The alien spaceship, disguised as a rogue planet falls into a parallel orbit with earth around the sun. The aliens send a message to earth that is unlike any other message ever received by human beings.
In the “old” days, an author would consult a scientist on the technical aspects of their story. But today, there is artificial intelligence instead. To see how I do this read below my conversation with artificial intelligence as we explore the science behind an alien spaceship, cloaked as a rogue planet, coming alongside the earth in a parallel orbit.
Chat history
You said:
Assume a second planet approximately the same size of earth falls into solar orbit exactly twice the distance from the earth to the moon. also assume the second planet was on the same plane as the moon’s orbit. As the moon circles the earth it approaches the mid-point between the rogue planet and its native planet. At that precise point, the moon veers off only to complete its circle by now going around the rogue planet. Upon concluding its circle around the rogue planet, it again approaches the mid-point between earth and the rogue planet. And again, at that precise point, the moon again veers off only to complete its circle by now going around the earth. And thus, the moon establishes a new path that treks around both planets in a figure eight pattern.
ChatGPT said:
Thought for 52s
Fun setup! If we keep Newtonian gravity and donât add propulsion or âmagic,â the figure-eight swap you describe wouldnât persist. Hereâs whyâand what would actually happen.
What two near-Earths do to a Moon
- Geometry you gave: second Earth-mass planet on the Moonâs orbital plane, separation = 2 lunar distances â 7.69Ă10^5 km between the two planets.
- For two equal-mass bodies, the L1 point (the saddle between their gravity wells) sits right at the midpoint. Thatâs only 1 lunar distance (â3.84Ă10^5 km) from each planetâexactly where our Moon currently lives.
The bound zone around each planet shrinks
Use the standard Roche-lobe/Eggleton estimate for how big a region can remain gravitationally bound to one body in a close binary (mass ratio q=1):rLaâ0.490.6+lnâĄ(2)â0.379arLâââ0.6+ln(2)0.49ââ0.379
- With a = 7.69Ă10^5 km (planetâplanet separation), each planetâs lobe radius is r_L â 2.91Ă10^5 km.
- The Moonâs distance (3.84Ă10^5 km) is outside either planetâs lobe, so it cannot stay stably bound to just Earth (or just the new planet).
The midpoint isnât a âswitch,â itâs a knife-edge
- The midpoint (L1) is unstable. A tiny nudge decides which gravity well wins.
- To âswitch ownersâ on every pass, the Moon would need exactly the right energy and phase each timeâan unrealistically precise, actively stabilized trajectory. Any tiny perturbation (tides, solar gravity, planetary oblateness, atmospheric drag on Earth isnât relevant at that height, but solar tides are) would break the pattern quickly.
What dynamics youâd really get
One of these (all are chaotic on human timescales):
- Chaotic transfers then impact/ejection. The Moon would surf the saddle region, suffer large energy kicks, and likely either hit a planet or get ejected to a distant solar orbit.
- Circumbinary orbit (P-type) around both planets. Stable only if far outside the pairârule of thumb: â„ 2â3Ă the planetâplanet separation. Here thatâs â„ 1.5â2.3 million km, far beyond the Moonâs current 384,000 km. The Moon would need energy gain to reach that; naturally, itâs more likely to be flung than neatly parked.
- Temporary captures (âexchange orbitsâ). You might see a few messy loops around one planet, then a lurch to the other, but not a clean, repeating figure-eight.
âBut Iâve heard about figure-eight orbitsâŠâ
There is a famous three-body âchoreographyâ where three comparable masses chase each other on a symmetric figure-eight around their common center of mass. That solution does not apply here: our masses are very unequal (two Earths vs. a 1/81-Earth Moon), and your Moon isnât one of the equal primaries.
Tides and planet stability (the backdrop may be apocalyptic)
Two Earth-mass worlds only 7.7Ă10^5 km apart would raise enormous tides on each otherâstrong torques, rapid spin synchronization, internal heating, likely intense tectonics and volcanism. Even before we worry about the Moon, the two planetsâ mutual tides could evolve the separation and spins quickly, further destabilizing any lunar path.
Bottom line: with two Earth-mass planets only 2 lunar distances apart, the Moon canât stay bound to one, and a clean, repeating figure-eight swap between them isnât a natural, stable orbit. Youâd get brief, chaotic trading at bestâfollowed by collision, ejection, or (with help) a distant circumbinary capture.
You said:
Assume one planet is actually an alien vessel disguised as a rogue planet that exerts an artificial gravity to maintain the figure 8 orbit. how would this affect earth?
ChatGPT said:
Thought for 38s
Cool twist. Two very different outcomes depend on how âartificial gravityâ works:
A) It behaves like real gravity (i.e., it pulls on Earth too)
If the disguised vessel produces a field equivalent to a big mass (say, ~Earth-mass) at ~2 lunar distances (~7.7Ă10^5 km from Earth, per your setup), then Earth and the vessel form a tight binary planet:
- Binary period â 55 days. Earth and the vessel would orbit their shared barycenter about every ~55 days, each wobbling with a radius ~3.8Ă10^5 km.
- Tides: ~10Ă stronger than todayâs lunar tides. Tidal forcing scales like M/r3M/r3. An Earth-mass at twice the lunar distance delivers ~10Ă the Moonâs present tidal torque. Expect regular, basin-filling tides (tens of meters), extreme coastal erosion, recurrent flooding, and powerful tidal currents. Many coasts become uninhabitable.
- Spin & interior: Gigantic tidal torques would lengthen Earthâs day rapidly and heat the interior (enhanced volcanism and quakes).
- Climate: The 55-day barycentric wobble changes EarthâSun distance by ~±3.8Ă10^5 km (~±0.26%), modulating solar input by ~±0.5%. Thatâs small compared with seasons, but itâs a persistent new rhythm; the tidal/oceanic chaos would matter far more than direct insolation changes.
- Satellites & space ops: GEO/MEO/HEO orbits get strongly perturbed; station-keeping costs soar. Cislunar trajectories become treacherous.
- The Moon: Your figure-8 path can be maintained, but the Moon repeatedly crossing the two planetsâ Roche/tidal zones risks fragmentation into rings if passes get too close, or chaotic energy kicks that ultimately eject or impact it unless the aliens keep guiding it.
Bottom line for (A): civilization-scale upheavalâcoasts re-drawn, infrastructure wrecked, faster day-length drift, heightened seismic/volcanic activityâunless the aliens deliberately keep their effective mass much smaller than Earthâs.
B) Itâs âselectiveâ gravity (they only tug the Moon)
If their field couples mostly to the Moon (sci-fi violation of the equivalence principle), Earth doesnât feel a big direct pull. You still get major knock-ons:
- Wild, time-varying tides anyway. Even if Earth isnât pulled, the Moonâs distance and track are being reshaped on each loop. Since tidal strength varies as 1/r31/r3, the tidal range would swing dramatically over the figure-8 cycleâpotentially large enough to be hazardous during the closer passes.
- Angular-momentum bookkeeping: Theyâre injecting/removing energy from the EarthâMoon system. That shows up as changes in Earthâs rotation rate (length-of-day jitter) and in the Moonâs long-term semi-major axis unless they actively counter it. Earthâs precession/nutation would also be altered.
- Seismic/volcanic responses: Rapidly changing tidal stresses can trigger quakes and modulate volcanic activity (small to moderate increases are plausible).
- Satellites & navigation: The Moonâs moving gravity well sweeps through unusual geometries; expect orbit perturbations, more eclipse events, and frequent ephemeris updates for navigation systems.
- If loops get too tight: Close Earth passes (<~2â3 Earth radii above the surface) risk Roche-limit tides on the Moonâpartial shedding (a transient ring) unless the aliens keep safe stand-offs.
Practical knobs the aliens would need to turn
- Cap effective mass/gradient to keep coastal tides tolerable (e.g., †current lunar tidal forcing).
- Hold the Moonâs perigee outside dangerous resonances and the Roche limit.
- Actively conserve system angular momentum to avoid runaway spin-down of Earth or ejection of the Moon.
- Provide satellite âtraffic controlâ windows so GEO/MEO donât get destabilized during tight loops.
Short take
- If their âgravityâ is ordinary and strong: Earth gets a catastrophic, 55-day binary-tide worldâcivilization-threatening.
- If they can target only the Moon and finely modulate forces: Earth avoids the worst, but still faces erratic mega-tides (at times), rotation jitter, more quakes/volcanism, and messy orbital dynamicsâserious but survivable with planning and with the aliensâ careful babysitting.
ChatGPT can make mistakes. Check important info.

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