Absolute Zero: Why the coldest temperature in the universe was made on Earth

Have you ever wondered where the coldest place on Earth is? Maybe you might have thought it was somewhere in the north or south poles. Maybe you thought it was somewhere in the highest snow-capped mountain peaks. Maybe, if you stretch the definition of “on Earth,” you might have thought the space surrounding the astronauts on the ISS was the coldest it could get. 

Unfortunately, those guesses are wrong.

The coldest place in the universe, for a few moments, was found in a German laboratory at the University of Bremen.

The scientists at the University of Bremen were investigating the properties of Bose-Einstein condensates (BEC), a unique state of matter that occurs when groups of particles at extremely low temperatures begin to behave as a single large particle. Since temperature is merely an expression for the movement of particles, to achieve the lowest temperature the atoms within an area must be slowed to the point where they functionally are stationary. While atoms tend to contain energy that causes them to vibrate, approaching absolute zero implies that there is no longer any atomic motion or heat.

In their investigation approaching absolute zero, they placed around 100,000 rubidium atoms trapped in a magnetic field inside of a vacuum chamber. This vacuum chamber was then cooled down to form a BEC. The tube containing this BEC was then dropped down the Bremen Drop Tower Research Facility while magnetic fields were turned on and off along the way, to cause the BEC to contract and expand, slowing the rate at which the gas expands. (Manners, 2021). As a result of this process, the recorded temperature within the tube containing the BEC was a mere 38 Picokelvin. That's only 0.000000000038 Kelvin.

To understand why this tube is the coldest place in the universe, let's compare it to the next coldest place, space. Space is actually quite hot. The areas around stars are filled with heat energy given off by solar radiation. The energy from this radiation is absorbed by individual particles floating in the void, gas giants and everything in between. But this doesn’t mean that being far away from any stars can guarantee a temperature close to absolute zero. (Lea, 2022)

Even in the space between galaxies, there exist temperatures that are relatively hot.

An example is cosmic microwave background radiation, which is leftover radiation from the Big Bang that carries energy equivalent to 2.7 Kelvin, clearly much hotter than the 38 Picokelvin achieved here on Earth. (Lea, 2022)

So if you’ve ever wondered where the coldest place in the universe was, you can count yourself lucky to be able to live on the “coldest” planet in existence, or at least the planet which managed to create the coldest place. 

References:

Lea, R. (2022, July 6). How cold is space? Physics behind the temperature of the universe. Space.com. https://www.space.com/how-cold-is-space 

Manners, D. (2021, October 12). Coldest-ever temperature achieved by Bremen University. Electronics Weekly. https://www.electronicsweekly.com/news/business/coldest-ever-temperature-achieved-bremen-2021-10/  

Renfro, K. (2017, November 27). 29 incredible close-ups of snowflakes shot with a homemade camera rig. Business Insider. https://www.businessinsider.com/pictures-of-real-snowflakes-macro-2016-12