12 ms·

The Color of Infinite Temperature

332 points by c1ccccc1 5y ago

perihelions 5y ago
The generalization of this is the Planckian locus: https://en.wikipedia.org/wiki/Planckian_locus https://en.wikipedia.org/wiki/Planckian_locus That's the image of the temperature range (0,∞), mapped to the corresponding blackbody color in chromaticity space. The limit T -> ∞ is a point discontinuity near the center of CIE space.
- riskneutral 5y ago
  Someone should implement a Planckian locus color space.
  - AprilArcus 5y ago
    Most programmable home LED lighting (e.g. Hue) provides a one dimensional color temperature color space.
  - nimish 5y ago
    Ye olde incandescent bulbs had this built-in, of course you needed a dimmer...
    - jrockway 5y ago
      I turned mine up to infinity and they had to build a new Earth. (These kids with their 11!)
      - MauranKilom 5y ago
        For reference: https://what-if.xkcd.com/35/ https://what-if.xkcd.com/35/
- mncharity 5y ago
  FWIW, that article's top graphic[1] is currently malformed[2]. Hmm, and the text incorrect[3]. Wikipedia's coverage of this topic has regrettably been unstable over the years. Broken chromaticity diagrams are so common, each time the graphic is swapped, it's a toss up whether it's a correct one. And then edits reflect that, and common misconceptions. Perhaps if WP had not just Article and conversational Talk pages, but also something like a writer's notebook, it might serve as memory, as immune system, as a place to caution "make sure when editing that you don't ...". Perhaps it will stabilize some day - the Sun[4] page seems to have at long last settled on a white-not-yellow Sun. Yay. That's more than several of the most used intro astronomy college textbooks have managed. Science education content is... something we struggle to do well. [1] https://en.wikipedia.org/wiki/File:PlanckianLocus.png https://en.wikipedia.org/wiki/File:PlanckianLocus.png https://commons.wikimedia.org/wiki/File:PlanckianLocus.png https://commons.wikimedia.org/wiki/File:PlanckianLocus.png (13:38, 3 January 2012) [2] Obvious errors: the blackbody curve shown doesn't go through white, and does go through yellow. Incorrect white-point math is a recurring cause. [3] "It goes from deep red at low temperatures through orange, yellowish white, white, and finally bluish white at very high temperatures." (emphasis added) [4] https://en.wikipedia.org/wiki/Sun https://en.wikipedia.org/wiki/Sun
  - alejohausner 5y ago
    Well, the biggest error for me is that the tongue-shaped region is completely filled with color! On any three-color device like an LCD display, the gamut of producible colors will cover a triangular region inside that tongue. Any chromaticity diagram that is filled completely is a lie.
    - Dylan16807 5y ago
      It's hard to call that an error. Do you want it to show garbled static? Every point on the diagram shows the closest available color based on the format.
    - raxxorrax 5y ago
      Well, you would not be able to see "mud": https://www.livescience.com/17948-red-green-blue-yellow-stunning-colors.html https://www.livescience.com/17948-red-green-blue-yellow-stun...
- graderjs 5y ago
  Out of curiosity...what background do you have to make such a wonderful highly technical comment in a casual way...I'm so interested in the field of your expertise that you know so much about that this stuff, that something so technical is familiar to you, that you can come up with this brilliant analogy straight away and do it so casually. Do you work in "color technology" for a media company or something? I have no idea. I'm so interested what part of the world people who know these things do work in. Strangely, I'm struggling to write this comment in a way that doesn't sound trolling...sorry, I don't mean trolling at all. If you could see my facial expression it would be easier...
  - srcreigh 5y ago
    I'd wager bachelor's degree+ in applied math or pure math or maybe physics.
  - nefitty 5y ago
    I think we should normalize expressions of awe and curiosity about other people. It's hard to do without sounding ridiculous. A model that helps me is, "I like the state that that person's brain is in. I'll let them know. If I'm lucky, my communication of appreciation might shake out some generalizable knowledge that I have not encountered before." A good set of people to practice this on is doctors, teachers and Twitter users you admire.
  - mdwrigh2 5y ago
    I'm not the parent you're asking, but figure you might be interested anyways since I could've likely made the same comment: I work on displays within an OS team. Having some basic understanding of colour theory is critical for a significant number of modern display projects, particularly for the high end. For example, enabling colour accurate rendering (games, photos, etc), shipping wide-gamut displays (how do you render existing content on a WCG display?), etc. More specifically to the planckian locus, it generally comes up when deciding which white point to calibrate a given display to at the factory (e.g. iPhone is 6470K, S20 is 7020K in Vivid)[1][2] and if you're doing any sort of chromatic white point adaptation, like Apple's True Tone[1][2]. My background before joining the team was a degree in math, but I really enjoyed doing low level projects in my spare time, so ended up on an OS team. We also have colour scientists who study this full time and have a _significantly_ better understanding of it all than I do :) [1]: https://www.displaymate.com/iPhone_13Pro_ShootOut_1M.htm#White_Point https://www.displaymate.com/iPhone_13Pro_ShootOut_1M.htm#Whi... [2]: https://www.displaymate.com/Galaxy_S20_ShootOut_1U.htm#White_Point https://www.displaymate.com/Galaxy_S20_ShootOut_1U.htm#White... [3]: https://support.apple.com/en-gb/HT208909 https://support.apple.com/en-gb/HT208909 [4]: http://yuhaozhu.com/blog/chromatic-adaptation.html http://yuhaozhu.com/blog/chromatic-adaptation.html
- deleted 5y ago
  [deleted]
areoform 5y ago
Can someone explain this to me with undergraduate level math?
- riskneutral 5y ago
  https://en.wikipedia.org/wiki/Black-body_radiation https://en.wikipedia.org/wiki/Black-body_radiation
- krastanov 5y ago
  The color you perceive is a weighted average of the intensities of different wavelengths of light that hit your eye. Ultra-violet and infra-red have a weight of zero (invisible). Most colors not at the edge of visible spectrum have weights that are roughly the same order of magnitude. Hot bodies emit various wavelengths, but the distribution of intensities is roughly a bell curve. If you sum up all these intensities, but weight them by the aforementioned weights in the previous paragraph, you would calculate what color would be perceived when looking at that object. Barely glowing hot objects emit a ton of infra-red (with perceptual weight zero) and a bit in the visual spectrum, on the red end of it (with a non-zero weight). So we perceive a red glow. Extremely ludicrously hot objects emit a ton of ultra-violet, X-ray and gamma rays (all with zero weight for visual perception), but also a bit on the blue end of the visible spectrum (with a non-zero weight for perception). So they look blue. Well, they would have looked blue, if the invisible bombardment of gamma rays did not immediately evaporate you.
- Dylan16807 5y ago
  A hot object emits light over a wide range of frequencies. At the low end of those frequencies, the intensity at each fequency is roughly proportional to the object's temperature multiplied by the frequency squared. Once an object is hot enough, all of visible light is in the low end of the frequency range. Which means the ratios between all visible frequencies are based on frequency squared and nothing else. That gives us a specific spectrum, where blue is about twice as intense as red. That spectrum has a specific color, the same color as #94B1FF. (Note that other RGB values also represent the same color at different brightnesses. That's fine, because we're not worried about brightness in this math. Brightness scales linearly with the temperature of the object.)
kelsolaar 5y ago
I haven’t seen the math for the conversion of the article but typically the conversion from CCT to xy/uv are given for a particular domain. One of the conversion with the largest domain, i.e. Ohno m, covers domain [1000K, 100000K]: https://github.com/colour-science/colour/blob/develop/colour/temperature/ohno2013.py https://github.com/colour-science/colour/blob/develop/colour... Infinity is very much in extrapolation territory.
- perihelions 5y ago
  Not really, since the shape of the blackbody emissions curve converges (when restricted to the visible wavelength range and normalized). 10^5 K should be very close to infinity.
  - kelsolaar 5y ago
    “Not really” to which part?
    - perihelions 5y ago
      That it's not an extrapolation. The physics part converges and stops varying.
      - kelsolaar 5y ago
        The article actually points out to the fact that colour is not dependent on the Planck’s Law: “So, for an extremely hot blackbody, the spectrum of light we can actually see with our eyes is governed by the Rayleigh–Jeans law. This law says the color doesn’t depend on the temperature: only the brightness does!” But then the Rayleigh-Jeans Law has been shown to be incorrect, see Ultraviolet Catastrophe.
        perihelions 5y ago
        Well yes but no: it's still the correct infrared limit (or high-temperature limit) of Planck's law, in fact Wikipedia has the derivation from one to the other: https://en.wikipedia.org/wiki/Rayleigh%E2%80%93Jeans_law#Comparison_to_Planck's_law https://en.wikipedia.org/wiki/Rayleigh%E2%80%93Jeans_law#Com...
exmadscientist 5y ago
Converting wavelength to sRGB is remarkably difficult. The conversion used here doesn't look quite right (see for example the sodium D lines), but I have never been able to figure out how to do much better.
- jetzzz 5y ago
  Colors of pure wavelengths are outside of the sRGB gamut and cannot be converted to sRGB, only approximated. Color of infinite temperature, on the other hand, is inside the sRGB gamut so no complication here.
  - exmadscientist 5y ago
    I'm not talking about the out-of-gamut problem. I'm saying that the standard algorithms simply do an awful job, such that you can easily beat them by eye. This is in the context of trying to produce the closest sRGB colors to a set of LEDs, for use in documentation. No published method could actually do it. I did have to assume the LED was a single-wavelength source, gaussian with specified FWHM, or Lorentzian, rather than measuring the spectrum (I was too lazy to mess with the spectrophotometer), but I don't think that would have made the difference for an LED.
    - kuschku 5y ago
      One major issue is that most displays aren’t properly calibrated to sRGB. Once I got two monitors profiled and calibrated properly, suddenly most of these algorithms matched much more closely than I had expected.
snidane 5y ago
If 0 Kelvin means object particles at complete stop and >0K meaning particles moving at a certain speed, shouldn't infinite temperature be impossible, since no particle can move faster than the speed of light?
- spenczar5 5y ago
  There are more problems than just that. The point is that the color converges to a single value, so even as you approach infinity it stops changing.
- krastanov 5y ago
  The temperature of a low-pressure non-relativistic gas is indeed related to the average speed of the atoms in a simple way. However, temperature, in the general case, is more closely related to the average energy of a particle (so the energy and temperature can both grow without bound as the speed approaches closer and closer to the speed of light). However, even that "definition" of temperature is rather imprecise.
  - McBeige 5y ago
    Weird and cool! Is the low-pressure low-speed definition of temperature a special case of the relativistic definition, or a completely different concept? What is the precise definition of temperature? How do these definitions relate to our everyday understanding of temperature, i.e. feeling hot/cold? Or which textbook should I read to find out? Sorry for asking so much...
    - krastanov 5y ago
      Great questions! There are many mathematically equivalent versions of the "complete" definition. My favorite is the zeroth law of thermodynamics: If body A and B have the same temperature (meaning there is no heat flow between them when they touch) and body B and C have the same temperature, then body A and C also have the same temperature. Basically, you define the words "thermal equilibrium" to mean "there is no heat flow when they touch" and you also define temperature to be the quantity that is equal in that case. This together with the "conservation of energy" and "growth of entropy" (basically the axioms of thermodynamics) is sufficient to derive most properties of temperature you know. If you have already defined entropy in some other way, you can say "the temperature of an object tells you how much the entropy of the object rises for a unit rise in the internal heat energy of the object": ΔEntropy = ΔEnergy / Temperature If you have not yet defined entropy, but have defined temperature (which I personally see as easier to understand), then the above equation can be your definition of entropy. Notice that "definition" just needs to be mathematically sound (i.e., self consistent). But for a physicist to want to use such definitions, they *also* need to be practical. Any of the (equivalent) definitions above are a fair choice, as they happen to be the self-consistent principles which do lead to behavior like the one we experimentally observe. I do imagine that a rigorous mathematician might have a reason to prefer one of the aforementioned definitions more than the other. I do not have such concerns. Lastly, concerning the gases: If you happen to know that gases are made out of moving atoms then you can do a bit more. Mind you, you can build most of thermodynamics without that knowledge. But if you know that fact, then you can derive that temperature is related to some measure of average energy per atom. If the atoms are relativistic, then energy per atom will need to be written in the relativistic form (which does not grow to infinity as velocity approaches the speed of light). At lower speeds, the formula for the energy becomes numerically indistinguishable from the one from classical mechanics. See https://en.wikipedia.org/wiki/Zeroth_law_of_thermodynamics#Foundation_of_temperature https://en.wikipedia.org/wiki/Zeroth_law_of_thermodynamics#F... Then I would suggest reading: - https://en.wikipedia.org/wiki/Zeroth_law_of_thermodynamics https://en.wikipedia.org/wiki/Zeroth_law_of_thermodynamics in its entirety - https://en.wikipedia.org/wiki/Temperature https://en.wikipedia.org/wiki/Temperature - https://en.wikipedia.org/wiki/Thermodynamic_temperature https://en.wikipedia.org/wiki/Thermodynamic_temperature
dane-pgp 5y ago
I can't help being reminded of the passage in the book of Revelation where John describes the throne room of God, and he notes "a rainbow round about the throne, in sight like unto an emerald". That's a little hard to imagine, because a rainbow contains a full spectrum of colours, whereas an emerald usually has a single colour, so some translations interpret the rainbow as being like the shine/gleam/glow of an emerald. But the idea that at infinite energy a spectrum might be perceived to human eyes as a single bluish hue is a nice thought, like the coincidence(?) that this colour happens to look like a clear summer's sky. Anyway, for comparison, here's an image from Wikipedia of a synthetic emerald: https://en.wikipedia.org/wiki/File:SyntEmerald_0302.jpg https://en.wikipedia.org/wiki/File:SyntEmerald_0302.jpg
- morsch 5y ago
  Maybe it's just bad writing.
- fastball 5y ago
  It's a nice thought, but describing the color in the OP as emerald seems like it would be a fairly poor attempt at describing your vision. It's more of a cornflower blue, or even as you say (and something easily accessible to the ancients): the color of a clear summer sky. For example if I was John and I saw the color of infinite temperature around God's throne, I would probably say something more like: > and there emanated from the throne an incredibly bright blue halo, as if a clear summer sky was shooting forth from God's throne.
  - pope_meat 5y ago
    The color blue hadn't been invented yet.
    - Rhinobird 5y ago
      that's probably true. https://en.wikipedia.org/wiki/Blue%E2%80%93green_distinction_in_language https://en.wikipedia.org/wiki/Blue%E2%80%93green_distinction...
choonway 5y ago
how about the color of negative temperatures?
- BenjiWiebe 5y ago
  If an absolute lack of all energy is 0, a negative temperature is kinda hard to reason about.
  - robin_reala 5y ago
    Negative temperatures are a thing, but you need to reframe temperature from inherent heat to energy flow between systems. https://en.wikipedia.org/wiki/Negative_temperature https://en.wikipedia.org/wiki/Negative_temperature
- contravariant 5y ago
  Assuming Planck's law still holds it should start absorbing radiation instead. That said Planck's law derives from Gibb's distribution and applying that rule to it suggests it immediately radiates all energy, until it stops having a negative temperature so I'm not sure if negative temperature is compatible with thermal radiation.
krater23 5y ago
Looks like the frame color of a C64 screen.
- echelon 5y ago
  Imagine in the far-distant future (past) where advanced machines have taken up the hobby of emulating the history of the earth on C64.
- nathell 5y ago
  It’s a secret plot by Atari to fry off the C64 users and rule the world. Fortunately, one is just a POKE53280,0:POKE53281,0:POKE646,1 away from evading this.
- jug 5y ago
  So it is then at least how I entered my current world. Close enough to the Big Bang, I suppose.
alphabet9000 5y ago
weird, several years ago i had a dream i had entered some kind of device that started to accelerate me towards the speed of light, and at the end of it i came to a point where it reached 'infinity' and it was like the most electric intense thing i had ever experienced, and i made a webpage to try and recreate and document what i remembered, and the color is almost exactly the same (strobe / flashing gif warning) http://jollo.org/LNT/public/dream.html http://jollo.org/LNT/public/dream.html
- mrtnmcc 5y ago
  I once had a near death out of body experience and that gif reminds me of it like nothing else I've seen.
  - colordrops 5y ago
    My out of body was from hallucinogens rather than near death, but it was very similar as well. The strobing is fascinating, going from a place of undifferentiated light back to the material world and back at a specific frequency.
- akersten 5y ago
  Ah jeez that's a very flashy GIF at the end of the page there. Might want to throw a sensory warning on that link as a courtesy
junon 5y ago
For once, a good article. Short, clear, to the point. Thank you, author.
- nextaccountic 5y ago
  I love John Baez's blog too! But actually I think his long winded, mathematically challenging posts are more interesting. Like this series https://johncarlosbaez.wordpress.com/2012/01/19/classical-mechanics-versus-thermodynamics-part-1/ https://johncarlosbaez.wordpress.com/2012/01/19/classical-me... https://johncarlosbaez.wordpress.com/2012/01/23/classical-mechanics-versus-thermodynamics-part-2/ https://johncarlosbaez.wordpress.com/2012/01/23/classical-me... https://johncarlosbaez.wordpress.com/2021/09/23/classical-mechanics-versus-thermodynamics-part-3/ https://johncarlosbaez.wordpress.com/2021/09/23/classical-me... https://johncarlosbaez.wordpress.com/2021/09/26/classical-mechanics-versus-thermodynamics-part-4/ https://johncarlosbaez.wordpress.com/2021/09/26/classical-me... An excerpt from the first article: > The big picture > Now let’s step back and think about what’s going on. > Lately I’ve been trying to unify a bunch of ‘extremal principles’, including: > 1) the principle of least action > 2) the principle of least energy > 3) the principle of maximum entropy > 4) the principle of maximum simplicity, or Occam’s razor > In my post on quantropy I explained how the first three principles fit into a single framework if we treat Planck’s constant as an imaginary temperature. The guiding principle of this framework is > maximize entropy > subject to the constraints imposed by what you believe > And that’s nice, because E. T. Jaynes has made a powerful case for this principle. > However, when the temperature is imaginary, entropy is so different that it may deserves a new name: say, ‘quantropy’. In particular, it’s complex-valued, so instead of maximizing it we have to look for stationary points: places where its first derivative is zero. But this isn’t so bad. Indeed, a lot of minimum and maximum principles are really ‘stationary principles’ if you examine them carefully. > What about the fourth principle: Occam’s razor? We can formalize this using algorithmic probability theory. Occam’s razor then becomes yet another special case of > maximize entropy > subject the constraints imposed by what you believe > once we realize that algorithmic entropy is a special case of ordinary entropy.
m3kw9 5y ago
Nice to know when it hits
rileyphone 5y ago
Baez is also a noted category theoretician - I need to get around to reading https://link.springer.com/chapter/10.1007%2F978-3-642-12821-9_2 https://link.springer.com/chapter/10.1007%2F978-3-642-12821-..., where he claims to find the conceptual framework unifying analogies behind physics, topology, logic, and computation. Discussion: https://news.ycombinator.com/item?id=15423027 https://news.ycombinator.com/item?id=15423027
kortex 5y ago
"Perano" is a terrible name. Some far better alternatives: - neutronium - catastrophic violet - Rayleigh-Blue-Jeans
- dr_dshiv 5y ago
  Well, it's the blue equivalent of pink. Blink? No. Periwinkle? Periwinfinite? I get super irritated by kids books that teach seven colors. We have an impoverished color vocabulary, as a result. Can't even describe the color of infinite temperature, sheesh.
  - yreg 5y ago
    https://en.wikipedia.org/wiki/List_of_colors_(compact) https://en.wikipedia.org/wiki/List_of_colors_(compact) to the rescue
    - Sharlin 5y ago
      This is my go-to page for coming up with names for computers and other hardware. Some examples, past and present: amber, auburn, carmine, cerise, indigo, magnolia, periwinkle, scarlet.
      - yreg 5y ago
        I have done the same with this list before!
    - dr_dshiv 5y ago
      That list is decidedly NOT cognitively ergonomic. Ends up being worse than useless by giving an appearance of authority. E.g. look at a periwinkle flower and look at the periwinkle in the list. They call periwinkle "Aero" but what is that?! https://images.app.goo.gl/8Qs5FARoBhEwYG2N8 https://images.app.goo.gl/8Qs5FARoBhEwYG2N8 I think color names should only be included if they match objects, have historical precedent or are composed of these plus basic descriptors. Or approved by the trans galactic color authority.
andrewflnr 5y ago
> gamma rays of arbitrarily high frequency What a delightfully, understatedly terrifying phrase.
nomilk 5y ago
Visited (from safari and chrome) on iPhone, it looks like entirely white [1]. It appears as the correct bluish colour on desktop. Might be just me. No idea why. [1] https://i.imgur.com/Bp1AW3u.png https://i.imgur.com/Bp1AW3u.png
- deleted 5y ago
  [deleted]
- nojs 5y ago
  Same here!
- nomilk 5y ago
  Seems it's not just me; here's the correct colour: https://imgur.com/a/OdHLrl9 https://imgur.com/a/OdHLrl9
- tzs 5y ago
  It also doesn't work from Safari on desktop, showing the little blue square with the question mark in it icon. Right-clicking and opening the image in its own tab works. Inspecting both, the server is setting Content-Type to "image/webp" on the page (and sending 58 bytes), but setting it to "image/png" when displayed in its own tab (and sending 139 bytes). On the request Safari says it can accept "image/webp,image/png,image/svg+xml,image/*;q=0.8,video/*;q=0.8,*/*;q=0.5" so the server choosing to send a webp is fine. For some reason apparently Safari cannot display this particular webp. The graph below that on the page, the one of intensity vs. frequency, is also a webp and Safari has no trouble with it.
DrTung 5y ago
Microsoft should change their BSOD screen background color to this.
- xxs 5y ago
  Is the color depth 24bit on blue/white part?
kelsolaar 5y ago
I have just computed the colour and find slightly different value, i.e. computed [154, 181, 255] vs article [148, 177, 255]. Here is a Google Colab Notebook that has the colour for 10^200 along with comparisons with a blackbody: https://colab.research.google.com/drive/1Oyn913zkXYB8Uf8k1hiM8_5gifuMVqta?usp=sharing https://colab.research.google.com/drive/1Oyn913zkXYB8Uf8k1hi...
- ginko 5y ago
  Well, 10^200K isn't quite infinity yet. Have you checked if the values change if you increase the temperature even further? Looks like their color is bluer than yours at least..
  - kelsolaar 5y ago
    Yes, it is minimal.
- dr_dshiv 5y ago
  I swear it's Periwinkle like the flower. https://images.app.goo.gl/8Qs5FARoBhEwYG2N8 https://images.app.goo.gl/8Qs5FARoBhEwYG2N8
- brohee 5y ago
  David Madore answered on Twitter : https://twitter.com/gro_tsen/status/1483054395524796421 https://twitter.com/gro_tsen/status/1483054395524796421, the discrepancy is likely due to you using Python's colourscience package SPECTRAL_SHAPE_DEFAULT which is based on ASTM E308-15 based on CIE and him using better color conversion functions from http://cvrl.ioo.ucl.ac.uk/index.htm http://cvrl.ioo.ucl.ac.uk/index.htm
  - kelsolaar 5y ago
    Hi, Yes, and as discussed on Twitter, sRGB is defined for the CIE 1931 2 Degree Standard Observer, not other observers. It is not defined spectrally but as a set of chromaticity coordinates (in the CIE 1931 Chromaticity Diagram). Thus, strictly speaking, sRGB values can only be computed for the CIE 1931 2 Degree Standard Observer. I tried four different observers, using strict integration: - CIE 1931 2 Degree Standard Observer: [ 153.9026317 , 180.75617631, 255. ] - CIE 1964 10 Degree Standard Observer: [ 150.32288938, 184.67113624, 255. ] - CIE 2012 2 Degree Standard Observer: [ 145.14899585, 180.69807338, 255. ] - CIE 2012 10 Degree Standard Observer: [ 148.44893332, 185.66849549, 255. ] - Article: (148,177,255)
deleted 5y ago
[deleted]
toolslive 5y ago
I've always felt that temperature is one of the quantities what was wrongly defined. As a consequence, It's working against you in most of the thermodynamics formulas. A better concept would have been (1/T).
- contravariant 5y ago
  Well, defining it so it's proportional to pressure etc. wasn't the worst idea.
dr_dshiv 5y ago
It looks like the blue equivalent of pink. But what is that, Periwinkle?
- denton-scratch 5y ago
  I'd go with Periwinkle. My periwinkles, though, are a rather sad, washed-out, faintly bluish white.
  - arbitrage 5y ago
    Your soil pH may be off.
    - denton-scratch 5y ago
      Hmmm. Too acid, or too alkaline? I had no idea that periwinkles were touchy about such matters. I thought they were considered an invasive weed that can grow on waste ground.
zokier 5y ago
Wouldn't infinite temperature object emit infinite amount of energy at all wavelengths, making the spectrum (and color) ill-defined?
- marcyb5st 5y ago
  Not at all wavelengths. An object of finite size and infinite temperature can produce all the wavelengths, but the probability of it generating, say visible light is really low approaching 0. So you can think about the relative number of visible photons you could observe and that gives you a color. My gripe with this is that if our understanding of quantum mechanics and general relativity is correct there is a limit of temperature. When a photon has a wavelength equal or smaller than the Planck length said photon contains enough energy to create a black hole. So, the upper limit of temperature should be the point at which the generation of black holes dominates the spectrum.
- londons_explore 5y ago
  You can still take the ratio of infinities and get a finite result.
stellalo 5y ago
“Perano” really sounds like it could be the name of some Italian village... oh wait: https://en.m.wikipedia.org/wiki/Perano https://en.m.wikipedia.org/wiki/Perano
twic 5y ago
It looks a similar colour to Cerenkov radiation. How similar? Is that a coincidence?
can16358p 5y ago
Is it just white? All I see is a white box as the color, though the text says otherwise.
- staticassertion 5y ago
  It's blue for me. Sort of a pastel or sky blue.
  - SketchySeaBeast 5y ago
    Yeah, tested on firefox and chrome. It's a pastel blue.
- dskloet 5y ago
  I see something blueish.
- jaqalopes 5y ago
  Yes it's absolutely a white box, at least for me on mobile Safari
  - can16358p 5y ago
    Same here, mobile Safari.
    - saurik 5y ago
      Huh. I am also using MobileSafari (on iOS 12 and 14) and it is rendering as a blue.
- mensetmanusman 5y ago
  On safari, can confirm it just looks white. Even tried turning off Night Shift. Not sure if this is a gold dress blue dress situation.
  - arjonagelhout 5y ago
SiempreViernes 5y ago
> And according to the experts who sip latte all day and make up names for colors, this color is called ‘Perano’ Unexpectedly salty coming from a pure mathematician! But maybe it's just professional jealousy of a field that comes up with new terms regularly? ;)
- kgwgk 5y ago
  He's a mathematical physicist.
causality0 5y ago
So, for an extremely hot blackbody, the spectrum of light we can actually see with our eyes is governed by the Rayleigh–Jeans law. This doesn't make sense to me. If we're talking about what color our eyes would see, all our cones would be 100% saturated. Correct me if I'm wrong, but we would still perceive that as white regardless of where the spectrum peak is.
- ani-ani 5y ago
  Looks like the color is simply normalized so that one of the values is at maximum (255) and the others follow the shape of the spectrum. It's all very theoretical. If you're talking about what's physically possible, then you could just stop at "infinite temperature" instead of going into eye cones. Maybe if a body's temperature approaches infinity, you could get this color by standing at a sufficient distance, or wearing adequate sunglasses with uniform attenuation, or doing the correct safety squint like we do at the workshop.
  - causality0 5y ago
    See that's the problem. The author is using the "color our eyes would actually see" thing but only in arbitrary ways that generate pageviews. It's inconsistent and dishonest.
kloch 5y ago
The general concept is correct but there are a few issues with the article: - Specific RGB values always depend on a selected white balance temperature. If the WB temp is the same as the object's temp it would be white, not blue. If the WB temp were higher than the object's temp it would appear red. EDIT: the article does say sRGB which implies a 6500K wb. - "infinitely hot" is not physically possible. The Neutron star example is fine, that temp would be around 10^12 K At that temperature virtually all of the emission would be in gamma rays, but emission in the visible spectrum would not be zero. Blue wavelengths would be stronger than green, which would be stronger than red so the color would appear Blue for any "normal" white balance temp (like 5500 K).
- rini17 5y ago
  It explicitly says sRGB which has commonly agreed white spot of 6500K. And thus it's reasonable assumption that photo of neutron star displayed on common monitor would have such color. Infinity is a well understood mathematical construct. I don't know what is the issue with evaluating limit value of some function, in this case color, "at infinity"? Nowhere it says it's physically possible.
marcodiego 5y ago
Considering that temperature is related to how agitated are the particles of a material and that there is a limit of how fast something can move (speed of light); doesn't it imposes an upper limit on the temperature? I mean, replacing v_rms by c in equation 3 in https://chem.libretexts.org/Bookshelves/Physical_and_Theoretical_Chemistry_Textbook_Maps/Supplemental_Modules_(Physical_and_Theoretical_Chemistry)/Physical_Properties_of_Matter/States_of_Matter/Properties_of_Gases/Kinetic_Theory_of_Gases/Connecting_Gas_Properties_to_Kinetic_Theory_of_Gases https://chem.libretexts.org/Bookshelves/Physical_and_Theoret... gives us an upper limit for the temperature of a gas, right?
- Etheryte 5y ago
  That is a somewhat simplified definition of temperature. While there's a parallel discussion on the same topic at [0], the term you're looking for is Planck temperature [1]. There is no "upper cap" on temperature per se, but we also don't have any models for describing what would happen beyond that point. See [2] for more discussion. [0] https://news.ycombinator.com/item?id=29963147 https://news.ycombinator.com/item?id=29963147 [1] https://en.wikipedia.org/wiki/Planck_units#Planck_temperature https://en.wikipedia.org/wiki/Planck_units#Planck_temperatur... [2] https://physics.stackexchange.com/q/420670/43412 https://physics.stackexchange.com/q/420670/43412
rikeanimer 5y ago
decent. I'm curious what it would be for a human tetrachromat (likely female) seeing in r4 space. Sadly, I can never know.
vagab0nd 5y ago
Boy am I glad to see this color! I was writing a black hole simulator, and needed to figure out the color shift of the stars as one approaches the black hole. The calculation gave me this blue at the one end of the spectrum which was very underwhelming tbh. For some reason I always though this color would be either 0xffffff, or some deep blue. Glad that my calculation is finally confirmed to be right!

332 points by c1ccccc1 5y ago

The generalization of this is the Planckian locus: https://en.wikipedia.org/wiki/Planckian_locus https://en.wikipedia.org/wiki/Planckian_locus That's the image of the temperature range (0,∞), mapped to the corresponding blackbody color in chromaticity space. The limit T -> ∞ is a point discontinuity near the center of CIE space.

riskneutral 5y ago
Someone should implement a Planckian locus color space.
- AprilArcus 5y ago
  Most programmable home LED lighting (e.g. Hue) provides a one dimensional color temperature color space.
- nimish 5y ago
  Ye olde incandescent bulbs had this built-in, of course you needed a dimmer...
  - jrockway 5y ago
    I turned mine up to infinity and they had to build a new Earth. (These kids with their 11!)
    - MauranKilom 5y ago
      For reference: https://what-if.xkcd.com/35/ https://what-if.xkcd.com/35/
mncharity 5y ago
FWIW, that article's top graphic[1] is currently malformed[2]. Hmm, and the text incorrect[3]. Wikipedia's coverage of this topic has regrettably been unstable over the years. Broken chromaticity diagrams are so common, each time the graphic is swapped, it's a toss up whether it's a correct one. And then edits reflect that, and common misconceptions. Perhaps if WP had not just Article and conversational Talk pages, but also something like a writer's notebook, it might serve as memory, as immune system, as a place to caution "make sure when editing that you don't ...". Perhaps it will stabilize some day - the Sun[4] page seems to have at long last settled on a white-not-yellow Sun. Yay. That's more than several of the most used intro astronomy college textbooks have managed. Science education content is... something we struggle to do well. [1] https://en.wikipedia.org/wiki/File:PlanckianLocus.png https://en.wikipedia.org/wiki/File:PlanckianLocus.png https://commons.wikimedia.org/wiki/File:PlanckianLocus.png https://commons.wikimedia.org/wiki/File:PlanckianLocus.png (13:38, 3 January 2012) [2] Obvious errors: the blackbody curve shown doesn't go through white, and does go through yellow. Incorrect white-point math is a recurring cause. [3] "It goes from deep red at low temperatures through orange, yellowish white, white, and finally bluish white at very high temperatures." (emphasis added) [4] https://en.wikipedia.org/wiki/Sun https://en.wikipedia.org/wiki/Sun
- alejohausner 5y ago
  Well, the biggest error for me is that the tongue-shaped region is completely filled with color! On any three-color device like an LCD display, the gamut of producible colors will cover a triangular region inside that tongue. Any chromaticity diagram that is filled completely is a lie.
  - Dylan16807 5y ago
    It's hard to call that an error. Do you want it to show garbled static? Every point on the diagram shows the closest available color based on the format.
  - raxxorrax 5y ago
    Well, you would not be able to see "mud": https://www.livescience.com/17948-red-green-blue-yellow-stunning-colors.html https://www.livescience.com/17948-red-green-blue-yellow-stun...
graderjs 5y ago
Out of curiosity...what background do you have to make such a wonderful highly technical comment in a casual way...I'm so interested in the field of your expertise that you know so much about that this stuff, that something so technical is familiar to you, that you can come up with this brilliant analogy straight away and do it so casually. Do you work in "color technology" for a media company or something? I have no idea. I'm so interested what part of the world people who know these things do work in. Strangely, I'm struggling to write this comment in a way that doesn't sound trolling...sorry, I don't mean trolling at all. If you could see my facial expression it would be easier...
- srcreigh 5y ago
  I'd wager bachelor's degree+ in applied math or pure math or maybe physics.
- nefitty 5y ago
  I think we should normalize expressions of awe and curiosity about other people. It's hard to do without sounding ridiculous. A model that helps me is, "I like the state that that person's brain is in. I'll let them know. If I'm lucky, my communication of appreciation might shake out some generalizable knowledge that I have not encountered before." A good set of people to practice this on is doctors, teachers and Twitter users you admire.
- mdwrigh2 5y ago
  I'm not the parent you're asking, but figure you might be interested anyways since I could've likely made the same comment: I work on displays within an OS team. Having some basic understanding of colour theory is critical for a significant number of modern display projects, particularly for the high end. For example, enabling colour accurate rendering (games, photos, etc), shipping wide-gamut displays (how do you render existing content on a WCG display?), etc. More specifically to the planckian locus, it generally comes up when deciding which white point to calibrate a given display to at the factory (e.g. iPhone is 6470K, S20 is 7020K in Vivid)[1][2] and if you're doing any sort of chromatic white point adaptation, like Apple's True Tone[1][2]. My background before joining the team was a degree in math, but I really enjoyed doing low level projects in my spare time, so ended up on an OS team. We also have colour scientists who study this full time and have a _significantly_ better understanding of it all than I do :) [1]: https://www.displaymate.com/iPhone_13Pro_ShootOut_1M.htm#White_Point https://www.displaymate.com/iPhone_13Pro_ShootOut_1M.htm#Whi... [2]: https://www.displaymate.com/Galaxy_S20_ShootOut_1U.htm#White_Point https://www.displaymate.com/Galaxy_S20_ShootOut_1U.htm#White... [3]: https://support.apple.com/en-gb/HT208909 https://support.apple.com/en-gb/HT208909 [4]: http://yuhaozhu.com/blog/chromatic-adaptation.html http://yuhaozhu.com/blog/chromatic-adaptation.html
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areoform 5y ago

Can someone explain this to me with undergraduate level math?

riskneutral 5y ago
https://en.wikipedia.org/wiki/Black-body_radiation https://en.wikipedia.org/wiki/Black-body_radiation
krastanov 5y ago
The color you perceive is a weighted average of the intensities of different wavelengths of light that hit your eye. Ultra-violet and infra-red have a weight of zero (invisible). Most colors not at the edge of visible spectrum have weights that are roughly the same order of magnitude. Hot bodies emit various wavelengths, but the distribution of intensities is roughly a bell curve. If you sum up all these intensities, but weight them by the aforementioned weights in the previous paragraph, you would calculate what color would be perceived when looking at that object. Barely glowing hot objects emit a ton of infra-red (with perceptual weight zero) and a bit in the visual spectrum, on the red end of it (with a non-zero weight). So we perceive a red glow. Extremely ludicrously hot objects emit a ton of ultra-violet, X-ray and gamma rays (all with zero weight for visual perception), but also a bit on the blue end of the visible spectrum (with a non-zero weight for perception). So they look blue. Well, they would have looked blue, if the invisible bombardment of gamma rays did not immediately evaporate you.
Dylan16807 5y ago
A hot object emits light over a wide range of frequencies. At the low end of those frequencies, the intensity at each fequency is roughly proportional to the object's temperature multiplied by the frequency squared. Once an object is hot enough, all of visible light is in the low end of the frequency range. Which means the ratios between all visible frequencies are based on frequency squared and nothing else. That gives us a specific spectrum, where blue is about twice as intense as red. That spectrum has a specific color, the same color as #94B1FF. (Note that other RGB values also represent the same color at different brightnesses. That's fine, because we're not worried about brightness in this math. Brightness scales linearly with the temperature of the object.)

kelsolaar 5y ago

I haven’t seen the math for the conversion of the article but typically the conversion from CCT to xy/uv are given for a particular domain. One of the conversion with the largest domain, i.e. Ohno m, covers domain [1000K, 100000K]: https://github.com/colour-science/colour/blob/develop/colour/temperature/ohno2013.py https://github.com/colour-science/colour/blob/develop/colour... Infinity is very much in extrapolation territory.

perihelions 5y ago
Not really, since the shape of the blackbody emissions curve converges (when restricted to the visible wavelength range and normalized). 10^5 K should be very close to infinity.
- kelsolaar 5y ago
  “Not really” to which part?
  - perihelions 5y ago
    That it's not an extrapolation. The physics part converges and stops varying.
    - kelsolaar 5y ago
      The article actually points out to the fact that colour is not dependent on the Planck’s Law: “So, for an extremely hot blackbody, the spectrum of light we can actually see with our eyes is governed by the Rayleigh–Jeans law. This law says the color doesn’t depend on the temperature: only the brightness does!” But then the Rayleigh-Jeans Law has been shown to be incorrect, see Ultraviolet Catastrophe.
      - perihelions 5y ago
        Well yes but no: it's still the correct infrared limit (or high-temperature limit) of Planck's law, in fact Wikipedia has the derivation from one to the other: https://en.wikipedia.org/wiki/Rayleigh%E2%80%93Jeans_law#Comparison_to_Planck's_law https://en.wikipedia.org/wiki/Rayleigh%E2%80%93Jeans_law#Com...

exmadscientist 5y ago

Converting wavelength to sRGB is remarkably difficult. The conversion used here doesn't look quite right (see for example the sodium D lines), but I have never been able to figure out how to do much better.

jetzzz 5y ago
Colors of pure wavelengths are outside of the sRGB gamut and cannot be converted to sRGB, only approximated. Color of infinite temperature, on the other hand, is inside the sRGB gamut so no complication here.
- exmadscientist 5y ago
  I'm not talking about the out-of-gamut problem. I'm saying that the standard algorithms simply do an awful job, such that you can easily beat them by eye. This is in the context of trying to produce the closest sRGB colors to a set of LEDs, for use in documentation. No published method could actually do it. I did have to assume the LED was a single-wavelength source, gaussian with specified FWHM, or Lorentzian, rather than measuring the spectrum (I was too lazy to mess with the spectrophotometer), but I don't think that would have made the difference for an LED.
  - kuschku 5y ago
    One major issue is that most displays aren’t properly calibrated to sRGB. Once I got two monitors profiled and calibrated properly, suddenly most of these algorithms matched much more closely than I had expected.

snidane 5y ago

If 0 Kelvin means object particles at complete stop and >0K meaning particles moving at a certain speed, shouldn't infinite temperature be impossible, since no particle can move faster than the speed of light?

spenczar5 5y ago
There are more problems than just that. The point is that the color converges to a single value, so even as you approach infinity it stops changing.
krastanov 5y ago
The temperature of a low-pressure non-relativistic gas is indeed related to the average speed of the atoms in a simple way. However, temperature, in the general case, is more closely related to the average energy of a particle (so the energy and temperature can both grow without bound as the speed approaches closer and closer to the speed of light). However, even that "definition" of temperature is rather imprecise.
- McBeige 5y ago
  Weird and cool! Is the low-pressure low-speed definition of temperature a special case of the relativistic definition, or a completely different concept? What is the precise definition of temperature? How do these definitions relate to our everyday understanding of temperature, i.e. feeling hot/cold? Or which textbook should I read to find out? Sorry for asking so much...
  - krastanov 5y ago
    Great questions! There are many mathematically equivalent versions of the "complete" definition. My favorite is the zeroth law of thermodynamics: If body A and B have the same temperature (meaning there is no heat flow between them when they touch) and body B and C have the same temperature, then body A and C also have the same temperature. Basically, you define the words "thermal equilibrium" to mean "there is no heat flow when they touch" and you also define temperature to be the quantity that is equal in that case. This together with the "conservation of energy" and "growth of entropy" (basically the axioms of thermodynamics) is sufficient to derive most properties of temperature you know. If you have already defined entropy in some other way, you can say "the temperature of an object tells you how much the entropy of the object rises for a unit rise in the internal heat energy of the object": ΔEntropy = ΔEnergy / Temperature If you have not yet defined entropy, but have defined temperature (which I personally see as easier to understand), then the above equation can be your definition of entropy. Notice that "definition" just needs to be mathematically sound (i.e., self consistent). But for a physicist to want to use such definitions, they *also* need to be practical. Any of the (equivalent) definitions above are a fair choice, as they happen to be the self-consistent principles which do lead to behavior like the one we experimentally observe. I do imagine that a rigorous mathematician might have a reason to prefer one of the aforementioned definitions more than the other. I do not have such concerns. Lastly, concerning the gases: If you happen to know that gases are made out of moving atoms then you can do a bit more. Mind you, you can build most of thermodynamics without that knowledge. But if you know that fact, then you can derive that temperature is related to some measure of average energy per atom. If the atoms are relativistic, then energy per atom will need to be written in the relativistic form (which does not grow to infinity as velocity approaches the speed of light). At lower speeds, the formula for the energy becomes numerically indistinguishable from the one from classical mechanics. See https://en.wikipedia.org/wiki/Zeroth_law_of_thermodynamics#Foundation_of_temperature https://en.wikipedia.org/wiki/Zeroth_law_of_thermodynamics#F... Then I would suggest reading: - https://en.wikipedia.org/wiki/Zeroth_law_of_thermodynamics https://en.wikipedia.org/wiki/Zeroth_law_of_thermodynamics in its entirety - https://en.wikipedia.org/wiki/Temperature https://en.wikipedia.org/wiki/Temperature - https://en.wikipedia.org/wiki/Thermodynamic_temperature https://en.wikipedia.org/wiki/Thermodynamic_temperature

dane-pgp 5y ago

I can't help being reminded of the passage in the book of Revelation where John describes the throne room of God, and he notes "a rainbow round about the throne, in sight like unto an emerald". That's a little hard to imagine, because a rainbow contains a full spectrum of colours, whereas an emerald usually has a single colour, so some translations interpret the rainbow as being like the shine/gleam/glow of an emerald. But the idea that at infinite energy a spectrum might be perceived to human eyes as a single bluish hue is a nice thought, like the coincidence(?) that this colour happens to look like a clear summer's sky. Anyway, for comparison, here's an image from Wikipedia of a synthetic emerald: https://en.wikipedia.org/wiki/File:SyntEmerald_0302.jpg https://en.wikipedia.org/wiki/File:SyntEmerald_0302.jpg

morsch 5y ago
Maybe it's just bad writing.
fastball 5y ago
It's a nice thought, but describing the color in the OP as emerald seems like it would be a fairly poor attempt at describing your vision. It's more of a cornflower blue, or even as you say (and something easily accessible to the ancients): the color of a clear summer sky. For example if I was John and I saw the color of infinite temperature around God's throne, I would probably say something more like: > and there emanated from the throne an incredibly bright blue halo, as if a clear summer sky was shooting forth from God's throne.
- pope_meat 5y ago
  The color blue hadn't been invented yet.
  - Rhinobird 5y ago
    that's probably true. https://en.wikipedia.org/wiki/Blue%E2%80%93green_distinction_in_language https://en.wikipedia.org/wiki/Blue%E2%80%93green_distinction...

choonway 5y ago

how about the color of negative temperatures?

BenjiWiebe 5y ago
If an absolute lack of all energy is 0, a negative temperature is kinda hard to reason about.
- robin_reala 5y ago
  Negative temperatures are a thing, but you need to reframe temperature from inherent heat to energy flow between systems. https://en.wikipedia.org/wiki/Negative_temperature https://en.wikipedia.org/wiki/Negative_temperature
contravariant 5y ago
Assuming Planck's law still holds it should start absorbing radiation instead. That said Planck's law derives from Gibb's distribution and applying that rule to it suggests it immediately radiates all energy, until it stops having a negative temperature so I'm not sure if negative temperature is compatible with thermal radiation.

krater23 5y ago

Looks like the frame color of a C64 screen.

echelon 5y ago
Imagine in the far-distant future (past) where advanced machines have taken up the hobby of emulating the history of the earth on C64.
nathell 5y ago
It’s a secret plot by Atari to fry off the C64 users and rule the world. Fortunately, one is just a POKE53280,0:POKE53281,0:POKE646,1 away from evading this.
jug 5y ago
So it is then at least how I entered my current world. Close enough to the Big Bang, I suppose.

alphabet9000 5y ago

weird, several years ago i had a dream i had entered some kind of device that started to accelerate me towards the speed of light, and at the end of it i came to a point where it reached 'infinity' and it was like the most electric intense thing i had ever experienced, and i made a webpage to try and recreate and document what i remembered, and the color is almost exactly the same (strobe / flashing gif warning) http://jollo.org/LNT/public/dream.html http://jollo.org/LNT/public/dream.html

mrtnmcc 5y ago
I once had a near death out of body experience and that gif reminds me of it like nothing else I've seen.
- colordrops 5y ago
  My out of body was from hallucinogens rather than near death, but it was very similar as well. The strobing is fascinating, going from a place of undifferentiated light back to the material world and back at a specific frequency.
akersten 5y ago
Ah jeez that's a very flashy GIF at the end of the page there. Might want to throw a sensory warning on that link as a courtesy

junon 5y ago

For once, a good article. Short, clear, to the point. Thank you, author.

nextaccountic 5y ago
I love John Baez's blog too! But actually I think his long winded, mathematically challenging posts are more interesting. Like this series https://johncarlosbaez.wordpress.com/2012/01/19/classical-mechanics-versus-thermodynamics-part-1/ https://johncarlosbaez.wordpress.com/2012/01/19/classical-me... https://johncarlosbaez.wordpress.com/2012/01/23/classical-mechanics-versus-thermodynamics-part-2/ https://johncarlosbaez.wordpress.com/2012/01/23/classical-me... https://johncarlosbaez.wordpress.com/2021/09/23/classical-mechanics-versus-thermodynamics-part-3/ https://johncarlosbaez.wordpress.com/2021/09/23/classical-me... https://johncarlosbaez.wordpress.com/2021/09/26/classical-mechanics-versus-thermodynamics-part-4/ https://johncarlosbaez.wordpress.com/2021/09/26/classical-me... An excerpt from the first article: > The big picture > Now let’s step back and think about what’s going on. > Lately I’ve been trying to unify a bunch of ‘extremal principles’, including: > 1) the principle of least action > 2) the principle of least energy > 3) the principle of maximum entropy > 4) the principle of maximum simplicity, or Occam’s razor > In my post on quantropy I explained how the first three principles fit into a single framework if we treat Planck’s constant as an imaginary temperature. The guiding principle of this framework is > maximize entropy > subject to the constraints imposed by what you believe > And that’s nice, because E. T. Jaynes has made a powerful case for this principle. > However, when the temperature is imaginary, entropy is so different that it may deserves a new name: say, ‘quantropy’. In particular, it’s complex-valued, so instead of maximizing it we have to look for stationary points: places where its first derivative is zero. But this isn’t so bad. Indeed, a lot of minimum and maximum principles are really ‘stationary principles’ if you examine them carefully. > What about the fourth principle: Occam’s razor? We can formalize this using algorithmic probability theory. Occam’s razor then becomes yet another special case of > maximize entropy > subject the constraints imposed by what you believe > once we realize that algorithmic entropy is a special case of ordinary entropy.

m3kw9 5y ago

Nice to know when it hits

rileyphone 5y ago

Baez is also a noted category theoretician - I need to get around to reading https://link.springer.com/chapter/10.1007%2F978-3-642-12821-9_2 https://link.springer.com/chapter/10.1007%2F978-3-642-12821-..., where he claims to find the conceptual framework unifying analogies behind physics, topology, logic, and computation. Discussion: https://news.ycombinator.com/item?id=15423027 https://news.ycombinator.com/item?id=15423027

kortex 5y ago

"Perano" is a terrible name. Some far better alternatives: - neutronium - catastrophic violet - Rayleigh-Blue-Jeans

dr_dshiv 5y ago
Well, it's the blue equivalent of pink. Blink? No. Periwinkle? Periwinfinite? I get super irritated by kids books that teach seven colors. We have an impoverished color vocabulary, as a result. Can't even describe the color of infinite temperature, sheesh.
- yreg 5y ago
  https://en.wikipedia.org/wiki/List_of_colors_(compact) https://en.wikipedia.org/wiki/List_of_colors_(compact) to the rescue
  - Sharlin 5y ago
    This is my go-to page for coming up with names for computers and other hardware. Some examples, past and present: amber, auburn, carmine, cerise, indigo, magnolia, periwinkle, scarlet.
    - yreg 5y ago
      I have done the same with this list before!
  - dr_dshiv 5y ago
    That list is decidedly NOT cognitively ergonomic. Ends up being worse than useless by giving an appearance of authority. E.g. look at a periwinkle flower and look at the periwinkle in the list. They call periwinkle "Aero" but what is that?! https://images.app.goo.gl/8Qs5FARoBhEwYG2N8 https://images.app.goo.gl/8Qs5FARoBhEwYG2N8 I think color names should only be included if they match objects, have historical precedent or are composed of these plus basic descriptors. Or approved by the trans galactic color authority.

andrewflnr 5y ago

> gamma rays of arbitrarily high frequency What a delightfully, understatedly terrifying phrase.

nomilk 5y ago

Visited (from safari and chrome) on iPhone, it looks like entirely white [1]. It appears as the correct bluish colour on desktop. Might be just me. No idea why. [1] https://i.imgur.com/Bp1AW3u.png https://i.imgur.com/Bp1AW3u.png

deleted 5y ago
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nojs 5y ago
Same here!
nomilk 5y ago
Seems it's not just me; here's the correct colour: https://imgur.com/a/OdHLrl9 https://imgur.com/a/OdHLrl9
tzs 5y ago
It also doesn't work from Safari on desktop, showing the little blue square with the question mark in it icon. Right-clicking and opening the image in its own tab works. Inspecting both, the server is setting Content-Type to "image/webp" on the page (and sending 58 bytes), but setting it to "image/png" when displayed in its own tab (and sending 139 bytes). On the request Safari says it can accept "image/webp,image/png,image/svg+xml,image/*;q=0.8,video/*;q=0.8,*/*;q=0.5" so the server choosing to send a webp is fine. For some reason apparently Safari cannot display this particular webp. The graph below that on the page, the one of intensity vs. frequency, is also a webp and Safari has no trouble with it.

DrTung 5y ago

Microsoft should change their BSOD screen background color to this.

xxs 5y ago
Is the color depth 24bit on blue/white part?

kelsolaar 5y ago

I have just computed the colour and find slightly different value, i.e. computed [154, 181, 255] vs article [148, 177, 255]. Here is a Google Colab Notebook that has the colour for 10^200 along with comparisons with a blackbody: https://colab.research.google.com/drive/1Oyn913zkXYB8Uf8k1hiM8_5gifuMVqta?usp=sharing https://colab.research.google.com/drive/1Oyn913zkXYB8Uf8k1hi...

ginko 5y ago
Well, 10^200K isn't quite infinity yet. Have you checked if the values change if you increase the temperature even further? Looks like their color is bluer than yours at least..
- kelsolaar 5y ago
  Yes, it is minimal.
dr_dshiv 5y ago
I swear it's Periwinkle like the flower. https://images.app.goo.gl/8Qs5FARoBhEwYG2N8 https://images.app.goo.gl/8Qs5FARoBhEwYG2N8
brohee 5y ago
David Madore answered on Twitter : https://twitter.com/gro_tsen/status/1483054395524796421 https://twitter.com/gro_tsen/status/1483054395524796421, the discrepancy is likely due to you using Python's colourscience package SPECTRAL_SHAPE_DEFAULT which is based on ASTM E308-15 based on CIE and him using better color conversion functions from http://cvrl.ioo.ucl.ac.uk/index.htm http://cvrl.ioo.ucl.ac.uk/index.htm
- kelsolaar 5y ago
  Hi, Yes, and as discussed on Twitter, sRGB is defined for the CIE 1931 2 Degree Standard Observer, not other observers. It is not defined spectrally but as a set of chromaticity coordinates (in the CIE 1931 Chromaticity Diagram). Thus, strictly speaking, sRGB values can only be computed for the CIE 1931 2 Degree Standard Observer. I tried four different observers, using strict integration: - CIE 1931 2 Degree Standard Observer: [ 153.9026317 , 180.75617631, 255. ] - CIE 1964 10 Degree Standard Observer: [ 150.32288938, 184.67113624, 255. ] - CIE 2012 2 Degree Standard Observer: [ 145.14899585, 180.69807338, 255. ] - CIE 2012 10 Degree Standard Observer: [ 148.44893332, 185.66849549, 255. ] - Article: (148,177,255)

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toolslive 5y ago

I've always felt that temperature is one of the quantities what was wrongly defined. As a consequence, It's working against you in most of the thermodynamics formulas. A better concept would have been (1/T).

contravariant 5y ago
Well, defining it so it's proportional to pressure etc. wasn't the worst idea.

dr_dshiv 5y ago

It looks like the blue equivalent of pink. But what is that, Periwinkle?

denton-scratch 5y ago
I'd go with Periwinkle. My periwinkles, though, are a rather sad, washed-out, faintly bluish white.
- arbitrage 5y ago
  Your soil pH may be off.
  - denton-scratch 5y ago
    Hmmm. Too acid, or too alkaline? I had no idea that periwinkles were touchy about such matters. I thought they were considered an invasive weed that can grow on waste ground.

zokier 5y ago

Wouldn't infinite temperature object emit infinite amount of energy at all wavelengths, making the spectrum (and color) ill-defined?

marcyb5st 5y ago
Not at all wavelengths. An object of finite size and infinite temperature can produce all the wavelengths, but the probability of it generating, say visible light is really low approaching 0. So you can think about the relative number of visible photons you could observe and that gives you a color. My gripe with this is that if our understanding of quantum mechanics and general relativity is correct there is a limit of temperature. When a photon has a wavelength equal or smaller than the Planck length said photon contains enough energy to create a black hole. So, the upper limit of temperature should be the point at which the generation of black holes dominates the spectrum.
londons_explore 5y ago
You can still take the ratio of infinities and get a finite result.

stellalo 5y ago

“Perano” really sounds like it could be the name of some Italian village... oh wait: https://en.m.wikipedia.org/wiki/Perano https://en.m.wikipedia.org/wiki/Perano

twic 5y ago

It looks a similar colour to Cerenkov radiation. How similar? Is that a coincidence?

can16358p 5y ago

Is it just white? All I see is a white box as the color, though the text says otherwise.

staticassertion 5y ago
It's blue for me. Sort of a pastel or sky blue.
- SketchySeaBeast 5y ago
  Yeah, tested on firefox and chrome. It's a pastel blue.
dskloet 5y ago
I see something blueish.
jaqalopes 5y ago
Yes it's absolutely a white box, at least for me on mobile Safari
- can16358p 5y ago
  Same here, mobile Safari.
  - saurik 5y ago
    Huh. I am also using MobileSafari (on iOS 12 and 14) and it is rendering as a blue.
mensetmanusman 5y ago
On safari, can confirm it just looks white. Even tried turning off Night Shift. Not sure if this is a gold dress blue dress situation.
- arjonagelhout 5y ago

SiempreViernes 5y ago

> And according to the experts who sip latte all day and make up names for colors, this color is called ‘Perano’ Unexpectedly salty coming from a pure mathematician! But maybe it's just professional jealousy of a field that comes up with new terms regularly? ;)

kgwgk 5y ago
He's a mathematical physicist.

causality0 5y ago

So, for an extremely hot blackbody, the spectrum of light we can actually see with our eyes is governed by the Rayleigh–Jeans law. This doesn't make sense to me. If we're talking about what color our eyes would see, all our cones would be 100% saturated. Correct me if I'm wrong, but we would still perceive that as white regardless of where the spectrum peak is.

ani-ani 5y ago
Looks like the color is simply normalized so that one of the values is at maximum (255) and the others follow the shape of the spectrum. It's all very theoretical. If you're talking about what's physically possible, then you could just stop at "infinite temperature" instead of going into eye cones. Maybe if a body's temperature approaches infinity, you could get this color by standing at a sufficient distance, or wearing adequate sunglasses with uniform attenuation, or doing the correct safety squint like we do at the workshop.
- causality0 5y ago
  See that's the problem. The author is using the "color our eyes would actually see" thing but only in arbitrary ways that generate pageviews. It's inconsistent and dishonest.

kloch 5y ago

The general concept is correct but there are a few issues with the article: - Specific RGB values always depend on a selected white balance temperature. If the WB temp is the same as the object's temp it would be white, not blue. If the WB temp were higher than the object's temp it would appear red. EDIT: the article does say sRGB which implies a 6500K wb. - "infinitely hot" is not physically possible. The Neutron star example is fine, that temp would be around 10^12 K At that temperature virtually all of the emission would be in gamma rays, but emission in the visible spectrum would not be zero. Blue wavelengths would be stronger than green, which would be stronger than red so the color would appear Blue for any "normal" white balance temp (like 5500 K).

rini17 5y ago
It explicitly says sRGB which has commonly agreed white spot of 6500K. And thus it's reasonable assumption that photo of neutron star displayed on common monitor would have such color. Infinity is a well understood mathematical construct. I don't know what is the issue with evaluating limit value of some function, in this case color, "at infinity"? Nowhere it says it's physically possible.

marcodiego 5y ago

Considering that temperature is related to how agitated are the particles of a material and that there is a limit of how fast something can move (speed of light); doesn't it imposes an upper limit on the temperature? I mean, replacing v_rms by c in equation 3 in https://chem.libretexts.org/Bookshelves/Physical_and_Theoretical_Chemistry_Textbook_Maps/Supplemental_Modules_(Physical_and_Theoretical_Chemistry)/Physical_Properties_of_Matter/States_of_Matter/Properties_of_Gases/Kinetic_Theory_of_Gases/Connecting_Gas_Properties_to_Kinetic_Theory_of_Gases https://chem.libretexts.org/Bookshelves/Physical_and_Theoret... gives us an upper limit for the temperature of a gas, right?

Etheryte 5y ago
That is a somewhat simplified definition of temperature. While there's a parallel discussion on the same topic at [0], the term you're looking for is Planck temperature [1]. There is no "upper cap" on temperature per se, but we also don't have any models for describing what would happen beyond that point. See [2] for more discussion. [0] https://news.ycombinator.com/item?id=29963147 https://news.ycombinator.com/item?id=29963147 [1] https://en.wikipedia.org/wiki/Planck_units#Planck_temperature https://en.wikipedia.org/wiki/Planck_units#Planck_temperatur... [2] https://physics.stackexchange.com/q/420670/43412 https://physics.stackexchange.com/q/420670/43412

rikeanimer 5y ago

decent. I'm curious what it would be for a human tetrachromat (likely female) seeing in r4 space. Sadly, I can never know.

vagab0nd 5y ago

Boy am I glad to see this color! I was writing a black hole simulator, and needed to figure out the color shift of the stars as one approaches the black hole. The calculation gave me this blue at the one end of the spectrum which was very underwhelming tbh. For some reason I always though this color would be either 0xffffff, or some deep blue. Glad that my calculation is finally confirmed to be right!