Field of Science

Chemists: Strangers to fiction

That Mars habitat?
"The basement corridor is dim, I can hear pumps chugging, hoods noisily venting, and the solid-state physicist down the hall swearing. 'Welcome to Mars!' says the cheery sign outside my colleague’s door. Perhaps it is the pile of grading on my desk or the endless round of meetings on my calendar that is fuelling my escapist fantasy, but every time I pass Selby’s office, I imagine the door is a portal and if I were to walk through, I’d  find myself in a habitat on Mars, its pumps working hard to compress the thin atmosphere." from "Strangers to Fiction" in Nature Chemistry8, 636-637 (2016).

I've been a sci-fi fan for going on five decades, imagining myself in labs on Mars, mining comets, and exploring strange new worlds. I don't read it for the chemistry, which is a good thing, because there isn't much fiction in which chemistry plays a key role.

My latest Nature Chemistry Thesis column looks at chemistry and fiction, suggesting that there are good reasons to both read SF, particularly for young chemists, and for chemists to encourage the writing of chemistry-inflected science fiction.  And if you have the talent for it (which I do not!) perhaps even give the writing of it a fly.

You can read the whole thing here.  My list of fictional chemistry is here.

A matter of degrees: when low temperatures were hot

Diagram of a thermometer similar to
the one describe by Leurechon, c. 1638.
Note that  hotter temperatures have 
smaller magnitudes degrees associated with 
them. Image from Wellcome collection, 
used under CC license.
We say the mercury is rising to mean it's getting hot out, despite the fact that most home thermometers have no mercury in them anymore.  Regardless of the liquid they contain, the level rises with increasing temperature in the iconic liquid thermometer.  But this was not always the case.

The word thermometer was first coined (in French) in a book of mathematical recreations written in 1626 by Jean Leurechon, SJ (writing as Hendrik van Etten).  In his description he notes the thermometer you can construct from a glass tube and small container of water (or other non-viscous liquid) can be used to quantify temperature by placing marks on the glass, associating each with some fraction of the classical four (or eight) degrees of hotness.  Such thermometers, he suggests, can be used to adjust the temperature of a room or a furnace, to record (and predict) the weather and to measure fevers in the ill.

But Leurechon's thermometer (and similar designs) were constructed such that as the temperature increased, the water level in the tube fell.  Increases in temperature caused the air trapped in the ball at the top of the tube to increase in volume, pushing the liquid down in the tube.  (These are air thermometers, in contrast to the familiar liquid thermometers in widespread use today.) A reading of 9 degrees on the thermometer shown in the sketch accompanying Leurechon's thermometer problem was colder than that of 2 degrees (see also the one in Robert Fludd's diagram, in the figure.)

A century later, Anders Celsius constructed a temperature scale based on water's phase changes which ran in the same direction.  Water on Celsius' scale boiled at 0 degrees and froze at 100 degrees. This reverse run didn't last long, two years later Carl Linnaeus (of taxonomic fame) used the scale to describe conditions in a greenhouse, but flipped it to the form in which we know it today, where 100 is the boiling point of water.

It is tempting to think that Celsius' scale ran in the direction it did because it mimicked the earliest marked thermometers. But Fahrenheit's scale, which preceded Celsius' by two decades, runs in the modern direction, things get hotter in the positive direction. This also parallels the classic notions of degrees of heat in play during the medieval period. There were four (or eight or six, depending on the source) degrees of heat, the first being more or less physiological temperature, the fourth being a blazing hot furnace.

The word degree has its roots in the Latin degradum, a down step.  This matches Leurechon and Celsius' use - 9 degrees is eight steps lower (colder) than 1 degree.