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You win again, gravity!
Zapp Brannigan, Futurama

When it is mentioned at all, the force of gravity is often portrayed as a sort of cosmic quicksand, an intractable mire that can yank spacecraft out of the sky without any consideration of inertia. Frequently accompanied by exclamations like, "We're caught in the planet's gravitational field!" or "We're being sucked in!"

Black Holes are particular offenders of this nature, not only in fiction but also in many people's perceptions in the real world. Few people seem to understand that a black hole will exert (roughly) the same amount of gravitational force as the star it was formed from[1].

The trope stems from a naive Aristotelian view of gravity, coupled with Space Friction. After all, a baseball falls to the ground; why shouldn't a spaceship? The answer, of course, is that the ship is falling, it's simply missing. If the ship is moving at any significant speed relative to the planet, in a direction other than straight up or straight down, its momentum will carry it past and it won't actually hit. This, boys and girls, is called an "orbit". Unless something like a gas cloud acts on the ship to slow it down, it will continue to miss the planet until slight variations in the path happen to bring it into the planet itself, which can take quite a long time.

As The Hitchhiker's Guide to the Galaxy tells us, flying is simply the art of throwing one's self at the ground, and missing...

Despite this, fictional spacecraft have the nasty habit of plummeting from the sky like bricks the moment their engines go off-line.

A related subtrope involves a spaceship trying to escape a Black Hole or other gravitational Big Bad by pointing the ship straight upwards, with the implication that it will fall back and be destroyed if the fuel runs out or something breaks. A more sensible approach would often be to thrust laterally, setting up a stable orbit and buying the Good Guys time to fix things. But that's not as dramatic, is it?

A subtrope of Space Does Not Work That Way and the cousin of Space Friction. See also Gravity Master, when a character has the power to control it.

Examples of Gravity Sucks include:


Anime

  • In Dragon Ball, the gravity from King Kai's miniature planet, which manages to be pull at 10 times the force as on Earth despite its size, doesn't affect anything unless it gets within a few hundred feet, then you immediately get pulled toward it. To be fair, that is in the afterlife, so there's no reason the physical laws would be the same, or even exist. Actually it's all about the radius, a few hundred feet is at least 10 times its radius, so according to that by that distance it would only be one tenth of Earth's.
  • In Pokémon: Giratina and The Sky Warrior, there is A LOT of sucking in and out of the Reverse world through super gravity portals. It happens so much, it's not even funny.

Film

  • When Mike crashes into, then attempts to save, the Hubble telescope in MST3K: The Movie, it immediately drops away and falls to Earth. An incredulous Mike points out that it couldn't possibly do that.
  • Star Trek III the Search For Spock. When the Enterprise's Self-Destruct Mechanism activates, the explosions in the saucer section are sufficient to knock it out of orbit and plummet dramatically as it burns up in the atmosphere.
  • In the 2009 Star Trek film, Kirk, Sulu and Ensign Ricky drop straight down toward Vulcan's surface as soon as they jump out of the shuttlecraft.
    • Perhaps justified since the Big Bad's ship is clearly not orbiting the planet either and the shuttlecraft is approaching much slower than orbital velocity. It is likely both are using antigravity technology.
  • In Star Wars, the Star Destroyers fall (into a planet, moon or even Death Star) immediately after being severely hit. Fridge Logic hits when you realize this doesn't happen to the Death Star at Endor.
    • Very clear example of this in Revenge of the Sith. The Separatist flagship gets shot once too often and promptly plunges straight down. The massive deceleration that would have been needed to allow this would probably have flattened everyone on board the ship.
      • Or it was just floating instead of being in orbit.
      • The Super-Star-Destroyer-into-Death-Star was explained in the novel as them being at full speed maneuvering through the battle, and that A-Wing crashing into the bridge disabled the controls and the entire command hierarchy. If they hadn't been aimed directly at the Death Star, then they could have reestablished control from engineering and brought her back around. As Imperial designers were more concerned about a mutiny than the 1-in-a-million chance that you would be aimed at an object large enough to do damage when the bridge is destroyed, it wasn't designed to be easy to do.
  • The Astronaut Farmer has loads of horrible physics, but one shining example is the eponymous character's reentry. After a de-orbit burn lasting less than a few seconds, the craft appears to stop, and just drops straight down.
  • Supernova has one scene where the medical ship Nightingale drops like a rock toward a moon as soon as it completes its FTL jump. Most of the movie's physics are accurate, but the ship would have retained the velocity and momentum it had before the jump. Even if the ship's velocity relative to the moon was below the moon's escape velocity, it would not have plummeted straight down.
  • The logical (illogical) extension of this occurs in Treasure Planet. The absence of gravity is the presence of antigravity. When the ship's gravity generators fail, everything falls up immediately -- and continues to accelerate upwards, even if it isn't touching anything else. Which begs the question of why they didn't just build everything on the ceiling and forgo the gravity generators.

Literature

  • Inverted Trope in Charlie and the Great Glass Elevator. When the Elevator gets "too high", it spontaneously starts orbiting the Earth.
  • Actually averted in the Star Wars Expanded Universe novel Vector Prime, where the weird gravity device used by the Yuuzhan Vong to Colony Drop Sernpidal's moon onto the planet does not cause a "sucking" effect, but instead the moon's orbit decays more or less realistically every time it passes over the device. Not that there's anything realistic about a superweapon that produces a gravitational force greater than a planet's.

Live Action TV

  • In the Doctor Who episode "Voyage of the Damned", the starship Titanic begins to predictably crash into the Earth as soon as its engines fail. This might be justified, though, as the ship's owner was planning to crash it, so it was already on a collision course to begin with.
    • Let's not forget "The Impossible Planet", where the Doctor repeatedly says that it's "impossible" for a planet to be in orbit of a black hole - and when the artificial gravity machine fails, the planet gets sucked straight inward, as is the spaceship in which the humans are trying to escape.
      • While its definitely not true that a planet orbiting a black hole is "impossible", the planet in question seemed to be very close to the black hole, probably too close for a stable orbit. Without the Phlebotinum field, it's likely that tidal forces would have spaghettified the rock at that distance.
  • An example of failing to recognize what an orbit is shows up in Stargate Atlantis. In "Inferno", they jump a ship to "orbit" using the hyperdrive and magically going into orbit (their sublight propulsion/maneuvering system was inoperable at the time). In reality, the ship would start to fall. Fast. Usually the problem of orbit vs. altitude is handwaved via the same mechanism which brakes the ship as it goes sub-light. That's the kind of thing which makes it so hard to make an actually realistic space simulator appear as realistic to the layman.
    • If the ship had a relative velocity to the planet when it's sub-light engines went offline and assuming that that their hyperdrive physics preserve pre-jump velocity when they exit hyperspace they could establish orbit by jumping in to the correct location for their initial velocity relative to the planet to cause them to enter a stable orbit. This would however require quite a lot of calculations.
    • Surely it could jump to geosynchronous orbit or a similar period orbit?
      • Every hyperspace jump shows the ship still moving at its original speed afterwards, and the ship in question had a velocity: Before the hyperspace jump it was being shot into the air by a supervolcano eruption. They used the hyperspace jump just before the eruption would have destroyed the ship, but they didn't really have time for the calculations, since the ship was just repaired when they thought up the plan and the explosion happened less than five minutes later.
  • In an early episode of Mystery Science Theater 3000, a number of space dog skeletons (or whatever they were called) were piling up onto the space station in such numbers that they were weighing the station down to the point where it was dropping the orbit. Remember the MST3K Mantra.
  • Star Trek the Original Series may be an example of this; loss of power will usually result in a "decaying orbit" with a time to impact measured in hours. For this to be true, the "standard orbit" must be ridiculously low, on the order of 50 miles. However, said "standard orbit" seems to never have the ship out of line of sight communication with the landing party, suggesting a geostationary orbit, which would be much higher for any reasonably Earthlike planet.
    • Easily resolved! "Standard orbit" is not a free-falling orbit at all - rather, it is planetostationary but atmosphere-grazing and requires continuous thrust from the engines to maintain. We don't do that with our existing spacecraft because we cannot possibly provide the necessary thrust, but a starship has energy and to spare. So you get the benefit of being in low orbit but line-of-sight, and the dramatic license to have interesting things happen when the power fails (a thousands-to-one long shot which, of course, affects the Enterprise with suspicious regularity).

Video Games

  • Unreal features Na Pali, a planet that is notorious for puling ships into its gravity field.
  • In Galaxy Angel II Zettai Ryouiki no Tobira, Kahlua loses control of her ship because it will only respond to her Super-Powered Evil Side, and it plunges toward a planet.
  • In Defense of the Ancients, the Enigma's Black Hole Last-Disc Magic Limit Break acts like the stereotypical black hole, sucking stuff towards itself.
  • The actual phrase appears as a graffiti in a prison cell in Space Quest 6.
  • As in the Film examples, Star Destroyers in the Star Wars Rogue Squadron series are prone to make sudden vertical 90-degree turns as soon as they're critically damaged; Rogue Leaders who aren't careful during the Battle of Endor will suddenly find the Star Destroyer they'd disabled swooping forward to crash into them.
  • Touhou has Suika and her ability to manipulate density. As this includes the creation of Black Holes, this trope is naturally present in the games she appears in.
    • Also Utsuho and her last spell card in TH 11. Koishi of the same game has a similar spellcard, but it pushes you away instead -- to a wall of danmaku with KILL written all over it.
  • Recca has this boss who fires out two kinds of gravity wells, blue ones which suck your ship towards them and white ones that repel your ship. Note that this is an NES game...
  • In Halo, Pelican dropships are shown dropping like a stone the second they are released from the ship suspending them above the surface of the planet below. Possibly justified if the parent ship deliberately flies low enough before releasing its cargo, but that's certainly not how it looks in the game. Notable because, like a lot of Halo, it is cribbed from Aliens.
    • Justified in that the dropships aren't just released, there is a minor propulsive force to put distance between the Pelican and the ship. Even then, they don't fall - they drift along until they engage their own propulsion. A more extreme mechanism is used for the ODST drop pods - they aren't dropped, they're literally shot out of the ship.
  • In Dead Space, the Ishimura ends up in a decaying orbit, and you have to restart the engines, and later Kendra tries to kill you by dropping a piece of the planet on you.

Western Animation

  • Explicated averted in The Magic School Bus episode "Out of This World". It helps that it's a science show.

Web Original

Notes

  1. When you're at the same distance from the center of the black hole as you were from the center of the original star, that is, assuming that distance is greater than the radius of the original star itself. If you go to a spot near the black hole that would have been inside the radius of the original star, the gravitational force will exceed that for the star at the same distance. And if you pass the black hole's event horizon, you can only go inwards, no matter how hard you try not to.
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