Conveniently-Close Planet

That's just the Earth and the Moon to scale.^[1]

"Space is big. Really big. You just won't believe how vastly, hugely, mind-bogglingly big it is. I mean, you may think it's a long way down the road to the chemist, but that's just peanuts to space, listen..."

—Douglas Adams, The Hitchhiker's Guide to the Galaxy

Space is huge, and the distances involved are far beyond normal human experience. On Earth, if your car breaks down on a country road, you can reasonably expect a rest stop or a gas station within 50 km (ca. 30 miles). Space, however, is not like that country road. If you set your space RV in a randomly-selected trajectory and continue going straight until you get within 50 million kilometers of a star, the chances are astronomically high that you will reach the edge of the galaxy, keep going, and never enter another galaxy... ever. On the off chance you do stumble across a star system, the sheer amount of fuel required to correct your course, match the speed of the star system (since it, too, moves through space), find a safe planet to land on, enter its orbit, and touch down safely would be far too great for your jalopy of a ship to handle.

This problem exists even for space travel restricted to within a solar system. Objects travel in orbits and don't occupy the same place all the time - planets orbit their sun, and other objects orbit something else that orbits that sun. A planet does not occupy its entire orbit at once, either. For example, the position of the Earth in its orbit during June and the position during December is a difference of 300 million kilometers. A space traveler who doesn't check his Earth calendar might be in for an unpleasant surprise. Add to this the fact that the sun itself is in orbit around the center of the galaxy, and the galaxy is also in motion, and things become rather complicated very quickly.

Of course, you could also just find a nearby spaceport, but those tend to be around planets and stars, too - not out in open space - and they are in an orbit you need to get to and then match speed with, just like a planet. A typical low-earth-orbit spot such as the one the International Space Station occupies takes 90 minutes to go around the earth at 27,743 km/h (17,239 mph), but if you're going a little too fast or a little too slow you're going to overshoot/hit or trail it. If you have matched the orbit you could wait until your orbits sync back up, but this could take many, many 90 minute orbits.

The above in a nutshell: Nothing in space is ever close, convenient, or in the same place it was a minute ago.

This does not deter sci-fi writers, though! A chance to visit a Single Biome Planet or a planet with a dark secret offers far more story options than a spacecraft silently cruising for eternity, running out of power and with a group of mummifying bodies on board.

A subtrope of Space Does Not Work That Way and Artistic License Astronomy. A common side effect of Sci-Fi Writers Have No Sense of Scale. A sort of Artistic License Geography, though the term "Geography" isn't usually applied to space because it's so big and different.

If characters not only find a planet but land next to what they're looking for see It's a Small World After All. Keep in mind that having Faster-Than-Light Travel would make things conveniently closer, but carries a laundry list of issues of its own. When asteroids are frustratingly close to each other, it's an Asteroid Thicket.

Examples of Conveniently-Close Planet include:

Anime and Manga

• The very last shot of Eureka Seven shows Earth with a dust ring and the "heart-Renton-Eureka"-carved Moon at a distance roughly the diameter of the planet. In other words, at collision distance.
• In The End of Evangelion, the moon is close enough to get splashed with blood upon Lillith's death. As big as she is, and as powerful as the jet of High-Pressure Blood is, that's still conspicuously close.
  • There is No Friction in Space, so the blood eventually would reach the moon. It was just matter of cutting a few days wait until our beloved satellite would be splashed.
  • The blood still need to reach escape velocity, that's 11 km per second. Faster than most railgun.
• Seiren, to the point that Earth takes up a sizeable portion of Seiren's skies on a clear day.

Film

• The movie Pitch Black starts off with the spacecraft being damaged and needing to find a safe haven. The ship's computer succeeds at this but decides to wake up the crew only as it enters the atmosphere.
  • The movie also says that they would be saved if they can take the small spacecraft up to the shipping lanes and wait for a passing ship - except that set shipping lanes in space doesn't really work because planets don't stay put, but to be fair, the coordinates of the shipping lanes could be modular and vary as a function of time, at which point the shipboard computer could calculate what the shipping lanes look like at that moment but that would leave the problem of the frequency of which the ships travel down the lane, which has to be high in order for them to be found before they run out of life support which is problematic since there's no obvious toilet facilities on that tiny spacecraft with three people onboard.
• In The Empire Strikes Back, the crippled Millennium Falcon searches for a nearby system to have its hyperdrive repaired. Wow! Not only is there a nearby system with what they need, but Han's old buddy runs it.
  • We don't really know how long it took them to get there, but we do know that Boba Fett and at least a Super Star Destroyer arrived ahead of Han, Leia and C-3PO.
  • The novelization includes the fact that the Falcon has a backup hyperdrive that doesn't work very well or go very fast, so it took a few days, the equivalent of walking to the grocery store instead of driving.
  • Also in the beginning of A New Hope, extreme convenience occurs. The Empire attacks the Rebel ship just as they're flying over a planet with the one man who she expects can save her from capture.
    • Although this may have been due to Vader toying with her, so she'd do something that would confirm that she's a Rebel. He just grew tired of the wait, or got the proof he needed, while she was orbiting Tatooine.
• In Galaxy Quest, the NSEA Protector is badly damaged, but no worries - there's a conveniently close planet!

Fred Kwan: Hey, Commander. Listen, we found some beryllium on a nearby planet, and we might be able to get there if we reconfigure the solar matrix in parallel for endothermic propulsion. What'd'ya think?

• Alien³, it's not known what course the Sulaco would have plotted to return to Earth, but it is very convenient that it should be passing Fury 161 when the titular monstrosity set off the fire alarm and jettisoned the survivors.
• In the 2001 version of Planet of the Apes, Mark Walberg travels from an unnamed ringed planet to Earth in what seems like a few minutes (there's no toilet on that tiny spacecraft, so it can't have been very long). Even if the ringed planet was Saturn, that's still pretty danged close.
• In Spaceballs the Winnebago comes out of Hyperspeed and promptly runs out of gas. Cue nearby desert planet to land on.
• In Space Camp the space shuttle is unexpectedly launched outside of its launch window into an unplanned orbit - but they still manage to make it to the unoccupied space station for supplies.
• In Star Trek, the planet Delta Vega is an apparently Class M planet (terrestrial, breathable atmosphere, earthlike gravity) that's far enough away from Vulcan that Kirk is exiled there after the Enterprise has already sped away from the ex-planet and Kirk and Spock have had a long fight about what to do next; it's far enough away from Vulcan not to be pulled into the black hole created by the destruction of Vulcan; and yet it's close enough to Vulcan for Ambassador Spock to be able to see it unaided in the daytime sky, as big as the Moon from Earth, as it implodes. Star Trek does at least have the excuse of the fact that the Enterprise has FTL travel, which would make a brief stop to drop off Kirk much more likely.
  • Word of God says that Delta Vega might not have actually been that close—we only see Spock's unaided view of a large Vulcan in the Delta Vega sky during Spock's mind-meld briefing for Kirk, which was meant to be "impressionistic" (in the words of Roberto Orci). That said, Delta Vega is nonetheless so conveniently located that it manages to service at least three different plot threads.
• At the end of Space Cowboys, the satellite's boosters fire on a trajectory that conveniently gets to the moon - and quickly enough that Hawk's air doesn't run out on the way.
• In Another Earth a twin of earth appears near Earth.
• A Conveniently Close Chunk Of Planet in Superman. Doesn't take Lex Luthor long at all to score a chunk of Kryptonite, despite Krypton having been a planet around another star. Kryptonite Is Everywhere...

Live-Action TV

• In Stargate SG-1, the human-built starship Prometheus breaks down on her maiden voyage. Fortunately for the crew, there is a planet within a few second hop of their overloaded hyperdrive. It's worth noting, however, that the voyage by sublight engine would have taken longer than the ship had resources left for.
  • In season 4, Teal'c and O'Neill are dragged away from earth, set to drift to Apophis's homeworld the slow way. Lucky thing Jupiter just happened to be on the way, making it both conveniently close and in 2-D Space. However in this case as the glider's navigational computer probably plotted a course out of the solar system that included at least one slingshot in order to reduce the fuel cost (like we do when launching probes to the outer planets and beyond).
  • At the season four finale, the destruction of a sun speeds up their spacecraft, sending it four million light years, where it stops inside another galaxy. The odds of taking a random trajectory out of your solar system and ending up in another solar system are already stated above as huge - the odds of getting to another galaxy at a set distance on a random trajectory are just astronomical.
• The Stargate Universe plays it straight in the episode "Light", but has a nice aversion when they mention there are three planets they could fly to - but one they can't scan yet because it's on the other side of the star at the moment.
• Firefly takes place in multiple close-together solar systems that, according to the official materials orbit a massive red giant, but it makes a big deal out of how far apart things are. In the episode "Out of Gas", the eponymous ship breaks down in the back of beyond, and the crew is well aware that they are out of range of anything habitable by shuttle.
• In Space: 1999, the moon is thrown out of the solar system on an uncontrolled trajectory. Nonetheless, it passes close to a different alien planet each week.
• In the Doctor Who serial The Daleks' Master Plan, the planet Desperus just happens to be sufficiently close to our heroes' flight from Kembel to Earth that they can be forced to land there.
  • On a whole, the show is able to avoid this trope thanks to having a ship which teleports and time-travel. Of course, this trope is averted in the episode 'Amy's Choice'. The TARDIS breaks down, and Rory asks why they can't just send a call for help; "Of course, because the universe is really just a small place, and somebody's sure to be near by," is the Doctor's snarky reply.
• All five Star Trek series are guilty of this, though it's forgivable because, as stated here and at Sci-Fi Writers Have No Sense of Scale, a centuries-long journey between any two given inhabited places doesn't make a very interesting show. Anyway, many are the times something happens to a shuttlecraft. Not only is there almost always a planet nearby, it's almost always habitable enough for its occupants to survive for the time being.
  • In TOS, given the speeds at which starships are canonically stated to cruise, every planet in the galaxy is conveniently close. Kirk routinely flies the Enterprise away from the Planet of the Week at warp 1 (i.e. at, not faster than, the speed of light). Its maximum safe cruising speed is warp 6, which is either 216x the speed of light or 392x the speed of light depending on whom you talk to—but even assuming the faster of these two speeds, it should still take four days just to get from the Solar system to Alpha Centauri (our closest neighbor in interstellar space). Getting from Earth to the edge of the (8000 light-year-wide) Federation should take a decade. Instead, Star Fleet routinely sends them on assignments to the Neutral Zone and back home to Earth again in a matter of weeks or even just a few days.
    • It is never made clear however just how far away from Earth the Neutral Zone is. In fact, given that the Romulans are one of Earth's earliest enemies, it's likely that their territory isn't that far away at all. Further evidence for this is provided in Star Trek: Enterprise".
• Averted in Battlestar Galactica Reimagined, particularly in season 1, episode 2, "Water."

Tigh to Roslin: "The galaxy's a pretty barren and desolate place when you get right down to it."

• • Although they did encounter a lot of planets in the series the "jump" method of travel obscured the distances; many of the hops were described as requiring several jumps.

Video Games

• Zig Zagged in EVE Online, traveling from one planet, asteroid belt, or Stargate to another generally takes only a couple minutes. At warp speed.
• Star Ocean: The Last Hope involves the ship getting sucked into a "black hole" and conventiently being spat out directly over an alternate universe Earth.
• Played a little crooked in Space Pirates and Zombies, where you travel from star-to-star and planet-to-planet in seconds. Granted, you use warp gates for both, but in planetary environments, you must first send out the warp gate to your destination before using it, which should take a while, but it doesn't. And it did take a while in the official story, so it's breaking its own rules. Then again, it is just a game.

Western Animation

• In Transformers: The Movie, all planets in the universe seem to be only a few minutes away from each other at sublight speeds.
• The New Adventures of Superman episode "Rain of Iron". A Villain fires iron balls out of a cannon in a specific direction. . They fly through space, hit an asteroid and bounce back to Earth at a specific location. Asteroids (a) aren't close enough to Earth for this to work and (b) travel in orbits around the Sun, so firing the balls in a specific direction would only work once.

Real Life

• If you take a look at the page image, think about how it took astronauts three days to travel from the Earth to the moon. If you added the sun to this scale - about 10 cm (ca. 4 inches) depending on your screen resolution - it's 38 meters (124 feet) away from where you're sitting and is about 35 cm (a foot) across. The dwarf planet Pluto is 1.235 km (0.77 miles) away, and the nearest star (Alpha Centauri at 4.3 light years IRL) is 10,473 km (6,508 miles) away. The speed of the Apollo would be roughly 1.4 milimeters per hour and the speed of the light approximately 280 meters per hour.
• The crew of Apollo 13 are probably the only humans to truly have a grasp of how terrifying it is in a crippled spacecraft to get back to a planet that's only 400,000 km away—a teeny hop in astronomical terms.
  • And it was actually easier for them, since Apollo 13 (and several other Apollo missions) had been launched in a free return trajectory, where if a mid-course correction is not done, the ship goes around the Moon and ends up back on Earth by gravity alone. They had already performed that mid-course burn, but were able to quickly do another burn (using the intact lunar module) to get back into a free return trajectory. Had they not been able to do that, they would have no way to get back, and would either crash into the moon or become another celestial object. And if the command module were not intact enough, they would burn up on reentry.
• Planet Earth itself is rather lucky to have a conveniently close satellite in the form of the Moon. The surface area of the Moon is about one thirteenth that of the Earth. If and when we ever start colonizing outer space, we will find the Moon to be large enough to be a world on its own, and far easier to reach than the other planets (let alone the stars, naturally). Sure, there's no air, water or life, but there's a decent gravitational field and lots of mineral resources. We don't know how common it is for an Earthlike planet to have a satellite like the Moon, but there's nothing like it in the rest of the solar system—Venus has no moons at all, and Mars' "moons" are far too small to be especially useful for colonizing space the way our Moon probably will be.
  • However Mars' satellites are still good for a very big space station protected from asteroids and radiation by kilometers of solid rock and low gravity is useful when you want to build a spaceport.
• Several probes have been sent out and are now entering interstellar space. How long will it take for them to reach the next star out on their path?
  • Voyager 1 is not heading towards any particular star, being sent out on a trajectory to examine the planets in our solar system, but in about 40,000 years it will pass within 1.6 light years of the star AC+79 3888 in the constellation Camelopardalis.
    • 40,000 years may not seem that long, but consider that the first human art is about that old (the Venus of Hohle Fels is presently considered the oldest figurative artwork at 35,000-40,000 years old). Recorded history, pah, that's only about 6,000 years old.
  • Voyager 2 is also not headed toward any particular star, for the same reason. If left alone, it should pass by star Sirius in about 296,000 years (and by "pass by", we mean "come within 4.3 light-years of," which is still about as far as the sun is from Alpha Centauri).
  • Pioneer 10 is heading in the direction of the star Aldebaran in the constellation Taurus at roughly 2.6 AU per year. If Aldebaran stays put where it is (which it won't), it will take Pioneer 10 about 2 million years to reach it.
  • Pioneer 11 is headed toward the constellation of Aquila, northwest of the constellation of Sagittarius. Barring incident, Pioneer 11 will pass near the star Lambda (λ) Aquilae in about 4 million years time.
  • The New Horizons probe to Pluto was launched in 2006 and is the fastest spacecraft ever lobbed off the planet. It's going to take a mere nine years to get there, so I hope it packed a lunch. In keeping with the trope in Real Life, the probe is going so fast that it will not be stopping at Pluto, as the amount of fuel and engines for braking to orbital speed would add considerable mass and therefore several years to an already long trip. The probe is doing the equivalent of a "drive by", shooting pictures as it passes.
    • Just think of how disappointed the probe will be when it gets there only to find out Pluto was demoted after it left....
• On 8 November 2011, the asteroid 2005 YU55 passed 324,900 kilometers (201,900 miles) near the Earth. This was incredibly convenient for the astronomy community, but even with the warning no spacefaring nation could scramble a mission to check it out up close, so we had to settle for observation from a distance.
• The planets of the Kepler-11 system or other compact planetary systems like 55 Cancri or Gliese 581 (the innermost ones in both cases). While in the best case if you were in one of them you'd see the other(s) like we see the Moon from the Earth, in astronomical terms and with the technology usually available on sci-fi shows/novels they're quite close to each other.

1. ↑ In case you didn't spot it, the Moon is the tiny, gray speck of dirt on the right.