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."
you should not have left out the graphic from page 21 of the print issue
Posted by frank on December 22,2007 | 10:42AM
I loved the article on the Coldest Place in the Universe (in the January 2008 issue)and want to use it in my classes, where we are about to begin thermodynamics. The trouble is, you used Fahrenheit degrees instead of Celsius, and never mentioned the Kelvin scale. My students are confused enough without having to translate your -459.67oF to -273.15oC. I wish Smithsonian would go to metric. Trying to be suitable for all, you make it tough for those of us who are teaching science. Thanks to Tom Shchtman for a really good piece. Regards. Paul Barra
Posted by Paul A. Barra on December 25,2007 | 06:15AM
Thoroughly enjoyed the article however one question came to mind. There was a chart explaining that the coldest temperature in deep space was -455°F. If light slows down to nearly stopping at absolute 0 (459.67°F) then how does the coldest temperature in space affect travel time from source to viewer? Astronomers have measured the distance to stars by knowing the speed of light but are these distances correct if the speed of light has slowed due to extremely cold temperatures? Just curious.
Posted by Ed on December 26,2007 | 06:56AM
If, "To physicists, temperature is a measure of how fast atoms are moving, ……", is it possible to talk about any temperature, let alone absolute zero, in a vacuum? Perhaps we need to define more rigorously "vacuum" - for us laymen. My on-line dictionary states, "vacuum - a space entirely devoid of matter." Trained as an electricaI engineer, I had assumed that "vacuum" meant a region in three-dimensional space wherein there is no matter of any kind whatsoever. Also, are we rigorously correct if we talk about "temperature" in "outer space"? Unless I am badly mistaken, are there not supposed to be only about 1 or 2 atoms per cubic yard in "outer space"? (or is it 1 or 2 molecules?) If so, what types of atoms (or molecules) do we assume those are? Maybe, also, we need to define more rigorously "outer space." For example, where is it? - how far between planets - or between galaxies? Or, frankly, is it merely a loose term in common parlance for discussing extra-earthly regions?
Posted by George A. Barnard on December 30,2007 | 09:48AM
Thank you for a great article. It is wonderfully up to date, and very interesting. I agree completely with Paul Barra re: Smithsonian updating to metric. As a Chemistry/Physics high school teacher, I struggle constantly to convince my students that working in Celsius, or in this case Kelvin, is the way to go. We don't even teach converting to/from Farenheit anymore. So, when I use this article with my students, we will have to spend some time "doing the conversions". Linda Martin
Posted by Linda Martin on December 31,2007 | 04:59PM
Prior to reading Ed's post, I had also got to thinking of how distances in our universe are measured in light years which presume the speed of light to be constant and began to wonder what effect there would be if it were to turn out that the universe actually contains cold regions where the speed of light might be slowed to a near-standstill or crawl. Assuming scientists have correctly calculated the age of light reaching us, it could turn out that distant galaxies might be a lot closer than we think. Imagine if, say, a million light years of cold empty space were equivalent in distance to a single light year of warmer, dust-filled space. On the other hand, if the distances believed to separate the stars and galaxies are indeed correct we could be looking back trillions and quadrillions of years in our telescopes as opposed to mere millions and billions and the universe could be exponentially older than the big bang theorists would have us believe... Just speculating...
Posted by Terry Phelan on December 31,2007 | 11:19PM
Ed makes a very good point. I'm wondering if anyone has thought to use the science of perspective to double-check and see if the apparent size of galaxies observed is appropriate for the distances they are alleged to be from us in terms of light years. It's a shame author Tom Shachtman didn't delve into astronomical implications in an otherwise excellent article as Wolfgang Ketterle's discoveries could provide simple explanations for phenomena that heretofore required elaborate theories. Black holes, for instance, could simply be pockets of space where the temperature is so cold the photons are immobilized. Likewise, our so-called "expanding universe" might be a simple illusion resulting from fluctuations in the speed of light due to subtle variations in the temperature of space. I'm curious to learn whether Dr. Ketterle has considered the astronomical implications of his research, for by creating the equivalent of a black hole in an earthly laboratory and thereby helping all of us to better understand the cosmos, Ketterle may deserve more than a simple Guiness Book record. In my humble opinion, a Nobel prize may be in order.
Posted by Terry Phelan on January 3,2008 | 10:39AM
I found your artical very informative and entertaining. A question does come to my mind. If the moon is -253 degrees when it faces the sun and -378 degrees at night, the sun must contribute very little to keeping its planets warm. To me this means that most of the warmth on earth is derived from its molten core and not from the sun. Thank you.
Posted by paul skillman on January 4,2008 | 08:05AM
If Ketterle's experiments are replicable, those who may still wish to view the speed of light as a constant will have to give him credit for demonstrating that temperature can infinitely stretch time. Think about it. If a patch of space the temperature that Ketterle has been able to produce in his lab were to intervene between ourselves and a star we were observing, the photons coming from the star would be stopped dead in their tracks like a frozen traffic jam but it would appear to an earthly observer that the star had somehow been sucked into some sort of black hole. Of course it wouldn't have been, any more than our sun gets gravitationally sucked into every passing cloud on a balmy day. What would our universe look like if light really did travel everywhere, all the time at the unimpeded "speed of light?" My guess is we'd have no night at all. Like the denizens of Asimov's "Nightfall", like the words to the Springsteen song, we'd be blinded by the light.
Posted by Terry Phelan on January 4,2008 | 01:25PM
I read some good comments on the article, but no one hit on the possibilty of harnessing light at absolute zero and using it indefinitely! Is it possible?
Posted by Steve A. Williams on January 5,2008 | 07:13PM
Good article, but the chart on page 21 show the Moon's surface temperature in sunlight to be -253. No mattrer which scale is used (C, F, K, R) the Moon's sunside is + degrees, not negative. Check with NASA the next time. If I am remiss, then blame my science education and attention to correct representations. The subsurface temperatures now are another issue. I hope this is helpful, andcauses a change. Thank You.
Posted by Terry Wilson on January 5,2008 | 07:47PM
While reading and thinking about the ideas described in "The Coldest Place in the Universe," an article in the January 2008 Simithsonian about Bose-Einstein condensates, this question popped into my head: are "time" and "temperature" some how related? might they be equivalent in the same manner as energy and matter? And if so, can the time variable in physics equations be replaced with a temperature variable? IF temperature simply measures the motion of atoms, and if we measure time by an interval between their vibrations, why not? When I finished my morning throne obligations, I went immediately to google and searched the string "equivalence of time and temperature" and found 29 articles: http://www.google.com/search?q=%22equivalence+of+time+and+temperature%22 and sure enough, there are a few people who have started to use the idea, mostly in materials and engineering as a principle for extrapolation from short-term test data to describe longer-term behaviors of materials under stress . . . My question to physicists among us is whether the Time-temperature superposition principle may have broader and deeper application beyond materials research?
Posted by David Addleton on January 12,2008 | 06:31AM
A very interesting article, I never imagined there was a temperature so cold.
Posted by Nicholas on January 12,2008 | 11:59PM
I'm only twelve and I fully understood each meaning! The topic made me want to keep reading. I'm going to present this article to my class and explain it to my peers. I can't wait to see the looks on their faces!
Posted by Karbelly on January 15,2008 | 06:57PM
Cool article, but exactly what device is capable of measuring temperature that cold?
Posted by Jody Wyse on January 17,2008 | 02:25PM
This is absolutly amazing! I was quite impressed at how easily I understood this article and I found the given information fascinating! I knew some about studies and experiments being preformed on and about the extreme cold, but this has taken my knowledge and interest to a higher level.
Posted by Margaret Pruitt on January 19,2008 | 05:19PM
Jody, it's been a while since I've looked at instrumentation for uses like this, but if memory serves, a device called a Straty-Adams gauge is capable of measuring temperatures down to a few thousands of 1 degree Kelvin. The temperatures cited in this article are still lower, though, so I don't know if a Straty-Adams gauge will suffice or whether another technique is required.
Posted by Rich Kulawiec on January 21,2008 | 06:16PM
Just a few points here in response to people's qeustions: Ed, The cosmic background radiation (CMB) has been measured as being around -455 degrees. This is the radiation left over from the big bang at the beginning of the universe. Light only slows down when it enters a tightly packed BEC composed of thousands or millions of particles. As these do not exist in the vacuum of space the speed of light would remain (relatively) constant. Paul, The heat from the sun contributes a great deal to the temperature of a planet. Consider how cold it can get at night and then how hot it can be during the day. However, this is due to the atmosphere of the earth being heated and trapping the heat energy in. The moon has no atmosphere to speak of and as such doesn't retain as much heat. Terry is right though, the temperature gets up to 253 degrees during the day. thats positive not negative. Steve, You could theoretically trap light indefinitely using these methods yes, but you could not use it for anything. As soon as you start using the light you would be using up its energy and it would eventually run out depending on how much was there to start with. Hope this info helps.
Posted by Ed Smith on January 21,2008 | 06:38PM
I never would have thought the coldest temp would be right here on Earth. I thought perhaps Pluto or some far off planet would be the place.
Posted by Stock Forums on January 21,2008 | 07:02PM
Ed, Terry, Paul, You misunderstand the reason for the slowing of the light, within an BEC. It is not explictly due to the cold, but rather the raw density of these states that enable them to slow light in such as fashion. The cold is merely the facilitator. Regions of deep space are 'cold' because of the lack of radiant energy, and the lack of matter, as far as I understand. Neither of these would impact the speed of light, in any serious way. The constant, C, is only the speed of light in a vaccum, but space is 'close enough'.
Posted by Vanna on January 21,2008 | 07:33PM
I am very curious as to the "slowing of light" inside a BEC, from an observer outside the BEC does the light appear at all or would i become an area void of light? I'd assume if no light is reaching your eyes it would appear dark. Also does anyone have any speculation as to why the sodium "defies" gravity and climbs up the walls of anything containing it?
Posted by Stuart on January 22,2008 | 03:47AM
If light slows down that much in almost absolute zero, wouldn't that mean that the light from stars and galaxies is slower and therefor the stars and galaxies much closer than we now think?
Posted by Christian in San Diego on January 22,2008 | 10:29AM
1 question: How can light be slowed down in a BEC, but as soon as it is released from it, it speeds back up to it's original velocity? I thought matter (and light is considered matter, specifically called a photon) could only speed up when some type of forced provided propulsion to it. How then does it seem to speed up with nothing pushing on it? And about using light for energy and other purposes: I've always been told that light has infinite energy, which is why nothing can go as fast as it. Therefore, there would be no way it could "run out." How can you run out of something if it never runs out?
Posted by Richard on January 22,2008 | 12:25PM
Enjoyed reading this one as it answered why on some nights every month the head lamps on my car are rubbish ,as most gas guzzler drivers will tell you you get dark nights and light nights where the light just will not travel as far as it normally does this seems to have a pattern repeated most months ,so maybe the scientists instead of searching deep space or making up gasses in a lab should drive around at night and find what gasses if any are causing this problem ,I think it would answer a lot more questions .
Posted by james smith on January 22,2008 | 01:47PM
So, if it is the resulting density (and not the temperature) that can slow the speed of light, and bring it to a stop, then do all the same light speed laws apply? That is, that nothing can exceed the speed of light. If the speed of light is reduced to zero, then I should think very odd things may be occurring. Is the speed of light utterly tied to density and nothing else? Can we go the other way? Is there anything less dense than a vacuum (even hypothetically?) - and therefore will we see an bump up in this constant?
Posted by Gregg on January 22,2008 | 03:27PM
If all the atoms slow down to 0, arn't they still travling as a group with the rotation of the speed of theerath on its axis and then the velocity of the earth around the sun, and the velocity of the sun in teh spiral galxy etc, their not standing still even when their not moving in relation to each other they move as a group in relation to the earth, so are they really at absolute zero?
Posted by Ian RoeBuck on January 22,2008 | 09:41PM
As for individuals complaining of the U.S. Standard Units vs. The International System of Units (SI or Metric System), the argument is truly unnecessary. U.S. Standard Units provide a superior system in regards to everyday usage. With Metric Units, you have to measure in Millimeters or Meters for close distances. However, in Standard Units you can measure in Inches, and Feet. Inches are far more manageable for everyday usage than miniscule Millimeters, while a Foot is far more precise than a Meter. Standard Units even include Yards which happen to be close enough to a Meter that they negate its necessity. As far as Fahrenheit is concerned, it has no disadvantage to Celsius (or the Centigrade Scale). Not to mention that Fahrenheit represents nearly equal temperature differences for Earth's Climatic Measurements (-129 to +134) and even the Mean Lunar Surface Temperatures (-242 to +224). Having 180 Degrees present, Fahrenheit may also be easily represented symmetrically through a circular scale.
Posted by JAK on January 22,2008 | 09:42PM
like the article and i think the gravity from ,the sun holds the solar system together ,gravity increas's with the tempiture of the star? ,ase i looked into are new location's that sciencetist change the position ase to whear we are in the galaxy? and most galaxy's have a few stars in the center rotating around a black hole ,some how gravity increase with the size of the star ?could a black hole be absolute zero ? opposite attract ?
Posted by mlton vincent on January 23,2008 | 12:12AM
I have thought for years that the "impossibility" of reaching absolute zero temperature is related to the "impossibility to exceed the speed of light in normal space. I believe this is because mass and energy must exist in an equilibrium. There can be no mass without energy and no energy without mass. From this assumption it follows that at absolute zero you would have mass without energy, but since they must exist in a equilibium some of the mass would be converted to energy. Conversely if one were in a state where the speed of light was exceeded then there would be massless energy. Instead some of the energy condenses into mass. The simple expression of E = Mc** algebraically at least implies that if either E or M is 0 then the other would be zero also.
Posted by Steve on January 23,2008 | 12:44AM
Suppose that we are traveling in a space vehicle and we are somewhere between our solar system and a distant star or our galaxy and a distant galaxy. From initial thrusts we have accelorated to a speed of 26100 miles per hour. When we pass through the voids in space where the tempurature is near enough to absolute zero to slow the speed of light to say 100 miles per hour--does that mean that we are traveling 26000 miles per hour faster than the speed of light? Or maybe I am just too wierd
Posted by don taufer on January 26,2008 | 11:39AM
i really enjoyed this articale i am learing about absolute zero in my 8th grade science class this year. I am using this articale as part of my research for a project i am doing on absolute zero. corey willette michigan
Posted by corey willette on January 28,2008 | 12:14PM
The reason why light slows down passing through BEC is because the particles are superimposed, remember that a BEC occurs when a number of atoms/particles are at the same quantum state, i.e. indistinguishable from one another (sort of) even in the extreme cold of the inter galactic space (-455 F) matter is so low in density that light does not slow down measurably and even if the space had a temp of absolute zero, without a BEC mass light would just pass through unhindered. Even the thickest dust clouds that allow passage to photons do not even begin to compare with BEC in its ability to "hinder" photons. So, do not be worried, universe is neither trillions of years old nor stars are much closer. Also when light stops all you'd see is a black void. If photons cannot reach (since they are not moving)our measurement tools we cannot see the light trapped. So it is impossible to stop light and use it indefinitely. Light needs to move, fast, to be of any use as light :)
Posted by pangaean on January 29,2008 | 01:38AM
We should correct a common fallacy that seems to be is a lot of these posts. The speed of light is not affected by the temperature but by the material its passing through. The BEC slows and stops light because of the state of matter it is. Light traveling through glass or water moves at a different speed than light through air or vacuum. That is why we are able to see rainbows through prisms and sprays of water. The speed of each wavelength through the medium is modified differently. In the vacuum of space, where the amount of matter is so diffuse, the speed of the light traveling is relatively unmodified.
Posted by J on January 29,2008 | 08:05AM
"Inches are far more manageable for everyday usage than miniscule Millimeters, while a Foot is far more precise than a Meter. " Uh, JAK, ever heard of centimeters? What on earth does 'a foot is far more precise than a meter' even mean? The metric system is far more intuitive and self-consistent than the imperial system ever was or could be.
Posted by Alex on February 1,2008 | 06:04PM
Thank you! This realy helped me! I had a Science paper to write! ~Jake
Posted by Jake on February 5,2008 | 12:23PM
I had always assumed that absolute zero will never be possible on Earth. As your article had discussed, the particles (being that of atoms) slow down so that gravity had (reasonably) no effect, but wouldn't gravity hinder the possibility of absolute zero? I'm thinking energy is still in play in respects to gravity, I have no proof of this but all I'm saying is wouldn't it be easier to achieve absolute zero in an zero 'G' environment such as space?
Posted by Anthony Wuhlar on February 8,2008 | 11:38AM
This was a great article and it taught me a lot, even though I'm only 14 I really enjoyed the piece and it was put very simply. That being said, thank you for NOT switching to the metric system. Please don't make the change, seeing as there are plenty of Americans out here that read Smithsonian regularly and would appreciate not having to convert to metric. Thanks!
Posted by N. Vlasek on February 11,2008 | 06:40PM
Regarding the metric system mini-debate going on here: while I believe that the statement that the US standard units are superior for everyday use is absurd, I do believe that a compromise would be best. Include both: use the SI units, with US standard units following in parentheses. One exception, temperatures in many cases are more appropriately given as Celsius instead of kelvin (again Fahrenheit would be in parentheses); however, for something like this article kelvin is probably more appropriate.
Posted by S. Bowling on February 22,2008 | 08:00AM
very good and informative article. it really provided me great information which i can include in my science essay. thank u.
Posted by rabi on February 26,2008 | 08:22PM
I sent this article to my grand daughter and quietly reminded this prodigy child age 12 that she IS our future... Thank you for your time. Kay
Posted by Kay Bishop on March 2,2008 | 02:32PM
I sent this article to my grand daughter and quietly reminded this prodigy child age 12 that she IS our future... Thank you for your time. Kay
Posted by Kay Bishop on March 2,2008 | 02:32PM
love it! love it ! LI ! so now that we can stop light I was wondering if these "new" observations or matter can be classified along with Dark Matter as being on and the same?? and it shadowy properties will this help of pinpoint the lost 80%matter or the known universe? and if freezing light has real world applications for astronomy!!! NEW tools for astronomy and particles (BEC) fascinating!!!
Posted by Brian D on March 4,2008 | 11:02PM
Cool! (No pun intended.) This article is a great example of why I have been reading Smithsonian since graduate school - when I saw a copy in a doctor's waiting room. Beyond being interesting, this and many other Smithsonian articles launch streams of thought in my mind and create a joy for learning. Sometimes learning information that is useful to ME, but more often just learning for the sake of advancing knowledge itself. Thank you, and keep up the great work!
Posted by Joe Reed on March 11,2008 | 12:50PM
I'm more interested in seeing a clip from it or something. It was an interesting read.
Posted by Sipifi on March 23,2008 | 05:51AM