It contains various superheroes such as Superman, Batman, Wonder Woman, Aquaman, and Flash; as well as teams such as the Justice League, the Suicide Squad, and the Teen Titans.

Similarly, they had characters such as Batman whose early adventures set in the 1940s could not easily be reconciled with stories featuring a still-youthful man in the 1960s.

[8] Although retcons were used as a way to explain apparent inconsistencies in stories written, editors at DC came to consider the varied continuity of multiple Earths too difficult to keep track of, and feared that it was an obstacle to accessibility for new readers.

For example, the Legion of Superheroes book acted as if the Pre-Crisis Earth-1 history was still their past, a point driven home in the Cosmic Boy miniseries.

It also removed the mechanism DC had been using to deal with continuity glitches or storylines that a later writer wanted to ignore (which is how Earths B and E came into existence) resulting in a convoluted explanation for characters like Hawkman.

The Convergence (2015) crossover officially retconned the events of Crisis after heroes in that series went back in time to prevent the collapse of the Multiverse.

The DC Rebirth initiative will reintroduce concepts from pre-Flashpoint continuity, such as legacy, that have been lost with The New 52 and build "on everything that's been published since Action Comics #1 up thru The New 52.

Technologies which are only theoretical in the real world, such as artificial intelligence or are outright impossible according to modern science, such as faster-than-light travel, are functional and reproducible, though they are often portrayed as highly experimental and difficult to achieve.

There are other minor variations, such as the Earth being slightly larger than ours (to accommodate the extra countries), and the planet Saturn having 18 moons rather than 19 because Superman destroyed one.

"New Earth" is the Earth-like home planet to the main storybook characters of the DC Universe - the one with Smallville where Superman grows up, and Gotham City where Bruce Wayne avenges his parents by becoming Batman.

[20] Many of the superhumans on Earth owe their powers to the "metagene", a genetic feature of unknown origin, which causes some people to develop superpowers when exposed to dangerous substances and forces.

However, due to a magical spell cast by Adolf Hitler (using the Spear of Destiny and the Holy Grail) the most powerful heroes were unable to enter Axis-held territories, leaving the offensive portion of the war to be fought mainly by normal humans such as Sgt.

Furthermore, even major heroes and cosmic entities have distinct vulnerabilities, such as: Superman's weaknesses to magic, kryptonite, and red sunlight; Green Lantern's initial problems with wood or the color yellow (which have since been largely overcome); or Batman's lack of superhuman powers, which he supplements with keen intellect, constant training, and specialized technology.

In general, DC Comics has led a parody of its own teams and organizations after the Watchmen storyline and the Batman run from a dark humor style which began during the 1980s and ended in the early 90s.

Superhero teams such as the Doom Patrol and Justice League International led the writers to have a more subtle approach of semiotic dark humor with its own version of over-powered egos dominating personalities.

Most members have been captured supervillains (and thus expendable and deniable assets), and were strongly "encouraged" to join (often with offerings of clemency if they survived their extremely dangerous missions).

Usually more powerful enemies are imprisoned in maximum-level facilities—such as Belle Reve Penitentiary (which also was secretly Task Force X's headquarters) and even alternate dimensions or outer space—because they cannot simply be killed by a bullet, electricity, or poison.

Most such teams are formed by a charismatic and/or fearsome criminal mastermind for specific purposes; an example is the Secret Society of Super Villains of which there have been several versions.

Most villain teams are usually small, having been formed of individuals who know each other personally, such as the Central City Rogues, or have some other reason to work together (mercenary groups like the H.I.V.E., fanatical cults such as Kobra, etc.).

Technology more advanced than that which currently exists in real life is available - but it is usually very expensive, and usually only rich or powerful individuals and organizations (or the scientific geniuses who create them) have access to them.

The government also runs the secret Project Cadmus (located in the mountains near Metropolis) to develop clones and genetic manipulation without the public's knowledge.

Morrow (maker of the Red Tornado), Dr. Will Magnus (who constructed the Metal Men) and Professor Ivo (who fabricated Amazo and other advanced androids using a form of Nano-technology developed by Lexcorp).

Among these are the Amazons of Themyscira and Bana-Mighdall and the last survivors of Atlantis, who changed themselves into water-breathing forms, including the human-like Poseidonians and the mermaid-like Tritonians.

Curiously, a large number of them are humanoid, even human-like, in form (such as Kryptonians, who outwardly appear identical to Earth-born humans); some can even interbreed with Terrans.

The Dominators are an imperialistic race of terrorist aliens who control most of the unknown cosmos in order to extract genetic resources from planets.

Due to an arrangement with the Psions, the Guardians did not intervene in that system, allowing a cruel empire called "the Citadel" to govern there, until it was overthrown by the Omega Men.

There are several lesser beings in the DC universe that possess god-like powers, through energy manipulation, magic ability, or technological advancement.

Magic and the supernatural are often depicted as being real in the DC Universe, though some skeptics, such as Mister Terrific, maintain that there are scientific explanations to all such events.

In this way, heroes originally published by different companies are now part of the same fictional universe, and interactions between such characters are no longer considered intercompany crossovers.

In addition, an enormously powerful being called the Time Trapper, an enemy of the Legion, has been known to manipulate the timestream, even creating "pocket universes".