Magda Konieczna

When did they first see ice in Hawaii?

appeared in Imprint February 8, 2002 (see the original)

Low temperature physicists, who can now work at temperatures mere hundredths of thousandths of degrees away from absolute zero, have come a long way.

Dr. Jan Kycia of UW's own physics department uses temperatures as low as -273°C to push the envelope of physical knowledge.

"We can [achieve very low temperatures] in the lab and found in nature, which is a powerful thing for us. Now we can go and see things that aren't regularly observed in nature," Kycia said. "That's why we can find a lot of mysterious and surprising things. We're going into a regime where nature isn't."

Temperature is the amount of coldness or heat felt from an object. This is related to the average motion of particles that make up the object -- the faster they move, the warmer it is.

When you cool something, in essence you are slowing down the particles within it. As a result, there is an absolute lowest temperature that can be reached. At this temperature, called absolute zero, the particles in a substance stop moving entirely.

The Kelvin temperature scale is based on this fact, with zero Kelvin representing absolute zero. This temperature is -273°C.

In day-to-day life, you experience only a tiny fraction of the entire possible range of temperature. Even taking into account these blustery winter days, the coldest temperature ever found in nature was -54 degrees Celsius, recorded at Vostok, the Russian Antarctic station, in 1983. The highest temperature was 58°C in Libya in 1922.

This range, of about 110 degrees, is tiny compared to the actual range of temperatures that can be created in a laboratory, where temperatures within a few hundred-thousandths of a degree from absolute zero have been created.

Because these low temperatures are never observed in nature, the behaviour of substances at these temperatures is not easily understood. Additionally, the difficulty of actually reaching very cold temperatures makes this a regime that has not been well explored by science in the past.

Dr. Kycia is interested in using the techniques of low-temperature physics to examine day-to-day phenomena which come to light only at these extremely low temperatures.

"[Low-temperature physicists] take advantage of very low temperatures," Kycia said. "You end up having less noise -- less electrical noise, less thermal fluctuation -- and that ends up not masking different types of physics that in nature are always masked or overlooked or wiped out."

The beginning of modern low-temperature physics was marked in 1911 by the liquification of helium, at just a few degrees above absolute zero, by Nobel-Prize winner Kamerlingh Onnes.

These days, people like Kycia are using techniques of low-temperature physics to investigate many cutting-edge phenomena. One high-profile example of this is quantum computing, which spells a veritable revolution in the world of computation.

Quantum mechanics tells us that small particles can behave in unpredictable ways. As computers become smaller and faster, knowing the position of tiny charges that make up currents is becoming imperative; however, because of quantum mechanical effects, there is a growing uncertainty in this information. This leads to instability in computers.

In essence, a quantum computer, rather than using a series of zeros and ones, or bits, like a classical computer does, uses fundamental properties of tiny particles. This means that information can be stored in very tiny spaces, and as a result, that computing can be done much more rapidly.

This also means that inherent uncertainties and instabilities of particles, which interfere with traditional computing, can be exploited to create even faster machines.

The catch? At this point, unfortunately, there are many. As far as the contribution of the low-temperature physicist goes, however, the problem is that at room temperatures, these tiny particles that could be used to store information are bombarded by all kinds of energy from vibrations, heat and electromagnetic waves from cellphones.

Currently, the only solution to this problem is to keep the particles under extreme temperatures. As the low-temperature field grows, it will become increasingly easier to maintain these temperatures, and one of the major barriers of quantum computation will be overcome.

Another important field that's interesting to low-temperature physicists is superconductivity. Only about 50 to 60 per cent of the electricity travelling down a traditional copper wire from a power plant to your home actually arrives -- the rest is lost because of electrical resistance. A superconductor is a substance with no resistance at all. If Ontario Power Generation used superconducting wires, 100 per cent of the electricity generated would arrive, making the process 10 times more efficient.

Another advantage of superconducting wire is that it generates no extra heat. Transmission down traditional copper wire is grossly inefficient because of the tremendous heat given off.

Currently, the highest temperature at which superconductivity occurs is -135°C, which is clearly impractical for conventional power transfer. In order to study these superconducting substances, then, a low-temperature physicist is needed.

In his lab, Kycia is looking closely at the properties of the superconductor Uranium-Platinum-3. Although you're not likely to ever have power delivered to your home on wires made of this substance -- it's highly radioactive and expensive, and becomes superconducting only within one degree of absolute zero -- it has proved to be a very interesting puzzle for low-temperature physicists.

"[Uranium-platinum-3] was discovered in 1983. It's still not understood what induces the superconductivity," Kycia said. "What we learned is that we have to improve our analysis techniques at low temperatures. At our fingertips we have an arsenal of different tools. There are experts in all those fields that have used these tricks to try to solve [the mysteries of] that material, and they're stumped.

"We have to come up with new tools and new measurement techniques to get the extra information."

In this sense, low-temperature physics has provided much insight into which fields of physics need to be focussed upon.

When asked whether absolute zero, the point where all the particles in a substance stop moving, is ever attainable, Kycia chuckled.

"You can always get colder, but you can never get to zero," he said.

This apparent paradox will pose an interesting question for physicists in the future as the low-temperature world is probed more and more deeply.

Try this at home

You too can observe one of the phenomena used by low-temperature physicists.

Materials required:

one thick elastic band or two thin ones

Experiment:

If you are using two elastic bands, put them together. Stretch the elastics quickly and touch them to your lips. They should feel warm.

Let the elastics cool down while stretched, then let them shrink. This time, they should feel cold on your lips.

Explanation:

The amount of 'randomness' is called entropy. A fundamental law of the universe states that entropy is always kept at a maximum. When you clean your room, you increase the entropy, because you put things in neat, organized piles. Your room, however, eventually goes back to its original messy state.

The same is true of particles -- they prefer to exist in disorganized states. When you stretch the elastic, you force the particles within it to organize. As they do so, heat is given off, which is why the elastic feels warm. When it goes back to its original shape, the particles become disorganized again, absorbing energy, and so it feels cold.

The cooling effect that you observed is used by physicists via a phenomenon called nuclear demagnetization to reach temperatures of two-hundred-thousandths of a degree from absolute zero.