop there.
With ultra cold refrigerators,
the decimal point shifts 3 places
to a few 1000ths of a degree,
and laser cooling takes it down
3 more places to a millionth of a degree,
the temperature of a Bose-Einstein condensate.
With magnetic cooling, we shift 4 more decimal places
until we reach the coldest recorded temperature in the universe,
at a lab in Helsinki:
100 pico Kelvin,
or a 10th of a billionth of a degree above absolute zero.
So will it ever be possible to go all the way,
to reach the Holy Grail of cold, zero °K?
(Seth Lloyd) Getting to absolute zero is tough.
Nobody's actually been there at absolute 0.000000...
with an infinite number of 0s.
That last little tiny bit of heat
becomes harder and harder to get out, and in particular,
the time scales for getting it out
get longer and longer and longer
the smaller and smaller the amounts of energy involved.
So eventually, if you're talking about extracting
an amount of energy that's sufficiently small,
it would indeed take the age of the universe to do it.
Also, actually, you'd need an apparatus
the size of the universe to do it, but that's another story!
Absolute zero may be unreachable,
but by exploring further and further
towards this ultimate destination of cold,
many fundamental secrets of matter have been revealed.
If our past was defined by our mastery of heat,
perhaps our future lies in the continuing conquest of cold.