What’s The Hottest Hot and Coldest Cold?

For a split second after the universe was born, temperatures were a thousand billion billion billion times higher than they are today: nonillions of degrees, one followed by 30 zeros or roughly the number of paper clips equal to the mass of the Jupiter.

Before that, physics as we know it didn't exist - it was simply too hot.

So hot that atoms hadn't yet formed!

This temperature, that the universe is thought to have been born into, is called the Planck temperature.142 nonillion degrees is more than steamy, it's the temperature at which our understanding of physics breaks down, and in a way, where it no longer makes sense to talk about temperature.

Is there a limit to how hot or cold something can be?

Turns out, at the extremes, physics gets freaky.

[FREEEAKKKY PHYSICS] [OPEN] The Kelvin scale of temperature, named after Lord Kelvin, a Scottish scientist and inventor, is what scientists often calibrate their thermometers to.

On this scale, room temperature, about 70ZFahrenheit or 21Z Celsius, translates to 294 Kelvin.

The lower limit of the scale was built to be OK - I mean zero K - what I'm trying to say is zero would be absolute zero.

What is absolute zero?

What we feel as temperature is the result of atoms zooming around and bouncing off of everything, including us- the faster their motion, the warmer the temperature.

When this motion stops, you've reached absolute zero.

Except you can't actually reach absolute zero.

Quantum mechanics has this rule: we can't simultaneously know how fast something is moving and where it is, so, if we could cool an atom to absolute zero, we would know exactly how fast it was going (zero), and where it was, which isn't allowed - you can't have your quantum cake and eat it too.

Furthermore, the laws of thermodynamics say that the more heat you remove from a system, the harder it is to remove the next bit of heat - meaning it would be infinitely difficult to get out very last bit of hot and reach ultimate cold.

This is a concept named the unattainability principle.

While *absolute * zero may be unachievable, scientists have been working to see how low we can go.

In the late 1800s scientists began liquefying gases like oxygen, hydrogen, nitrogen, and helium, and by 1908, Heike Kamerlingh Onnes had liquefied helium down to 1.5K, winning him a Nobel prize.

In 2016, scientists used lasers to squeeze atoms, reaching a low temperature of 360 millionths of a kelvin - that's almost imperceptibly above absolute zero and even lower than physicists once thought was possible.

At these super-low temperatures,verging on absolute zero, traditional physics gets a little freaky.

[FREEEAKKKY PHYSICS] We typically think of atoms as dispersed, like in a cloud, acting like individual particles.

But when matter gets very cold, close to absolute zero, those atoms begin to behave together more like a single wave.

This creates what's known as a Bose-Einstein condensate, sort of a mega-atom with all the atoms acting as one.

What's also freaky [FREEEAKKKY], liquid helium cooled below a certain point becomes what's called a superfluid - a fluid that can flow with absolutely no resistance - it can even appear to flow against gravity.

Magnets that are cooled with liquid helium below about 4 K become abnormally strong.

We often use these supercool superconducting magnets in MRI machines.

These super-magnets are also important for running particle accelerators, the only place where scientists can recreate the super-hot temperatures seen in the early universe.

A few millionths of a second after the Big Bang, all that existed was a soup of fundamental particles known as quarks and gluons, before they'd cooled enough to create the atoms we know and love today.

At places like CERN, scientists use giant, subterranean magnetic race tracks, some up to 16.6 miles long, -to smash gold and lead particles together at nearly the speed of light.

So far they've melted particles at temperatures over 5 trillion degreesZC similar to those early conditions.

By studying this primordial plasma, scientists can learn about its properties, like how it acts more like a liquid than a gas.

[FREEEAKKKY] So it turns out, the laws of physics governing our temperate lives don't always hold in the hottest and coldest conditions.

We're learning how fundamental matter behaves differently at the hottest temperatures and discovering new properties in the the universe's chillest materials.

That's pretty cool.

You might even say, it's...neat.

Stay curious.