Note from the writer: I wrote this piece of writing with an aim of popular science communication, but I did add some stylistic characteristics of a historical fiction. The scenes of Somerville working on her book are imagined, but they are based on later historians of science reconstructing her potential working habits and her family conditions.
Writer: Justin Wang
Editor: Altay Shaw
In the morning of a day in the 1830s, a Scottish lady shut up her door and told her maid to take care of everything. As always, she did this so no one would bother her work. Her name was Mary Somerville, a polymath of all-around expertise, a natural philosopher by the appraisal of her contemporary, and an accomplished woman in the male-dominated field of the natural sciences.
Somerville had just been criticised for her experiments; her recent hypothesis was just falsified. A self-taught woman of immense talent in mathematics and language compositions, Mrs Somerville felt like she must prove herself, not in front of any of the men in science, but in front of the scattered but unified secrets of the universe. All of those, and with a small financial problem: the pay cheques were almost making the Somerville family bankrupt. Gosh, she must finish writing that book!
In this about-to-be opus, Somerville discussed the optics in depth about the secret of light, described the long tail of a comet, and explained the properties of oxygen and hydrogen, all in the simplest language (for a 19th-century reader, of course). The Connexion of the Physical Sciences – what a wonderful name for a book that congregates so many different fields of science together! Somerville entered a moment of silence, searching for ways to describe and explain the cutting-edge science of her time – electromagnetism, the relationship between bright zaps and attractive metals.
A few years ago, another brilliant mind of the time, Michael Faraday, conducted a most curious study: if one can magnify a piece of metal with an electrified current, can the reverse also be possible? What Faraday finally discovered was magnetic induction: if a magnetic object is moving relatively close to a circuit, electricity will be induced as the circuit moves across the magnetic field of the object. Faraday quickly built upon this exciting idea to invent the first generator. From now on, electric power can be harvested not only through chemical reactions but also with magnetic induction between moving coils and magnets.
“What a brilliant idea Faraday has made! But where to locate a favourable magnetic field, every reader must be aware of?” Somerville, at her desk, quickly thought of the compass: a good and durable piece of instrument, in interaction with the magnetic field of… the Earth! Somerville thus wrote down the following hypothesis for her book Connexion:
“From the experiments of Mr. Faraday, and also from theory, it is possible that the rotation of the earth may produce electric currents in its own mass. In that case, they would flow superficially in the meridians, and if collectors could be applied at the equator and poles, as in the revolving plate, negative electricity would be collected at the equator, and positive at the poles; but without something equivalent to conductors to complete the circuit, these currents could not exist.”
Mrs Somerville skilfully pulled out a hypothesis so wild and surprising that it resonated all the way to today. What if we harness the geomagnetic energy by building a circuit and allowing the Earth’s magnetic field to pass through it? Further studies by later physicist S. J. Barnett have shown that circuits located on the ground are effectively moving in alignment with the geomagnetic field. If we place Somerville’s hypothesised device on Earth, it will not generate any electricity. How would we bypass this restriction?
One approach here is to keep the circuit moving in a desynchronised manner with the Earth’s rotation and its rotating magnetic field. Imagine a closed circuit, just like what Somerville suggested. The circuit is allowed to move at a velocity different from the rotational movement, such that it can change in relative position to the geomagnetic field.
The best place to experiment with this concept is in space. Introducing the electrodynamic space tether, a long conductor cable dangling in the middle of space near Earth. In 2012, NASA scientists proposed launching a satellite in a close orbit. By allowing the satellite to move across Earth’s magnetic field, it generates electricity within a dangling wire that acts as part of a closed circuit. This process is made possible thanks to the electrons widely present in the ionosphere. As the technology gets repetitively tested in space, the ED tether may revolutionise the energy source of satellites. Tethers may enable detectors to be sent to distant planets if they have a planetary magnetic field to generate electricity via induction and floating electrons in the environment to form a circuit.
Bravo! But that did not faithfully fit Somerville’s proposal. What if we want to use the Earth as a generator while on the ground?
Somerville was an advocate of social justice and a diligent writer in her last years, living to the age of 91. Unfortunately, the pieces capable of solving her Earth Generator puzzle were not all gathered when she had touched the hand of Death in 1872. A series of electromagnetic scientists postceding her death brought in new mathematics and new paradigms. In 2016, American scientists Christopher Chyba and Kevin Hand entered the race. After one and a half centuries, Somerville found her questions answered, only partially, yet cleverly.
In their paper, Chyba and Hand condensed historical evidence showing that induction on the surface of Earth, an enormous rotating magnet, was conceptually possible. Yet the proposition was quickly determined to be impossible by the two scientists through some mathematical deductions. However, it was later proven possible again, due to a “loophole” in the conclusion. The key part here is bypassing the assumptions in the mathematical model with intricate designs for the testing device and the selection of the correct materials. Both turned out to be harder than anticipated; tricking a mathematical proof by tweaking the presumptions was not an effortless task to realistically achieve.
The end of the story, after Somerville had left her desk for so long, was a group of scientists (including Chyba and Hand, who worked diligently to bring theories into reality) waiting anxiously in a room with a special metal tube in 2025. Utilising developed statistical methods and precise measurement devices, they determined they have yielded statistically significant – albeit only a few microvolts – of electric power.
It is a small amount, but if Somerville lived to see the results, she would climb out of her bed another morning to record this message in the most exciting way any scientific writer wishes: “The Earth, as a generator; the geomagnetic energy now open to the human world!”
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