Absolute zero is really cold – −273.15 °C to be exact. At temperatures close to absolute zero matter begins to act strangely at an atomic scale.
In nature when matter undergoes a transition from one form to another, such as a liquid into a gas, it is known as a phase transition. In physics this is well understood and is present in many of the things we encounter in nature, not to mention the formation of the universe more generally. But at the quantum level phase transitions are even more involved and fascinating.
For starters it’s challenging to view them experimentally, although it is possible to catch glimpses of what is taking place, capturing the whole picture of what is happening during a phase transition is another matter. Very different systems show the same phenomena, a concept known as ‘universality’ in physics.
Extremely cold states of matter are tested in Bose-Einstein condensates in which atoms ‘gather’ together and behave as if they were a single atom, thereby allowing quantum effects to be visible on a much larger scale.
Condensates are incredibly exciting in physics, and are relevant across a broad range of conditions — from sub-atomic particles to the early Universe itself – leading to bizarre phenomena such as superfluidity and superconductivity, which are useful to technologies.