The Coldest Place in the Universe is Closer than You Think

where is the coldest place in the universe you might be picturing a frozen world full of ice and snow or a distant and completely empty patch of space far from any stars or galaxies if you're picturing the latter then you're right or you would have been right until fairly recently now though the coldest place in the entire universe is much much closer to [Music] home between August 2009 and January 2012 the coldest spot in the entire universe was on this tiny spacecraft meet Plank and while he may look like an unlikely record Setter there is good reason that we had to make him colder than any other object in the universe most of the time the coldest place we know of in the universe is indeed a distant frigid cloud in space it's called the boomerang nebula it's a planetary nebula and it's absurdly chili a planetary nebula is a cloud of dust and gas left behind as dying Stars blow off their layers as they die despite the name it's got nothing to do with planets the average temperature on planet Earth is about 15° C the temperature of empty space is around - 270. 49 73 that's right there is somewhere out there in space that is somehow colder than space itself it's around 5,000 light years away from Earth in the constellation Centaurus and it makes even the coldest places on Earth look positively tropical the boomerang nebula isus 27215 de C that's - 47° F or just about 1° above absolute 0 absolute 0 is the limit for cold temperatures you see temperature is a measurement of how fast atoms are moving and jiggling around the faster they move the hotter something is and vice versa absolute zero is when all Atomic movement stops and is the hard limit for cold temperatures it actually seems to be pretty much impossible to actually reach absolute zero for a few reasons quantum mechanics might prevent it entirely by not really allowing atoms to be in one place and it also seems like it would require an infinite amount of energy to reach absolute zero in a lab but it's still the limit for coldness even if can never reach it we even Define a temperature scale based on this fact it's called the Kelvin scale 0 Kelvin is absolute zero equivalent to minus 273. 15 de C and then the scale goes up in ticks of Celsius even empty space isn't at Absolute Zero the number I gave earlier minus 27.

4 de C is about 2. 73 Kelvin so a few degrees above the limit it never reaches this limit because of of the cosmic microwave background this radiation is often called the oldest light in the universe or the Afterglow of the Big Bang the CNB as we call it for short deserves a whole video of its own but it's light that was released about 300,000 years after the big bang it was released everywhere in the universe at the same time and as a result it fills space almost perfectly uniformly it was very hot and energetic when it was first released but over the last 13. 7 billion years is thanks to the expansion of the universe this light has cooled down to become microwaves that are 2.

73 Kelvin since this radiation is everywhere in space that's how we know that empty space is also 2. 73 Kelvin and this tpid radiation is what stops empty space reaching absolute 02 how then does the boomerang nebula a natural place in the universe become colder than this the nebula is just 1 Kelvin a single degree above absolute zero so it seems like somehow it is actively cooling itself compared to space in fact this is the only known natural object that is cooler than the CNB and some temperatures in the boomerang go down to just a few ten above absolute zero so it's very good cooling as well the boomerang nebula has a dying Red Giant star at its core and this is surrounded by the beautiful cloud of dust and gas that we can see in the image here this envelope of gas is expanding in incredibly fast at over 160 km/s that's hundreds of times faster than a fighter jet and is actually the reason the nebula is so cold lots of molecules moving fast and colliding would be a very hot environment but as this Cloud expands the atoms lose energy they don't Collide very much and cool down very efficiently this allows the boomerang to cool to the coldest natural temperature we've ever seen at just 1° above absolute zero this is more or less the same principle that fridges use to stay cold but of course this is on a vastly different scale this is all well and good but I've just made a big deal about this being the coldest natural place in the universe in recent years the coldest known temperature in the entire universe has been on the earth different Labs across the globe trade the record of coldest recorded temperature reasonably frequently and as I'm recording this the current record is 138 trillion of a degree above absolute zero or 38 Pico Kelvin for all you prefix fans out there that record was achieved at a lab in Germany in 2021 but for a while the coldest place on the universe was man-made but it wasn't on Earth for a few years from August 2009 until its coolant ran out in January 2012 the coldest place on the universe was the plank satellite it was actively cooled to just 0. 1 Dee above absolute zero this is remarkable and it had to be done for the plank mission to achieve its goal that goal was to measure the temperature of the cosmic microwave background that we've just been talking about it's important to many areas of cosmology to know the temperature and how it fluctuates across the sky as well as possible there had been missions before plank to measure this but plank promised to do it better than ever before resolving tiny fluctuations in the temperature the satellite flew 1.

5 million km away to the same patch of space that jwst now lives in order to scan the entire sky and measure the CMB radiation more precisely than ever before the thing is we knew the CMB was just a few degrees above absolute zero but we didn't know it exactly so to measure temperatures that low and eradicate as much noise as possible the satellite measuring it needs to be much much colder than the CNB itself we don't want any heat from the spacecraft overwhelming the measurements it's trying to make or leaking onto plank sensors plank measured very far infrared light also known as microwaves effectively a heat map of the universe so if the satellite was hot too it would cause a lot of issues with this measurement using both passive Cooling and active cryocoolers containing liquid helium plank was cooled to minus 273. 5 de C just 0.