Wednesday Wonders: Baby, it’s cold inside

April 8, 1911: Heike Kamerlingh Onnes makes an interesting discovery while futzing around with very low temperatures. It’s a discovery that will lead to many modern innovations that affect us just over a century later.

Strange things happen as the temperature drops toward absolute zero, which is basically the temperature equivalent of the speed of light in a vacuum (C) being the velocity limit for anything with mass. Oh, we’ve gotten really close to absolute zero — within nanokelvins — and in theory could get really close to the speed of light, although that would take ridiculous amounts of energy.

But… where matter can’t be is right at these two figures: Exactly absolute zero, exactly C. There’s nothing in the equations, though, that say that objects with mass cannot move faster than the speed of light or be colder than absolute zero.

Practically speaking, it would require infinite energy to jump from 99.99999% to 100.00001% of C, so that’s not possible, but scientists in Germany think they may have achieved temperatures below absolute zero.

Of course, these create weird situations like negative temperatures in an absolute sense, and not just as measured. That is, while we can say that it’s 24 below zero outside, that really isn’t a negative temperature by strict definition. It’s just a temperature that’s negative on the scale we’re using.

Remember: 1º on the Kelvin scale is actually –457.87ºF.

These kinds of negative temperatures are actually below that absolute physical limit, and so they represent thermal energy that behaves the opposite as temperatures above absolute zero. And, in all likelihood, an object moving faster than light would also travel backwards in time thanks to the time dilation effect being reversed.

These, though, are theoretical arguments. What we do know is that things get weird as the temperature drops. At a few nanokelvin, the only energy left in the system is quantum, and so these strange effects take over on a massive scale, pun intended.

The key here is that as atoms lose energy and cool down, they stop moving as much, eventually reaching a point where they’re just sitting there. But… there’s a principle in physics, Heisenberg’s uncertainty principle, which says that there is a fundamental limit to the precision with which you can measure two connected properties of any particle.

For example, if you measure position precisely, you can’t measure momentum with much accuracy, and vice versa. The sharper one measurement is, the fuzzier the other one becomes. Not to get too deep into the science of it, but there are two classes of elementary particle, Fermions and bosons.

Fermions are elitists, and when they’re in a bunch, they don’t like to occupy the same quantum energy state. Electrons are totally fermions, which is why that whole concept of an atom as electrons neatly orbiting a nucleus like planets orbit the Sun is only a metaphor and very inaccurate.

Each electron in an atom occupies a different quantum energy state, which is why there’s the concept of electron “shells” filling up, but the location of each electron is not a unique point that changes over time. It’s a statistical probability of a particular electron being in a particular place at any given time, and so the “shape” of those shells can vary from a sphere to two squashed and joined spheres to distended ovoid shapes, and so on.

Bosons, on the other hand, are egalitarians, don’t mind sharing the same quantum energy state. In fact, they love to do it. This leads to a very interesting form of matter known as a Bose-Einstein Condensate.

Basically, at a low enough temperature, a bunch of atoms can suddenly coalesce into a single quantum particle with the same energy state and even become visible to a regular microscope.

Why? Because when we stop their movement, we can measure their momentum at near zero. Therefore, our ability to measure where they are becomes very inaccurate. It’s like the fermions all gather together and then balloon up into one entity in order to hide their individual locations.

This would be the equivalent of a bunch of people preventing GPS tracking of each of them by leaving their phones in one room and then all of them heading out in opposite directions in a big circle. Or sphere, if they can manage that.

The discovery that Onnes made in 1911 is related to this phenomenon. In his case, he dipped a solid mercury wire into liquid helium at 4.2 degrees Kelvin and discovered that all electrical resistance went away. That is, he discovered a property of matter known as superconductivity.

The same principle and the low temperature led to the electromagnetic force interacting in a different way — fermions meet bosons under extreme conditions, and electric and magnetic sort of separate, or at least keep themselves at arm’s length, as it were.

This can lead to all sorts of interesting effects, like levitation.

This is the technology taking maglev trains to the next level. But superconductivity is also used in things like medical imaging devices, motors, generators, transformers, and computer parts.

But the holy grail of the field is finding he so-called “room temperature” superconductor. All right. In some ways, “room temperature” is a bit of a misnomer, and the warmest superconductor yet found has a transition temperature of –23ºC. But a more promising substance could be a superconductor at 53ºC. That’s the good news. The bad news is that it requires ridiculously high atmospheric pressures to do it — in the range of a million or more times the pressure at sea level.

Oh, well.

Of course, the U.S. Navy did file a patent for a “room remperature” superconductor just over a year ago, but it’s not clear from the patent whether they used the “Not 0ºK” definition of room temperature or the popular press definition of about 77ºF.

It makes sense, though, that barring low temperature, some other extreme would be needed to achieve the effect. Nature just seems to work like that, whether it’s extremely low temperatures or very high pressures required to create superconductivity, or the extreme gravity and energy conversion required to create that other holy grail so beloved of alchemy: transmutation of matter, specifically turning lead into gold.

Ah, yes. If those alchemists only knew that every star was constantly transmuting elements every second of every day strictly through the power of enormous gravity and pressure — hydrogen to helium and so on, right down to iron — then who knows. One of them might have managed fusion centuries ago.

Okay, not likely. But just over a century ago, superconductivity was discovered, and it’s been changing the world ever since. Happy 109th anniversary!

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