Temperature measures the energy associated with the motion of particles, and absolute zero is where that all stops. It's the "off" state of motion. Absolute zero isn't just an end of the temperature scale; it's the only edge of the temperature scale. The so-called "absolute hot" is a misnomer. It's the temperature at which our current ability to describe thermal energy breaks down, not a limit on thermal energy itself. Calling that point "absolute hot" is like using a child's wooden ruler and calling six inches "absolute length" -- someone trying to sound impressive while clutching an inappropriate tool.

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Where no average man has gone before.

Absolute zero isn't just a number on the thermometer. It's a boundary on existence, the reference from which everything else starts off and expands out, a perfect point of eternal theory. If we work out warp drive, it'll work from absolute zero. If we play a grand unified symphony on superstring violins, it won't change absolute zero. It's the utter, the ultimate, and we understood it before we understood our own evolution. We knew about entropy's Elysium, the perfect place where there was no toil or waste, before we even knew what entropy was. We found energy's end point before we had fridges, and the former led directly to the latter. We found the bottom of existence, and used that theory to ice our mojitos.

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Absolutely zero worries.

What's even more impressive is how cool it makes us. We're only as far above absolute zero as a decent pizza oven is above us.

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Just one more way pizza makes the Universe worthwhile.

The Cosmic Microwave Background (CMB) is the Universe's first light. For the first 400,000 years of existence, that existence was too dense to let light shine. Understand: Everything was too intense even to see, because there was nowhere for photons to fly without being immediately reabsorbed into more matter.

Over 13 billion years ago, the Universe finally expanded enough to let some light shine out through the gaps in everything. And that light is still going. And we can see it. Some of the ultra-compressed matter left behind cooled off, and worked, and improved itself into an astonishing new life. A life which built satellites to welcome that childhood light back after its long travels, and now, together, we know so much more about how everything works. It's a romantic reunion based on true understanding. A love story across everything ever.

NASA
Much more meaningful than any engagement ring.

We're looking at a baby picture of all the matter in existence, and it's a live transmission. And it's telling us even more about the Universe right now. Because the Universe has expanded since that light first flew. The light waves have been stretched by the expansion of spacetime as they shone through it, and we can see that effect in the light, telling us even more about everything. When the light left, the baby Universe was around 3,000 C. Now we see the afterglow at only three degrees above absolute zero.

It's perfectly understandable to ask, "What's so impressive about that?" The complexities behind that image are hard to grasp, even from a scientific standpoint. But when you consider that not all that long ago, we thought that the Universe was laid by a turtle or something, being able to actually see what really took place is pretty mind-blowing.

The Boomerang Nebula has the coldest naturally-occurring temperature in the observed Universe, at only one K (-272 C), through turning an entire protoplanetary system into a cosmic refrigerator. Interesting side note: It's also called the Bow Tie Nebula. If we solved cosmic problems with double-oh-Galactus, this is what he'd wear.

NASA

A nebula is a cloud of interstellar dust, and this nebula uses that dust to turn a dying star into a thermodynamic cooling engine. The star is pumping titanic flows of gas into interstellar space. This gas cools as it expands without any other heat source (called "adiabatic cooling"), and so much is flowing out that the relatively warm cosmic microwave background can't penetrate to heat it back up. The system is throwing out its own mass so that it can use convection and evaporative cooling in space. Never mind merely hearing you scream: in space, the Boomerang Nebula could freeze your face off as it happened. Forget Maxwell's Demon; this is Maxwell's God.

And while what the entire universe does is pretty impressive, if you want reallycool things then good news! You're a member of the right species...

We placed the coldest speck in the sky in order to observe everything else. The Planck space observatory's High Frequency Instrument (HFI) collected original photons from the Cosmic Microwave Background, mapping it even more accurately than the WMAP, and it did so by becoming even colder than that background, so that the photons' effects would register more clearly. In other words we had to out-cool all of existence, and this instrument did it.

ESA
We increased the resolution of our picture of the beginning of light and matter. But your new plasma TV is cool, too.

Planck's four-stage cooling system is a masterpiece of low-temperature engineering. It performed perfectly for over four years, providing the most accurate cosmological measurements ever made. It didn't just give us a glimpse of the early Universe. It gave us a map, and a timeline, and the startup settings.

ESA
We are made of star stuff. We used it to build something better.

If Earth had a Techno-Louvre, the Planck would still be flying above it, because the real gallery of our most impressive achievements is space. Our entire history is the use of tools. Our entire glory is increasing understanding. Space is reality's New Game+ Iron Mode, in which we ascend to a whole new level to build tools which have to work, where we can't fix or reload them, where a single error can mean failure or death. But the rewards are the coolest cutscenes which explain the whole story.

Planck's still up there. It's in a parking orbit around the sun, all fuel and coolant expended ... a system so cool that when it died, the impossibly cold depths of space actually warmed it up. The final shutdown command was sent at 12:10:27 on the 23rd of October, 2013. But it'll show that we were worth existing for as long as the sun shines.

At these temperatures, we cross into a whole new phase of matter: Bose Einstein Condensates, which are as cool and collected as plasma is hot and exciting. BECs are the hidden levels of existence -- the physics programming is encoded in the structure of spacetime, but our Universe never actually goes there. Anywhere. Ever. But we built systems to exploit this unexplored region of reality and see the glitches in existence itself.

MIT
But I'll just talk about it. These people, and many more, actually do it.

An MIT group used a gravito-magnetic trap to balance a collection of sodium atoms against gravity. Then they cooled it even further by blasting it with lasers, because that's just how awesome lasers are. Optical tweezers used other lasers as tiny tractor beams, manipulating the cooled atoms into the right position. Altering the magnetic trap frequencies allowed the material to adiabatically cool even further, expanding and chilling, and proving that these people have even cooler traps than the Ghostbusters. Finally, evaporative cooling let the most energetic particles in the sample escape, carrying away their excess energy to leave an even colder sample behind. We built our own Boomerang Nebula in the lab.

MIT
Coils of copper wire replacing an entire star.

People have claimed even lower temperatures by restricting their definition of "temperature" to certain axes of certain systems, and that's still stunningly impressive work. But this was full three-dimensional ultra-cooling, the coldest anything ever.

But we're humanity. Of course we can get better, and be cooler. That's what science does. And we already know the coolest science of all is in space. And that's where we'll find ...

In 2016, the Cold Atom Laboratory will almost automate the previously-described cooling systems. The entire rest of the Universe can't make Bose Einstein Condensates, and we're fitting our space station with a BEC vending machine. It's already achieved 200 nanoKelvin in testing, without ever leaving the ground. And in space, the advantages of microgravity will offer unprecedented lifetimes for even colder samples. And then it's going to go one step further with Delta-Kick Cooling. In DKC, a pulsed magnetic field lets the particles exchange their kinetic energy for potential energy in the field, then removes the field to leave the particles with almost nothing. I think physicists learned this trick by studying bankers.

The Cold Atom Laboratory could achieve temperatures as low as one picoKelvin, a trillion times lower than anything else in the observable Universe. Because any random accident can release heat, but only deliberate intent has ever driven things so close to absolute zero. Ultracold experiments exemplify the most important aspects of humanity, and therefore the most important things in the Universe: the intelligence to find reality's limits, the ability to build the tools to get there, and most importantly of all, the curiosity to care about both.

So all those Facebook memes were right. Science really is the coolest thing ever.

Enjoy the opposite with some of the worst things ever made in The Worst Jaws Merchandise Ever Made, or enjoy The Fantastic Four If They Were Turned Into Cocktails.

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