[HN Gopher] What's a fire and why does it burn? ___________________________________________________________________ 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. ___________________________________________________________________ (page generated 2022-03-23 23:00 UTC)