Many of my students ask about the concept of absolute zero during discussion of the Kelvin temperature scale. They don’t understand why we can’t reach this temperature, but that we know it should exist. I do my best to explain to them as well I as understand, but I know that I need more information myself to teach them properly, and that I did not have that information ready. I always say that I’m going to look it up, but since teaching that concept is so short, I inevitably move on to the next topic and forget about it completely until the next year. I figured researching more about the concept of absolute zero for this post would be perfect!
Absolute zero is the slowest possible oscillation of a substance’s atoms and molecules. It is a theoretical temperature that has never actually been reached, but scientists have come close – to within one billionth of its value – 273.15°C, or zero Kelvin. Most of the imformation I learned about absolute zero came from a PBS documentary I found online called Absolute Zero which came out in January of 2008. There are various other online sources with definitions, physics labs, and discussion of current scientific work, but I found this documentary to have the most history of this concept and including ongoing research. It could be viewed during the grade eleven gases unit, or the grade twelve energy changes unit, but probably better just to show clips of it instead of the entire film.
The study of cold was not a major focus until the seventeeth century – scientists were much more interested in hot! During a very cold time in Earth’s history, in 1665 during the “Little Ice Age” when people were freezing and barely surviving, the spark in the interest in low temperatures began. This interest was led by questions from people all over the world wondering why it was so cold outside – it was society driven. Today we have heaters when freezing, but when being cold is a life or death situation, most people are much more concerned. Again, scientists were looking to heat, but there were a few alchemists, who were interested in cold, including Robert Boyle, which working with changing volumes of ice. He thought that cold was a substance that atoms absorbed, but after a series of experiments concluded that it wasn’t a substance, but something that happened to particles, like a form of motion. The limitations to any scientist’s study at that point was the lack of technology – there were no thermometers made and readily available that could accurately measure temperature. There were some made but none of them have the same scale – and so a problem of standardizaiton occurred, which is where the Farenheit and Celsius scale came from. Somewhat later in the beginning of the eighteeth century, Guillaume Amontons was working with volumes as well, and heating and cooling substances to see the effects. He noticed that cooling a substance decreased its pressure, and wondered what would happen if it just kept cooling. He could plot his pressure and temperature data and extrapolated it back to a zero pressure. He didn’t actually publish his work, but later scientists used his information to determine the value of -273°C – very close to our current value of absolute zero. This is what I can explain to students – how scientists figured out this number, but I don’t feel that this information is enough – what would happen if we could reach this temperature? There would be no pressure?
I looked into it further, and found that little research with absolute zero specifically took place after Amonton’s work until the mid nineteeth century. The reason for this lack of focus was because of Antoine Lavoisier’s ideas of heat being a substance, a weightless fluid called caloric, and because his past research was so successful and he had so much power, his theories were believed for a long time. This stop in true absolute zero research was due to political and social aspirings of one individual, with scientists too afraid to refute him. It took a long time before people believed that temperature is a measure of the movement of particles again. In the meantime, the economy took over as scientists focused on freezing substances, specifically creating ice, and keeping it cold for long periods of time. When this technology was discovered, there was a great demand and the focus of science was on making money with a new technology. Once Lord Kelvin and James Joule developed some of our current laws of thermodynamics, some research into reaching colder temperatures began, but it was still in effort to keep substances cold and develop technologies, rather than reaching theoretical values to see what would happen. The limitations also had to do with cost – it is expensive to find the lab equipment necessary to do the experiments needed to find these answers.
By the late nineteenth century, physicists had started to find the idea of getting to these low temperatures more fascinating, and started competing against one another. There were great cultural pride in being the one who could reach the lowest temperature, and although this escalated the research, the competition left little information known to anyone outside the laboratory. Scientists were not willing to help one another and so a lot of the same mistakes were made across Europe. Getting to such cold temperatures with such fragile equipment resulted in a lot of damage to apparatus, many missing eyes from flying high-pressure glass, and a lot of money used. Freezing the elements thought to be permanent gases, such as hydrogen and helium, became a challenge, and one by one, this was accomplished. There was still a lot of competition and results were based on who could get the most funding and support from people in powerful political and social positions.
Scientists reached temperatures within five degrees of absolute zero in 1908. Still they wanted to go lower, and as they did so, they discovered new properties of the elements. Scientists like Satyendra Bose and Albert Einstein found that elements seemed to be superconductive at extremely low temperatures, and acted as superfluids – ones acting as if they had zero viscosity. All the particles acted as a “team” instead of the individual – one big quantum system. Eventually they called these elements Bose-Einstein condensates, and research into these substances is the major focus of low temperature science today. The difference is that today many scientists are working together, collaborating, instead of hiding their information and the competition is still there, but used in a much more healthy way – to keep them motivated.
One major thing I took away from this documentary as well as many websites is that the concept is still foreign – it is in constant experiment even today, and we are learning more and more about it. This is important for students to know – our concepts about life and chemistry and things to have thought known for sure can change, and that’s why science is so important. One quote by Daniel Kleppner in the film said “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.” This shows that even someone deeply involved in this research is still learning and doesn’t have all of the answers. Students also need to know that technology can limit a scientific process – from a more powerful computer all the way down to a simple thermometer. They need to know that sometimes making money overshadows the desire for pure knowledge in today’s society, and political and economic influences occurred from the start in 1665 to today that both inhibited and acted as a catalyst to this research. There is an important lesson in collaboration, and that although you may want a Nobel Prize for yourself, the results are much more rewarding when you can work together as a team and share your victory with the world.
I realize now that this is not as “brief” as a summary that the expectations for this assignment may have wanted, but I really got into this research and wanted to share my findings with everyone. Please know that you can find more information about the documentary based on this concept, along with other related documents and teacher guides at http://www.pbs.org/wgbh/nova/zero/.
1 Oldfield, M., Mitchinson, J. 13 January 2011. “Quite Interesting Facts about the Cold” http://www.telegraph.co.uk/culture/qi/8258009/QI-Quite-interesting-facts-about-the-cold.html. Accessed 3 February 2011.
2 Dugan, D. (2007) Absolute Zero. [DVD]. Meridian Productions Inc. and Windfall Films Ltd.
Bardi, J. 10 February 2010. “American Institute of Physics announces the winners of the 2009 AIP Science Communication Awards”. American Institute of Physics. http://www.aip.org/press_release/aip_science_comm_award_09.html. Accessed 4 February 2011.
Goldader, J. April 2008. “Determining Absolute Zero Using a Tuning Fork”. The Baldwin School, Bryn Mawr, PA. American Association of Physics Teachers. http://tpt.aapt.org/resource/1/phteah/v46/i4/p206_s1?bypassSSO=1. Accessed 3 February 2011.
Knuuttila, T. 8 December 2000. “World Record in Low Temperatures.” http://ltl.tkk.fi/wiki/LTL/World_record_in_low_temperatures. Accessed 3 February 2011.
WGBH Educational Foundation. 1996-2008. “Nova – Absolute Zero.” http://www.pbs.org/wgbh/nova/zero/. Accessed 4 February 2011.