Wow. I read the initial blog post (well I read the start, and skimmed the rest) and I thought it was interesting but I am just not motivated to dive into something so complex. I learned nothing.
Then I watched Richard Feynman's explanation and feel like I learned something! And was motivated about it!
Feynman's explanation is obviously great, but it and the blog have different goals. There is really no sense in which fire is best explained by Planck's Law. Obviously the goal of the blog post is to explore how physics is nested, with complex phenomena the result of simpler laws which are the result of even simpler laws. I mean, the part that's about chemistry specifically, which most would call the part that's about fire, is only the first 1/5 or so. It is easier to learn and feel motivated to learn less physics rather than more, and Feynman's gift was imparting the most essential information with the least physics possible, a sort of distillation of physicist-intuition for the layman.
>>I watched Richard Feynman's explanation and feel like I learned something!
I don't know the link to the video on YouTube, but there was one interview where they were discussing why Math appears hard to so many people. Basically people look at solving Math problem like an elaborate heuristic needed to be memorised to solve the problem.
He proceeds to explain that's for people who don't understand what they are doing.
To understand anything at all, is to start with basic assumptions/axioms and logical rules of manipulating them and moving forward from there.
What if... the author wasn't aiming this post for a completely lay audience, but rather someone with a undergraduate/graduate level of mathematics/physics background who was interested in learning more about some phenomenon?
Nope everything needs to be completely intuitive, explaining in detail is completely wrong /s
I think both can complement each other, but it is definitely nice to go into the details. Watch the Feynman explanation then try to use that as you go through the actual details. The initial more hand wavy, but morally correct explanation, gives you something to latch onto, and then you can use that to guide your reasoning in the more complicated steps.
Honestly the idea or expectation that things need to be read linearly is also wrong, you should include some reasonable level of detail and elaboration in your writing, but organise it so it can be picked over. You can switch betweeen levels too.
Or Michael Faraday's masterpiece "the chemical history of a candle", which deep-dives not only into what every part of the fire is, but also how we know what it is.
The whole book is a delight to read, but I really like this part:
> And now I want you to follow me in this explanation. You would hardly
think that all those substances which fly about London, in the form of
soots and blacks, are the very beauty and life of the flame, and which are
burned in it as those iron filings were burned here...
> I want you now to follow me in this point,--that whenever a substance
burns, as the iron filings burnt in the flame of gunpowder, without
assuming the vaporous state (whether it becomes liquid or remains solid),
it becomes exceedingly luminous. I have here taken three or four examples
apart from the candle, on purpose to illustrate this point to you; because
what I have to say is applicable to all substances, whether they burn or
whether they do not burn,--that they are exceedingly bright if they retain
their solid state, and that it is to this presence of solid particles in
the candle-flame that it owes its brilliancy.
>... This flame has carbon in it; but I will take
one that has no carbon in it. There is a material, a kind of fuel--a
vapour, or gas, whichever you like to call it--in that vessel, and it has
no solid particles in it; so I take that because it is an example of flame
itself burning without any solid matter whatever; and if I now put this
solid substance in it, you see what an intense heat it has, and how
brightly it causes the solid body to glow. This is the pipe through which
we convey this particular gas, which we call hydrogen, and which you shall
know all about next time we meet. And here is a substance called oxygen,
by means of which this hydrogen can burn; and although we produce, by
their mixture, far greater heat[8] than you can obtain from the candle,
yet there is very little light. If, however, I take a solid substance, and
put that into it, we produce an intense light If I take a piece of lime, a
substance which will not burn, and which will not vaporise by the heat
(and because it does not vaporise, remains solid, and remains heated), you
will soon observe what happens as to its glowing. I have here a most
intense heat, produced by the burning of hydrogen in contact with the
oxygen; but there is as yet very little light--not for want of heat, but
for want of particles which can retain their solid state; but when I hold
this piece of lime in the flame of the hydrogen as it burns in the oxygen,
see how it glows! This is the glorious lime-light, which rivals the
voltaic-light, and which is almost equal to sunlight. I have here a piece
of carbon or charcoal, which will burn and give us light exactly in the
same manner as if it were burnt as part of a candle. The heat that is in
the flame of a candle decomposes the vapour of the wax, and sets free the
carbon particles--they rise up heated and glowing as this now glows, and
then enter into the air. But the particles when burnt never pass off from
a candle in the form of carbon. They go off into the air as a perfectly
invisible substance, about which we shall know hereafter.
> Is it not beautiful to think that such a process is going on, and that
such a dirty thing as charcoal can become so incandescent? You see it
comes to this--that all bright flames contain these solid particles; all
things that burn and produce solid particles, either during the time they
are burning, as in the candle, or immediately after being burnt, as in the
case of the gunpowder and iron-filings,--all these things give us this
glorious and beautiful light.
>... That, however, is not
the only thing I wish to mention. If I take a flame sufficiently large, it
does not keep that homogeneous, that uniform condition of shape, but it
breaks out with a power of life which is quite wonderful. I am about to
use another kind of fuel, but one which is truly and fairly a
representative of the wax or tallow of a candle. I have here a large ball
of cotton, which will serve as a wick. And, now that I have immersed it in
spirit and applied a light to it, in what way does it differ from an
ordinary candle? Why, it differs very much in one respect, that we have a
vivacity and power about it, a beauty and a life entirely different from
the light presented by a candle. You see those fine tongues of flame
rising up. You have the same general disposition of the mass of the flame
from below upwards; but, in addition to that, you have this remarkable
breaking out into tongues which you do not perceive in the case of a
candle. Now, why is this? I must explain it to you...
James Burke's Connections episode 9: Countdown [1], covers the invention of limelight, gives a history of the technology and places it in context. The entire series is intertwined (thus the title, Connections), but if you start watching Ep. 9 at 18:30 it gives plenty of preamble for the need for the invention before introducing it and covering its adoption.
I was so on the fence as a high school senior and (as a good Indiana boy) got an offer from Rose-Hulman to major in physics. Instead, I went to a SLAC and studied philosophy, eventually convinced a neuropsychology lab in a clinical psych PhD program to take a chance on me, and now study a bunch of neurological conditions.
This video made that old pull come back, but of course life has constrained me to stick with what I've got going. At least after almost 20 years I get to geek out with the MRI physicist on a regular basis.
My new goal is to be as giddy explaining brain function as Feynman is explaining just about anything.
For odd reasons I'm deeply interested by neuropsychology, is there a main journal to read ? mostly representation of the "somatic" self (and others), perception of emotions.
It's very cool field, in my opinion. Some good journals for your topic would be Journal of Affective Neuroscience, and Social Cognitive and Affective Neuroscience.
For books, I really enjoyed LeDoux's The Emotional Brain and Damasio's Looking for Spinoza.
But the general neuropsych journals like Neuropsychology,Neuropsychology Review, Journal of the International Neuropsychological Society, The Clinical Neuropsychologist, and Archives of Clinical Neuropsychology touch on those topics as well, but not as consistently.
That could be said of me as a dev. I don't see (formal) education itself as an asset. It's a means to an end. Most of the education is not used and forgotten. The type of people who are able to learn, might be better off learning what they want without an education.
It's possible that in many areas of life ignorance truly is bliss. Being educated might mean you see through the BS but there's nothing you can do to change it.
Thanks for this. Almost 20 years ago I was in high school and I asked my physics teacher "what is fire?". He looked at me with an expression that clearly said (but without words): "this kid is stupid". After I re-affirmed my question and my desire to know what "actually" was fire, he just couldn't answer. Everybody laughed, of course.
Now, almost 20 years after, I have a partial answer.
I had a similar experience with static electricity. The explanation was something like 'When you rub wool on a glass rod you develop a charge between them'. Ok, so.... why? And why does the charge develop with one polarity and not the other?
Now I'm a bit older I understand that the explanation is somewhere between "the geometry of pointy things" and "get a PhD and you'll understand some of it"
Bah. The article doesn't appear to answer my long-standing question which is : where exactly do the photons come from? It says black bodies emit photons, but...how exactly? It says maybe its emission spectrum photons which aren't black body radiation. I have a slightly better idea where those photons come from: an electron changes energy state in an atom and as a side-effect a photon is released. Still don't really know where the photon came from though..
IIRC (from high school chemistry?) electrons go into higher energy levels due to the release of chemical energy, then emit photons as they fall back to lower energy levels (the energy of the photon being the delta between the energy levels). Is that accurate/am I missing anything?
> It says black bodies emit photons, but...how exactly?
When an object has any temperature above 0K, that means the chemically bonded particles are moving around/vibrating. This movement of charged particles (release of internal energy) creates electromagnetic radiation (photons).
The other radiation you are talking about is also energy being released as photons, but it is from electrons in an excited state falling to a lower energy state.
Molecules can take in energy differently. Some frequencies of incoming energy produce bond movement/vibrations, and other frequencies can excite an electron's state. Consequently, when the energy is released, it can be in different frequencies (infrared/heat, visible light, UV, etc.) depending on the amount of energy lost. Since electron orbitals are discrete states, the release of energy from an electron going to a lower orbital is a discrete frequency of light.
And if we get two photons above a certain energy and slam them together we get an electron and a positron. So where did they come from and where did the photons go? The electron emits a photon: photons from photons.
And all those virtual photons that make the electron hang around near the the nucleus.
> [ways to extinguish a fire] remove the heat (e.g. spraying a fire with water)
I've always wondered about this. To me i assume water smoothers not makes cold. After all, water doesn't extinguish an oil fire, (which is i presume because oil floats) which i would expect it to if its solely about cooling things down.
Are there any experiments i could convince myself its really about cold and not smoothering?
There's definitely cases where water can be used to smother fire (think: plunging something burning into a large body of water). But if you're throwing water onto a fire..
Consider that in order to smother a fire - to form an actual barrier between fuel and oxygen - water would have to remain liquid, which it can only do if its temperature stays below 100°C.
For water to stay below 100°C, whatever the water is in contact with also needs to be below 100°C.
So you can't actually permanently smother something with liquid water without also cooling it down to below 100°C.
An experiment you could try would be to maybe take a matchstick and soak it in some water. Then dry off the outside of it, so you can tell there's definitely no water covering the fuel of the stick. Then try to set fire to it.
Much of that I was familiar with - the very end did throw me a curve ball:
"Planck’s law doesn’t just stop at the maximum, so nuclear explosions also produce even shorter wavelength radiation, namely gamma rays. This is solely the radiation a nuclear explosion produces because it is hot, as opposed to the radiation it produces because it is nuclear, such as neutron radiation."
I have heard that in different ways but I guess I didn't grok it until reading that last sentence in particular. I always love unexpected insights.
I would note, that I think the units of the last two equations of 0.5um to 0.3um for a nuclear fire, should probably be 0.5nm to 0.3nm to be Xrays, since they should be a bit more than 1000x hotter.
It kind of blew my mind to learn (and internalize) that everything burns under the right conditions (mostly temperature). Metals, bodies, water, everything.
Burning certainly does not require breaking chemical bonds (or else Hydrogen is not flammable). I always considered burning to be oxidation; possibly only when oxygen is the oxidizing agent.
