The Coldest Place in the Universe

Physicists in Massachusetts come to grips with the lowest possible temperature: absolute zero

  • By Tom Shachtman
  • Smithsonian magazine, January 2008, Subscribe
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Bright idea Wolfgang Ketterle (in his M.I.T lab) hopes to discover new forms of matter by studying ultracold atoms. Bright idea: Wolfgang Ketterle (in his M.I.T lab) hopes to discover new forms of matter by studying ultracold atoms.

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    Wolfgang Ketterle’s MIT Website
    Lene Vestergaard Hau’s Harvard University Website

    Related Books

    Absolute Zero and the Conquest of Cold

    by Tom Shachtman
    Mariner Books, 1999

    More from Smithsonian.com

    Where's the coldest spot in the universe? Not on the moon, where the temperature plunges to a mere minus 378 Fahrenheit. Not even in deepest outer space, which has an estimated background temperature of about minus 455°F. As far as scientists can tell, the lowest temperatures ever attained were recently observed right here on earth.

    The record-breaking lows were among the latest feats of ultracold physics, the laboratory study of matter at temperatures so mind-bogglingly frigid that atoms and even light itself behave in highly unusual ways. Electrical resistance in some elements disappears below about minus 440°F, a phenomenon called superconductivity. At even lower temperatures, some liquefied gases become "superfluids" capable of oozing through walls solid enough to hold any other sort of liquid; they even seem to defy gravity as they creep up, over and out of their containers.

    Physicists acknowledge they can never reach the coldest conceivable temperature, known as absolute zero and long ago calculated to be minus 459.67°F. To physicists, temperature is a measure of how fast atoms are moving, a reflection of their energy—and absolute zero is the point at which there is absolutely no heat energy remaining to be extracted from a substance.

    But a few physicists are intent on getting as close as possible to that theoretical limit, and it was to get a better view of that most rarefied of competitions that I visited Wolfgang Ketterle's lab at the Massachusetts Institute of Technology in Cambridge. It currently holds the record—at least according to Guinness World Records 2008—for lowest temperature: 810 trillionths of a degree F above absolute zero. Ketterle and his colleagues accomplished that feat in 2003 while working with a cloud—about a thousandth of an inch across—of sodium molecules trapped in place by magnets.

    I ask Ketterle to show me the spot where they'd set the record. We put on goggles to protect ourselves from being blinded by infrared light from the laser beams that are used to slow down and thereby cool fast-moving atomic particles. We cross the hall from his sunny office into a dark room with an interconnected jumble of wires, small mirrors, vacuum tubes, laser sources and high-powered computer equipment. "Right here," he says, his voice rising with excitement as he points to a black box that has an aluminum-foil-wrapped tube leading into it. "This is where we made the coldest temperature."

    Ketterle's achievement came out of his pursuit of an entirely new form of matter called a Bose-Einstein condensate (BEC). The condensates are not standard gases, liquids or even solids. They form when a cloud of atoms—sometimes millions or more—all enter the same quantum state and behave as one. Albert Einstein and the Indian physicist Satyendra Bose predicted in 1925 that scientists could generate such matter by subjecting atoms to temperatures approaching absolute zero. Seventy years later, Ketterle, working at M.I.T., and almost simultaneously, Carl Wieman, working at the University of Colorado at Boulder, and Eric Cornell of the National Institute of Standards and Technology in Boulder created the first Bose-Einstein condensates. The three promptly won a Nobel Prize. Ketterle's team is using BECs to study basic properties of matter, such as compressibility, and better understand weird low-temperature phenomena such as superfluidity. Ultimately, Ketterle, like many physicists, hopes to discover new forms of matter that could act as superconductors at room temperature, which would revolutionize how humans use energy. For most Nobel Prize winners, the honor caps a long career. But for Ketterle, who was 44 years old when he was awarded his, the creation of BECs opened a new field that he and his colleagues will be exploring for decades.

    Another contender for the coldest spot is across Cambridge, in Lene Vestergaard Hau's lab at Harvard. Her personal best is a few millionths of a degree F above absolute zero, close to Ketterle's, which she, too, reached while creating BECs. "We make BECs every day now," she says as we go down a stairwell to a lab packed with equipment. A billiards-table-size platform at the center of the room looks like a maze constructed of tiny oval mirrors and pencil-lead-thin laser beams. Harnessing BECs, Hau and her co-workers have done something that might seem impossible: they have slowed light to a virtual standstill.

    The speed of light, as we've all heard, is a constant: 186,171 miles per second in a vacuum. But it is different in the real world, outside a vacuum; for instance, light not only bends but also slows ever so slightly when it passes through glass or water. Still, that's nothing compared with what happens when Hau shines a laser beam of light into a BEC: it's like hurling a baseball into a pillow. "First, we got the speed down to that of a bicycle," Hau says. "Now it's at a crawl, and we can actually stop it—keep light bottled up entirely inside the BEC, look at it, play with it and then release it when we're ready."


    Where's the coldest spot in the universe? Not on the moon, where the temperature plunges to a mere minus 378 Fahrenheit. Not even in deepest outer space, which has an estimated background temperature of about minus 455°F. As far as scientists can tell, the lowest temperatures ever attained were recently observed right here on earth.

    The record-breaking lows were among the latest feats of ultracold physics, the laboratory study of matter at temperatures so mind-bogglingly frigid that atoms and even light itself behave in highly unusual ways. Electrical resistance in some elements disappears below about minus 440°F, a phenomenon called superconductivity. At even lower temperatures, some liquefied gases become "superfluids" capable of oozing through walls solid enough to hold any other sort of liquid; they even seem to defy gravity as they creep up, over and out of their containers.

    Physicists acknowledge they can never reach the coldest conceivable temperature, known as absolute zero and long ago calculated to be minus 459.67°F. To physicists, temperature is a measure of how fast atoms are moving, a reflection of their energy—and absolute zero is the point at which there is absolutely no heat energy remaining to be extracted from a substance.

    But a few physicists are intent on getting as close as possible to that theoretical limit, and it was to get a better view of that most rarefied of competitions that I visited Wolfgang Ketterle's lab at the Massachusetts Institute of Technology in Cambridge. It currently holds the record—at least according to Guinness World Records 2008—for lowest temperature: 810 trillionths of a degree F above absolute zero. Ketterle and his colleagues accomplished that feat in 2003 while working with a cloud—about a thousandth of an inch across—of sodium molecules trapped in place by magnets.

    I ask Ketterle to show me the spot where they'd set the record. We put on goggles to protect ourselves from being blinded by infrared light from the laser beams that are used to slow down and thereby cool fast-moving atomic particles. We cross the hall from his sunny office into a dark room with an interconnected jumble of wires, small mirrors, vacuum tubes, laser sources and high-powered computer equipment. "Right here," he says, his voice rising with excitement as he points to a black box that has an aluminum-foil-wrapped tube leading into it. "This is where we made the coldest temperature."

    Ketterle's achievement came out of his pursuit of an entirely new form of matter called a Bose-Einstein condensate (BEC). The condensates are not standard gases, liquids or even solids. They form when a cloud of atoms—sometimes millions or more—all enter the same quantum state and behave as one. Albert Einstein and the Indian physicist Satyendra Bose predicted in 1925 that scientists could generate such matter by subjecting atoms to temperatures approaching absolute zero. Seventy years later, Ketterle, working at M.I.T., and almost simultaneously, Carl Wieman, working at the University of Colorado at Boulder, and Eric Cornell of the National Institute of Standards and Technology in Boulder created the first Bose-Einstein condensates. The three promptly won a Nobel Prize. Ketterle's team is using BECs to study basic properties of matter, such as compressibility, and better understand weird low-temperature phenomena such as superfluidity. Ultimately, Ketterle, like many physicists, hopes to discover new forms of matter that could act as superconductors at room temperature, which would revolutionize how humans use energy. For most Nobel Prize winners, the honor caps a long career. But for Ketterle, who was 44 years old when he was awarded his, the creation of BECs opened a new field that he and his colleagues will be exploring for decades.

    Another contender for the coldest spot is across Cambridge, in Lene Vestergaard Hau's lab at Harvard. Her personal best is a few millionths of a degree F above absolute zero, close to Ketterle's, which she, too, reached while creating BECs. "We make BECs every day now," she says as we go down a stairwell to a lab packed with equipment. A billiards-table-size platform at the center of the room looks like a maze constructed of tiny oval mirrors and pencil-lead-thin laser beams. Harnessing BECs, Hau and her co-workers have done something that might seem impossible: they have slowed light to a virtual standstill.

    The speed of light, as we've all heard, is a constant: 186,171 miles per second in a vacuum. But it is different in the real world, outside a vacuum; for instance, light not only bends but also slows ever so slightly when it passes through glass or water. Still, that's nothing compared with what happens when Hau shines a laser beam of light into a BEC: it's like hurling a baseball into a pillow. "First, we got the speed down to that of a bicycle," Hau says. "Now it's at a crawl, and we can actually stop it—keep light bottled up entirely inside the BEC, look at it, play with it and then release it when we're ready."

    She is able to manipulate light this way because the density and the temperature of the BEC slows pulses of light down. (She recently took the experiments a step further, stopping a pulse in one BEC, converting it into electrical energy, transferring it to another BEC, then releasing it and sending it on its way again.) Hau uses BECs to discover more about the nature of light and how to use "slow light"—that is, light trapped in BECs—to improve the processing speed of computers and provide new ways to store information.

    Not all ultracold research is performed using BECs. In Finland, for instance, physicist Juha Tuoriniemi magnetically manipulates the cores of rhodium atoms to reach temperatures of 180 trillionths of a degree F above absolute zero. (The Guinness record notwithstanding, many experts credit Tuoriniemi with achieving even lower temperatures than Ketterle, but that depends on whether you're measuring a group of atoms, such as a BEC, or only parts of atoms, such as the nuclei.)

    It might seem that absolute zero is worth trying to attain, but Ketterle says he knows better. "We're not trying," he says. "Where we are is cold enough for our experiments." It's simply not worth the trouble—not to mention, according to physicists' understanding of heat and the laws of thermodynamics, impossible. "To suck out all the energy, every last bit of it, and achieve zero energy and absolute zero—that would take the age of the universe to accomplish."

    Tom Shachtman is the author of Absolute Zero and the Conquest of Cold, the basis for a future PBS "Nova" documentary.


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    Comments (130)

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    plurghch. Never heard so much absolute pish. "Hawking radiation"!? - I call it a "Hawking Hole". Please tell me how warm the Universe is... from the outside.

    Posted by layman on January 13,2012 | 11:40 PM

    Fahrenheit? That ruined this article.

    Posted by Oscar on April 6,2011 | 10:12 AM

    Are that temperature (zero absolute) be reach in trillions year time when all stars die and there's no radiation left? Or there's still be radiation throughout black holes?

    Posted by Aladje on December 10,2010 | 11:00 AM

    If one is commenting about the speed of light, it should be said that the speed of light 'in this dimension' is such and such. In hyperspace co-dimensions the speed of light has a different value depending on the physics constants of the dimension. For example, the hyperspace speed of light can be 1 meter/second. Because space-time is actually a large 3D spring with a spring constant, a low speed of light reduces the spring constant so that space-time becomes wavy like water. Moving through this soft space-time creates gravitational waves like a boat moving through water. Newton's gravitational constant G is equal to the speed of light squared divided by the linear mass of the universe. With a speed of light equal to 1 m/s and a linear mass of .078 kg/m, the gravitational constant increases to 12.8 rather than 6.673200002x10^-11. Because Planck's constant h depends on the speed of light, a slow light speed will reduce Planck's constant. In a hyperspace co-dimension, light has a soft misty glow compared to our harsh glaring light in this dimension.

    Posted by JohnStClair on May 12,2010 | 02:25 PM

    I think that he is stoping time,and by doing so gives the appeance that light has been stoped.We know can travel faster that this light in the same environment?The light is still there,its the movement of the light that was stoped,not light it self.By freezing the space that light occupies only stopes its movement in time.

    Posted by Charlie on December 26,2009 | 10:57 AM

    does this mean it's possible that dark matter is just really really really cold?

    Posted by Lauren on December 6,2009 | 08:24 PM

    very interesting. how about making a cloud at absolute zero, at this size? 7,926 miles
    x 3?
    ____________
    Its said before movies that the sun is going to have a solar blast capable of destroying the earth. why not cover the earth 3 times (outterside of atmosphere), using sattelites as magnets, clouds reaching 0 Kalvin. easy solution. I mean all of it would be free for our governments... makes you think though. satellites must contain a strong magnetic field in order to stay within the orbit (around the earth). Can we not magnify the gravity pull make it a negative force and push this solar flare away from earth?

    Posted by Jonathan on November 18,2009 | 10:19 PM

    What's this fareniheit thing? Is it a new scientific measurement?

    Posted by Benjamin Lewis on September 18,2009 | 01:55 AM

    From what I understand about temperature, it is the measurement of the movement of molecules and atoms that bang up against the measureing device or the vibration that they make. So then wouldn't the absence of molecules and atoms in space be absolute 0. But the measureing device would give off heat. So then it couldn't actually ever be measured.

    Posted by Jeffrey Lentz on June 12,2009 | 01:32 AM

    I thought the coldest place on earth was Vostok, Antarctica.

    Posted by on May 21,2009 | 02:46 PM

    Hawking radiation occurs because of the interaction of the black hole with the nonzero energy of physical vacuum when examined at very short time-scales. The vacuum is really a sea of various so-called 'virtual' particles and antiparticles being created and annihilated continuously. Some of the antiparticles are trapped by the black hole's gravity and disappear over the event horizon before they can recombine. When one antiparticle is attracted over the event horizon and its matching particle escapes, radiation seems to be emitted. The antiparticle that crosses the event horizon combines with the black hole to cause a loss of matter (matter interacting with antimatter is annihilated and turns into pure energy). So actually the black hole would look hotter after this occurs, but the energy would have to be carried away by photons that cannot ever cross the event horizon going outward. So there is no way to observe this energy.

    The thing that fascinates me is the asymmetry of this process. If it occurred equally easily each way, so that virtual particles and antiparticles of the vacuum crossed the event horizon in equal numbers, there would be no net loss of mass. However, I believe that the asymmetry must be due to the way these particles interact with the strong gravitational field near the event horizon. But someone who knows more about this might be able to correct me.

    By the way, not all 'black holes' or 'singularities' that have been proposed would undergo the weirdnesses of this process and give off heat while losing mass. There are 'naked singularities' postulated that have no event horizons due to the conditions under which they exist, say in extremely dense particle clouds.

    Posted by John Trombley on March 5,2009 | 06:47 PM

    Great article. I couldn't even begin to explain the thought process this has sent my mind, the conspiracies and possibilities of this science. And regarding the metric vs US measurements. If I pick up an american magazine, please place all the foreign stuff in parenthisis. As the previous poster said, would you want to pick up a french magazine just to find out it was all in spanish?

    Posted by Kurt on January 6,2009 | 08:22 PM

    The way that super-cooled temperatures seem to have a productive effect on electrical applications (circuits and so forth), there must be a correlation as well with the human brain and more productive brain activity in cooler environments. Not to say that the locals among the Court of Neptune are on the short side of the intellectual staff, or anything. However, it would make an interesting study to determine intellectual, academic, political, emotional, and/or other factors that may be common among people within common climatic regions. It may also affect how one would even determine the results of experiments such as the absolute 0, depending on their ability of perception of those results.

    Posted by Angela Renee on November 27,2008 | 05:53 AM

    Ed has a very valid point.I was just wondering that if in near-zero temperature matter behave differently that what is predicted by physical laws, how do physicists bring all of that deviation to be explained on a common platform of theoritical physics.Also intergalactic distance measured this far, I guess would be needing complex correction. How could that be achieved or rationalised. also it just cropped up in my mind that what would be the state of movement of light in a Black Hole (where its trapped by immense gravity.Is there a speed-temperature co-relation work-out for that matrix?...

    Posted by George Stephen on November 20,2008 | 03:13 AM

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