Neil deGrasse Tyson Explains Why You Can’t Reach Absolute Zero

[Music] hey neil i got another one for you you know these right these never end you know good i got another one it's a good thing that they're going on people love these so i thought maybe we'd talk about um hot and cold all right hot and cold hot and cold so we're discussing my marriage what's happening okay what is going hot and cold so a couple of things you realize there's no real upper limit to how hot you can make something right in fact the early universe was like trillions of degrees you just can keep going if you concentrate enough energy into a small enough volume you can just keep increasing the temperature essentially without limit wow but you can only do that because such a thing as heat exists you can just keep adding more heat okay all right if you have something right have more always pile it on pile it on okay so now if heat exists and cold does not exist then what happens when you just start taking away the heat so wait a minute are we defining is the definition of cold the absence of heat let me just yes yes okay okay yes so i got heat i can add as much of it as i want but if i start taking it away the temperature begins to drop right okay so now there comes a point the heat energy i should say so there comes a point as you keep removing it right where then there's no heat left to remove right okay and there's a guy named lord kelvin a physicist who let me hear you imitate the peerage of of course lord kell indeed today i believe i shall endeavor to find out exactly what happens when i remove heat so he he explored what would happen if you remove all the heat from something if you remove all the heat what temperature should you call that um i would say the no heat temperature give a number to it what number would it be zero zero fine so he created a brand new temperature scale where where there is no heat it is zero smart therefore there can be no negative temperatures on his scale nice that there it is so that's called the absolute temperature scale the kelvin scale so that's the scale we use in science and in engineering typically now wait a minute so here's what i'm curious though uh if if there is no heat at all first of all you have to go someplace where there is no heat or created yes oh okay so now that's my next question how do you create a place where there is no heat that's everywhere on earth there's no there's heat that's really hard to do it turns out and so in fact initially it was sort of a theoretical limit of you sort of approach it asymptotically never actually reaching that point but i'll get back to that in a minute so the celsius scale named after anders celsius which put 100 degrees at boiling water zero degrees at freezing water and everything else came along the way there because to him why not put zero at freezing water but of course you can be colder than that therefore you got to introduce negative temperature right okay so so so the kelvin scale was developed after the celsius scale celsius scale was originally or commonly is also called the centigrade centigrades centi as in 100 right a degree is a hundredth of the 0 to 100 from boiling to freezing to boiling so this celsius gap already existed so he said let me not rock the boat let me put zero at the coldest point but have each interval of temperature be the same as the celsius scale okay okay so no no conversions you just subtract yeah basically yeah yeah and and then before you know it you're you're really measuring kelvin in terms of self celsius yes using this celsius unit right so if you so you can now ask what temperature is absolute zero on the celsius scale gotcha you can do that so you go below zero and it's way colder than freezing water you just keep going and going and going and it's 273 degrees below zero on the celsius scale so minus 273 celsius is zero degrees kelvin absolute zero and that's all you got to do that's so cool so there we have absolute zero so now the question is how do you get there okay right and so it's all about the removal of of thermal energy what is thermal energy it's the vibration of particles gotcha all right so if you have some thing that has a higher temperature than some other thing and you go in and measure the particles and how they're moving they're vibrating faster gotcha okay so temperature is the average kinetic energy of vibrating particles in any substance at all okay so everything vibrates if you have a solid hunk of iron right does it have temperature yes then you get in there and you'll see the the iron atoms are vibrating okay within whatever lattice they're located if they're vibrating now there's another layer here i'm not going to get into but i will say it okay all the particles especially in a gas all the particles are not vibrating at the same rate some are faster than others some are slower than others okay and there's and and the distribution of these has it has a name it's called a maxwellian distribution named after james clark maxwell who studied the distribution of the vibration of particles depending what temperature they were right but as you raise the temperature all the vibratory speeds get higher there you go okay okay so that so it's why for example when you're boiling water and some water evaporates off the top how come the entire pot doesn't evaporate all at once right okay only the fastest moving particles will vibrate we'll we'll jump out okay at any given moment it's only the fastest ones getting out and all the rest are still in there and then others populate the fast zone and then they get out so there's a range of speeds over which the particles vibrate now a a subtle and very physically point i have to make heat energy is the total energy carried by all the particles that's it okay the total energy that makes sense the temperature however is the average kinetic energy of the particles okay so in other words a cup of coffee hot coffee in the morning is hotter than the ocean however the ocean has more total energy in it right because it's the total sum of all the particles so it's total sum of all the particles so i just want to distinguish sort of temperature and and and and thermal energy there's a distinction between those two that makes sense okay so let's get back to kelvin all right so how do i make something colder so what i have to do is i need something else next to it that can take the heat away okay i put food in your refrigerator the air around the food is colder than the food has less heat energy than your food does so it's taking the heat energy from it okay then what then what does it do with it it goes through your coils in the back of the refrigerator and then if you ever hang out in the back your refrigerator it's hot there absolutely that heat used to be in the food that you put in it right that's where that came from see now what we should do instead of having an oven beneath our stove we should have a refrigerator and use the heat to cook on top and that would make sense it doesn't get that hot i don't know what you put in your refrigerator so so so it means you need something colder something with sort of less heat energy attached to the one that has more so that it can basically extract it well let's keep doing this and you keep doing let's get down to like you know 100 degrees kelvin and 50 degrees kelvin and 10 degrees calm i keep doing this and i'm at like one degree kelvin i need something colder than that i i need something colder to pull away that heat right but if i always need something colder how am i ever going to get to zero yes this is the challenge this is the challenge okay so now it turns out you can take a gas which is vibrating okay at a certain rate and expand it and that will slow down the vibration of the particles and the gas will cool you have to put energy to do that but you can that you can do that by the way that's how compressors work point is point is um you can make things colder a gas holder by expanding it you just keep doing this okay you keep doing it so we we can get to within like micro degrees of absolute zero but you can never philosophically and theoretically you can never actually get to absolute zero for this reason right because you need something you can get like arbitrarily close now there's another problem uh oh okay okay there's another problem okay quantum physics takes over and in quantum physics one of the tenets is you can never know precisely where anything about anything i believe i read that that that is quantum physics you can never know anything about anything it's not that bad okay the point is it means in quantum physics nothing is ever stationary so it means there's a entire branch of physics that says you may try to stop the motion of this particle but you will never succeed because there's a quantum vibration that goes on no matter how much heat you've taken out and this is quantum physics taking over so the point is not only is there sort of a classical physical limit to reaching absolute zero there's a quantum limit that prevents it entirely wow and so there it is a little bit more probably more than you care to know about absolute zero no that's fascinating stuff that's very cool because you hear about i mean listen everybody learns about absolute zero in school but you don't learn about it to the extent that not to the extent let me add one other thing go ahead okay so this is this is just so cool all right but i'll let you to be the judge all right all right as a particle slows down you've you've heard in quantum physics you can have wave and particle duality you might have heard about it that's light but of course okay i believe i believe lord kelvin this is actually um schrodinger showed us that you can have a particle that also functions as a wave now here's the thing as you slow down the particle right the wave associated with it gets longer ah okay cool now watch what happens if you have a system of particles and you begin to slow them down and their waves become longer there's a point where all their waves match up and the material becomes a coherent functioning new state of matter really and it's called bose-einstein condensate and so this was predicted that if you froze something enough these free particles froze them enough and there they are doing their own thing doing their own vibratory dance if you get it cold enough all of the wavelengths will begin to match and then the entire substance will function as though it's one object nice it's a whole new state and behavior of matter and it happens at those very cold temperatures below one degree kelvin so you can shape shift matter yes yes yes i love that shape shifting it yes and it all happens together and you warm it up then it goes back to you know what it's like it's like birds that flock right they come down and then they're pecking away separately and then they start flying then they all go together yeah that movie scared the hell out of it exactly yes so that's a it's a bad analogy but it's visually similar yeah okay it's not physically similar just visually similar wow so cool things happen at low temp you get super conducting fluids you get super supe you get super you know what super fluidity is uh when you cool something enough and once again you get these wavelengths that match up and if it's in a fluid state you can plunge your hand through the fluid and the fluid just parts in front of your hand and there is no resistance to moving through the liquid wow it's called a this superfluid another quantum state that arises then you have superconductivity where there's no resistance to to the current of electricity so if you filled a tube with super fluid and there's zero resistance correct you could actually travel in that tube at enormous speeds yeah you travel faster than the speed of sound in the the normal speed of sound in a liquid that's correct yes oh cool yeah it's very very cool and and so it's interesting imagine being a funder and some physicist says i want to play with cold temperatures and see what's the point of that what are you going to learn it's just going to get cold and then you realize that matter behaves completely differently under those conditions and different matter behaves differently from other matter and so it is it's an extraordinary new place to visit in the world of physics and who ordered that who would have thought that this would was laying there waiting to be discovered but it was that's amazing and all i can say is this uh as a black man i do not like the cold but you have just changed my entire outlook on it because you want to get some of that super fluid [Laughter] oh and also the kelvin as a unit of temperature has been elevated to be its own unit without even having to mention the word degree it's just the kelvin well no it's not even the it's uh what's the temperature 29 kelvin kelvins that's right oh kelvin and it is elevated so high that it's now a lowercase k wow that's how you know you're bad but that's what you know you made it right what's that it's not kelvin degrees degrees kelvin kelvins it's and you know who else has that newton their newtons is a unit of of uh force so nice all right so what would you want to be measured and we i know we got to go we don't but i'm gonna i just want to end on something weird and fun what would you want to be measured that would be measured in tysons oh i got to think about that let me think about that i don't have an answer right yeah actually i don't want to be remembered for anything i just want to for me education is empowering you to understand what it is you're talking about with any reference back to me at all and that but thereby you take ownership of your own enlightenment see that's too damn noble see i want you to remember me okay we'll work on what what what unit will be called the nice all right dude we got to call it quits there all righty more than you ever care to know about the kelvin at absolute zero temperature scale uh this is at star talk yet another explainer video chuck always good to have you always a pleasure as always [Music] you

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Keywords: startalk, star talk, startalk radio, neil degrasse tyson, neil tyson, science, space, astrophysics, astronomy, podcast, space podcast, science podcast, astronomy podcast, niel degrasse tyson, physics, Chuck Nice, temperature, hot, cold, Kelvin scale, absolute zero, heat energy, Maxwell-Boltzmann distribution, quantum physics, superfluidity, Bose-Einstein condensate, shape-shift, absolute zero temperature, neil degrasse tyson explains, chuck nice neil degrasse tyson

Id: aYBEcFvI8o8

Length: 17min 11sec (1031 seconds)

Published: Tue Aug 11 2020