Set in the modern days, our moon suddenly disappeared but we can still experience high and low tides. The mass of the new moon doesn't change but the size of the event horizon is much smaller than a pea and somehow this change seems permanent. I know people will just go about their daily lives but I want to know if this event could cripple our economy or affect some species of migratory animals? Most importantly will future space program be affected at all?

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    $\begingroup$ We would very quickly learn a lot more about black holes and confirm (or disprove) experimentally a lot of theoretical physics! $\endgroup$
    – Plutoro
    Commented Oct 1, 2015 at 3:13
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    $\begingroup$ Well, it would greatly affect our ability to build a base on the moon. A lot less convenient. $\endgroup$
    – timuzhti
    Commented Oct 1, 2015 at 4:35
  • $\begingroup$ I guess the most impacting thing will be how we will see our sky after this...what happens when the moon is aligned with the sun blocking all the light to come to earth? This question can be very interesting if you think more than on the physics or how the budget of spacial agencies would increase worldwide $\endgroup$
    – Freedo
    Commented Oct 1, 2015 at 5:30
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    $\begingroup$ I believe that your question is elegantly summed up by Randall Munroe here: what-if.xkcd.com/129 (note: this doesn't answer this specific question. But it is amusing!) $\endgroup$
    – Joe Bloggs
    Commented Oct 1, 2015 at 9:40
  • $\begingroup$ As currently worded, I think this question is too broad. Please try to narrow the focus of the question - especially since I'm interested in the answers :) $\endgroup$
    – Jim2B
    Commented Oct 1, 2015 at 12:59

9 Answers 9


Some countries have laws allowing you to ride a bicycle at night without lights, but only when there's a full moon. Those laws would probably change.

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    $\begingroup$ why change them? a full moon will never occur again. $\endgroup$ Commented Oct 1, 2015 at 6:37
  • $\begingroup$ This answer doesn't address any of the specific aspects mentioned in the question. $\endgroup$
    – user
    Commented Oct 1, 2015 at 12:34
  • $\begingroup$ How will the world react if the moon turns into a black hole? People will never ride bikes on a full moon again. Seems valid to me! $\endgroup$
    – Joe Bloggs
    Commented Oct 1, 2015 at 15:45
  • $\begingroup$ There is more to the question than the question title. $\endgroup$
    – user
    Commented Oct 2, 2015 at 5:09

So your moon has been replaced by a black hole, eh? Well, here's some of what you can expect.

Immediate Reaction (days to months)

Panic, depression, and fear will strike a significant portion of the population. Something that we all just take for granted has suddenly disappeared, so a lot of people will be upset. We can expect riots in riot-prone areas, and lots of unrest as many conclude that this is a signal of the end of the world. While society as a whole will eventually settle down, a large minority will probably continue to believe that this is the End Times, and their behavior will reflect this belief.

Some people will calm down a bit when it's discovered that the moon has become a black hole. After all, we don't have to worry about ecological collapse because of lack of tides, and conservation of mass/energy hasn't entirely gone out the window. At the same time, however, this is still extremely terrifying. If the moon can suddenly become a black hole, what about the sun? What about the earth? Songs and poems about the certainty of astronomical events ("The Sun will come up tomorrow, bet your bottom dollar that tomorrow, there'll be sun!") will seem like pitiable naivety. This will cause stress in the entire population, much as cold war fears of nuclear attack did.

Many national space programs will reconfigure their orbiting telescopes to look at the moon, and we can expect a lot of probes will be launched into orbit of the moon/black hole. It's a good time to be an astrophysicist or aerospace engineer.

Near Term Reaction (months [is "month" a trigger word now?] to 10 years)

Over time, as the world persists in not ending, many people will begin to become accustomed to the new reality. Memories of the moon will be tinged with sad nostalgia and a hint of fear. It will be a lot like how Americans remember the World Trade Center towers, but more extreme and worldwide. Images of the moon will be useful for stirring these emotions in audiences, or just used in establishing shots to show what year a movie is set in. Love songs which discuss the moon will be re-purposed as memorial songs for the moon.

Stress over the risk of the earth or sun becoming a black hole will decline with time, but still be part of the global consciousness. Fears will also emerge about the increased likelihood of a large rock hitting earth (the moon used to shield us some), or of x-rays from the black hole killing us all (as unlikely as that may be).

Annual Facebook appearance of "Like if you remember the moon, share if you miss it!" gradually gives way to "This year all new [nth]-graders will have never seen the moon".

Moon rocks will go from "rare scientific curiosity" to "absolutely priceless".

Biologists will discover whether various approximately 28-day cycles are caused somehow by the moon's light, whether wolves howl at the moon, whether cats/cattle/people are driven mad by the moon, etc. Some animals may navigate by the moon, and could be impacted by the loss.

End-times believers will still be a large portion of the population, and their numbers may not decline with time. They will become more "moderate" with time, however, becoming rather like the spectrum of today's religious extremists.

Robotic missions to the lunar black hole are launched, and data streams back. Lots of advances in knowledge of black holes and all related phenomena. Some quantum theories of gravity discarded, dozens more pop up. Good time to be an astrophysicist or aerospace engineer. Manned missions announced, but not launched in this time frame.

Long Term (10-50 years)

Population stress level returns to normal over this period. While everyone knows that the black-hole-ification could happen again, most people just can't worry about things that happen on astronomical timescales. Unless scientists discover that what happened to the moon is likely to happen often or with increasing frequency, it will likely have been a one in a trillion chance, and will join asteroid impact as a big disaster that few people seriously worry about.

End-timers are somewhat in decline, but still numerous. Some of the less radical groups are beginning to "go legit" by modifying their beliefs to something more in line with mainstream religions. Maybe the end of the world was a "spiritual re-creation" or something. Hardliners continue to carry out terrorist attacks.

New radical groups emerge among the younger generation claiming that the moon never existed. NewTube (successor to YouTube) videos and long blog rants will "prove" that the moon never existed and is just an excuse for the older generation and the 1%, the patriarchy, the matriarchy, cyborg-immortal Donald Trump, or whatever the Illuminati front of the day is, to continue to rule the world. These groups are small, but a surprisingly large portion of the population begins to believe their claims (this is rather like the people who believe that the moon landing is a hoax, a large minority of the population actually believes the claim, but doesn't really care). A big media frenzy happens every time a pop star produces a music video that seems to play into this conspiracy theory.

Scientists finally agree (mostly) on a quantum theory of gravity, though the exact "interpretation" of this theory has several different camps. Research on the black hole has lead to the discovery of a new level of complexity in physics, meaning that a quantum theory of gravity is not enough to combine General Relativity with Quantum Mechanics to form a "Grand Theory of Everything". PBS Nova specials try to explain this new branch of physics, but only serve to confuse viewers. It becomes less and less of a good time to be an astrophysicist.

Physicists agree that the moon was turned into a black hole by a "quantum resonance inversion" which is shockingly rare (unless it isn't, for story purposes, in that case, expect more panic). Since it's mind-bogglingly rare, people begin to relax (as mentioned above).

A new International Space Station is established in orbit of the black hole. Planning takes 20 years, construction takes 10, budget cuts lead to it being abandoned after 5 years in service; the supply chain is too long and frankly people are losing interest. While a black hole is a lot more scientifically interesting than a normal rocky moon, it's a whole lot less visually compelling. It becomes less and less of a good time to be an aerospace engineer.

Longer Term (50-500 years)

Soon nobody who remembers the moon is alive (except for immortal cyborg Donald Trump, of course). All emotional connection to the moon comes from old books, old movies, and old web pages. People believe weird things about the moon, like that it never existed, or that it was actually made of cheese, or it's where Noah survived the flood. These odd beliefs have little impact on daily life, because they refer to something which no longer exists.

Radical end-timers are now viewed as a small branch of an otherwise legitimate religion. End-time religions are formalized, and end-timer beliefs also become formal parts of some older religions.

Particle physicists join with astrophysicists and construct experiments using the black hole as a particle accelerator. Big public furor over finding "The God String", and minority fears that the experiment will destroy the earth or universe. The experiment revolutionizes some theories, but raises even more questions than it answers. No theory of everything yet. Overall, it's an average time to be an astrophysicist.

Over the centuries, a "moon shell" replaces the "Dyson sphere" as the default energy-generating megastructure. Conceptually, it's a spherical shell built around the black hole, with energy-absorbing plates on the inside (like solar cells). Feeding small amounts of material into the hole should cause release of large amounts of energy from the accretion disk, allowing "limitless, nearly-free energy". Proposed designs range from a classic solid megastructure to "cloud" systems consisting of many orbiters.

Late in this time period, a cloud-type moon shell is built, and becomes an important source of energy for the earth and for the giant lasers which propel ships to the asteroid belt and beyond. It's an increasingly good time to be an aerospace engineer.

Space Opera (10,000 years in the future)

The final Moon Shell has been completed. Built of materials we can't imagine today, this enormous construct is a spherical shell around the black hole with a radius of about 700 kilometers. The outer surface has earth-like gravity and almost as much "land" as Australia, while the inner surface captures energy from feeding the black hole. The collapse of the moon into a black hole is remembered as one of the best things to happen to humanity.

Even better, detailed analysis of millennia of black hole data has taught humanity how to make more moons into black holes. Collapsing any moons becomes a standard part of terraforming new worlds. One rogue group (descended from End-Timers) embarks on a mission to "bless" all primitive civilizations in the galaxy by collapsing all their moons, unknowingly mirroring the intentions of the race which destroyed our own Luna.

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    $\begingroup$ A note on the space opera range shell. It would need correction mechanisms to offset perturbations from the norm. Fortunately it's regularlily sending mass in against the black hole. By variying the thrust it imparts to these masses, as well as the locations they are sent from it can keep the moon shell stable. $\endgroup$
    – Taemyr
    Commented Oct 1, 2015 at 17:43

Interestingly enough, Wikipedia has some stats on a Moon-massed black hole:

A black hole of $4.5 \cdot 10^{22} \; \text{kg}$ (about the mass of the Moon, or about $13 \; \mu\text{m}$ across) would be in equilibrium at $2.7\; \text{K}$, absorbing as much radiation as it emits.

However, it's still possible for us to utilize our new moon hole as a power source.

Accretion process can convert about 10 percent to over 40 percent of the mass of an object into energy as compared to around 0.7 percent for nuclear fusion processes.[5]

Put a shell around it. Now launch hydrogen (not directly) so that it forms an accretion disc. Use the outputted energy from this to heat water -> drives turbines -> generates electricity.

Converting even 10% of mass to energy is massively more efficient from fusion, so you should be able to get quite a lot out of this.

Unfortunately it's not very conveniently located, but you now have abundant cheap energy for your space program.

  • $\begingroup$ Building that shell is going to be hideously expensive. $\endgroup$
    – Taemyr
    Commented Oct 1, 2015 at 9:02
  • $\begingroup$ @Taemyr how expensive? It's a very small black hole, and the gravity is quite low. $\endgroup$
    – NPSF3000
    Commented Oct 1, 2015 at 10:15
  • $\begingroup$ @NPSF3000 Low? 1 meter above the singularity the gravity is about $5*10^{11} g$ - That is pretty darn strong. Further out the gravity is weaker, but the surface area of your shell is larger. The gravity is weak at the radius of our moon, but you are now talkin about building a shell the size of the moon. $\endgroup$
    – Taemyr
    Commented Oct 1, 2015 at 10:44
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    $\begingroup$ @Taemyr would you mind explaining how you get the 5∗10^11g figure? $\endgroup$ Commented Oct 1, 2015 at 11:06
  • $\begingroup$ You don't really need a full shell, it's just there to collect the energy. Also really high local gravity doesn't matter for an object in freefall. It's the tidal forces that count. We can put collectors into orbit at about 1km out. It's not something that can be done today, but it's still pretty practical. $\endgroup$
    – Fhnuzoag
    Commented Oct 1, 2015 at 11:10

Space travel outside of earth orbit just got a whole lot cheaper. The efficiency of both gravitational slingshots and the Obearth effect increases the deeper into a gravity well you can go. Having tidal forces as the chief limiting factor to how close you can get to the moon is much better than having the surface of the current moon as that limiting factor.


I think life would go on as normal for the majority of people, while scientists and academics frantically postulate on what is happening.

Certain species will go extinct as moonlight is apart of their biological clock. They will not be able to synchronise their spawning seasons.

There would be a renewed interest in a space race to the moon because we can now do experiments involving "micro-black holes" which apparently are a thing.


The budget for all space agencies worldwide would increase a lot, because there would be a new race to go to the moon to study, but at same time will make a lot of scientists mad because studying the universe with a black hole distorting all the light will be a little harder.

About economy : Well the public and privates companies who operate, fabricate or maintain business related to this area will have a big increase on the stock market, but don't expect any big changes on our economy, everything keeps the same.

I don't believe that many species would be extinct, they would eventually adapt and evolve fast because this is a giant evolution pressure on this species(which is good because we will be able to observe and study that happening)

What happens in a Solar Eclipse that last one hours just like the recent Lunar Eclipse we had? Well it won't kill us i think, probably will just make snow fall for the first time on a lot of places on Earth...

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    $\begingroup$ The black hole will only distort the light from the stars if you're looking straight through the space where the moon used to be. In all other directions, it will have exactly the same effect on the light as the moon had. $\endgroup$
    – Mike Scott
    Commented Oct 1, 2015 at 6:02
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    $\begingroup$ Even if you're looking through the space where the moon used to be, the gravity of the black hole won't noticeably distort the light of the stars. The spacetime curvature caused by the moon's mass is tiny and is probably imperceptible to the human eye. I think that it would look as if the moon had just disappeared completely. I don't understand your last paragraph about snow falling - how would it affect the weather? $\endgroup$ Commented Oct 1, 2015 at 11:03

Night will get darker, which'll take some getting used to (I imagine a lot of animals could be negatively affected, especially in the short term).

People will be scared, if it can happen to the moon then it can happen to us. This will cause global destabilization, fear, rioting etc. Hopefully not enough to significantly damage civilisation in mid term, but it will be fearful times.

Such a loss is an issue of national security, as such science especially physics and space exploration will get increased funding. The relevant industries will grow larger, more important and lobby government to ensure that they stay important - a new cold war for the defense industry.


The ability of a black hole to convert a large fraction of the mass of an object passing close into energy would be of grave concern. The next time a meteor passes close to the lunar black hole while parallel to the surface of the Earth, the jet of high-energy particles and radiation will be pointed straight at the Earth. This could be life-threatening if it's pointed at you. If it's a large enough object that gets sucked in, enough of the Earth's atmosphere might get converted to NOx for it to be an extinction-level event for all land-based animal life, or even for all life period.

On the other hand it's a small black hole, and most times something falls in, the jet won't be pointed straight at us. There will be spectacular celestial fireworks far more often than any danger. However, when there is danger we probably won't see it coming, just a bright flash and terminal radiation sickness? Cue all sorts of religious nuttery here on Earth, as well as a greatly increased sense of anxiety affecting everyone?

Oh, and I'm not sure, but I think a missile launched at the black hole with extremely precise navigational accuracy would be a doomsday weapon - something which those religious nutters might think is their path to paradise.

Disclaimer: I'm aware of the physics in general terms but I haven't run any maths, which is not easy to do.

  • $\begingroup$ This scenario would provide a strong motivation to construct the shell as soon as possible. $\endgroup$ Commented Oct 7, 2015 at 1:17

(Warning: spit balling while my build is running)

Cripple our economy? Probably not. There might be some short term panic and, perhaps, it would ruin the burgeoning space tourism industry but we would never be able to afford it anyway so no big deal. Also, werewolf movies would go away, but I fail to see a downside here.

Ecologically, it would be sort of interesting to see what would happen. Adding to the things mentioned in Freedo's and Lorry's answers: nocturnal predators would be more successful for a time. I remember reading an article mentioning that nocturnal predators are more successful during the new moon and less so on the full moon because they're more easily seen during a full moon and less so during the new moon.

The future space program is harder to predict. Short term: "Yay better gravitational slingshot" say the NASA space engineers, "Yay a thing to experiment on" say the experimental physicists, "boo the experiments don't align with the math" say the theoretical physicists because I am a pessimist. However, in the long term who knows. It could be used as a local power source for longer space flights, maybe it would confirm string theory a la Susskind and we would be able to make some kind of weird string theory drive to go to Saturn in 34 seconds.


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