Condensates are also known as superfluids. As the name suggests, a superfluid possesses properties similar to those possessed by ordinary liquids and gases, such as the lack of a definite shape and the ability to flow in response to applied forces. However, superfluids possess some properties that do not appear in ordinary matter. For instance, they can flow at low velocities without using any energy. This means that they can climb up and into containers all by themselves, as the image shows. Condensates are typically very cold, and can only form at temperatures just above absolute zero: −273.15 °C.
Interesting properties
Condensates all have the unique quality that all their atoms act together as if they were just one single super-atom. This means they all have the same momentum: if one moves, they all move together. This allows them to move without friction through the tiniest of cracks, and as we have already noted, they will even flow up the sides of a jar and over the top.
They are also amazingly good at transferring heat. When heat is introduced to a normal fluid, it diffuses through the system slowly by convection. In a condensate, heat is transmitted so fast that it travels in waves, just like sound.
If you spin a bucket full of ordinary water, a whirlpool like pattern will occur (called a vortice), with the water at the center moving slowly and gradually speeding up as you move out from the center. Condensates do not rotate as a whole along with bucket, instead many little vortices appear rotating within the material. And if you stir a superfluid the resulting whirlpool will continue to rotate forever, because the material has no internal friction.
Types of condensate
Condensates come in two flavours: fermionic and bosonic. Fermions and bosons are the two families of sub-atomic particles that together make up all matter in the Standard Model. These two families of particles posses a property known as spin. You can think of spin a bit like you would for a cricket ball – a rotation of the particle around its own axis. But in the strange world of quantum mechanics wherein we know dip our toes, spin is also very weird. For example, spin has a value and the same types of particles always the same spin value. Moreover, spin values only come in two categories: half-integer spin and integer spin. (If all this talk of spin makes your head spin, don’t worry – all you need to know in relation to condensates is that fermions are half-integer spin particles and bosons are integer-spin particles).
So a fermionic condensate is one made of fermions, and a bosonic condensate is one made of bosons. For now, we won’t worry about how you create such substances except to note that it is much harder to make a fermionic condensate because they are half-integer spin substances, whereas making a bosonic condensate, being an integer spin substance, is a piece of cake by comparison. And if you’re truly curious as to why its difficult to make a fermionic condensate, you’ll want to learn about the Pauli Exclusion principle. But I warn you: once you venture through the looking-glass into the sub-atomic world of quantum physics, you will find yourself in a very strange land, where extremely disturbing notions of what is really real may make you question everything you have ever thought obvious. And if that doesn’t put you off – congratulations! Anyway, I digress; let us return, as the French say, to our sheep:
Bosonic condensates
These were the first types of condensate to be discovered. They are often called Bose-Einstein condensates, in honour of the two scientists who first predicted their existence. (In fact it was Satyendra Bose who got there first, but Einstein helped his ideas gain acceptability and then expanded them, so he gets a mention too). And if you’re wondering about the suspicious similarity between the names boson and Bose, you’d be right: bosons were named in honour of Satyendra Bose.
Although bosonic condensates were predicted to exist in 1925, it wasn’t until 1995 that the first bosonic condensate was actually created in the laboratory. It was made by super-cooling Helium atoms (specifically the isotope Helium-4, which is a bosonic atom). Helium is unique among matter in that it cannot be made to freeze at ordinary pressures, so in its liquid form it can just be made colder and colder.
Fermionic condensates
The prediction that fermionic condensates must also exist was made shortly after it was realised that bosonic condensates must exist, but due to the extreme difficulty in creating fermionic condensates, the first one wasn’t demonstrated in the laboratory until 2006. Again Helium was used, but a different isotope: Helium-3.
Superfluid videos on YouTube
A physics lecture from 1963 is available on YouTube showing the strange properties of a partial Bose-Einstein condensate (the superfluid Helium II). Because of YouTube limitations, the video is in five parts:
Liquid Helium II – Segment 1
Liquid Helium II – Segment 2
Liquid Helium II – Segment 3
Liquid Helium II – Segment 4
Liquid Helium II – Segment 5
The JILA Anomaly
In 2001 a team at JILA (a research institute in Colorado) produced a new kind of Bose-Einstein Condensate from an isotope of rubidium. They applied an electromagnetic field to it in order to cause a stronger attraction between the atoms, but then something truly mysterious occurred. The condensate began to shrink, then suddenly exploded like a supernova, releasing streams of different particles, and leaving behing a much smaller amount of material. The explosion released more energy than existed in the condensate, and half the rubidium atoms simply disappeared! This is a REALLY BIG DEAL, because it breaks the known laws of physics: you can’t get more energy out of something than it contains, and matter does not simply disappear – it can only be transformed to other matter or turned into energy in accordance with Einstein’s famous formula e=mc²
Eight years later, this event is still unexplained, despite two formal scientific investigations. Where did all those atoms go? Nobody knows. Where did the extra energy come from? Nobody knows. This might be of academic interest only if it weren’t for the fact that the Large Hadron Collider at CERN when it is switched on will be using 120 tonnes of super-cooled Bose-Einstein condensate in the vicinity of enormous electromagnetic forces in an attempt to discover the Higgs boson… What if it doesn’t want to be discovered?
Filed under: basic science
What if it doesn’t want YOU to disturb it? After all, by applying energy, even photons, you change either the energy or the position, or both of whatever you touch, Dirac knew this.
Is this the Genesis, Garden of Eden moment, and the 120 tonnes of BEC is the Tree of Knowledge?
If there were more energy released in the explosion than existed before, could the explosion find perhaps a Gravity, a timeless elusive energy that causes thing to attract, but in its design is that untouchability will that resents being controlled or gathered into a SpaceTime event.
Really proficient post. Theoretically I could write something like this too, but taking the time and effort to make a good article is a lot of effort…but what can I say….I’m a procrastinater. Good read though.