• Critical to the plot, Earth needs to be taken out of the Sun's orbit around 2050 (i.e., not destroyed; nor merely darkened via "indirect" solutions such as alien Dyson swarms surrounding the Sun, blacking out the sky as in The Matrix, etc).
  • Therefore, either the Sun has to be destroyed (including its mass), or the Earth needs to be accelerated by a further 12 km/s to achieve escape velocity from the solar system.
  • This needs to happen with a warning period (e.g. 2 - 10 years) so that civilization has a change to get at least minimally ready, such as beginning underground bunker construction; the Earth's surface needs to remain at least somewhat habitable during this period.
  • The Earth itself has to be preserved in a more or less intact way (though Hollywood style disasters like earthquakes, tsunamis, etc. are perfectly fine and even welcome).
  • Source of disruption has to be within ~75 light-year "cone" of Earth, i.e. half of the time period from when we first started radio emissions (though can be handwaved if necessary).

Potential Solutions

Destroying the Sun's mass

  • Massive increase in coronal mass ejections (Problem: Masses involved are far too big to be realistic, and if this happens, Earth will be fried).
  • Sun going supernova prematurely. (Problem: Earth will get fried).
  • One of Peter Hamilton's ideas: Nanomachines that exponentially multiply and transmute Sun's mass into elements that don't support fusion. (Problem: Sun's mass remains, so Earth doesn't deorbit).
  • Micro-black hole tossed into center of Sun. (Problem: Will dissipate quickly due to Hawking radiation; the radiation pressure around its accretion disk will be too hot for any of the Sun's mass to actually fall into it; finally, the mass itself will remain, so Earth will remain in orbit anyway).

Therefore, I see no physically plausible way of doing it this way while fulfilling most of the conditions.

Knocking the Earth itself out of orbit ( Passing Rogue Planet or Rogue Star)

This seems a slightly easier challenge, since the Earth is so much smaller than the Sun.


  • We know this happens frequently in the early stages of solar system formation; it's been estimated that half the planets in our galaxy are rogue/"Steppenwolf" planets.
  • Passing rogue planet knocking Earth off orbit is what happens in the short story "A Pail of Air" by Fritz Leiber.
  • Is physically plausible to laymen, so the fine details can be handwaved, if necesssary.


  • The Rogue Object ("RO"), if it is traveling fast (which it probably has to be if it was launched within the past 150 years), will also have to be very heavy to exert sufficient gravitational force on Earth to fling it out of orbit as it passes by. I assume that all such objects, even rogue neutron stars and rogue black holes, would have already been detected within at least a 50 light year vicinity of Earth?
  • If the RO is a rogue planet, then it will have to pass by the Earth more slowly, and closer to it, which risks running into the Earth's Roche limit and breaking it apart entirely.
  • What would be the best way to triangulate between these considerations, i.e. less mass and higher speed for the RO; and non-violation of Earth's Roche limit?
  • What would be the mathematical formula relating the mass and velocity of the rogue object, the mass of the Earth, the closest distance between them, and the resulting acceleration of the Earth?

Knocking the Earth itself out of orbit (exotic possibilites)

Focused gravitational beam, perhaps channeled through a wormhole "tethered" to Earth and a massive body somewhere else in the galaxy. The Earth's orbit slowly, but at an accelerating pace, becomes elliptic, and eventually flies off into space.

Problem: Requires some major handwaving. Gravity is far weaker than the other forces, and most likely can't really be focused as we don't know of any materials that can reflect them

Perhaps alien civilizations have mastered energy-to-mass conversion to such an extent that they can fire off a beam of focused energy (at light speed), then have it convert to mass object at a time of their choosing, such as a chunk of neutronium.

Problem: Fantastical.

There must be many other possibilities I haven't considered, though I suspect many of them will be more and more purely fantastical. But I'll be happy to hear more suggestions.

Thanks in advance for your input!


closed as too broad by Azuaron, James, L.Dutch, JDługosz Apr 4 '17 at 6:09

Please edit the question to limit it to a specific problem with enough detail to identify an adequate answer. Avoid asking multiple distinct questions at once. See the How to Ask page for help clarifying this question. If this question can be reworded to fit the rules in the help center, please edit the question.

  • $\begingroup$ have you given a look at worldbuilding.stackexchange.com/questions/72181/… ? $\endgroup$ – L.Dutch Apr 3 '17 at 12:49
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    $\begingroup$ Just so you know, de-orbiting is usually used to refer to satellites that are crashed into the Earth's atmosphere. So the phrase 'Earth quickly de-orbit the sun without being destroyed' makes literally no sense. I think you want to say 'How quickly could the Earth be removed from the Sun's orbit..." $\endgroup$ – kingledion Apr 3 '17 at 13:10
  • $\begingroup$ Most of the earth is just dead mass. What do we want earth core for? Build a space elevator or launch loop or orbital ring or... (many plausible ways to space) and start building huge spaceships with fusion rockets. Get out the way of the disaster and you will have somewhere to live while you look for another planet, or decide you like living in space. $\endgroup$ – Donald Hobson Apr 3 '17 at 17:22

The "easiest" solution would be a rogue object, but it's still not easy to make it work.

A "dark star" would need to be large enough that it could not avoid radiating massively in the infrared. At 0.05 solar masses you still have a magenta dwarf. Micro-black holes and neutronium stars also radiate massively through their accretion disks.

To minimize damage (as much as possible), you would need such an object to approach Earth along the ecliptic. Possibly, by composing carefully the Solar System's own motion, we can make it so this object is not itself orbiting the Sun. This would mean having the encounter in early Spring.

Then the Earth gets accelerated towards the object (its orbital radius increases) while the object approaches, it misses the object itself (this is the awkward moment in which the planet is devastated by tides in both oceans and its liquid mantle, causing tsunamis and earthquakes), and finally gets launched towards outer space at a speed comparable to the rogue object's final approach speed.

The more massive the object, the farther out can the Earth be at periastron, which reduces tidal damage but increases the object's chances of being detected. Also, if its radius of significant influence increases too much, it will have disruptive effects on the Solar System while it's still far enough not to be able to deorbit Earth.

On the other hand, a black hole with no significant accretion disk might not be detected until it's close enough. It would reacquire an accretion disk passing through the Sun's Oort cloud, though.

A far more fantastic possibility is that of a very focused stellar jet coming by and destroying the Sun. It would need to be a jet almost perpendicular to the ecliptic. The Sun would be accelerated (in reality, not very much, I suspect) and, if the acceleration was enough, the Earth would find itself left behind.

The same thing could perhaps be accomplished with a black hole of several solar masses and sufficient speed to capture the Sun around itself and whip it away, but the resulting irradiation would probably be enough to sterilize the Earth (assuming there was no colossal explosion soon after the impact).


Nope, sorry.

Without heavy handvavium this is not going to happen. If you will remove Earth tto from the Goldilocks zone, temperature will drop. First water will freeze. Then, plants and animals will die. Then, atmosphere will condense and partially freeze. End of the life as we know it. Without atmosphere, each and every rock close to Earth would hit surface directly, with nothing to slow it down. Face of Earth would change. UV radiation will split water into hydrogen and oxygen. Hydrogen will escape. You need to be fast to return Earth to it's original position. No matter how fast, you will not make it to any other star.

And by the way, in the process we are going to either crash with the Moon, with instant disastrous effect, or lose the Moon and it's stabilizing function. Maybe Moon isn't really needed, but what if it is?

Rogue object?

As long as you are not close enough to cross each other's Roche limit, this might work. But remember that you need something heavy. Really heavy. If you don't want to destroy our solar system altogether, let me suggest a couple bodies that would throw Earth further and further away. Perpendicular to the ecliptic, to minimize strength of interactions with other planets. Of course, this would ultimately destroy Earth, but maybe, just maybe, not instantaneously, not in a way directly related to this knocking out mechanism.

  • $\begingroup$ Using more objects is more difficult to explain, but it's a great idea! You can have smaller objects and still get the same effect in the end. $\endgroup$ – LSerni Apr 3 '17 at 13:31
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    $\begingroup$ This needs to happen with a warning period (e.g. 2 - 10 years) so that civilization has a change to get at least minimally ready, such as beginning underground bunker construction; the Earth's surface needs to remain at least somewhat habitable during this period.- As stated in this answer, with orbital bombardment and low temperatures with no atmosphere, the tech level of this civilization would need to be MUCH more than we have at present and and with this tech level it could be more plausible to just avert the disaster entirely $\endgroup$ – Cameron Leary Apr 3 '17 at 14:38
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    $\begingroup$ Of course moving Earth from the Goldilocks zone is going to drop temperatures and rapidly make surface life unfeasible - that's the whole point! :) I am interested in exploring what happens and whether humans could survive. Since there's geothermal power, and air and water (if now large in frozen form), survival should still be a bit easier than in many generation ship scifi stories. $\endgroup$ – ak7 Apr 3 '17 at 14:55

Assuming it's a case of Calculate a solution, or everyone on Earth will die, we could reasonably expect the world's astrophysicists, aerospace engineers, etc. to commandeer virtually all the computing resources of Google, Facebook, Apple, etc.

Expanding on the possibilities of the Butterfly Effect, it seems to me we (just! :) need to work out a careful series of "nudges" (to asteroids and other celestial objects whose trajectories we could feasibly adjust) that would progressively destabilise larger bodies (Jupiter, Saturn, etc.) in such a way that the Earth gets gravitationally accelerated right out of the Solar System.

Given that many scientists think Jupiter kicked a giant planet out of the solar system 4 billion years ago with no intelligent species carefully setting up the situation, I don't see why we couldn't do something similar for our little planet.

We might have a problem keeping warm in the depths of interstellar space, but I'm gonna assume that as soon as we have that first butterfly wing flap worked out, we'll devote all our computing power to developing AI's to sort out the heating problem before we get too far away from the sun.

  • $\begingroup$ Er The butterfly effect will only let you escape on millions of years timescales. This is how long it takes little nudges to grow. $\endgroup$ – Donald Hobson Apr 3 '17 at 17:17
  • $\begingroup$ @Donald: Surely it all depends on which nudges are used? I'm assuming the boffins could calculate the combined effect of thousands (millions?) of different "nudges" applied in a carefully-orchestrated sequence, and that they would obviously select a series that would have the desired effect within the available timeframe. Do you know of some reason why such an approach is impossible, as opposed to simply difficult? $\endgroup$ – FumbleFingers Apr 3 '17 at 17:48

You could have a close encounter with something like a rogue gas giant, that flings earth out of its current orbit (with massive earthquakes and insane weather effects). If that orbit then happened (through a horrifically unlikely but theoretically possible co-incidence) put it onto a gravitational assist with a number of other gas giants similar to how voyager 1 and 2 did it then with a bit of hand waving you could get solar system escape velocity without needing to add all that energy in the initial interaction.

The whole scenario is still pretty far fetched but you might be able to get something to work with that way.


Your list of approaches is not complete.

I don't think there's any way to boost the Earth by 12 km/sec without causing a lot of problems. It could be accomplished by an appropriately-aimed mass sent hurling through the solar system setting up a gravity assist maneuver. However, I see no way to avoid substantial tidal influence from the intruder. (It will need to be a degenerate body of some kind.)

You considered destroying the sun and quite correctly ruled it out. What about removing it, though? Since you talk about radio signals you are obviously considering aliens being behind this.

There are some malevolent ETs out there who have a legal problem. The law of their land does not permit them to harm developing races but they don't want the competition. Thus the easy answer of throwing an asteroid or the like isn't an option. They want us gone, though.

Thus they deploy some gravity manipulators around the sun that produce directional gravity. Material is drawn in from the sun, undergoes fusion (some of this power is tapped to run them) and ejects it out the back. Presto, rocket engine. Boost the sun by 12 km/sec and Earth is lost to the interstellar void where we die in the cold--but the aliens didn't harm a single human.

  • $\begingroup$ Loren Pechtel - yes they did, and the galactic police and courts will never accept that as a defense. PS if the aliens move the Sun, will the Earth be dragged along with it by the Sun's gravity? $\endgroup$ – M. A. Golding Apr 4 '17 at 5:26
  • $\begingroup$ @M.A.Golding You're assuming an honest system. I'm looking at compliance with the letter of a poorly worded law. As for the sun dragging the Earth--yes, but it will escape anyway. 12 km/sec is 12 km/sec whichever body moves. $\endgroup$ – Loren Pechtel Apr 4 '17 at 18:07

Possibly astronomers discover the mouth of a stable wormhole in the direction the solar system is headed toward. They calculate that most objects in the solar system will pass by the mouth of the wormhole.

But Earth, and maybe also the moon, will pass through the wormhole mouth and leave the solar system.

If astronomers can see through the wormhole mouth they can have some idea of what is in the area of space Earth is headed for, otherwise they will have no idea.

No doubt many will speculate that the wormhole is artificial, created by alien super science to take Earth out of the solar system.


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