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 70˚Fahrenheit
or 21˚ 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 degrees˚C 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.
Crazzzzyyyyy Physics