Moonless Nights

The Earth’s Moon is unusual in our solar system for its size relative to our planet. While larger moons, such as Ganymede or Titan, orbit the Solar System’s gas giants, these have masses well under a thousandth of the mass of their primary, and sizes less than a twentieth of their planet’s diameter. By contrast, the Moon’s mass is a full hundredth of that of the Earth, and its diameter a quarter.

As such, the Moon has been a powerful influence on Earth, both creatively and physically, throughout the history of humanity. So, perhaps unsurprisingly, the often space-focussed genre of what-ifs has explored a big one: what if the Moon no longer existed?

Here we take a look at the science and SF of moonless nights.

Broken Moons

The idea that the Moon might be destroyed entirely seemed all too real in the darkest years of the Cold War. The proliferation of nuclear weapons, and the fear that they might be used in earnest, raised the possibility that the entire Moon (or even entire Earth) might be blown apart.

This fear is articulated in Richard Savage’s 1955 novel When the Moon Died. The narrative is presented as an ancient recording, recovered long after humanity becomes extinct. The recording in turn looks back into its own distant past, two millennia before the narrator was born, when the Moon was destroyed in our own era (in fact, in 1999). As becomes clear as the story progresses, this was done deliberately by a scientific committee who wished to see an end to cold war politics and peace under their rule. In the short term this was a success - the scientistic regime creates a utopian united world. However in the long term this utopia stifles creativity and suppresses dissent, leading to the decline of the race. The rediscovery of this past sets in motion a chain of events which eventually break the stasis into which the resultant civilisation has sunk - although it’s unclear whether or not this is for the best.

In this narrative, the destruction is caused by a nuclear missile which triggers the surface of the Moon to burn in a twenty-million-degree chain reaction. This in turn causes the Moon to spin up and fall toward Earth, causing panic, before eventually detonating outside the atmosphere.

“Apart from the destruction caused by the madness of multitudes, the scientists could claim that little harm had been done. A few people were blinded; but they had been warned against watching the first flash. The disturbance to the tides in the now tideless oceans had caused some destructive floods and changed the contours of certain coasts” … “A few areas of the earth were infected by radio-activity, but these were isolated regions, mere freaks. The glowing carbon fragments of the moon that now formed the supernova were too far away to do any harm.”

On the whole the story doesn’t lay any great claim to scientific accuracy - it’s not clear what there is on the Moon that could burn or fuse as described, or where any carbon came from, and it’s far from obvious why the Earth is not bombarded and rendered uninhabitable by the resulting debris, but the theme here is not so much what might be possible in terms of the science, but rather what might be possible in terms of human actions and their consequences.

The same theme appeared in other cold war narratives, another interesting example being the radio drama “If I Should Wake Before I Die”, written and directed by Wyllis Cooper as part of the Quiet Please anthology series for MBC and then ABC radio, and broadcast in 1949. This cautionary tale focuses on Dr Anderson, a scientist in denial about the weapons implications of his pure science research, motivated in part by an uncritical patriotism. The first missile sent to the Moon as part of "Project Phaeton" triggers a much larger reaction than expected, destroying the satellite. The consequences are spelled out by a friend in a string of single line laments interspersed with indifferent comments from the scientist::

“Never again the sweet moonlight of the lovers. Never more the harvest moon rising above the hills. ”

“And, in every harbour of the world, the tides rushed out and the very floor of the sea was plain to human eyes. “

And, far out on the breast of the ocean, great tidal waves that overtook and destroyed everything that floated.”

And thousands dead for miles inland from the shore when the waters returned.”

And man has destroyed what god has wrought.”

Ultimately, the friend decides that the scientist must be stopped, as his narrow-minded worldview in which scientific progress trumps all else will lead to ever greater destruction.

Amongst narratives where the Moon is destroyed, The Ceres Solution (novel, 1981) by Bob Shaw is unusual in proposing that the Moon was actually a deeply negative influence on mankind to begin with.

In this narrative, humanity began on the alien world of Mollan and has spread across hundreds of planets, with the typical lifespan of an individual being seven centuries and that on Mollan itself more like fifty centuries. Humans from all worlds have the ability to ‘skord’ - to travel between nodal space-time coordinates as a result of an intrinsic sensitivity to ‘third-order forces’, essentially the tidal influences of neighbouring planets and objects. However Earth’s Moon is atypical. Being relatively massive and close, it exerts enormous tides, and thus acts to deafen those conceived and born here, resulting in Earth humanity being stunted and short-lived. While most Mollanians are happy simply to observe and record the consequences, a rebel group considers this immoral and come up with a different plan: to destroy the Moon by crashing the dwarf planet Ceres (the largest body in the asteroid belt) into it. 

“It won’t happen immediately,” Lorrest spoke as though explaining some minor mechanical process. “It won’t be a head-on collision, you see. What we’ve got to do is strike the Moon a glancing blow at a precisely calculated angle and start it spinning fast. Very fast. The rotation will set up gravitational stresses in the Moon and tear it to pieces, and the pieces will go on spinning and breaking up into smaller pieces and scattering themselves. According to our calculations, the end result will be a whole swarm of little moonlets strung out along the Moon’s orbit. All the second-order and third-order forces will be pretty well neutralized, especially gravity.”

 The remainder of this story follows both the pro- and anti-intervention advocates until the Moon’s destruction and then jumps forward a number of years to evaluate the result. However while the narrative discusses the possibility of coastlines changing and ocean tides ending, the foreseen consequences of replacing the Moon with a ring are not particularly serious.

This rather cavalier approach to the Moon’s dissolution contrasts rather dramatically with the much harder 2015 science fiction novel SevenEves by Neil Stephenson. The opening scenes of this narrative show the Moon being broken into seven large pieces by an unknown 'Agent' (possibly a naturally occuring microscopic black hole, but this is never resolved). However the first subsequent collision between major pieces, breaking off another large fragment, raises an alarming possibility.

“We’ll see an increasing number of meteorite impacts. Some will cause great damage. But overall, life is not going to change that much. But then” - he clicked again and the plot bent sharply upward, turning white - “we are going to witness an event that I am calling the White Sky. It’ll happen over hours, or days. The system of discrete planetoids that we can see up there now is going to grind itself up into a vast number of much smaller fragments. They are going to turn into a white cloud in the sky, and that cloud is going to spread out.”
Click. The graph continued shooting upward, rocketing up into a new domain and turning red.
“A day or two after the White Sky event will begin a thing I am calling the Hard Rain. Because not all of those rocks are going to stay up there. Some of them are going to fall into the Earth’s atmosphere.”

As the narrative explains, this bombardment will sterilize the surface of the Earth and set the atmosphere aflame… and it will last for more than five millenia. The rest of SevenEves describes the efforts made by humanity to survive, following the politics, technical challenges, survivors and their descendants into a distant future where the remaining debris has been used to construct an orbital ring around the devastated but now recovering planet.

While it’s possible Bob Shaw’s earlier The Ceres Solution might have claimed some degree of super-technological alien intervention in shepherding the lunar debris into a stable ring, Stephenson’s Hard Rain is undoubtedly the more likely of the two scenarios if the Moon were to break up in its current orbit.

A range of other narratives explore similar themes of an Earth devastated by debris, ranging from Jack McDevitt’s 1998 novel Moonfall (which describes an American vice-president trapped on the Moon when it’s shattered by an interstellar comet impact) to the 2013 blockbuster movie Oblivion (in which aliens blew up the Moon some decades before in the film’s backstory). In each case, the surface of the Earth suffers major disasters as a result of the kinetic bombardment by rocks falling from orbital velocities.

While Shaw’s ring is unlikely and devastated-Earth stories are common, there might be ways to lose the moon but escape a bombardment of debris. How we lost the Moon, a true story by Frank W Allen (short story, 1999, by Paul McAuley) is an enjoyable story about how a microscopic black hole generated in a particle physics experiment drops into the core of the Moon. This causes the core to melt and the black hole to accrete due to friction and distortion as it oscillates around the centre of mass. The tale is told from the point of view of a geologist who works in the Moon’s general labour pool (since even manual workers on the Moon have science PhDs). Before too long, the disturbance leads to the Moon’s evacuation, and eventual collapse into its devourer.

The Earth is bombarded by radiation by the final accretion event but not by the consumed debris, and is left with a black hole in orbit of the same mass as the Moon - neatly preserving the tidal forces on Earth, preventing any larger consequences, and providing a conveniently close black hole for study.

This story is notable for being written at about the same time as the planning phases of CERN’s Large Hadron Collider and as Brookhaven’s Relativistic Heavy Iron Collider was about to begin operations. More than one physicist at the time sounded ultimately-unfounded warnings about the miniscule but non-zero possibility that a black hole generated accidentally at the facility could do the same to Earth as McAuley’s characters did to the Moon, although repeated careful analyses showed this was impossible [1]. As such the story is an example of both a fun what-if speculation, and a warning in a science fictional context of the need for caution in experimentation. Fortunately, the LHC was activated without incident, and indeed calculations show that any black hole small enough for it to generate would evaporate by Hawking radiation in 10^-27 seconds (unlike the larger one in the story). The more general question of whether even an infinitesimal risk of great disaster is justified in pursuit of pure knowledge nonetheless remains.

Altered Moons 

While many of the narratives discussed above consider the immediate consequences for Earth of the Moon’s destruction. However another strand of science fiction considers instead what would happen if the moon were removed or otherwise changed.

The UK television series Space: 1999 was developed by Gerry Anderson Productions and broadcast between 1975 and 1977. The premise was a simple, if eye-opening, one. In the opening episode, “Breakaway”, a series of nuclear dumps on the Moon go supercritical and explode, blowing the Moon out of Earth’s orbit. The dumps act as a rocket motor, giving the Moon an acceleration equivalent to many gravities, and causing substantial damage to the lunar surface space station Alpha. In the final scenes of “Breakaway”, the survivors on the moonbase, now rapidly travelling beyond the signal radius of Earth, pick up a stray news report from Earth:

“The totally unforeseen accident on the lunar surface has caused very serious repercussions here on Earth. The gravity disruption, the earthquakes in the United States along the San Andreas Fault, and in Yugoslavia, as well as southern France, has caused enormous damage to life and property. The International Lunar Commission, with its new chairman, is in executive conference at this moment, deciding what steps might be taken to rescue the three hundred and eleven men and women on Moonbase Alpha. Little hope is held, however, of any survivors.”

While this is clearly a serious occurrence, based on this account, the worst of the damage appears to be mostly restricted to localised tectonically unstable zones, and contact is lost before any long-term damage to climate or otherwise can play out. Speculation regarding the full extent of the consequences appears occasionally, but is never resolved in the series. Interestingly, the 2019-2023 audio adaptation of Space: 1999 by Big Finish Productions did more to recognise the seriousness of the Earth suddenly losing its Moon, speculating overtly and repeatedly that the personnel of Moonbase Alpha might be the last remaining humans as a result of tectonic and climactic readjustments on Earth’s surface, and discussing the impact of the destabilisation of our world’s axial tilt when the moon was lost. 

In the television series, and counter to expectations, sufficient people do indeed survive on the Moon to become somewhat self-sufficient. Over the next two seasons, the former Moon, now dubbed Alpha, was thrown across the Galaxy at apparently super-lucent speeds, visiting a range of planets and civilisations. During this odyssey the surviving crew of Moonbase Alpha have to repair the damage caused by the Breakaway, deal with alien encounters and adjust to existence as an unplanned independent colony on a newly-isolated and barren world.

Despite this somewhat far-fetched premise, Space: 1999 took itself rather seriously. A more ridiculously nonsensical scenario, from a scientific point of view, can be found in the Doctor Who episode “Kill the Moon” (TV episode, 2014). This Twelfth Doctor story focuses on broken trust in the relationship between the Doctor and his companion Clara. The tense storyline, in which Clara and the people of Earth have to make a decision over the fate of a newborn alien life, provides a fitting scenario to test that relationship. The premise is that the Moon is the egg of an alien lifeforms, which is hatching, and which humanity must decide to leave be or destroy. The choice is made difficult by the fact that the lifeform is causing the Moon’s influence to fluctuate wildly, causing massive tidal destruction on Earth.

However beyond that, any sense of scientific realism in the story takes a very low priority, with incomprehensible mass fluctuations in a closed system, germs the size of large dogs and the newborn creature somehow laying an egg with exactly the same mass as itself and its shell (i.e. the Moon) before these changes took place. Despite the many absurdities, the idea that the Moon’s mass can cause disasters on the Earth’s surface, and that Earth without a Moon would be in trouble, comes across clearly.

Changes to the Moon’s orbit appear elsewhere in science fiction and indeed in fantasy, often unexplained. Such a scenario is crucial to the plot of the science fiction, fantasy hybrid novels of the Broken Earth trilogy (2015-2017) by N K Jemisin [2], where many of the disruptions on an initially-inexplicable far-future Earth prove to result from a displacement of the Moon into an extremely elliptical orbit. This destabilises Earth’s axial tilt and seasons.

By contrast, the young adult novel Life As We Knew It (2008) by Susan Beth Pfeffer considers a different displacement of the Moon’s orbit.

In this case a large, dense asteroid strikes the satellite pushing it into a closer orbit to Earth’s surface. Since tidal forces depend on the cube of the distance between two objects rather than the square, halving the distance between Earth and the Moon would increase the gravitational pull by a factor of four, and the tidal effects by a factor of eight. While the protagonist, safely inland, sees no immediate consequences beyond the Moon looming larger in the sky, this results in tsunami wiping out both US seaboards and most other coastal cities around the world, as well as intense electrical storms, widespread volcanic eruptions and other secondary effects. The resultant disruption causes a breakdown of civilisation’s infrastructures, including telecommunications, resource and food supply, and the story follows the teenage protagonist’s effort to survive, along with her family [3].

 Moonfalls

Of course, the extreme end of alterations to the Moon’s orbit is the idea that it might be brought crashing down to Earth. Counter-intuitively to many, this is substantially harder than actually breaking up the Moon in situ at its current orbit, since it would require the intact body to shed a colossal amount of angular momentum and kinetic energy. In the case of a break-up, some fraction of the Moon would fall inward while transferring its angular momentum to another fraction that is blown outward, while the remainder would form a ring at the Moon’s orbital distance. In the case of a falling-in of the Moon, there is no obvious way for its angular momentum to be conserved.

The idea of an intact Moon falling towards Earth is nonetheless surprisingly attractive and a number of works have explored this idea with more or less attempt at scientific accuracy. It’s become a common theme in anime, video games and graphic novels, and plots to accomplish such an impact appear, for example, in The Sarah Jane Adventures (TV episode “The Lost Boy, 2007, in which it’s correctly explained that gravity will tear both worlds apart before any impact).

A much earlier example is The Hopkins Manuscript by R C Sheriff (novel, 1939). This slightly satirical parable about survival in a world on the brink of catastrophe was published under the looming shadow of the Second World War. It describes a record left by the eponymous Mr Hopkins of the seven months before, and eight years after, an impact on Earth by the Moon brings the life he knew to its end. Hopkins is an amusing, self-important, retired schoolteacher of comfortable means who lives a life that revolves around prize show chicken breeding, with amateur astronomy as a sideline. Finding out early about the sudden, unexplained orbital decay of the Moon (presaged by the delayed arrival of a predicted eclipse), he watches as the world prepares, describes the cataclysm of earthquakes, tornadoes and even a brief period of vacuum that kills most of the population, the rebuilding of a rural idyll and then the rise of populism and nationalism, conflict over the mineral resources deposited by the Moon (which crashes into what was the North Atlantic [4]), and finally a race-motivated uprising that wipes out the remnants of the European peoples.

The physics here is far from robust. The origin of the Moon’s ever-steepening rate of descent is never explained, it appears to have virtually no effect until literally the last few hours before impact, and then, despite a brief earthquake, atmospheric disturbance and a single inrush of water (which subsided within twenty four hours), the climate appears to be undisturbed and everyone who survives the initial cataclysm has a reasonable chance of continuing to survive. Within a couple of years they are going on day trips to see the pancaked Moon off the coast of Cornwall. By contrast, in reality, and such impact would carry enough kinetic energy to boil the oceans, melt the crust, destroy the atmosphere and leave the surface of Earth unsurvivable. However the focus of the story is on the human foibles and preoccupations of Hopkins, the way the disaster brings out the best and worst of humanity, and the dangers of acquisitiveness and nationalism on a global scale.

From a scientific standpoint the 2022 feature film Moonfall (completely unrelated to the earlier McDevitt book) also falls into the category of so-bad-it’s-almost-good, all the more so because of the improvements of our understanding of the Moon compared to 1939 when The Hopkins Manuscript was written. It ranges from the ludicrous (the Moon is a giant alien megastructure intended to wipe out life on Earth) to the naive (an astronomer can phone up a major observatory on a whim and get data; twenty-first century astronomers are capable of forming a global conspiracy of silence). Its representation of earthquakes, tidal waves, volcanos and even compression of the atmosphere, are plausible reactions to an increase in tidal forces. The fact that these reverse instantly after the Moon’s instantaneous change of direction, and that humanity survives the Moon getting halfway into the atmosphere, is not. Again, the focus is on human survival and emotional journeys rather than the physics. It’s best enjoyed as a run-of-the-mill disaster movie and its premise not examined too closely.

The same is more generally true of other narratives of the less serious end of this science fictional scenario. In the animated supervillain movie Despicable Me (film, 2010), the protagonist Gru shrinks the Moon and puts it in his pocket, bringing it to the surface without any noticeable ill effects on the planet. And if that wasn’t enough silliness, there’s also the classic 1980 film Flash Gordon, in which the Emperor Ming the Merciless sets the Moon on a collision course with its homeworld, resulting in the classic cry of “Flash! I love you, but we only have fourteen hours to save the Earth!”

The Perfect Moon

Until recently, the existence of the Moon was very much taken for granted. After all, since its formation in the very early years of Earth’s development, it has been a constant companion, present throughout the formation of life on this planet, including the evolution of recent arrivals such as humanity.

So why are lunar-destruction narratives so common?

Well, first and foremost, there’s the classic answer ‘because it’s there’. Anything that happens on or to the Moon can be seen by the whole Earth and acts as a dramatic statement of either malicious intent or the fragility of humanity, in the context of the vastness of space.

This propaganda potential of the Moon was not overlooked during the Cold War. Plans to detonate nuclear explosives on the Moon never progressed to an operational point, but that’s not to say they were never discussed.

The US Air Force’s Project A119 was developed in 1958-9 with the objective of creating a powerful visual impact that would counteract the public relations victory of the Soviets in their launching of Sputnik. In his enjoyable non-fiction book Nuking the Moon (2019), Vince Houghton describes how astronomers including Gerald Kuiper and Carl Sagan became involved and investigated both the visibility of a lunar detonation and its use as a probe of the chemistry and structure of the Moon. On the other hand, the programme was rapidly cancelled and effort refocussed towards a lunar landing for reasons that remain unclear - whether they involved consequences for the moon itself or a fear that the public would respond unfavourably to the defacing of our satellite.

What is certain is that the nuclear weapons of the time would have been incapable of doing any substantial harm to the Moon, let alone knocking it out of orbit. The energies involved were well beyond the yield of an early atomic warhead. Nonetheless, before the composition and structure of the Moon was understood, there was at least a chance (albeit a slim one) that it might contain radioactive materials or other volatiles which would lead to the kind of catastrophic reaction described in some 1950s narratives, or perhaps be sufficiently unstable to shatter given the right stimulus. Even after nuclear proliferation (and by the 1970s, when nuclear dumps on the Moon sounded plausible to the writers of Space: 1999) the detonation of the entire Earth stockpile was more likely to have blasted debris off the surface of the Moon than to destroy it entirely, let alone knock it out of the Solar System (for which a truly colossal energy input would be required). Indeed astronomer Phil Plait has calculated that the events seen on screen would require: “the energy yield of 1 quadrillion one-megaton bombs! In other words, take a million one-megaton bombs and blow them up. Now do that a billion more times.” This is more than enough to vapourise the entire satellite.

It is nonetheless undeniable that the idea of destroying the Moon is more impressive in SF than merely blasting another crater amongst many, particularly when the Moon’s lack of atmosphere would deny viewers on Earth the familiar visual impact of a mushroom cloud. The mid-twentieth century was the first era in which it appeared realistic that human actions could make permanent and significant changes to a planet-sized body, and it’s perhaps unsurprising that a lot of the fiction of this period, for example The Ceres Solution, invoke phrases such as ‘playing god’ and question humanity’s right to make such changes. This fits into a wider context of one of science fiction’s key roles: to challenge and question the wisdom of proceeding to exploit scientific advances without careful examination of the practical, political, ethical and very human consequences.

As well as commentary on the hubris and morality of human actions, however, the science fiction in this genre also reflects our growing recognition of the crucial role the Moon plays in Earth’s own habitability. Early science fictions considered the Moon more or less disposable, while recognising potential hazards during a transition period (including one or more impacts and earthquakes or tidal waves caused by shifting gravitational stresses) they suggested normal life would be resumed thereafter. We now know, though, that even if the Moon could be painlessly removed (a big if), the long term consequences for Earth would not be good. The life-cycles of many lifeforms on Earth, which are tied to the lunar cycle, would be disrupted. Ocean tides would continue, since they are driven nearly equally by the Sun and Moon (causing the spring-tide/neap-tide extremes when the two align), but would be substantially weaker, affecting vast swathes of coastal ecosystems, as well as potentially disrupting ocean current circulation. Perhaps more importantly, the axial tilt of the Earth would be destabilised. This tilt gives us our seasons (with a far greater influence than eccentricity of the orbit), but cannot be maintained without the large Moon acting as a form of counterweight, orbiting at an angle to Earth's orbit. The resulting instability would lead to substantial wobbling around the Earth’s rotation axis over geological eons, destroying our seasonal cycle and rendering large swathes of the Earth either uninhabitable or with dead ecosystems left unable to cope with the new climate.

Our growing recognition of the extent to which losing the Moon would present a catastrophe, in one form or another, for Earth is recognised by the increasing fraction of twenty-first century science fictions in which the result is catastrophic, as seen, for example, in Seveneves.

There is likely also another, perhaps less strictly scientific and more emotional factor in play, but one that speaks to how the public around the world perceive the issue and engage with it. In Life As We Knew It, Pfeffer’s narrator comments that

 “Even though we knew it was going to, we were still shocked when the asteroid actually made contact with the moon. With our moon. At that second, I think we all realised that it was Our Moon and if it was attacked, then we were attacked.”

It is indeed Our Moon, deserving of its capital letter in the same way as Our Sun, Earth and even Universe are capitalised. The science fiction of lunar destruction is as much about the emotional impact of science that fails to recognise that common connection, and the arrogance that entails, as it is about possibilities or probabilities in basic physics

Fortunately, in so many ways (and despite the best efforts of science fiction writers), to the best of our knowledge, the Moon is here to stay.