Generating Extremes: Pressure

By Kenneth Freeman

‘Extreme’ is a relative word. At 250m below the surface of the ocean the pressure is 26 times higher than at the surface. This is about as deep as a human has ever free-dived, but is far too shallow and at too low a pressure for the blobfish that lives comfortably around 1km deep.

Pressure isn’t as intuitive to us as, say, temperature. The few times we notice it could be feeling your ears pop on takeoff as the cabin pressure quickly (and only slightly) drops, or feeling the building pressure as you dive towards the bottom of a pool.

The standard scientific unit for pressure is the Pascal (written Pa); typical atmospheric pressure  (1 atmosphere) is around 1×105  Pa (100 kPa), the pressure at the top of Everest is about a third of that and the pressure at the bottom of a 6m deep pool is around 160 kPa.

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The coolest atoms in the universe

By Dainius Kilda

Where do we look for the coldest atoms? The official record on Earth is -89°C at the Vostok station in Antarctica. Outer space is even colder: a distinctly chilly -270°C, which is only about 3°C above the lowest possible temperature, known as absolute zero. But hidden from our eyes, an even colder spot exists in physics labs, where some adventurous physicists cool atoms down to only a few billionths of a degree (0.000000001°C) above absolute zero!

Cold matter is a big hit in physics for a reason: it is a breeding ground for quantum phenomena, including new phases of matter that only exist because of quantum mechanics. In the everyday world around us, we usually see only the familiar phases of matter: solids, liquids, gases, and plasma. But at extremely low temperatures, atoms in an ordinary gas condense into a single entity – the exotic fifth phase of matter called a Bose-Einstein condensate, in which the atoms behave like a huge quantum wave. Bose-Einstein condensates can flow without friction, cannot be rotated, and may have important applications in precision sensing, quantum computing, and several other areas.

In this article, we’ll describe what it even means for an object to get this cold, how Bose-Einstein condensates are made, and what we can do with them now we’ve got one.

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