The Marvel Universe is strongly based on the real world. Earth in the Marvel Universe has all the features of the real one: same countries, same personalities (politicians, movie stars, etc.), same historical events (such as World War II), and so on; however, it also contains many other fictional elements: countries such as Wakanda and Latveria (very small nations) and organizations like the espionage agency S.H.I.E.L.D. and its enemy, HYDRA and A.I.M. In 2009 Marvel officially described its world's geography in a two-part miniseries, the Marvel Atlas.
Most importantly, the Marvel Universe also incorporates examples of almost all major science fiction and fantasy concepts, with writers adding more continuously. Aliens, gods, magic, cosmic powers and extremely advanced human-developed technology all exist prominently in the Marvel Universe. (A universe incorporating all these types of fantastic elements is fairly rare; another example is the DC Universe.) Monsters also play a more prominent role with east Asian origins of magical incantation, outlandish sorcery and manifesting principle in the Marvel Universe. One such case is Fin Fang Foom arising from the ashes of tantric magic. Thanks to these extra elements, Earth in the Marvel Universe is home to a large number of superheroes and supervillains, who have gained their powers by any of these means.
Comparatively little time passes in the Marvel Universe compared to the real world, owing to the serial nature of storytelling, with the stories of certain issues picking up mere seconds after the conclusion of the previous one, while a whole month has passed by in "real time". Marvel's major heroes were created in the 1960s, but the amount of time that has passed between then and now within the universe itself has (after a prolonged period of being identified as about ten years in the mid-to-late 1990s) most recently been identified as thirteen years. Consequently, the settings of some events which were contemporary when written have to be updated every few years in order to "make sense" in this floating timeline. Thus, the events of previous stories are considered to have happened within a certain number of years prior to the publishing date of the current issue. For example, Spider-Man's high school graduation was published in Amazing Spider-Man #28 (September 1965), his college graduation in Amazing Spider-Man #185 (October 1978), and his high school reunion in Marvel Knights: Spider-Man #7 (December 2004). Because of the floating timeline, where stories refer to real-life historic events, these references are later ignored or rewritten to suit current sensibilities. For instance, the origin of Iron Man was changed in a 2004 storyline to refer to armed conflict in Afghanistan, whereas the original Iron Man stories had referred to the Vietnam War.[volume & issue needed]
Marvel Comics itself exists as a company within the Marvel Universe, and versions of people such as Stan Lee and Jack Kirby have appeared in some of the stories, whereas characters like Steve Rogers, (Captain America's alter ego), have worked for Marvel.[volume & issue needed] The Marvel of this reality publishes comics that adapt the actual adventures of the superheroes (except for details not known to the public, like their secret identities); many of these are licensed with the permission of the heroes themselves, who customarily donate their share of profits to charity. Additionally, the DC Comics Universe is also said to exist in the Marvel Universe as one of the many alternative universes. The reverse may also be said with respect to the DC Universe. This is one method of explaining the various crossover stories co-published by the two companies.[volume & issue needed]
Pop culture characters such as Dracula and Frankenstein actually exist in the Marvel Universe. This is usually justified as a second hand account of events as told to credited authors Bram Stoker and Mary Shelley although the general public continues to believe them as fictional. Robert E. Howard's Conan the Barbarian, Red Sonja, Kull the Conqueror, and Solomon Kane also have real life existences in the Marvel Universe. The Hyborian Era of Conan and Kull is considered part of Earth-616 pre-recorded history. However, they rarely encounter modern Marvel superhero characters. This is most likely possible due to the uncertain legal status of Howard's works prior to 2006 when they became public domain. Other licensed works that have been incorporated into the Marvel Universe include Godzilla, 2001: A Space Odyssey (in the character of Machine Man), ROM: Spaceknight, the Micronauts, and the Shogun Warriors. In most cases, such material is either restricted from use after the license expires or the characters redesigned or renamed to avoid infringement.[volume & issue needed]
Within the fictional history of the Marvel Universe, the tradition of using costumed secret identities to fight or commit evil had long existed, but it came into prominence during the days of the American "Wild West" with heroes such as the Phantom Rider. During the 20th century, the tradition was reinvigorated by Captain America and the Invaders in the 1940s, who fought for the Allies of World War II.
Marvel's most prominent heroes were created during the Silver Age of Comic Books in the 1960s to early 1970s, including Spider-Man, Iron Man, Thor, the Hulk, Doctor Strange, Daredevil, Ant-Man and the Wasp (Hank Pym and Janet van Dyne), Black Widow, Hawkeye, Quicksilver and Scarlet Witch, the Vision, Wonder Man, Hercules, Ka-Zar, Groot, Nick Fury, Black Panther, Mar-Vell (the first Captain Marvel), Carol Danvers (also known as the first Ms. Marvel and the current Captain Marvel), Polaris, Falcon, the Black Knight, the Silver Surfer, Jane Foster (also known as the second Thor), Angel, Beast, Cyclops, Iceman, Jean Grey (also known as Marvel Girl and Phoenix), Professor X, Mister Fantastic, Invisible Woman, the Human Torch and the Thing. Other notable heroes from the Bronze and Modern Ages from the mid 1970s to the early 1990s include Wolverine, Storm, Colossus, Nightcrawler, Luke Cage (also known as Power-Man), Iron Fist, Misty Knight, Colleen Wing, White Tiger (Hector Ayala), Shang-Chi, Tigra, Jessica Drew (also known as Spider-Woman), Valkyrie, Ghost Rider (Johnny Blaze), Hellstorm, Satana, Man-Thing, Blade, Morbius the Vampire, Howard the Duck, Monica Rambeau (also known as Photon, Pulsar, Spectrum and the second Captain Marvel), Moondragon, Drax the Destroyer, Star-Lord, Gamora, Rocket Raccoon, the Punisher, Moon Knight, Mockingbird, the Eternals, War Machine, Nova (Richard Rider), Adam Warlock, Power Pack, Psylocke, Scott Lang (the second Ant-Man), Black Cat, Silver Sable, Kitty Pryde (also known as Shadowcat, Ariel, Sprite and Star-Lady), Emma Frost (also known as the White Queen), She-Hulk, Cloak & Dagger, Captain Britain, Squirrel Girl, Elektra, the New Mutants, the New Warriors, Legion, Thunderbird, Rogue and Jubilee. Some of Marvel's more recent creations from the mid-to-late 1990s, 2000s and 2010s such as Deadpool, Gambit, Cable, Domino, Blink, the Thunderbolts, the Runaways, the modern Guardians of the Galaxy, the modern Defenders (based off the Netflix MCU version of the same name), X-23 (aka the second Wolverine), Shuri, the Dora Milaje, Daisy Johnson (also known as Quake), Phil Coulson, Melinda May, the Winter Soldier, Maria Hill, Miles Morales (the second Spider-Man of the Ultimate Marvel Universe), Hope van Dyne (also known as the Red Queen and the second Wasp), Cassandra Lang (also known as Stature, Stinger, Ant-Girl and Giant-Girl), the Stepford Cuckoos, Amadeus Cho (also known as the second Hulk), Kamala Khan (also known as the second Ms. Marvel), Kate Bishop (also known as the third Hawkeye), Moon Girl, America Chavez (also known as the second Miss America), Robbie Reyes (also known as the fourth Ghost Rider), Ironheart and Spider-Gwen (Gwen Stacy of Earth-65) have become popular characters in their own right. Unlike the DC Universe, few of Marvel's 1940s characters have risen to prominence in modern publications; Captain America is one exception, and to a lesser extent, his contemporary, Namor the Sub-Mariner, primarily because both of these characters were reintroduced to readers and to the Marvel Universe during the 1960s.
Prominent teams of superheroes include the Avengers, the X-Men, the Fantastic Four, the Defenders, the Inhumans, S.H.I.E.L.D., the Howling Commandos, Guardians of the Galaxy, the Runaways, the Midnight Sons, the Thunderbolts. All these groups have varying lineups; the Avengers have included Marvel's major heroes as members at one time or another. The X-Men are a team of mutants led by Professor X and include many of Marvel's most popular characters, such as Wolverine and others. The Fantastic Four are viewed as "Marvel's First Family" of superheroes, usually consisting of Mister Fantastic, the Invisible Woman, the Human Torch and the Thing, as well as siblings Franklin and Valeria Richards. The Defenders were an ad-hoc team usually brought together by Doctor Strange which has included the Hulk, Namor the Sub-Mariner and the Silver Surfer, while the most recent incarnation of the team consists of street-level New York City heroes Daredevil, Jessica Jones, Luke Cage and Iron Fist. The Guardians of the Galaxy include Marvel's cosmic characters such as Star-Lord, Gamora, Drax the Destroyer, Groot and Rocket Raccoon, but the team has also introduced other heroes into the roster such as Kitty Pryde, the Silver Surfer, the Thing and Nova. The Inhumans are a royal family comprised of Black Bolt, Medusa, Crystal, Gorgon, Triton, Lockjaw and Karnak, who rule the city of Attilan. The Runaways are a group of teenagers and a dinosaur who rebel against their evil parents The Pride: Alex Wilder, Nico Minoru, Karolina Dean, Chase Stein, Molly Hayes and Gert Yorkes. The Midnight Sons consist of supernatural heroes such as Blade, Ghost Rider, Elsa Bloodstone, Hellstorm, Werewolf by Night and Man-Thing. The Thunderbolts' original incarnation were supervillains disgused as superheroes consisting of Citizen V (aka Helmut Zemo), MACH-IV (aka Beetle), Songbird (aka Screaming Mimi), Moonstone (aka Meteorite), Techno/Ogre (aka Fixer) and Jolt while the current incarnation of the team is made up of reformed supervillains working for the government: Deadpool, the Punisher, Red Hulk, the Winter Soldier and the Ghost. Although teams of supervillains are few and far between, notable examples include the Masters of Evil, the Brotherhood of Mutants, the Sinister Six, the Frightful Four, the Black Order, the Annihilation Wave, the Starforce and the Cabal.
Most of the superhumans in Marvel's Earth owe their powers to the celestials, cosmic entities who visited Earth millions of years ago and experimented on our prehistoric ancestors (a process they also carried out on several other planets). This resulted in the creation of two hidden races, the godlike Eternals and the genetically unstable Deviants, in addition to giving some humans an "x-factor" in their genes, which sometimes activates naturally, resulting in sometimes superpowered, sometimes disfigured individuals called mutants. Others require other factors (such as radiation) for their powers to come forth. Depending on the genetic profile, individuals who are exposed to different chemicals or radiation will often suffer death or injury, while in others it will cause superhuman abilities to manifest. With the exception of psionic abilities, these powers are usually random; rarely do two people have exactly the same set of powers. It is not clear why the Celestials did this, although it is known that they continue to observe humanity's evolution. A Marvel series titled Earth X explored one possible reason for this: that superhumans are meant to protect a Celestial embryo that grows inside the Earth against any planetary threats and have done so for eons. An X-Men villain known as Vargas claims to be a new direction in human evolution, as he is born with superpowers even though his genetic profile said he was an ordinary human being. The majority of the public is unaware of what may cause superhuman powers.[volume & issue needed]
Other possible origins for superhuman powers include magic, genetic manipulation and/or bionic implants. Some heroes and villains have no powers at all but depend instead on hand-to-hand combat training or advanced technological equipment. In the Marvel Universe, technology is considerably more advanced than in the real world; this is due to unique individuals of genius intelligence, such as Reed Richards (Mister Fantastic) of the Fantastic Four. However, most of the really advanced devices (such as powered armor and death rays) are too expensive for the common citizen, and are usually in the hands of government organizations like S.H.I.E.L.D., or powerful criminal organizations like A.I.M. One major company producing these devices is Stark Industries, owned by Tony Stark (Iron Man), but there are others. Advanced technology has also been given to humans by hidden races, aliens, or time travelers like Kang the Conqueror, who is known to have influenced the robotics industry in the past.[volume & issue needed]
In superhumans the energy required for their superpowers either comes from within using their own body as a source, or if the demand of energy exceeds what their body is capable to deliver, comes from another source. In most cases, this other source seems to be what is called the universal psionic field (UPF), which they are able to tap into. Sometimes they are connected to another source, and more rarely they are even a host for it.[volume & issue needed]
Marvel tries to explain most superpowers and their sources "scientifically", usually through the use of fictional science-like concepts, such as:
A degree of paranoid fear against mutants exists due to stories of mutants being a race or even a species (Homo superior or Homo sapiens superior) that is evolving and is meant to replace normal humans. This has caused organizations to form to deal with the problem, who can be divided into three camps: those who seek peaceful coexistence between mutants and normal humans (the X-Men and their affiliated groups), those who seek to control or eliminate humans to give mutants safety or dominance (Magneto and his followers, as well as other mutants such as Apocalypse), and those who seek to regulate or eliminate mutants in favor of humans. The latter often use the robots known as Sentinels as weapons. Certain species are regarded as subhuman, like the Morlocks who lurk beneath New York City and have been discriminated against by the outside world because of their mutant deformities. The Morlocks have recently joined the terrorist organization Gene Nation.[volume & issue needed]
In addition to mutants, Eternals and Deviants, several other intelligent races have existed secretly on Earth. These include: The Inhumans, another genetically unstable race (like the Deviants, but in their case it is due to their use of a substance called the "Terrigen Mists") that was created by a Kree experiment long ago; The Subterraneans, a race of humanoids adapted to living below the surface, created by the Deviants (some subterraneans were transformed into 'Lava Men' by a demon); and Homo mermanus, a humanoid race of water-breathers that lives in Earth's oceans. Most of these races have advanced technology but existed hidden from humanity until recent times. More variants of humanity can be found in the Savage Land (see places, below.) Most of the Savage Land races have their origin from a group of primitive ape men who seems to have escaped the Celestial experiments whose influence is present in all modern Homo sapiens. Other leftovers from the era where primitive humanoids walked the earth still exist, such as the altered Neanderthal known as Missing Link, an old enemy of the Hulk.[volume & issue needed]
The Marvel Universe also contains hundreds of intelligent alien races. Earth has interacted with many of them because a major "hyperspace warp" happens to exist in the Solar System.
The three major space empires are:
The three are often in direct or indirect conflict, which occasionally involve Earth people; in particular, the Kree and Skrulls are ancient enemies, and the Kree-Skrull War has involved humans on several occasions.
The Skrulls have also been known to be in a long and consistent war against the Majesdanians, who live in a milky planet named Majesdane. The war between the two had started after two Majesdanians, Frank and Leslie Dean of The Pride had been kicked out for criminal activities; the two travelled to Earth, where Frank and Leslie stopped the war against Earth in exchange for giving the Skrulls the location of Majesdane, which was hidden behind the corona of a white dwarf. The war had gone on for sixteen years minimum; it ended abruptly after the Skrulls shot a barrage of missiles at Majesdane, who retaliated.
Another prominent alien race is The Watchers, immortal and wise beings who watch over the Marvel Universe and have taken a sacred vow not to intervene in events, though the Watcher assigned to Earth, Uatu, has violated this oath on several occasions.
The Elders of the Universe are ancient aliens who have often had great impact on many worlds, for billions of years, acting alone or as a group. A power called Power Primordial is channeled through them.
Many other races exist, and have formed an "Intergalactic Council" to have their say on matters that affect them all, such as interference from Earth humans in their affairs.
Also abundant in the Marvel Universe are legendary creatures such as gods, demons and vampires. The 'gods' of most polytheistic pantheons are actually powerful, immortal human-like races residing in other dimensions who visited Earth in ancient times, and became the basis of many legends. However, all of these 'gods' share a common ancestry and connection to Earth due to Gaea, the primeval Elder Goddess that infused her life essence into all living things on Earth. Gaea is known by various names and appearances in other cultures and among the various pantheons, but she's the same being. As a result, she's a member of every polytheistic pantheon of 'gods' worshipped by humans. Besides mythological gods, many deities made up by Marvel writers exist as well, such as the Dark Gods, enemies of the Asgardians. The Dark Gods are a race of 'gods' that have been worshipped by extraterrestrial races. Well known alien races like the Shi'ar and Skrulls also have beings they worship as 'gods', though little has been revealed about them.[volume & issue needed]
Many persons and beings have falsely pretended to be gods or demons during history; in particular, none of the ones claiming to be major figures from Judeo-Christian beliefs has turned out to be the real article, although a number of angels have appeared in recent years, as well as an apparent true rebellion and expulsion of angels from a higher realm known as Paradise, proving that some form of Heaven and Hell do exist in this Universe, seemingly like those in keeping with common real world religious belief. Similarly, demons are evil magical beings who take affairs in the matters of the universe. Some of the most powerful are Blackheart, Mephisto, Nightmare, Satannish, and Zom. There are also powerful benevolent mystical entities such as The Vishanti; or amoral and malevolent entities who are not truly demonic in nature, such as Dormammu and The Octessence, or ones heavily drawing upon the mythologies of H.P. Lovecraft and Robert E. Howard. Some supernatural beings, entities and human characters created by Lovecraft & Howard, who were friends and influenced each other's work, have been adapted by Marvel and include Abdul Alhazred, Conan the Barbarian Nyarlathotep and Set. Some deities or demonic beings that are original characters of Marvel have been heavily influenced by these mythologies, such as Shuma-Gorath.
Most of the current generation of gods have been revealed to be the descendants of the Elder Goddess Gaea. The two most featured pantheons are the Asgardians (of whom Thor is a member) and the Olympians (of whom Hercules is a member). The lords of the various pantheons sometimes gather in groups known as the Council of Godheads and Council of Skyfathers. The gods were forced to stop meddling with humanity (at least openly) a thousand years ago by the Celestials, and most people today believe them to be fictional. There are other pantheons that have been depicted in the Marvel Universe that are still actively worshipped in the real world including those worshipped by the Aboriginal inhabitants of Australia, the gods of Hinduism, the Shinto gods and the gods of Zoroastrianism. These deities are rarely depicted, however. One such appearance generated a good deal of controversy as the depiction involved a fight between Marvel's incarnation of Thor and the Hindu god Shiva, a battle which Shiva lost. As Shiva is one of the principal deities of Hindu religion, his defeat offended some followers of Hinduism. This battle was retconned later as having been the deity Indra, the Hindu god of thunder, who was posing as Shiva, that met defeat. In order to avoid offending believers of still active religions, Marvel features such deities as characters in the background or who make very brief cameo appearances.
Marvel's depiction of vampires has been heavily influenced by various interpretations of popular media, such as Bram Stoker's Dracula. As with many other supernatural creatures, Marvel entwined the origin of vampires with aspects of the mythologies created by Lovecraft and Howard. They were originally created by magical rites performed by priests of Atlantis prior to the Great Cataclysm that destroyed much of the world with Varnae becoming the first vampire. Marvel would depict vampires as frequent antagonists during the Hyborian Age to Howard characters such as Kull and Conan. In recent years, Marvel's depiction of vampires has altered greatly by creating various subspecies of vampires that exist in clans that greatly differ in appearance and belief. All vampires are depicted with varying degrees of superhuman strength, speed, stamina, agility, reflexes and accelerated healing. Many are capable of transforming into animals such as bats or wolves, some can transform into a mist like substance; some of the most powerful are capable of controlling the weather to a somewhat limited degree. All vampires must ingest blood in order to maintain their survival and physical vitality. So long as they do so regularly, they cease to age and are immune to diseases. They retain the well known vulnerabilities common to vampires in other media interpretations including sunlight, garlic, religious icons and weapons made of silver. Vampires can be killed by a wooden stake driven through the heart, though they return to life if the stake is removed. Vampires are highly allergic to silver and can be killed with it. While they normally heal rapidly, injuries inflicted by silver weapons heal at a much slower rate if the injuries aren't fatal. Vampires can also be killed by decapitation or being set on fire, with burning them to ashes and then scattering the ashes being the most effective means of ensuring their demise.
The cosmic entities are beings of unbelievably great levels of power (the weakest of whom can destroy planets) who exist to perform duties that maintain the existence of the universe. Most do not care at all about "lesser beings" such as humans, and as a consequence their acts are recurrently dangerous to mortals. When dire threats threaten the universe it is not uncommon for these beings to gather together to discuss the threat, and even act.[volume & issue needed]
Most conceptual entities are simply interested in furthering their own essential function, or to keep the balance with an opposing force. However, certain cosmic entities, such as Galactus, In-Betweener, Maelstrom, or The Stranger have demonstrated personality, motivations, or (except for the first mention) even ambitions beyond their functions, but often maintain the perspective that morality is entirely relative, or that destroying civilisations of "lesser" beings is no more evil than if these beings destroyed an anthill. Others such as Uatu the Watcher, Eon, or the Celestials Ashema and Tiamut are aberrations in the sense of sympathising with and occasionally coming to the defense of humanity.[volume & issue needed]
The "Fulcrum" is a comparatively recent addition to the hierarchy, that "all" cosmic entities allegedly serve, of a level of raw power stated to far surpass the might of the Watchers and the Celestials. Unlike most other entities it is capable of conscience, compassion, and even a sense of humour, and has stated that it wants other cosmic beings to develop such as well. He is a possible manifestation/avatar of The One Above All.[volume & issue needed]
The Phoenix Force first received personification in Jean Grey. The Force is composed of the psionic energy from all living beings, past, present and future, and is an embodiment of rebirth and destructive transformation through "burning away what doesn't work", and helped to restart the universe before the Big Bang.[volume & issue needed]
The Marvel Universe is part of a multiverse, with various universes coexisting simultaneously usually without affecting each other directly.[volume & issue needed] According to Reed Richards, the ultimate fate of the Multiverse is to perish in an all-encompassing heat death.
The action of most Marvel Comics titles takes place in a continuity known as Earth-616. This continuity exists in a multiverse alongside trillions of alternative continuities. Alternative continuities in the Marvel multiverse are generally defined in terms of their differences from Earth-616.
Continuities besides Earth-616 include the following (for a complete listing see Multiverse):
In addition, multiple continuities are visited in the comic book series What If, What The--?! (formerly Not Brand Echh) and Exiles. The concept of a continuity is not the same as "dimension" or "universe"; for example, characters like Mephisto and Dormammu hail from alternative dimensions and Galactus from another universe, but they all nevertheless belong to the Earth-616 continuity (where all the dimensions and universes seems to be connected to the same main timeline). A continuity should also not be confused with an imprint; for example, while the titles of some imprints, such as Ultimate Marvel, take place in a different continuity, some or all publications in other imprints, such as Epic Comics, Marvel MAX, and Marvel UK, take place within the Earth-616 continuity.
Within and sometimes between continuities, there exist a variety of dimensions, sometimes called pocket dimensions which typically are not depicted as separate continuities, but rather part of one, typically Earth-616. There are a score of such dimensions, ranging from the Earthlike to the totally alien. Some are magical in nature and others are scientific; some are inhabited and others are not. These include realities like the Microverse, the Darkforce Dimension, Limbo, the Mojoverse, and many more. The Astral Plane is a dimensional plane which is the source of telekinesis and various other psychic powers. It is a dimension created by the Elder Goddess Oshtur that is sometimes referred to as the "Temple of Oshtur" or the "Realm of the Mind".
Despite various contradictions, the term, dimension is sometimes interchangeable with universe or reality. Every reality of the Marvel Universe has numerous interconnected dimensions, with each dimension differing from those of other realities; for example, the Ultimate Asgard has clearly been shown to be distinct from the Asgard known to Earth-616 characters. Such dimensions, such as Asgard or the Dark Dimension are technically not "pocket dimensions" as they clearly reside completely outside the boundaries of the Marvel Universe, instead of within, as the former does.[volume & issue needed]
One cannot normally alter the Marvel Universe's history; if a time-traveller should cause an alteration to the established flow of events at some point in the past, a divergent universe will simply "branch out" from the existing timeline, and the time-traveller will still return to his or her unaltered original universe. Those realities can also spawn realities of their own. There exists hundreds, probably thousands of such realities. It is unknown why this happens, though a warp known as the Nexus of All Realities exists in a swamp in the Florida of Earth-616. For the most part this does not matter, as most beings are unaware that this occurs, or even that their universes were recently "born" from another. However, individuals and organizations exist that try to monitor or manipulate the various realities. These include Immortus, the Captain Britain Corps, the Time Variance Authority, the Timebreakers/Exiles, and Kang the Conqueror's forces. It has been shown to be possible to travel through time without creating a new alternative universe, instead altering events in the future, but this seems to have devastating and very far-reaching repercussions, as depicted in Marvel 1602 (it almost destroyed the whole multiverse, including the afterlife).
Also, time itself passes much differently within the confines of the Marvel Universe than it does in the real world. Despite various characters having appeared within company publications for decades, few if any have aged to any appreciable degree. For example, the patriotic hero Captain America was created in 1941 but stopped appearing in titles soon after the end of World War II. The character was revived more than twenty years later, explained as having been frozen in a block of ice though believed to be dead, to lead Marvel's latest team of superheroes the Avengers. This first Avengers team featured several characters that would go on to be some of the company's most famous and most popular. Although the characters would be portrayed in hundreds and even thousands of adventures over the decades, they have been portrayed as having aged little or none at all.
Naturally this tendency is purely due to story conveniences (or a somewhat haphazardly shifting patchwork pattern of authors), and mainly that the fictional "continuity" has been maintained and expanded far beyond what Stan Lee and others originally planned or hoped for. Hence, the passing of time was more discernible in the very early years, such as the graduation of Spider-Man; and what started as children or teenaged characters, such as Kitty Pryde, Franklin Richards, Valeria Richards, Power Pack, or the New Mutants are all allowed to age at wildly shifting rates (in the second case even backwards at times), whereas surrounding characters somewhat dependent on a certain age limit do not change at all. This recurrently creates inherently contradictory effects, as events are routinely described to have happened several years ago, even in cases when this would mean that some of the involved characters would have been toddlers. Different approaches also exist regarding allowing "second-generation" descendants of heroes or villains, fully grown over 18 years after an event (for example Hulkling, other members of the Young Avengers, Runaways, and Secret Warriors), whereas other books, such as Young Allies use the inherent contradiction to debunk similar claims. If a past storyline wherein a direct depictions of a then-current president or similar is referred to in a later era, it tends to become updated accordingly, sometimes with an "in-joke" acknowledgement.
A more recent explanation was given by Galactus to the Ultimates, namely that some important events - for instance, the creation of the Fantastic Four or the Avengers - have a 'gravity' all their own and warp time around them, causing the timeline to subtly change to accommodate this.
While the Marvel Universe is presumably as large as the non-fictional universe comic book readers inhabit, for all intents and purposes the Local Group is the universe; practically all action takes place in it. The Skrull Empire is located in the Andromeda galaxy, the Kree Empire in the Magellan clouds which are satellites of the Milky Way galaxy in which Earth of course is found, while the Shi´ar Empire is located somewhere between them in one of the smaller galaxies (perhaps Triangulum); frequently, these three empires are quoted as the main political powers "in the universe". Similarly, the Local Group seemed to be the only affected area when the Annihilation Wave cut its bloody swath "across the universe".
Four role-playing games have been set in the Marvel Universe:
For more complete lists of inhabitants of the Marvel Universe, see List of Marvel Comics characters, List of Marvel Comics teams and organizations, and List of Marvel Comics alien races.