Luminiferous Aether Earth: History
(Or: A guide to the divergent history in which my WIP novelette When In Erebus is set. The first part of this guide, an explanation of the physics of aether and EM radiation, can be found here.)
Antiquity: The starscape visible from Earth is a bit different in this universe, owing to neutron stars being much more luminous due to their effects on aether (and therefore light).
9th century AD: The second most luminous star in the sky is first officially referred to with the name that will be used in star catalogues for centuries to come: Najm-Ul-Wahaj, the Blazing Star. (In our world, it is known as RX J1856.5-3754.)
Most of the 19th century: As in our world, various experiments are conducted to test the luminiferous aether hypothesis. They are inconclusive because the measuring equipment is not sufficiently sensitive and / or they operate on incorrect assumptions about the properties of aether.
April - July 1887: The Michelson-Morley experiment gives a positive result. In the following years, more experiments following similar principles do as well, and aether captures the public imagination.
July 1898: When Marie Skłodowska-Curie and Pierre Curie isolate polonium from pitchblende, they notice that it glows. It is hypothesized that radioactivity strongly excites the aether — accurate, but only in certain cases.
(Note: Real-life polonium does emit light even in small quantities, but in this universe the glow is brighter and its mechanism is different.)
(Note 2: While uranium and thorium were discovered before polonium, both in real life and here, the known isotopes weren't radioactive enough / had half-lives too long to produce an observable effect regarding aether.)
1899: Ernest Rutherford figures out there is a difference between alpha and beta radiation. He hypothesizes that a sufficiently radioactive beta emitter (stronger than the uranium he used in his experiment, which has a very long half-life and therefore no visible glow) will glow more brightly than any alpha emitter.
1900s: Much research is done regarding aether and radioactivity. The knowledge of the latter progresses much faster than it did in our world. (A bonus is that its dangers were discovered earlier. The radium paint fad is short-lived.)
1910: Neutrons are discovered during an experiment with polonium and lithium (similar to what happened in real life, just earlier and by different people). The discovery of gamma rays is initially taken as proof of Rutherford's hypothesis, with them being misinterpreted as the extra-aether-exciting effect of beta radiation he predicted.
1912: The first nuclear reactor is built in New York (state). Its operators kind of just test samples of all the elements they can get their hands on. They notice something strange: some of the irradiated samples don't glow, but rather seem to suck light away around them. This is soon found out to be the actual effect of beta radiation on aether, posing a scientific mystery until the weak force is discovered decades later.
An American scientist first effectively isolates aether from the air, using a mass of strontium-90 to create a small lightless space. This is the precursor to the deaetherizing apparatus.
1913: A German scientist reads the article on the strontium-90 experiment and gets the idea of using aether instead of hydrogen to fill zeppelins. Being lighter than hydrogen, it should provide increased lifting power, and as it isn't flammable its use should eliminate the risk of explosion. However, there is no method of actually transporting aether (yet).
1914: At the start of World War I, Germany builds its own nuclear reactor and sets to isolating aether. (Thankfully, no one gets the idea of making nuclear weapons. All the focus on radioactivity in this time period pertains to its interactions with aether.)
1915: A way to effectively transport aether through pipes / hoses is figured out. Basically, when aetherons are clumped around a beta emitter, they become liable to move like regular matter. All you have to do is blow a little air (or other gas) on them to get them moving. With this, the first aether zeppelins are built. It's discovered that they have an issue of deflating quite rapidly through diffusion, but their speed and carrying capacity makes up for it.
The Allies catch wind of this and start working on defences. A plan is devised: create a series of massive deaetherizing apparatuses, large and powerful enough to collectively suck the light out of an entire city. When engaged, they will make navigation impossible (except through sonar), as well as accelerating the diffusion of the aether from the balloons.
Early 1916: A series of large-scale deaetherizing apparatuses are built. Some are installed throughout New York City, and some are shipped out to other major cities in the Allied countries. This is all kept top secret, of course.
June 1916: First official use of the apparatuses. The Central Powers launch an aerial assault on New York City and arrive to primordial darkness. The planned battle ends quickly with no casualties. This becomes a major point of American national pride.
1916-1918: Deaetherizing apparatuses are deployed several more times in various cities. Though the aether zeppelins are soon retired altogether, the impenetrable darkness effect is still very useful for confusing and deterring attackers. Some advances in sonar tech are made on both sides before the war ends and the apparatuses are closed.
1918-1932: The American government leans hard into promoting the country’s scientific achievements. Aether control is particularly celebrated, not only for saving the country some very nasty battles but also for the whole “we’ve learned how to control a basic part of nature on a large scale” factor.
1923: A group of scientists and politicians come up with the Erebus Project. All of New York City’s deaetherizing apparatuses will be turned on, and whatever changes need to be made from that point on will be made. This includes the building of aether transport infrastructure underground and throughout all the buildings, as well as special vehicles equipped with sonar devices. This is agreed to on the grounds that it will a) be “the ultimate show of scientific progress” b) serve as a ground for more study and c) provide more impetus for the construction of large buildings. Much advertising material showing a glamorous eternal nightlife is made. The populace generally agrees, and construction begins.
December 16, 1926: The Erebus Project is launched, to general applause from the American populace. The tops of the apparatuses are opened once more, and all of the aether is sucked out of the air and rerouted into buildings.
Late December 1926: The project quickly stops seeming cool to any of NYC's inhabitants who aren't involved in the Erebus Project. Humans generally are not made for a lack of sunlight, and only the people who profit from it have anything to gain from toughing out the discomfort.
The heads of Erebusian Management promise it won’t be forever. The project will end after the strontium-90 in the apparatuses undergoes a half-life… in, uh, 1944.
Spring 1927: Coordinated groups of protestors gain access to the pipes near the largest deaetherizing apparatuses and damage them. For a brief period of time, some light seeps back into the sky of Erebus. Most of the protestors are swiftly arrested and imprisoned, and guards are employed around the apparatuses.
1928: Further crackdowns on protesting, and placement of limits on travel out of the city.
December 16, 1929: On the third anniversary of the Erebus Project, New York City is officially renamed after it.
1930: Dielism, an artistic movement focusing on day and night imagery, officially comes to be. The "Dielism Evening" becomes a popular gathering.
March - December 1932: The events of When In Erebus take place.
I don't have concrete ideas for anything that happens after WIE. I will repeat that despite the more rapid advancement of nuclear science, the eventual situation around the development of nuclear weapons is not worse than it was in our world because of the focus on its use for aether control. (In other words, the Axis powers do not get atom bombs, nor does the Cold War end in a nuclear apocalypse. I'm not interested in writing stuff like that.)