In my story, Earth gets invaded by evil aliens. Good aliens provide troops, tech, etc. to fight off the evil aliens, and the invasion is fought off in a month and a half. Here are some major events in the invasion, which starts in mid-November 2020 and ends on Christmas Eve of the same year:

  • Sixty days before the invasion begins, a warning as cast across all devices, so TVs, radios, smartphones, etc. on Earth. It tells the people to prepare for war.
  • When the invasion begins, before ground troops are sent, 195 antimatter missiles each packing the explosive energy of 1 Tsar Bomba are sent flying at each and every capital city on Earth. This causes the complete and utter breakdown of society, as well as starting a possible nuclear winter, but works to unify humanity as one.
  • Four complexes are set up around the globe to limit interplanetary travel, and to provide base for troops. One is set up in northern BC's forests, another is set up on a remote Siberian island, another is set up in the Atacama Desert, and another one is set up in Challenger Deep. However, Earth's defenders are able to destroy each and every one of them halfway through the invasion.
  • A counter-attack is launched, which succeeds in destroying the planet-sized flagship that is the alien invaders' main base of operations, and killing their godlike leader shortly afterwards, ending the invasion. The flagship has a bit more than twice Earth's radius and about seven times Earth's mass.

And here's the consequences afterwards:

  • The presence of superhumans with powerful abilities is able to limit the aftershocks, but they're still there. Globally, about one billion people perish, making it the bloodiest war in human history by far.
  • The environment is (obviously) in shambles, as there's now these big clouds of soot blotting out the Sun, and an planet-sized spaceship exploded.
  • Whatever alien troops didn't switch sides, be KIA/MIA, or flee are kept as POWs.
  • Earth becomes open to the cosmic community, with the people who saved it seen as war heroes. However, anti-alien sentiment runs high, but immigration and emigration to and from Earth begins.
  • Reverse engineering of alien technology allows for a second Industrial Revolution, which aids the people of Earth with recovery.
  • The massive empire of the alien leader, which has been existing ruled by one being for an uninterrupted million of Earth's years, and having territory that includes 1% of the entire universe, crumbles to a power vacuum. Warlords and crime lords, once united by respect and fear of the alien leader, now squabble over territory.
  • Earth is forced into a global recession, but is now run by one democracy, led by the courageous teenage girl who was able to successfully unite Earth and allied beings and worlds under one banner, as its first-ever President. She serves for 8 full years before retiring, deciding that she's done enough helping people and deserves a break, and knowing that she has already created a gold standard that will result in her successors being derided for having the audacity to not be her.

And the flagship was located about six light-hours from Earth. The aliens have access to terraforming technology, which can be used to minimize, even reverse, the damage to the environment. The purpose of invading Earth was to use the superhuman beings that cropped up a bit more than a year there to build an army that could conquer the universe. I have tried calculating the consequences of the flagship being destroyed before, but it's only an estimate. Would the economic, environmental and human life toll be realistic?

  • $\begingroup$ Hi Tyson. Please remove one of your tag and replace it with reality-check. Thanks. $\endgroup$
    – JBH
    Dec 2, 2020 at 18:40
  • $\begingroup$ It's unwise to argue with each answer. They are rightly pointing out the issues and the implausibles that you asked for. Use their feedback to improve your story and your narrative. $\endgroup$
    – user535733
    Dec 2, 2020 at 19:32
  • $\begingroup$ I will. I do understand their feedback, and I do hope to add them to my story. As there is after all, beings powerful enough to affect weather patterns and geniuses capable of reverse-engineering alien tech in my story's narrative. $\endgroup$ Dec 2, 2020 at 20:05
  • $\begingroup$ "She serves for 8 full years": Am I to understand that the humanity was unified by being conquered by the peace loving and totally altrustic United States of America? Many countries of this world do not even have presidents; many others have purely decorative presidents; only one country has an all-powerful president who is term limited to 8 years (or, with luck, up to 10). $\endgroup$
    – AlexP
    Dec 2, 2020 at 20:51
  • $\begingroup$ AlexP, humanity was forced to work together against a common adversary. Of course, people would be more in favour of a one world order afterwards, as united we stand, divided we fall. And she's proven herself to be an effective leader, being able to win despite being the underdog, and having great resolve and self-sacrifice. $\endgroup$ Dec 2, 2020 at 21:53

3 Answers 3


I'll start with a disclaimer, I'm really only knowledgeable about US procedures here.

Starting with the damage done by the opening salvo, I'm guessing that you're going with the 50mt that the Tsar Bomba was actually tested at, not the theoretical 100mt they thought they could get with u-238. A total casualty rate of only a billion for the whole war seems a bit small. The bombs/missiles would pretty much do that all by themselves.

The targets are actually more symbolic and demoralizing from my point of view. Yes the loss of life would be horrific, but with six days of prior warning none of the people that qualify as strategic targets would still be anywhere near them. You have to take into account that we spent 40 years planing for the other guys to nuke us, and even now there are still procedures and plans in place to assure the continuity of government. So I can't see the massive lost of command and control happening in that particular manner. I'd have them do a no-notice first strike if you want to knock out the majority of world leadership.

The fallout, assuming non-radioactive, would indeed be an issue, if you didn't have those "beings powerful enough to affect weather patterns and geniuses capable of reverse-engineering alien tech" on hand. Not the mention the friendly aliens with terraforming tech. Also, the amount of debris tossed in the air will depend heavily on whether those 50mt antimatter missiles were air-burst (and at what altitude) or ground-burst detonations. Air-burst actually has a larger destructive radius, but ground tosses up a whole lot more debris, for obvious reasons. Still at 50mt that's probably nitpicking.

The parts and debris from the mothership shouldn't pose a credible threat. You don't mention exactly how your heroes achieve it, but if the tech exists to scrap something twice the size and seven times the mass of good ol' Terra, then slowly floating parts are a non-issue.

The economy... eh, if we're retreating to the Challenger Deep, the economy as we know it is gone. It'll have to be rebuilt after the war, and after the clean up.

As for all of us coming together under one government? I personally don't have that much faith in mankind, but it could conceivably happen. I don't think it would be bloodless though. Or quick.

  • $\begingroup$ They're airburst, and the flagship is destroyed by overloading the reactor, causing a chain reaction that causes the reactor to explode with enough energy to tear the thing apart. So, there will be some debris, but the chances of it hitting Earth will be astronomically low, as most of it will either settle in an orbit with no chance of crossing Earth's, or get ejected out of the solar system altogether. $\endgroup$ Dec 8, 2020 at 17:41
  • $\begingroup$ Okay, so with airburst munitions in the 50mt range every capitol city is flattened, though it wouldn't do much to and of the infrastructure underground, so there could actually be survivors (subways, underground bunkers, and whatnot). $\endgroup$
    – Teak
    Dec 8, 2020 at 19:59
  • $\begingroup$ Also, I miss-read the part about the four invasion points, thought those were Earth-side forces. With only four invasion points, the war might not even last a month. Nukes are a thing (nothing you've mentioned takes them out of play) and the majority of the world's armed forces are largely intact (from the data you've given), If we can find them, they're crispy critters. $\endgroup$
    – Teak
    Dec 8, 2020 at 20:12
  • $\begingroup$ The complexes are designed so that a tactical nuke won't do much to them. And, the giant forcefield they provide will probably block the path of launched nukes. $\endgroup$ Dec 8, 2020 at 21:22
  • $\begingroup$ Tactical nukes are kind of a myth of politicians. The tactical part is more about the delivery system as opposed to the actual yield (some were up 100kt Hiroshima was only 15kt). If 195 cities are now gone, nobody would be worried about staying at the low yield, single shot response. The forcefield changes things, but maybe not by much. Does it protect from radiation? Are the aliens even susceptible to it? Most living things are, but fiction so it's possible. If it can block simultaneous detonations of multiple megaton warheads, without being overwhelmed, you could negate a nuclear response. $\endgroup$
    – Teak
    Dec 8, 2020 at 21:58

"Graveyard Earth" theme park opening soon.

According to research, 100 "small" nuclear weapons is enough to initiate a nuclear winter lasting a decade, with temperatures dropping 4C.

Ok, that is from 100 nuclear weapons in the 250Kt range.

Now substitute that with 195 Tsar Bombas, each 400 times as powerful. That is more than the combined nuclear power of all nations on Earth at present. About 1.2 billion will die in the direct blast. 3.3 million square kilometers of the earth surface will be set on fire by the light flash from the explosions. That's 13.7 times the surface area of the whole UK. With all the resulting smoke and ash ending up blocking the sun.

Think glaciers in London, and icebergs floating through the bahamas. Complete and utter crop collapse.

The Human race will be relegated to alien-run homeless shelters, and charity. Human "civilization" will be gone.

  • $\begingroup$ Black comedy 101. And the terraforming tech is used to keep the planet usable for the aliens, and once within human hands, keeps the planet usable. And they brought crops and livestock that can survive the new planetary conditions, so that's why Earth is still usable. But the damages would force human populations to stay low for the next few decades, and it is a costly victory. And I've even looked into the nuclear winter, and I estimated that temperatures would drop by 5 K/year for the next two years. $\endgroup$ Dec 2, 2020 at 18:53
  • $\begingroup$ "a nuclear winter lasting a decade, with temperatures dropping 4C." Great. Now I know what kind of final solution ecofascists (I'm talking about actual ecofascists here, as in fascists co-opting ecological conservation for their purposes, classic example of ecofascist is anyone claiming something along the lines of "overpopulation in africa causing global warming") are going to suggest soon. $\endgroup$
    – M i ech
    Dec 2, 2020 at 20:35
  • 1
    $\begingroup$ Temperatures dropping by 4 °C for a few years is not global winter. InEurope, for example, average temperatures were 4 °C lower than at present in several occasions during the last not more than 2,000 years. People survived just fine. If you look at painting of Dutch Old Masters, such as Pieter Brueghel the Elder, you will notice extensive snowy landscapes, which do not ever happen in the Low Countries nowadays. $\endgroup$
    – AlexP
    Dec 2, 2020 at 20:43
  • Destroying the flagship, at 6 lighthours (some 45 AU) distance, should have little impact.
  • The big bombs will kill significant numbers of people. Each of them killing 5 million might be in the right ballpark, give or take a factor of 10, if they really go against each and every capital. (Port Moresby gets one, but New York doesn't? Are the aliens nuts?)
  • The breakdown of commerce will kill more, but not immediately.
  • I don't see how "utter and complete breakdown of society" and "unify humanity as one" can be in the same event. Perhaps military command and control breaks down (but what about Offut or Cheyenne Mountain?), but either society holds or it does not. You cannot have both.
  • $\begingroup$ Well, there's the debris. The intense flash of energy is too far away and has too little duration to really mess stuff up, as for the capital cities, they're the capital cities of countries. New York City gets wrecked by a kaiju fight. Evacuation efforts would minimize death tolls, and the scope and danger of the crisis will force humanity to unite as one or die. From the ashes of the old comes the new. But while unlikely, a chunk of debris that's at least a few kilometers wide could slam into the Earth and kill everyone. $\endgroup$ Dec 2, 2020 at 18:47
  • $\begingroup$ @TysonDennis, that debris would take much too long in flight. While it is not exactly comparable, consider the events when Shoemaker-Levy hit Jupiter? Mankind watched for weeks and months. $\endgroup$
    – o.m.
    Dec 3, 2020 at 5:03
  • $\begingroup$ The debris may take years, decades, even centuries, to reach Earth’s orbit, but while the possibility of planet-threatening debris hitting Earth is incredibly slim, it’s still there. Atmospheric reentry probably won’t completely burn up a miles-wide chunk of space metal. $\endgroup$ Dec 3, 2020 at 5:40
  • $\begingroup$ @TysonDennis, by then Earth should be able to build a dug to deflect the fragment. $\endgroup$
    – o.m.
    Dec 3, 2020 at 5:47
  • $\begingroup$ Yeah, we could use satellites or something to keep the debris away! Or build a dome and make the aliens pay for it! That’s what a majority of us Earthlings would be thinking afterwards. Even though #notallaliens $\endgroup$ Dec 3, 2020 at 6:00

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