# Blog

## Absolute zero is absolutely impossible!

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What’s the coldest thing in the universe? You may have heard of absolute zero, the coldest temperature possible. But a clever bit of mathematics has shown it might not be possible after all!

Before we go further, you may be asking yourself: why can’t things get colder than absolute zero? The answer is that temperature measures the amount of heat energy in an object. If you add more heat energy, it gets hotter. If you take away heat energy, it gets colder. An object with no heat energy at all is at absolute zero.

Scientists have worked out many equations to help us understand how heat functions. And recently, Lluís Masanes and Jonathan Oppenheim from the University College of London took a closer look. If they could manipulate the equations creatively, then maybe it would help them find a way to reach absolute zero.

With a bit of fiddling, the physicists noticed that there might actually be a way to pump all the heat out of an object. But they also discovered a catch. In order to do that, you need an ‘infinite reservoir’, a place to put all the heat you pump out. Even the largest objects in our universe are not infinite, so this approach is impossible.

Undaunted, the physicists tried a different approach. They started working the equations with a non-infinite reservoir, and tried again. This time they had a different problem. If they wanted to remove absolutely all the heat from an object, they would need to do an infinite amount of work. To get all that work done would take an infinite amount of time, which is longer than the lifespan of the entire universe. So that way doesn’t work either!

Although we will never get to absolute zero, there’s a silver lining. Experiments have already reached incredibly cold temperatures, just 0.000 000 000 1 degrees above absolute zero. But this research suggests with better methods and equipment, we should be able to get much closer. But for those dreaming of an impossible temperature, it might be cold comfort.

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