A Two-Hour Special, Original PBS Broadcast Dates: January 8 & 15, 2008
TV Program Description
Air-conditioning, refrigeration, and superconductivity are just some of the ways technology has put cold to use. But what is cold, how do you achieve it, and how cold can it get? NOVA explores these and other facets of the frigid in two one-hour programs. The two-part special follows the quest for cold from the unlikely father of air-conditioning, the court magician of King James I of England in the 17th century, to today's scientists pioneering superfast computing in the quantum chill near absolute zero—the ultimate extreme of cold at minus 273.15 C (minus 460 F).
Along the way, viewers learn about the invention of thermometers, the origin of the ice business in 19th-century New England, Clarence Birdseye's fishing trip that led to the invention of frozen food, and a couple of cold-inspired scientific races towards absolute zero that ended in Nobel Prizes.
NOVA brings the history of this frosty subject to life with historical recreations of great moments in low-temperature research and interviews with noted historians and scientists, including Simon Schaffer of the University of Cambridge, and Nobel laureates Eric Cornell and Carl Wieman of the University of Colorado at Boulder and Wolfgang Ketterle of the Massachusetts Institute of Technology.
The program is based on the definitive book on cold: Absolute Zero and the Conquest of Cold by Tom Shachtman.
Part One, "The Conquest of Cold," opens in the 1600s when the nature of cold and even heat were a complete mystery. Are they different phenomena or aspects of some unified feature of nature? Are they added to a substance or qualities of the substance itself? The experiments that settled these questions helped stoke the Industrial Revolution, which exploited such fundamental insights as that heat always flows from hot to cold. (Learn about the mysterious opposite to absolute zero.)
The key moments in cold in this episode include: Cornelius Drebbel's spooky trick of turning summer into winter for the English king, achieved in much the way that homemade ice cream is produced; Antoine Lavoisier's battle with Count Benjamin Rumford over the caloric theory of heat, an intellectual contest set against the backdrop of the French Revolution, in which Lavoisier unfortunately lost his head; and Michael Faraday's explosive experiments to liquefy gases, which established the principles that make refrigerators possible.
Part Two, "The Race For Absolute Zero," picks up the story in the late 19th century, when researchers plunged cold science to new lows as they succeeded in reaching the forbidding realm at which oxygen and then nitrogen liquefy. (See if you can liquefy oxygen yourself.) The master of this technology was Scottish chemist James Dewar, who pursued the holy grail of the field—liquefying hydrogen at minus 253 C, just 20 degrees above absolute zero. When he succeeded, he faced the unexpected and even more daunting challenge of liquefying the newly discovered gas helium at a mere 5 degrees above absolute zero. However, he had a talented competitor—Dutch physicist Heike Onnes—and the ensuing race to the bottom of the temperature scale was as zealous as the contemporaneous race to the Earth's poles.
The end of the 20th century produced another low-temperature contest. No one had ever seen an exotic form of matter called a Bose-Einstein condensate, which only forms at temperatures vanishingly close to absolute zero. But new techniques developed in the 1990s by Daniel Kleppner at the Massachusetts Institute of Technology set the stage for a race to create this truly bizarre substance—and with it win the latest heat in the quest for cold.
NARRATOR: The greatest triumph of civilization is often seen as our mastery of heat, yet our conquest of cold is an equally epic journey, from dark beginnings to an ultracool frontier.
For centuries, cold remained a perplexing mystery, with no obvious practical benefits. Yet in the last 100 years, cold has transformed the way we live and work. Imagine supermarkets without refrigeration, skyscrapers without air conditioning, hospitals without MRI machines and liquid oxygen.
We take for granted the technology of cold, yet it has enabled us to explore outer space and the inner depths of our brain, And, as we develop new ultracold technology to create quantum computers and high speed networks, it will change the way we work and interact.
How did we harness something once considered too fearsome to even investigate? How have scientists and dreamers, over the past four centuries, plunged lower and lower down the temperature scale to conquer the cold and reach its ultimate limit, a holy grail as elusive as the speed limit of light? Absolute Zero, up next on NOVA.
Major funding for NOVA is provided by David H. Koch. And...
Discover new knowledge: HHMI.
Major funding for Absolute Zero is provided by the National Science Foundation, where discoveries begin. Additional funding is provided the Alfred P. Sloan Foundation, to portray the lives of men and women engaged in scientific and technological pursuit.
Major funding for NOVA is also provided by the Corporation for Public Broadcasting and PBS viewers like you. Thank you.
NARRATOR: Extreme cold has always held a special place in our imagination. For thousands of years it seemed like a malevolent force associated with death and darkness.
Cold was an unexplained phenomenon. Was it a substance, a process or some special state of being?
Back in the 17th century no one knew, but they certainly felt its effects in the freezing London winters.
SIMON SCHAFFER (University of Cambridge): Seventeenth century England was in the middle of what's now called the "Little Ice Age." It was fantastically cold by modern standards. You have to imagine a world lit by fire in which most people are cold most of the time. Cold would have felt like a real presence, a kind of positive agent that was affecting how people felt.
NARRATOR: Back then, people felt at the mercy of cold. This was a time when such natural forces were viewed with awe, as acts of god, so anyone attempting to tamper with cold did so at his peril.
The first to try was an alchemist, Cornelius Drebbel. On a hot summer's day, in 1620, King James the First and his entourage arrived to experience an unearthly event. Drebbel, who was also the court magician, had a wager with the king that he could turn summer into winter. He would attempt to chill the air in the largest interior space in the British Isles, the Great Hall of Westminster.
Drebbel hoped to shake the king to his core.
ANDREW SZYDLO (Chemistry Historian): He had a phenomenally fertile mind. He was an inventor par excellence. His whole world was steeped in a world of alchemy, of perpetual motion machines, of the idea of time, space, planets, moon, sun, gods. He was a fervently religious man. He was a person for whom nature presented a phenomenal...a galaxy of possibilities.
NARRATOR: Dr. Andrew Szydlo, a chemist with a lifelong fascination for Drebbel, enjoys his reincarnation as the great court magician.
Like most alchemists, Drebbel kept his methods secret. Dr. Szydlo wants to test his ideas on how Drebbel created artificial cold.
ANDREW SZYDLO: When Drebbel was trying to achieve the lowest temperature possible, he knew that ice, of course, was the freezing point, the coldest you could get normally. But he would have been aware of the facts, through his experience, that mixing ice with different salts could get you a colder temperature.
NARRATOR: Salt will lower the temperature at which ice melts. Dr. Szydlo thinks Drebbel probably used common table salt, which gives the biggest temperature drop. But salt and ice alone would not be enough to cool the air within such a large interior. Drebbel was famous for designing elaborate contraptions, a passion shared by Dr. Szydlo, who has an idea for the alchemist's machine.
ANDREW SZYDLO: So here, we would have had a fan, which would have been turned over, blowing warm air over the cold vessels there. And as the air blows over these cold jars we would have had, in effect, the world's first air conditioning unit.
NARRATOR: But could this really turn summer into winter?
ANDREW SZYDLO: The idea is to stir it in as well as possible, in the five seconds that you have to do it.
NARRATOR: Dr. Szydlo stacks the jars of freezing mixture to create cold corridors for the air to pass through.
ANDREW SZYDLO: Now we can feel it's very cold. In fact, I could feel cold air actually falling on my hands, because cold air, of course, is denser than warm air, and one can feel it quite clearly on the fingers.
NARRATOR: The vital question: would the gust of warm air become cold?
ANDREW SZYDLO: I can feel, certainly, a blast of cold air hitting me as that second cover was released. Well, temperature...we're on 14 at the moment.
Yes, keep it going. That's definitely the right direction.
NARRATOR: King James would have been shaken by his encounter with manmade cold. Had Drebbel written up his great stunt, he might have gone down in history as the inventor of air conditioning, yet it would be almost three centuries before this idea would actually take off.
To advance knowledge and conquer the cold required a very different approach, the scientific method. The fundamental question, "What is cold?" haunted Robert Boyle nearly 50 years later. The son of the Earl of Cork, a wealthy nobleman, Boyle used his fortune to build an extensive laboratory.
Boyle is famous for his experiments on the nature of air, but he also became the first master of cold. Believing it to be an important but neglected subject, he carried out hundreds of experiments.
SIMON SCHAFFER: He worked through, very systematically, a series of ideas about what cold is: "Does it come from the air? Does it come from the absence of light? Is it that there are strange so-called "frigorific" cold-making particles?"
NARRATOR: In Boyle's day, the dominant view was that cold is a primordial substance that bodies take in as they get colder and expel as they warm up. It was this view that Boyle would eventually overturn by a set of carefully devised experiments on water.
First, he carefully weighed a barrel of water and took it outside in the snow, leaving it to freeze overnight. Boyle was curious about the way water expanded when it turned to ice. He reasoned that if, once the water turned to ice, the barrel weighed more, then perhaps cold was a substance after all.
But when they re-weighed the barrel, they discovered it weighed exactly the same.
SIMON SCHAFFER: So what must be happening, Boyle guessed, was that the particles of water were moving further apart, and that was the expansion, not some substance flowing into the barrel from outside.
NARRATOR: Boyle was becoming increasingly convinced that cold was not a substance but something that was happening to individual particles, and he began to think back to his earlier experiments with air.
As matter like air becomes warmer, it tends to expand. Boyle imagined the air particles were like tiny springs, gradually unwinding, and taking up more space as they heat up.
SIMON SCHAFFER: Boyle's conclusion, here, was that heat is a form of motion of a particular kind, and that as bodies cool down they move less and less.
NARRATOR: Boyle's longest published book was on the cold, yet he found its study troublesome and full of hardships, declaring that he felt like a physician trying to work in a remote country without the benefit of instruments or medicines.
To properly explore this country of the cold, Boyle lamented the lack of a vital tool, an accurate thermometer.
It was not until the mid-17th century that glass blowers in Florence began to produce accurately calibrated thermometers. Now it became possible to measure degrees of hot and cold.
Like the air in Boyle's experiment, heat makes most substances expand. Early thermometers used alcohol, which is lighter than mercury and expands much more with heat, so these early thermometers were sometimes several meters long and often wound into spirals.
But there was still one major problem with all thermometers: the lack of a universally accepted temperature scale.
HASOK CHANG (University College London): There are all kinds of different ways of trying to stick numbers through these degrees of hot and cold. And they, on the whole, didn't agree with each other at all. So one guy in Florence makes one kind of thermometer, another guy in London makes a different kind, and they just don't even have the same scale. And so there was a lot of problem in trying to standardize thermometers.
NARRATOR: The challenge was to find events in nature that always occur at the same temperature and make them fixed points. At the lower end of the scale, that might be ice just as it begins to melt; at the upper end it could be wax heated to its melting point.
The first temperature scale to be widely adopted was devised by Gabriel Daniel Fahrenheit, a gifted instrument maker who made thermometers for scientists and physicians across Europe.
He had several fixed points: he used a mixture of ice, water, and salt for his zero degrees; ice melting in water at 32 degrees; and for his upper fixed point, the temperature of the human body at 96 degrees, which is close to the modern value.
HASOK CHANG: One of the things that Fahrenheit was able to achieve was to make thermometers quite small, and that he did by using mercury, as opposed to alcohol or air, which other people had used. And because mercury thermometers are compact, clearly if you're trying to use it for clinical purposes, you don't want some big thing sticking out of the patient. So the fact that he could make them small and convenient, that seems to be what made Fahrenheit so famous and so influential.
NARRATOR: It was a Swedish astronomer, Anders Celsius, who came up with the idea of dividing the scale between two fixed points into 100 divisions.
HASOK CHANG: The original scale used by Celsius was upside down, so he had the boiling point of water as zero, and the freezing point as 100, with numbers just continuing to increase as we go below freezing. And this is another little mystery in the history of the thermometer that we just don't know for sure. What was he thinking when he labeled it this way? And it was the botanist Linnaeus, who was then the president of the Swedish Academy who, after a few years, said, "Well, we need to stop this nonsense," and inverted the scale to give us what we now call Celsius scale, today.
NARRATOR: A question nobody thought to ask when devising temperature scales was "How low can you go? Is there an absolute lower limit of temperature?" The idea that there might be would become a turning point in the history of cold.
HASOK CHANG: The story begins with the French physicist Guillaume Amontons. He was doing experiments heating and cooling bodies of air to see how they expand and contract.
NARRATOR: Amontons heated air in a glass bulb by placing it in hot water. Just like a hot air balloon, the air in the glass bulb expanded as the increased pressure forced a column of mercury up the tube. Then he tried cooling the air.
HASOK CHANG: He was noticing that, well, when you cool a body of air, the pressure would go down. And he speculated, "Well, what would happen if we just kept cooling it?"
NARRATOR: By plotting this falling temperature against pressure, Amontons saw that as the temperature dropped, so did the pressure, and this gave him an extraordinary idea.
ANDREW SZYDLO: Amontons started to consider the possibility, "What would happen if you projected this line back until the pressure was zero?" And this was the first time in the course of history that people had actually considered the concept of an absolute zero of temperature: zero pressure, zero temperature.
HASOK CHANG: It was quite a revolutionary idea, when you think about it, because you wouldn't just think that temperature has a limit of lower bound, or zero, because in the upper end it can go on forever, we think, until it's hotter and hotter and hotter. But somehow, maybe there's a zero point where this all begins. So you could actually give a calculation of where this zero point would be. Amontons didn't do that calculation himself, but some other people did later on. And when you do it, you, you get a value that's actually not that far from the modern value of, roughly, minus-273 centigrade.
NARRATOR: In one stroke, Amontons had realized that although temperatures might go on rising forever, they could only fall as far as this absolute point, now known to be minus-273 degrees centigrade. For him, this was a theoretical limit, not a goal to attempt to reach.
Before scientists could venture towards this zero point, far beyond the coldest temperatures on Earth, they needed to resolve a fundamental question. By now, most scientists defined cold simply as the absence of heat, but what was actually happening as substances warmed or cooled was still hotly debated.
SIMON SCHAFFER: The argument of men like Amontons relied completely on the idea that heat is a form of motion and that particles move more and more closely together as the substance in which they're in gets cooler and cooler.
NARRATOR: Unfortunately the science of cold was about to suffer a serious setback. The idea that cooling was caused by particles slowing down began to go out of fashion. At the end of the 18th century, a rival theory of heat and cold emerged that was tantalizingly appealing, but completely wrong. It was called the caloric theory, and its principle advocate was the great French chemist Antoine Lavoisier.
Like most scientists of the time, Lavoisier was a rich aristocrat who funded his own research. He and his wife, Madame Lavoisier, who assisted with his experiments, even commissioned the celebrated painter David to paint their portrait.
Lavoisier carried out experiments to support the erroneous idea that heat was a substance, a weightless fluid that he called "caloric."
HASOK CHANG: He thought, in the solid state of matter, molecules were just packed close in together, and when you added more and more caloric to this, the caloric would insinuate itself between these particles of matter and loosen them up.
So the basic notion was that caloric was this fluid that was, as he put it, "self-repulsive." It just tended to break things apart from each other. And that's his basic notion of heat. So cold is just the absence of caloric, or the relative lack of caloric.
NARRATOR: Lavoisier even had an apparatus to measure caloric, which he called a calorimeter. He packed the outer compartment with ice. Inside he conducted experiments that generated heat, sometimes from chemical reactions, sometimes from animals, to determine how much caloric was released. He collected the water from the melting ice and weighed it to calculate the amount of caloric generated from each source.
ROBERT FOX (University of Oxford): I think the most striking thing about Lavoisier is that he sees caloric as a substance which is exactly comparable with ordinary matter, to the point that he includes caloric in his list of the elements.
SIMON SCHAFFER: Indeed, for Lavoisier, it's an element, like oxygen or nitrogen. Oxygen gas is made of oxygen plus caloric, and if you take the caloric away, presumably, the oxygen might liquefy. So it's a very hard model to shift, because it explains so much, and, indeed, Lavoisier's chemistry was so otherwise extraordinarily successful. However, Lavoisier's story about caloric was soon undermined.
NARRATOR: But there was one man who was convinced Lavoisier was wrong and was determined to destroy the caloric theory. His name was Count Rumford.
Count Rumford had a colorful past. He was born in America, spied for the British during the Revolution, and after being forced into exile, became an influential government minister in Bavaria.
Among his varied responsibilities was the artillery works, and it was here, in the 1790s, that he began to think about how he might be able to disprove the caloric theory using cannon boring.
Rumford had noticed that the friction from boring out a cannon barrel generated a lot of heat. He decided to carry out experiments to measure how much. He adapted the boring machine to produce even more heat by installing a blunt borer that had one end submerged in a jacket of water. As the cannon turned against the borer, the temperature of the water increased and, eventually, boiled. The longer he bored, the more heat was produced.
SIMON SCHAFFER: For Rumford, what this showed was that heat must be a form of motion, and heat is not a substance because you could generate indefinitely large amounts of heat simply by turning the cannon.
NARRATOR: Despite Count Rumford's best efforts, Lavoisier's caloric theory remained dominant until the end of the 18th century. His prestige as a chemist meant that few dared challenge his ideas, but this did not protect him from the revolutionary turmoil in France, which was about to interrupt his research. At the height of the Reign of Terror, Lavoisier was arrested and eventually lost his head.
SIMON SCHAFFER: Once he was guillotined, his wife left France and eventually met Rumford, when he moved to Western Europe in the early 1800s. Rumford then married her. So he'd married the widow of the man who'd founded the theory that he'd destroyed.
NARRATOR: The marriage was short-lived. After a tormented year, Rumford left Madame Lavoisier and devoted the rest of his life to his first love, science.
It would be nearly 50 years before Rumford's idea that temperature is simply a measure of the movement of particles was accepted. With heat, the particles—what we now know as atoms—speed up, and with cold, they slow down.
Rumford's dedication to science led him to become a founder of the Royal Institution in London, and it was here that the next major breakthrough in the conquest of cold would occur.
Michael Faraday, who later became famous for his work on electricity and magnetism, would take a critical early step in the long descent towards absolute zero, when he was asked to investigate the properties of chlorine using crystals of chlorine hydrate.
This experiment was potentially explosive, which is perhaps why it was left to Faraday—and perhaps also why Dr. Andrew Szydlo is curious to repeat it today.
ANDREW SZYDLO: We are about to undertake an exceedingly dangerous experiment in which Michael Faraday, in 1823, heated this substance here, the hydrate of chlorine, in a sealed tube.
Is that sealed?
LAB ASSISTANT: That's sealed, Andrew.
ANDREW SZYDLO: That's absolutely brilliant!
NARRATOR: In the original experiment, Faraday took the sealed tube and heated the end containing the chlorine hydrate in hot water. He put the other end in an ice bath. Soon he noticed yellow chlorine gas being given off.
ANDREW SZYDLO: Because the gas is being produced, pressure's building up.
Ray, this is where it starts to get dangerous, so if you now take a few steps back...
NARRATOR: When Faraday did the experiment, a visitor, Dr. Paris, came by to see what he was up to. Paris pointed out some oily matter in the bottom of the tube. Faraday was curious, and decided to break open the tube.
ANDREW SZYDLO: Right, so let's have a look inside here.
NARRATOR: The explosion sent shards of glass flying. With the sudden release of pressure, the oily liquid vanished.
ANDREW SZYDLO: And there we are.
LAB ASSISTANT: Is that what happened?
ANDREW SZYDLO: Yeah, that's exactly what happened. It popped open, glass flew, and...can you detect the strong smell of chlorine?
LAB ASSISTANT: I can now.
ANDREW SZYDLO: Absolutely. Well, he detected the strong smell of chlorine and this, this was a major mystery for him.
NARRATOR: Faraday soon realized the increased pressure inside the sealed tube had caused the gas to liquefy. And when the tube was broken, the liquid evaporated,