{{Location Infobox
|location=High Earth orbit, WikipediaSolar System|Solar System
|maps=sp_a4_finale4 (''Portal 2'')
{{Quote|Take one last look at your precious human moon. Because it cannot help you now!|Wheatley|Portal 2|Filebw finale04 button press05.ogg}}

The '''Moon''' is Earth's only natural satellite, and the setting of the final sequence of ''Portal 2''. It is also the last known location of Wheatley.

In the Half-Life and Portal universe|''Half-Life'' and ''Portal'' universe, the Moon first appears in ''Half-Life'' above the High Altitude Launch Center, and then in ''Half-Life Decay'', above the Gamma Labs. It is seen again above Ravenholm in ''Half-Life 2'', and in the ''Half-Life 2 Deathmatch'' map ''Resistance (multiplayer map)|Resistance'', until it gets an actual role in ''Portal 2''.

FileMoon 2.jpg|thumb|left|200px|The surface of the Moon seen with the Apollo landing site with Earth in the background.

At some point in the late 1970s or early 1980s, Cave Johnson, CEO of Aperture Science, managed to acquire roughly $70 million worth of Moon rock. Upon grinding it up and mixing it into gel, he discovered that it made a great Aperture Science Handheld Portal Device|portal conductor, and also that ground Moon rock was "pure poison." He then put it to use in testing, under the name Conversion Gel. Cave Johnson eventually passed away from 'moonrock poisoning.'

An undefined amount of time later, after Wheatley had taken over the Aperture Science Enrichment Center|Enrichment Center and allowed it to fall into serious disrepair, part of the ceiling collapsed from the Central AI Chamber during his final confrontation with Chell. This allowed the Moon to be viewed through the opening made. Chell took advantage of this, and the Moon's portal conducive properties, and shot a portal at the moon. This caused both herself and Wheatley to be sucked into the near-total vacuum of the Moon's atmosphere. Chell was returned to Earth when GLaDOS, newly restored to power, pulled her back in through the portal. However, Wheatley was left to drift through space indefinitely, along with a Aperture Science Personality Construct Core|corrupt Personality Core.

==Related Achievements==
{|class=wikitable style="vertical-aligncenter;" width=50%
!colspan="2" style="text-alignleft"|''Portal 2 Achievements and Trophies|Portal 2''
|rowspan=2 width=64px|FileSHOOT THE MOON.jpg
!style="text-alignleft"|Lunacy (20G)
|''That just happened.''

FileMoon surface.jpg|right|thumb|200px|Concept art for the Moon's surface.

*The Moon has gravity approximately 1/6 of Earth's gravity, meaning that an object on its surface would remain on the surface unless acted upon, but the force needed is much less than that of Earth. Due to the bi-directional teleportation nature of the portal Chell launched to the Moon, Wheatley and Chell were both blown away from the surface by the negative pressure vacuum resulting.
*Chell always fires a blue portal at the surface, regardless of what portal one tries to fire.
*There is a goof during the brief Moon sequence. Chell fires the portal near the middle of the side of the Moon facing the Earth. So to see the planet, she would have had to look at least 60 degrees ''up''. Yet when she is on the Moon, the Earth is just above the horizon. For that to happen, she would have had to fire at the "edge" of the Moon.
*Another goof is that the escape velocity from the Moon's surface is 1.4 km/s, which faster than an artillery shell as it leaves the barrel. GLaDOS is not hitting Wheatley that hard, nor is the air escaping that fast. If it did, there is no chance Chell could hold on since it would be equivalent to holding on to an aircraft at three times the speed of sound. This means Wheatley would fall to the Moon's surface within a couple of minutes at most instead of floating around in space.
*The Earth looks similar to what our Earth looks like today, despite the draining of the world's oceans by the Combine as seen in ''Half-Life 2''. This suggests that either the Combine has been overthrown and/or the oceans were somehow restored. This may not be true, however, as in the credits the photo of Earth is credited to NASA, indicating that it was not created by the developers, and therefore does not have further-reaching implications.
*It is unknown how the Moon could be seen from the Central AI Chamber. The end credits show that the Enrichment Center's location is hidden deep underground underneath a shed. However, given the modular and internally mobile nature of the Enrichment Center, it is possible that Wheatley moved the chamber closer to the surface and that GLaDOS moved it back deeper underground while Chell was unconscious.
*Inhaling Moon dust is, in fact deadly to humans, which explains Cave Johnson's fatal condition. Due to the Moon's near lack of atmosphere, the jagged texture of the dust is not worn away as it would be by Earth's natural processes. Breathing it in causes lung conditions similar to anything between hay fever and emphysema, depending on how much exposure there was. 
*According to an interview with Erik Wolpaw in the ''Portal 2'' Official Guide, they were originally going to place signs in old Aperture that read things such as "The Moon is not your friend." They were even going to put skeletons on the Moon during the ending sequence. This was cut with Wolpaw calling it "A good gag that didn't make it in." This connects with Cave Johnson's recording where he says Aperture Science was called to a congressional hearing on "missing astronauts".
*Doug Rattmann has an extreme obsession with the Moon, as it is seen in all of his drawings and murals. He also states in ''Portal Lab Rat'' that he would have rather have gone to the Moon than help build GLaDOS. The Moon is often referenced in the game as well, including an image hidden in his final transmission showing a companion cube on the Moon. It is unknown if this is foreshadowing, or the Moon serves a greater purpose.
*During the Moon sequence, a portal is fired at a point on the Moon which is approx. 275 miles (442 km) from the nearest Moon landing site, Apollo 17, making it impossible for a Moon landing site to be seen in-game, unless it is an Aperture owned lunar module.


FileMoon Black Mesa.jpg|The moon from near Black Mesa's High Altitude Launch Center in ''Half-Life''.
FileMoon Decay.jpg|The moon above the Gamma Labs in ''Half-Life Decay'', where the ''Half-Life'' skybox is used.
FileRavenholm menu bg.jpg|The moon from Ravenholm in ''Half-Life 2''.
FileDm resistance moon.jpg|The moon from the map ''Resistance'' in ''Half-Life 2 Deathmatch'', where the ''Half-Life 2'' skybox is used.
FileMoon US flag.jpg|Model of the US flag as seen on the Moon at the Apollo landing site.
FileLunar module.jpg|Model of the descent stage of the Apollo Lunar Module.
FileLunar rover.jpg|Model of the Lunar Roving Vehicle.
FileMoon rock.jpg|Model of one of the Moon rocks.

==List of appearances==
* ''Half-Life'' {{1st}}
* ''Half-Life Decay''
* ''Half-Life 2''
* ''Half-Life 2 Deathmatch'' {{Nc}}
* ''Portal 2''

|title=''Portal 2'' journey (4)
|before=Central AI Chamber (3)
|after=Central AI Chamber (4)

CategoryPortal 2