Universal Fire

In L. Sprague de Camp’s fan­tasy story The In­com­plete En­chanter (which set the mold for the many imi­ta­tions that fol­lowed), the hero, Harold Shea, is trans­ported from our own uni­verse into the uni­verse of Norse mythol­ogy. This world is based on magic rather than tech­nol­ogy; so nat­u­rally, when Our Hero tries to light a fire with a match brought along from Earth, the match fails to strike.

I re­al­ize it was only a fan­tasy story, but… how do I put this...


In the late eigh­teenth cen­tury, An­toine-Lau­rent de Lavoisier dis­cov­ered fire. “What?” you say. “Hasn’t the use of fire been dated back for hun­dreds of thou­sands of years?” Well, yes, peo­ple used fire; it was hot, bright, sort of or­angey-col­ored, and you could use it to cook things. But no­body knew how it worked. Greek and me­dieval al­chemists thought that Fire was a ba­sic thing, one of the Four Ele­ments. In Lavoisier’s time the al­chem­i­cal paradigm had been grad­u­ally amended and greatly com­pli­cated, but fire was still held to be ba­sic—in the form of “phlo­gis­ton”, a rather mys­te­ri­ous sub­stance which was said to ex­plain fire, and also ev­ery other phe­nomenon in alchemy.

Lavoisier’s great in­no­va­tion was to weigh all the pieces of the chem­i­cal puz­zle, both be­fore and af­ter the chem­i­cal re­ac­tion. It had pre­vi­ously been thought that some chem­i­cal trans­mu­ta­tions changed the weight of the to­tal ma­te­rial: If you sub­jected finely ground an­ti­mony to the fo­cused sun­light of a burn­ing glass, the an­ti­mony would be re­duced to ashes af­ter one hour, and the ashes would weigh one-tenth more than the origi­nal an­ti­mony—even though the burn­ing had been ac­com­panied by the loss of a thick white smoke. Lavoisier weighed all the com­po­nents of such re­ac­tions, in­clud­ing the air in which the re­ac­tion took place, and dis­cov­ered that mat­ter was nei­ther cre­ated nor de­stroyed. If the burnt ashes in­creased in weight, there was a cor­re­spond­ing de­crease in the weight of the air.

Lavoisier also knew how to sep­a­rate gases, and dis­cov­ered that a burn­ing can­dle diminished the amount of one kind of gas, vi­tal air, and pro­duced an­other gas, fixed air. To­day we would call them oxy­gen and car­bon diox­ide. When the vi­tal air was ex­hausted, the fire went out. One might guess, per­haps, that com­bus­tion trans­formed vi­tal air into fixed air and fuel to ash, and that the abil­ity of this trans­for­ma­tion to con­tinue was limited by the amount of vi­tal air available.

Lavoisier’s pro­posal di­rectly con­tra­dicted the then-cur­rent phlo­gis­ton the­ory. That alone would have been shock­ing enough, but it also turned out...

To ap­pre­ci­ate what comes next, you must put your­self into an eigh­teenth-cen­tury frame of mind. For­get the dis­cov­ery of DNA, which oc­curred only in 1953. Un­learn the cell the­ory of biol­ogy, which was for­mu­lated in 1839. Imag­ine look­ing at your hand, flex­ing your fingers… and hav­ing ab­solutely no idea how it worked. The anatomy of mus­cle and bone was known, but no one had any no­tion of “what makes it go”—why a mus­cle moves and flexes, while clay molded into a similar shape just sits there. Imag­ine your own body be­ing com­posed of mys­te­ri­ous, in­com­pre­hen­si­ble gloop. And then, imag­ine dis­cov­er­ing...

...that hu­mans, in the course of breath­ing, con­sumed vi­tal air and breathed out fixed air. Peo­ple also ran on com­bus­tion! Lavoisier mea­sured the amount of heat that an­i­mals (and Lavoisier’s as­sis­tant, Seguin) pro­duced when ex­er­cis­ing, the amount of vi­tal air con­sumed, and the fixed air breathed out. When an­i­mals pro­duced more heat, they con­sumed more vi­tal air and ex­haled more fixed air. Peo­ple, like fire, con­sumed fuel and oxy­gen; peo­ple, like fire, pro­duced heat and car­bon diox­ide. Deprive peo­ple of oxy­gen, or fuel, and the light goes out.

Matches catch fire be­cause of phos­pho­rus—“safety matches” have phos­pho­rus on the ig­ni­tion strip; strike-any­where matches have phos­pho­rus in the match heads. Phos­pho­rus is highly re­ac­tive; pure phos­pho­rus glows in the dark and may spon­ta­neously com­bust. (Hen­ning Brand, who puri­fied phos­pho­rus in 1669, an­nounced that he had dis­cov­ered Ele­men­tal Fire.) Phos­pho­rus is thus also well-suited to its role in adeno­sine triphos­phate, ATP, your body’s chief method of stor­ing chem­i­cal en­ergy. ATP is some­times called the “molec­u­lar cur­rency”. It in­vi­go­rates your mus­cles and charges up your neu­rons. Al­most ev­ery metabolic re­ac­tion in biol­ogy re­lies on ATP, and there­fore on the chem­i­cal prop­er­ties of phos­pho­rus.

If a match stops work­ing, so do you. You can’t change just one thing.

The sur­face-level rules, “Matches catch fire when struck,” and “Hu­mans need air to breathe,” are not ob­vi­ously con­nected. It took cen­turies to dis­cover the con­nec­tion, and even then, it still seems like some dis­tant fact learned in school, rele­vant only to a few spe­cial­ists. It is all too easy to imag­ine a world where one sur­face rule holds, and the other doesn’t; to sup­press our cre­dence in one be­lief, but not the other. But that is imag­i­na­tion, not re­al­ity. If your map breaks into four pieces for easy stor­age, it doesn’t mean the ter­ri­tory is also bro­ken into dis­con­nected parts. Our minds store differ­ent sur­face-level rules in differ­ent com­part­ments, but this does not re­flect any di­vi­sion in the laws that gov­ern Na­ture.

We can take the les­son fur­ther. Phos­pho­rus de­rives its be­hav­ior from even deeper laws, elec­tro­dy­nam­ics and chro­mo­dy­nam­ics. “Phos­pho­rus” is merely our word for elec­trons and quarks ar­ranged a cer­tain way. You can­not change the chem­i­cal prop­er­ties of phos­pho­rus with­out chang­ing the laws gov­ern­ing elec­trons and quarks.

If you stepped into a world where matches failed to strike, you would cease to ex­ist as or­ga­nized mat­ter.

Real­ity is laced to­gether a lot more tightly than hu­mans might like to be­lieve.