[HN Gopher] What's a fire and why does it burn?
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What's a fire and why does it burn?
Author : kvee
Score : 21 points
Date : 2022-03-23 21:38 UTC (1 hours ago)
(HTM) web link (qchu.wordpress.com)
(TXT) w3m dump (qchu.wordpress.com)
| marethyu wrote:
| Oh, did Qiaochu finally returned to math after long hiatus?
| jiggawatts wrote:
| Compare a bunch of chemical formulas and equations in this blog
| with Richard Feynman's explanation of fire:
| https://www.youtube.com/watch?v=N1pIYI5JQLE
| [deleted]
| jbay808 wrote:
| 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.
|
| https://www.gutenberg.org/cache/epub/14474/pg14474.txt
|
| 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.
| qiskit wrote:
| Here is feynman on AI:
| https://www.youtube.com/watch?v=ipRvjS7q1DI
|
| Feynman turned his focus to computing ( AI, heuristics, quantum
| computing ) later on his life.
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