Same question as, "Why can things go faster and faster, but cannot go slower than STOPPED." As long as atoms are moving, there is (ideally) measurable temperature. When the atoms stop, that's *absolute zero* - that is, cannot get colder.


Great explanation! It's worth noting for those interested that absolute zero doesn't necessarily equal no movement (but that's well outside the realm of ELI5.)


Wait, expand for someone who is at least 6


Quantum uncertainty principle forbids this because that would mean position is known to 100%. There is always some kinetic energy in the lowest possible energy state of a system


Where can I read more for level 7


Check out PBS Spacetime on YouTube. That's where I learned this particular fact, although I can't remember which episode.


I love this channel, but I always get completely lost halfway through each video... It's more like level 30 than 7.


First 5 min I'm like yeah I get it I'm following... last 15 min I'm like uh how did we get here I'm lost, scared and confused...


Absolute zero actually refers to the ground state (lowest energy possible) which isn't "no movement" because that's how confining potentials work.


Are black holes hot or cold?


When black holes are devouring the accretion disks around them can get quite hot as particles in orbit can be accelerated to relativistic speeds and release a lot of energy as heat. So the outside of a black hole can get pretty hot. In the millions of degrees. Inside a black hole on the other hand models suggest it's incredibly cold, a black hole with the mass of the sun would be a millionth of a degree above absolute zero. So black holes continue to be some of the most extreme objects in space.


Can anything be at absolute zero?


Leafs chances of winning the cup


One day they're going to win, and these jokes will be meaningless. Of course, this will only happen when the last people on earth are one maple leafs player and a six year old with a bruins jersey. It's gonna be a close one though still.


That 6 year old is Bergeron's descendant, and that kid absolutely shreds at the dot


They lost to their own minor league teams Zamboni driver. I wouldn’t count on them beating a six year old.


And you'd better believe I bought his jersey after that game


And the Canterbury tales will shoot up to the top of the best-seller list


Is this… is this a CUBS IN FIVE reference? This is like finding the only needle on HayWorld


Haha you know it


Nothing makes my day like a random, deep cut reference to something I love. Thank you 🙏


Ffs, to read this when just casually browsing reddit after yet another embarrassing Leafs loss hurts an extra amount lmao. Well played.


Jesus Christ, they have families man


They only have families because their wives let the shots in


Toronto isn't safe anywhere




Freaking awesome burn


That comment is both hot and cold.


This comment warms my heart




This comment might even hold up in /r/askscience.


Leafs fans take strays anywhere and everywhere


Nowhere is safe


How do you know it’s springtime in Toronto? The Leafs are out!


Oohh this is where my elementary physical chemistry knowledge comes into play. For anything to be at absolute zero, it must also have zero entropy. Entropy is a measure of the number of microstates a system can have; at 1 microstate the entropy is 0. For a system to have no entropy then it must be in a state of perfect crystalline structure with no motion. Each atom and every particle must be in place with absolutely NO variance throughout the system (this also violates the Uncertainty Principle). But for a system to achieve this, it must have an infinite volume. It must take up the entirety of the universe and everything else. Why? Because it must have no imperfections, and the mere presence of surface (which indicates a finite volume) induces imperfections. This imperfection propagates throughout the entire system, one single atom out of place would mean that it has an entropy equal to the magnitude of all atoms in the entire system (ie the # of microstates). Therefore the entropy≠0 so temperature≠0K. Source : [this dude](https://www.ips.kit.edu/2890_2995.php)


Holy shit, which elementary? We were just learning about colors and stuff.


Facts lol


Thanks for taking the time to explain this! The studies of molecules, atoms and such is really cool.


Citing your chem professor made me crack up


You forgot to ELI5


Unless everything everywhere is set stone solid, then it’s not at absolute zero, as something might be jiggling around. If it’s moving, it’s got energy. Since we cannot, at super small scales, be really sure of the position of anything, there will still always be some warmth or energy left over in a frozen universe.


Would heat death be at absolute 0 then?


Yes, but It’s going to be slightly above that, as whatever is left is slowly still expanding at the edge of the universe. Practically everything would be so dispersed that nothing meaningful would happen again at our scales of time.


That would technically be the same thing as frozen time. Chemical reactions would not occur. Any cosmic particle that interacted with the area would break it.


I don’t think so, if something were to be absolute zero, if it were to contact any other particle (above that temperature) it’s temperature would increase. Also I don’t think anything can get to that point if it wasn’t previously, as when bodies contact one another effectively their mean temperature (weighted for the bodies masses) becomes the temperature of that system so as to my understanding you couldn’t cool anything to that temperature. Feel free to correct me anyone!


My sex life is proof of this.


Appearently yes, and can even go below, don’t ask me how, I don’t pretend to understand this link I’m posting https://www.nature.com/articles/nature.2013.12146


I can answer this! TL;DR is that the definition of temperature is much more general than what people realize. So most people think of temperature as how fast the constituent atoms of a gas are moving, but thats not the whole story. Fundamentally, temperature is how a system **changes** as energy is added to it. If I have a bunch of non-interacting particles and I add energy, they will start moving faster. So in that simple model the temperature is directly related to the speed of the particles--hence why this is the most common conception of it. But imagine a chemical reaction that releases heat and therefore increases the temperature of its surroundings. The temperature of the reaction surely (in every case) can't be the atoms moving, because often times for exothermic reactions they'll start as a molecule. A better definition of temperature than being just movement of particles (kinetic energy) is "how the configuration of a system changes with respect to it's energy". When we say "configuration" we mean it's entropy, which is a measure of how disordered it is. Now, we can imagine a cloud of atoms with low temperature. Intuitively, it will stay pretty still. But if we add energy to it the atoms will move faster and the cloud will expand. This expansion means the configuration of the gas is getting *more disordered*. So when we add energy it gets more disordered-- the amount of disorder **increases positively** with respect to the energy we've added. So negative temperature is just a system that becomes more ordered when we add energy-- the amount of disorder **increases negatively** with respect to the energy we've added. For gases this doesn't make sense, we add energy but they slow down? This is why temperature is not just defined with respect to movement of atoms. Imagine a bunch of coins, all heads down. If tails is "low energy" and heads is "high energy" then starting with all tails, adding "energy" increases the disorder (i.e. they'll no longer all be tails) and therefore we are increasing the "temperature". But eventually, you'll have a 50-50 mix of heads and tails. Now when we add energy the coins start to become more ordered. This means after the 50-50 mix is passed, the system actually jumps to start having "negative temperature", because adding more energy makes it less disordered. This analogy works for systems with more than just kinetic energy. Specifically: quantum spins, ising models, basic magnetic dipole models. Turns out this definition of temperature, along with some other equations defined by Maxwell, explain all of thermodynamics. Source: I have PhD in physics. And also Ph-Deez nuts got'em.


>Imagine a bunch of coins, all heads down. If tails is "low energy" and heads is "high energy" then starting with all tails, adding "energy" increases the disorder (i.e. they'll no longer all be tails) and therefore we are increasing the "temperature". But eventually, you'll have a 50-50 mix of heads and tails. Now when we add energy the coins start to become more ordered. This means after the 50-50 mix is passed, the system actually jumps to start having "negative temperature", because adding more energy makes it less disordered. If I understand correctly, this is using Boltzmann's entropy formula to achieve a negative measurement in a nutshell




My shitty understanding is that all bets are off once anything quantum comes into play. Some of the "laws" and such for the universe stop applying the same for odd reasons.


Quantum= Magic That's really all there is to it. It's sufficiently advanced that to even the best science of the age, it's magic. If we one day truly understand quantum mechanics, we will have ascended. To what is unknown.


Humanity has actually quite a good understanding of Quantum Mechanics. We wouldn’t have those tiny transistors on chips, LEDs, lasers or nuclear energy if we didn’t It’s not magic, it’s just weird It’s only magic in fiction


What i was gonna say. Quantum mechanics is how, and why is that it's magic that breaks physics until we figure out how it actually works. And from what I've seen... Uhhhh yeah good luck, scientists.


So the Futurama joke isn't a joke? >with wind chill it's twenty degrees below absolute zero.


So basically they cheated the universe. So entropy is what allows us to define absolute zero. Entropy is pretty much the capacity for disorder. If you had a perfect crystal without any energy it would be 0 K. (Second law of thermodynamics.) So in their little cheat they get the atoms very very cold. They then used magnetic fields to hold a crystal in an unfavorable position (a disordered crystal). Then when energy is transferred into this causes the system to shift into what would normally be the more favorable system (more ordered). But due to the magnets it doesn't like it. So even though. So you've added energy to a system and made it more ordered. Which the universe really doesn't like. So the way the math works out you end up with a negative sign on the temperature. It's not really below absolute zero in the sense that it's broken the rules of the universe. It's more like in a video game if you cheat to give yourself so much money it glitches out and shows a negative number. What's even weirder, despite being technically below 0 K. It's "hotter" than it was when it was just above 0 K. (Because of the added energy.)


So like a space tornado


Figuring out the equation for th temperature of a black hole is what initially got Steven hawking famous. It is inversely proportional to the radius,so since all currently known black hole are very large, they are all extremely cold far below 1 kelvin.


Purely guesswork, but it depends on your way of looking at them, and I am not an astrophysicist. Black hole as a whole, with accretion disk: Incredibly hot, surrounded by extremely speedy particles from matter disintegrating at near light speed. Event horizon, raw: virtually unable to emit heat towards an observer, so technically shows as measuring cold. Beyond horizon: Theoretical and unobservable realm. In my assumption extremely hot, but not in an easily explained way. Possible that if you managed to magically introduce an object in this sphere without having it ripped apart, you'd find it obliterated by gamma radiation hitting it from all sides simultaneously, except from the direction of the singularity. (Big maybe) The singularity: I don't know if the term hot even makes sense here. A singularity is a point of unfathomable energetic potential, where our understanding of physics doesn't reach.




isnt the speed of light the top speed possible?


Brilliantly simple explanation


I love this, except Absolute Fast also exists. Try light, or matter.


It seems that there is also a maximum hot https://www.reddit.com/r/explainlikeimfive/comments/yhfmp4/eli5_why_do_temperature_get_as_high_as_billion/iuebf54/?utm_source=share&utm_medium=ios_app&utm_name=iossmf&context=3


Temperature can be thought of as the speed of atoms. At -273 Celsius atoms would stop, since they can’t get slower than not moving that’s the coldest it can get.


So is there a maximum temperature when atom’s speed approaches the speed of light?


The hottest theoretical temperature is the Planck Temperature > The Planck temperature is 1.416 784(16)×10^32 K. At this temperature, the wavelength of light emitted by thermal radiation reaches the Planck length. There are no known physical models able to describe temperatures greater than TP; a quantum theory of gravity would be required to model the extreme energies attained (the Planck length being the shortest meaningful length in our current understanding of physics) also I don’t understand wikipedia’s notation there with the space and (16) but whatever also lol: > Hypothetically, a system in thermal equilibrium at the Planck temperature might contain Planck-scale black holes, constantly being formed from thermal radiation and decaying via Hawking evaporation. Adding energy to such a system might decrease its temperature by creating larger black holes, whose Hawking temperature is lower


>also I don’t understand wikipedia’s notation there with the space and (16) but whatever It means that value has an uncertainty of 16 whatever the last digits are, in this case it would be: 1.416 784 +/- 0.000 016 \[x10^(32)K\] The space is just there to easily count the digits.


There's a recommendation that a short space be used instead of a dot or a comma when writing large numbers. So instead of 12,345,678 The number would be written 12 345 678 This is in order to avoid ambiguity as different countries use dots and commas, and sometimes in different places. Edit: wiki link: https://en.m.wikipedia.org/wiki/Decimal_separator#Digit_grouping You as seeing that in the decimals above too. Wikipedia's science and maths based articles tend to use this notation.


So, to avoid ambiguity between two systems of writing numbers, a third system was introduced? Lol


I don't even have to link it, you are already imagining it.


... here it is: https://xkcd.com/927/






X.K C,D(16)


> two systems There are actually more than 2 systems. But, yes.


For a Canadian who meets both the English 1,234.56 and the French 1.234,56 on the daily, thank you. Spaces are so much cleaner


As a guy who frequently deals with CSV files that are space delimited, I hate this. Thanks.


Fuck I hate CSV ... SO much. And don't get me started on ambiguous timestamps or flip-flop date formats. Gimme ISO YYYY-MM-DD and 24hr time with a God damn time zone (ideally UTC, and specify it still) thank you very much! Edit ISO, not ANSII. Oops.


In France, dots aren't used, only commas and spaces, perhaps it's different in Canadian french Country | Notation -:|:- France | 1 234,56 USA | 1,234.56


Wow. An ELI5 within an ELI5. Brilliant!


Planck Temperature is not actually a limit for temp- as it says, there is no known model to predict what happens at or past the Plank temp We literally don't know what happens. All models break at this point. We can't create it nor have we observed it. There are theories with little basis. If you wanna argue it opens up a time portal, sure, can't rule that out


Would something be able to be planck temperature without collapsing into a black hole?


Most likely no. We can make some pretty good guesses and time portal is not one of them. Collapsing itself into multiple blackholes is certainly up there on the "more realistic" chart


I like that "more realistic" is in quotes. It conveys the extremity nicely.


One of my favorite parts of long standing unsolved problems is how often you come across hypotheses that are clearly the most likely option aesthetically, but that haven't been supported in any real way. P≠NP is another great example.


What is P and NP?


P is the set of problems that can be solved in polynomial time (to simplify - problems where very large inputs aren't *that* much slower than very small inputs), and NP is the set of problems who's solutions can be verified in polynomial time. To use an example of something that's (probably) in NP but not in P, imagine you have a bunch of cities, and every city has a direct route to every other city (i.e. the route doesn't pass through any other cities). Now imagine you want to ask "is there a route which passes through every city once that's shorter than 1000 miles?" In order to solve the problem, you might need to check every single possible order to visit cities in - you can eliminate some with clever trimming down of possibilities, but it's still going to take a while if you're dealing with 100+ cities. However, if someone gives you a solution, you can easily check it - you just add up the distances and check if it's below 1000 miles or not. Now, we're pretty sure that not all NP problems are in P as well. If they were, then there'd be some ultra fast algorithm to figure out exactly what combination of cities gets the shortest route. However, we haven't been able to prove it, so it's still not something we can rely on in mathematical proofs and such. P =/= NP is a highly sought after proof.


The Planck temperature would correspond to particles moving with the Planck energy each; above the Planck energy per particle, collisions between particles create larger, colder black holes. Since temperature isn't meaningful for single particles, only for systems of particles, the Planck temperature is the hottest temperature and heating things beyond that temperature makes them colder again since the heat capacity of the system becomes negative.


The description of black holes forming reminds me of cavitation bubbles occurring at the base of a kettle. The Planck temperature is like the universe boiling.


Thanks. I love an occasional random mind blowing. See you next time!


That's a good way to describe it.


This is why there's a heat limit, the Bubble Theory is correct!


It does seem like the old joke “the more cheese there is the more holes there are, therefore the less cheese there is” makes sense for temperatures being Planck temperature?


I think if you can convert the joke to mathematical notation, you might win an award or two.


> If you wanna argue it opens up a time portal, sure, can't rule that out But we don’t have to rule it out. If they make the claim, they’re obligated to provide evidence or we continue with the null hypothesis.


I would like to argue it would create a time portal but I would prefer not to provide evidence, just state that it would be cool.


Hypothesis: Makes a Time Portal Reasoning: Please?


Reason: it would be cooler than not making a time portal. Quod erat demostrandum.


But there is no null hypothesis. The rules of physics have no theory of what will happen at that point.


If you keep dumping energy into a system to increase the temperature, at a certain point, wouldn't you start to create more matter?


That's a possibility but the question then becomes 'by what mechanism?'. We understand how to convert mass to energy by fusion and fission, and we mostly understand the mechanisms there. Going the opposite direction is a little less well understood AFAIK.


Photons can undergo pair production to create an elementary particle and antiparticle, AFAIK that's the main energy-to-mass conversion. Quite often these pairs annihilate each other and form photons again though.


Well butter my buns and call me a biscuit. > Two gold ions (Au) moving in opposite directions close to the speed of light (v≈c) are each surrounded by a cloud of real photons (γ). When these photons collide, they create a matter-antimatter pair: an electron (e-) and positron (e+). https://www.energy.gov/science/np/articles/making-matter-collisions-light Fancy that we actually did it. TIL.


So we've taken 1 infinitesimally small step towards making a star trek style replicator.


> also I don’t understand wikipedia’s notation there with the space and (16) but whatever The space is an SI recommended way of separating triples of numbers so eg. thousands, millions and thousandths and millionths etc. The (16) is a shorthand for expressing the uncertainty or error in the rightmost significant figure(s). e.g. 1.9(8) would be 1.9 plus or minus 0.8.




Most metric rulers are marked in 10ths. Most imperial rulers are marked in 16ths of an inch, not 10ths. Those exist, but are typically for drafting, not regular use. Your point still stands.


Yeah, it was just an example to make the numbers easier since this is ELI5.


Shoot, you really hit a nerve with the ruler crowd, didn't you?


The Planck length is *not* the shortest meaningful length; this is a persistent myth. The Planck length is a "natural" length that arises when you set a system of units to get certain universal constants to equal 1. There is nothing special about the Planck length as a *limit*. It *happens* to be extremely small, small enough that we don't have the technology to look at something that small and that interesting quantum effects are happening. Therefore it is commonly used as a shorthand for "really small things". But we have no evidence of physical laws that would make it a "limit". There are other Planck units. Some Planck units are very large, some are very small, and some are actually near the human scale - for example, the Planck mass is about 22 micrograms; certainly 22 micrograms is not the smallest possible mass!


> There are other Planck units. Some Planck units are very large, some are very small, and some are actually near the human scale - for example, the Planck mass is about 22 micrograms; certainly 22 micrograms is not the smallest possible mass! What you're saying is that it's possible to become an accomplished enough physicist that you end up with so many concepts named after you it starts to confuse people.


Mathematicians had a similar problem, they started naming things after the first person to prove them who wasn't Leonhard Euler.


In dog agility competitions, there is an open class called ABC, short for Anything but Border Collie. Apparently the Border Collie is Euler’s spirit animal.


> What you're saying is that it's possible to become an accomplished enough physicist that you end up with so many concepts named after you it starts to confuse people. [Laughs in Euler](https://en.wikipedia.org/wiki/List_of_things_named_after_Leonhard_Euler)


Planck units were made by Max Planck to have a set of units based on universal constants instead of objects we randomly decided to base a unit off of. Here's a page with a few similar systems of units: https://en.wikipedia.org/wiki/Natural_units


> The Planck length is not the shortest meaningful length; this is a persistent myth. > The Planck length is a "natural" length that arises when you set a system of units to get certain universal constants to equal 1. There is nothing special about the Planck length as a limit. It happens to be extremely small, small enough that we don't have the technology to look at something that small and that interesting quantum effects are happening. Therefore it is commonly used as a shorthand for "really small things". But we have no evidence of physical laws that would make it a "limit". From the Wikipedia article on Planck length: *It is possible that the Planck length is the shortest physically measurable distance, since any attempt to investigate the possible existence of shorter distances, by performing higher-energy collisions, would result in black hole production. Higher-energy collisions, rather than splitting matter into finer pieces, would simply produce bigger black holes.*


It's only a "limit" insofar as it's a limit to our current models and understanding of physics. We don't know what happens below that number, only that our current laws of physics can't describe it.


> The Planck length is not the shortest meaningful length; this is a persistent myth. No, that statement is perfectly accurate. If they had said the shortest length, then you'd be right, but they said the shortest *meaningful* length. As below that length we get physics equations that have tons of infinities, divide by zero, etc., nothing about a length smaller is *meaningful*. That says nothing about a smaller length *existing*.


that’s good to know


I believe the (16) is the degree of uncertainty (?) in the value. So we are confident this number is correct to .00000016x10^32. Sorry on mobile.


The citation breaks down the uncertainty: https://physics.nist.gov/cgi-bin/cuu/Value?plktmp


Because the amount of energy needed to accelerate mass increases exponentially with speed it would take and infinite amout of energy. So there is no limit to how hot something can be


There is a theoretical limit at the Planck Temperature I believe.


There's a "limit" in the sense that our models don't work above that temperature. Maybe it isn't possible, maybe we just need better models.


Not really. There's a point called the "Planck temperature" but we don't know what happens past it. Higher temps might be completely impossible, or completely unremarkable, or have their own weird behavior. But we don't have the math to understand it.




Technically they never stop moving. But they do reach a point where it’s physically impossible to have any less energy.


Technically, I think they never reach absolute zero, right?


Interesting to note, we can artificially induce a temperature closer to absolute zero than is possible to occur naturally. This means the coldest temperature in the entire universe is on earth.


And any other planet inhabited by a sufficiently advanced species. ;-)


A phenomenon we have yet to ever see or verify.


To be fair we haven't looked very far.


Aliens contact us and the first thing we ask is "how cool can you get?"


Ice cold! All right all right all right all right all right all right all right all right


Damn. That's cool.


ICE COLD!! Alright Alright Alright Alright Alright Alright Alright Alright Alright Alright Alright Alright Alright Alright Alright Alright Alright Alright Alright


If you make a sufficiently large region of space sufficiently cold you unlock the universe's cheat menu.


Then it is time to build big freezer and send it to orbit.


What, you e never seen the documentary *Men In Black*


Also interesting; While this is true, and we have reached incredibly low temperature (look up Boze Einstein Condensates, super interesting read), we estimate that in order to reach absolute zero you need a machine the size of the universe, operating for the lifetime of the universe, to actually reach it. This is because each degree lower takes an exponential amount of effort. So while theoretically possible to reach absolute zero, it is effectively impossible.


Oh I wasn't disagreeing on that point, just they we have created conditions to get *closer* to absolute zero than what can occur naturally.


I figured haha but I thought it would be fun to expand


Well, the coldest *known* temperature. It's possible that in some other galaxy there are alien scientists with better laser refrigeration equipment than us.


Wikipedia says: > Absolute zero is the lowest limit of the thermodynamic temperature scale, a state at which the enthalpy and entropy of a cooled ideal gas reach their minimum value, taken as zero kelvin. The fundamental particles of nature have minimum vibrational motion, retaining only quantum mechanical, zero-point energy-induced particle motion. The answer to "Absolute zero means zero motion so they never reach it?" is "No" because absolute zero is defined as the minimum possible energy. The answer to "Is it possible for something to actually reach absolute zero?" is "No, as far as we know" for reasons others mentioned. We can't build a machine that would do that and we don't know of any natural process that would do that.


Is it like the speed of light? i.e. we can calculate its value but no matter can ever reach it.


I mean, the phone screen in your hand is emitting light traveling at the speed of light quite happily. We don't have anything actually at 0K.


Yes, you cannot measure absolute 0. Measurements requires energy and the act of measuring create something from nothing




psst, you don't need the degree symbol for Kelvin


There's a sci-fi novel "Ice" by J. Dukaj where he imagines a world where temperatures (slightly) lower than absolute zero can be achieved. At 0K the atoms are immobile; at below 0K they are immobile AND differently organized - into crystalline structures that are more "perfectly organized" than in regular ice and thus have less entrophy. But that's SF, of course.


Interesting take, but in reality it’s basically conflating two independent measured values into one composite value - energy and entropy, kind of how “enthalpy” is used as a sum of thermal and mechanical (pressure/volume) energy


Sure, just wanted to share. I also read the book ages ago so the author probably did a better job of explaining his idea than I did.


It's the same thing as the stock market. It can go up 1 million percent. But it can only go down 100% and then it hits nothing.


Technically it could go negative, i.e. they pay you to take the shares off their hands.


That can happen with commodities, because there's a hidden expense to taking possession and storing them. I can't quite think why that would happen with stocks, since shareholders don't ever have liability to holding shares.


Heat is a thing. Cold is an absence of that thing. Theoretically, you can get to a point where there is none.


I immediately thought of it same as black / white "colors"


Hmm since you can't have anything darker than just black- the absence of any light, would you say it can always be brighter or is there a limit? 🤔


There might be. Light is counted as a form of energy, and there is an equation that defines a limit of energy density before it collapses into a singularity. If you have enough light photons in defined area, it will become a black hole. Is that a limit or can a black hole be "bright"?


I posted about this to another user but following up on your energy equation, this follows for heat and light and any other energy, there is an upper limit where the system collapses onto itself and forms a special type of black hole called a kugelblitz, putting an upper limit on light, heart, any energy.


Yeeessss, issue you might be hung up on is "visible spectrum." Light is a wave, if we could expand our visual capabilities you could see more frequencies, regretting from 0-∞


> is there a limit? 🤔 There is. Well.. there are two different ones, and they're both rediculously high energy effects. (Like: way *way* higher than we've ever gotten experimentally). Starting with the relatively "easy" option: - Schwinger Limit: when your light is so intense that its electric field is strong enough to straight-up create electron/positron pairs out of thin air. - Klugelblitz: when you manage to pack so much light into a small enough volume that it forms a black hole. (Light may not have mass, but it does have energy. And it does have gravity. So if you get enough of it...)




You can go backwards * taps head *


That's speed in another direction and moving **Untaps head*


At the end of your turn I tap my head to add 2 blue mana to my mana pool, and immediately untap my head during my untap phase


Is your head an artifact or a creature? Or both?


Mind stone is an artifact, but I dunno why he's tapping it for 2U when it's just a colorless


Uh... c


Temperatures humans find comfortable are much closer to the lowest possible temperature than the highest. Therefore the scale we use to measure temperature is much closer to absolute zero than the maximums.


This is one of the best answers. The OP didn’t ask about what absolute zero was or why there is an upper limit. It was a question about scale.


Temperatures that tend to be useful for humans are, on the grand scheme of things, remarkably cold. There's no need for our "human useful" scales to be calibrated to such high numbers. To humans, there isn't really a difference between 10,000C and 1,000,000C. They're both too dang hot. That's the same reason scientists use Kelvin, starting from zero makes the most sense in experiments.


This helped me (not OP) understand better. My understanding of the question is not about why there is a minimum, but why are we not close to the middle. Since our bodies are close to the minimum (0K limit), the Celsius and Kelvin scales make sense.


"Why are we not close to the middle" has different answers depending on what you mean. If you mean "Why is the human-made scale so close to the bottom of the overall scale?" Well, because we made those scales in the context of temperatures we can actually handle. Fahrenheit tries to be convenient for us specifically, and Celsius is based on water's freezing and boiling points. If you mean "Why is the range of temperatures that humans exist at so close to the bottom?" This is harder to answer but the gist of it is that life requires complex chemistry and complex chemistry only happens at those temperatures, because hotter temperatures rip everything apart into a boiling, swirling soup and colder temperatures don't allow for liquids to work their magic that makes chemistry possible.


Yes. This is the response that actually answers the question. The question is not “what happens at absolute zero?” The question is “why is our scale so much closer to absolute zero than silly hot”


Yep, there's a pretty common saying that 0-100 Fahrenheit is "how hot is a human?", Celsius is "how hot is water?", and Kelvin is "how hot are atoms?". And Rankine is the bastard stepchild.


Yeah this looks like the first thing I read that actually answers the question. OP didn't need any explanation on what temperature is or how it works. It's more about why we assigned those kinds of numbers. To OP. Note that -270 (-273.15 to be more precise) is just one value on one system of measurement. If you use Fahrenheit it's -460 (ish. Forgot the exact value). It's just a matter of assigning numbers and it just so happened, that as was said above, people assigned numbers to whatever is useful to them on a daily basis, so 100C is boiling water and stars are at thousands or millions. You could invent a new temperature scale that has stellar temperature at hundreds (and absolute zero at negative millions) but that's not gonna have the same applicability as the ones we currently have.


0°K < cold < {*cool* |<--**people**-->| *warm*} < hot < dang hot < really dang hot < Planck dang hot ≈ **∞**


You forgot the inside of a fresh hotpocket


the average temperature of the universe is about -270.4C so you could say that any temperature survivable by humans is super hot.




A few sci-fi novels have aliens that exists at temperatures like that. Sector General and Dragon's Egg come to mind.


This is why I'm not an international best selling author yet. Still not got an original idea 😔


There are no original ideas. You could definitely still write a book from the perspective of them


the originality doesn't come from the idea, it comes from you telling a story about the idea. nobody will tell that story quite like you will.


There was such a species in the 'Star Control' or 'Ur-Quan Masters' - a 1992 PC game (that was actually really good and I was still playing it circa 2005). It was noted that their ships power consumption was 98% life support.


Isn't everything/most matter either gas or supercritical fluids depending on pressure at those temperatures? E.g. even metals evaporate unless extreme pressure force them to stay as a fluid. Further any thing going from 10^5 K planet to space will have some interesting challenges seeing as the temperature and pressure drop will force matter to liquefy and then solidify pretty fast. Any challenges our spacecraft have is nothing compared to this theoretical planet. Saving space for someone more knowledgeable to swoop in and correct me


Why can things go with 100 or even 1000 km/h, but only as slow as 0 km/h? The answer is the same.


Temperature is actually a measurement of how much molecules are vibrating. Higher temps means more vibrations, lower temps less. At freezing, water molecules crystalize. -270 is the theoretical limit at which absolutely everything stops. There's no going below that




How do you make something that cold though to even know how many Celsius is required to freeze atoms and or that u can't go any Lower than that?


Because degrees are stupid. Let's ask a different question: why does length get as high as trillions of light years but only as low as 0? And... that's a silly question, isn't it? Same with mass: why does mass get as high as 10^52 kg but only as low as 0? Again, silly question. Same thing with temperature: why does temperature get to billions of kelvins but only as low as 0? Except that temperature is usually measured in these stupid units called degrees. Imagine a unit of length such that 273.15 meters was 0 of this unit, and 100 of this unit was 373.15 meters. That would be stupid, right? 0 units isn't actually 0 length! Well, that's how we do temperature. 0 degrees is not actually 0 temperature. 0 temperature is called absolute zero, but for historical reasons, we have this unit called degrees such that a temperature of 0 is actually –273.15 of these degrees. So 20 degrees is not twice as hot as 10 degrees. Not even close. Because 10 degrees is actually 283.15 K, and 20 degrees is actually 293.15 K, so their ratio is 293.15/283.15, not 2/1. But this challenges the way we normally assume things about math, because the 0 isn't actually the zero. It makes sense that you can't really have negative temperature, except we have these stupid units where it *can* be negative. Of course, when the Celsius scale was invented, people didn't know about absolute zero. That's why you have similar scales like Fahrenheit. There was even a scale that counted *down* as you got hotter. People didn't know what temperature actually was: the average kinetic energy of the particles in an object. That energy could be 0 in theory, but it certainly can't be negative! But they didn't know that at the time.


Everyday temperatures are really, really cold. That is to say, they're quite close to how cold things can possibly get, and quite far away from how hot certain things out there can get.


Because cold isn’t a thing, there is just a lack of heat. So when there is no more hot, there is only nothing. At -273 c absolute zero, all is halt.


The simplest answer is that your thermometer is stupid. When Fahrenheit and Celsius were invented, we didn’t know how cold the coldest cold could be, so the inventors picked an arbitrary temperature and said “This is zero”. They could have picked anything. Celsius picked the freezing point of water because, hey, water is everywhere, and decided that 100 would be the temperature at which water boils. Then the range between was divided into “degrees” to be an arbitrary unit of temperature. Later, we figured out that there is a limit to how cold the coldest cold can be, and there was a new temperature scale invented called Kelvin. The absolute coldest a thing can ever theoretically be is 0 Kelvin. And then you work your way up by those degrees and eventually get to the temperatures we normally experience between ~250-350 Kelvin. So, if your thermometer was smart, it would be using Kelvin and start at zero and only ever go up-no negative temperatures. Since temperature is a measure of how much/fast atoms are moving around (average kinetic energy) negative temperature doesn’t really make sense, any way. It’s not like you can move slower than being completely stopped, which is the state at 0 Kelvin. So, in short, your question highlights a symptom of the fact that the commonly used temperature scales were made arbitrarily. Because of this, they don’t make sense once you get outside of the ranges we normally experience in weather.


That being said, for regular human use, kelvin doesn't serve a purpose. Most people will only ever theoretically interact with things in a range from like -100C to +1250C, and those are extremes. Normal stuff happens between -20 and +40 day to day besides cooking. Starting at absolute zero would mean regular day to day temperatures would be in 3 digits all the time which is harder for most people to think about comparatively.


It is not quite like that. If we use the proper temperature scale, there are simply *no negative temperatures*. Then the question becomes: why in our everyday life the environment is mostly at 300 Kelvin, plus or minus a few tens of degrees, even though there are places in the universe where it is much hotter? And the answer to that would require talking about our biology etc. It is not a question of fundamental physics.


There's a floor to how much energy you can remove from something before there's nothing left. However, there might not be a ceiling for how much energy you can put in.


I remember a question similar to this and the best answer was something along the lines of temperature is just a measure of how much an atom wiggles. It stops wiggle at -270 degrees but there isn't an upper boundary for the wiggle.