Hidden assassins and witless patsies. Shadowy cabals. Secretive meetings in smoky rooms. According to conspiracy theorists, the truth is out there -- it's just being kept from the public by secret societies out to control the world (or save it). Call it apophenia (humans' tendency to see patterns in random data), or call it realities too awful for the rest of us to acknowledge -- for whatever reason, conspiracy theories have been a part of human culture since Cain suspected God and Abel had a racket going. Here are some of the more common conspiracy theories still in play today. We'd give you the real story behind them all, of course, but then we'd have to kill you.
2 The Moon Landings Were Faked
In 1969, millions of people watched as men walked on the moon for the first time in human history. Or did they? According to one remarkably enduring conspiracy theory, the U.S. government faked the moon landings with the use of movie sets and props.
3 The Freemasons Were Jack the Ripper
With their secret rituals, highly symbolic art and architecture, and long history with some of the world's most powerful and controversial figures, the Freemasons have had been at the center of countless conspiracy theories, including some blaming them for the Jack the Ripper killings. Pictured: A museum worker displays hairbrushes that belonged to Edward VII inside the Grand Temple of Freemason's Hall in London. Edward VII was the Grand Master of the United Grand Lodge of England from 1874 to 1901, when he was still Prince of Wales.
4 The Freemasons Have Orchestrated History
Among the more popular conspiracy theories about the Freemasons: They secretly control the world's governments; they worship a divine entity known as the Great Architect of the Universe and seek the world's destruction so it can be rebuilt more perfectly; they have long infiltrated nearly aspects of American society, from the layout of Washington, D.C., to the mysterious symbols on the dollar bill. Pictured: the Grand Temple inside of Freemason's Hall in London.
5 The Bilderberg Group Rules the World
Since 1954, a small group of the world's most powerful and influential people have met every year in various place for what's called the Bilderberg Group (it now numbers around 130 invitees), with the aim of fostering understanding between the U.S. and Western Europe. It's a secretive event, and conspiracy theorists claim the leaders are meeting to further any of various plots for world domination, including the spread of communism. Here: World Bank President Paul Wolfowitz (not exactly a communist) leaves the Bilderberg Group meeting in 2007.
6 JFK Was Killed by a Conspiracy
The official reason for the death of President John F. Kennedy was shots fired by a lone gunman, Lee Harvey Oswald. But a vast number of people believe Kennedy was really killed by a shadowy conspiracy, usually involving the CIA, the Mafia, and survivors from the Bay of Pigs.
7 LBJ Killed JFK
Any number of people are fingered by conspiracy theorists as having plotted JFK's death, from his successor, Vice President Lyndon B. Johnson, to Republican rival Richard Nixon, to Fidel Castro.
8 Oswald Was a Patsy
A wide number of conspiracy theories say that Kennedy's official killer, Lee Harvey Oswald, was either not working alone in Dallas that day, or that he wasn't anywhere near the site of the shooting. Many posit that he was set up to be the fall guy, and that an Oswald lookalike (possibly arranged by Soviet Premier Nikita Khruschev) was the actual killer. Such speculation even led to Oswald's body being exhumed in 1981 -- when it was definitively proven that the man buried in his grave really is Lee Harvey Oswald.
9 Jack Ruby Was Framed
Only two days after he was arrested, Lee Harvey Oswald was himself killed by nightclub owner Jack Ruby. There aren't too many conspiracy theories that Ruby wasn't the killer -- after all, the photograph of him shooting Oswald is one of the most famous pictures of all time. But Ruby claimed he was being set up by people "in high positions" who wanted to overthrow the government. Plenty of people took him at his word. He himself died of cancer less than four year after JFK's assassination -- and you can bet there are conspiracy theories about that, too.
10 The United Nations Is Engineering a One-World Government
Various New World Order theories exist, sharing the idea that a cabal of powerful individuals is slowly but surely arranging to destroy the sovereignty of all nations and replace them with a single totalitarian government to rule the entire world. The United Nations often figures in these conspiracy suppositions. (Pictured: Secretary of State Condoleezza Rice speaks to the United Nations General Assembly in New York in 2005.)
11 Marilyn Monroe Was Killed by the Kennedys
The iconic blonde bombshell, Marilyn Monroe, died of a drug overdose (listed as "probable suicide") on Aug. 5, 1962, at the age of 36. But ever since author Norman Mailer wrote in 1973 that he suspected a cover-up, theories have swirled that she was killed at the behest of President John Kennedy or his brother Attorney General Robert Kennedy, both of whom conspiracy theorists have linked her to romantically. Pictured: Monroe just days before her death.
12 Aliens Crash Landed in Roswell
In 1947, a mysterious crash that the U.S. military says was a surveillance balloon sparked the most enduring alien conspiracy of all -- that it was in fact an alien spacecraft that was wrecked in Roswell, N.M., and that the government has kept the alien corpses, their technology, and the certain knowledge of life on other planets among its most highly guarded secrets. Pictured: conspiracy theorists dressed as aliens in Roswell, N.M.
13 The U.S. Government Keeps Alien Technology at Area 51
The high-security military base in Nevada known variously as Dreamland, Groom Lake, and Area 51, is believed by conspiracy theorists to hold more secrets than the spy planes tested there. It's conjectured that Area 51 is where government scientists reverse-engineered alien technology, possibly including the Roswell debris. Their research supposedly gave rise to everything from stealth technology to time travel. It's also spawned conspiracy-theorist hunting grounds like the nearby Alien Research Center (pictured).
14 Paul Is Dead
Conspiracy theorists say that Ringo Starr (second from right) is the sole surviving Beatle, and that Paul McCartney (far left) died decades ago, killed in a car accident and replaced by a lookalike. Supposedly, various Beatles songs, played either backward or forward, give hints to the conspiracy. Yet another conspiracy theory states that Paul isn't dead, but that the Beatles started the rumor themselves as a prank that they've been perpetuating ever since.
15 The Skull and Bones Society Controls the U.S.
A secret club at Yale University, the Skull and Bones is, according to most mainstream accounts, more of a fraternity than a sinister league, but it often shows up in the allegations of conspiracy theorists, who point out that its members include the most powerful men in the country (such as former Presidents George W. Bush and George H.W. Bush, and U.S. Sen. John Kerry), and accuse it of everything from controlling the government to starting wars.
16 The One-Dollar Bill Is Full of Occult Symbols
Yank out your wallet, pull out a single, and gawk at all the symbols you don't understand plastered all over the place (for example, if you look very closely near the front, top right corner, you'll see an owl peeking back out at you). Well, conspiracy theorists have plenty of explanations for you, many of the most popular being that they're occult symbols placed there to hint at the mystical -- and malevolent -- origins of the United States. The pyramid on the back, for example, has 13 steps, and is hovered over by what they say is the Egyptian Eye of Horus, as well as the words "Novus Ordo Seclorum," which conspiracy theorists mistranslate as "New World Order."
17 FDR Knew About the Impending Attack on Pearl Harbor
Many conspiracy theorists don't include President Franklin D. Roosevelt among America's "Greatest Generation." According to them, the U.S. military knew well ahead of time that the Japanese were going to attack Pearl Harbor, but that FDR allowed some 2,400 people to be killed so that he'd have popular support for entering World War II. Pictured: FDR signing the declaration of war against Japan the day after Pearl Harbor was bombed.
18 NASA Is Covering Up an Alien Civilization on Mars
In 1976, the Viking 1 space probe took a photograph of the Cydonia region of Mars that included what appeared to be a huge human face gazing up at the sky (bottom). The images created a furor among those believed that it was proof of an ancient Martian civilization. In 1998, the Mars Global Surveyor (top photos) took better-resolution photos that seemed to prove that the Face on Mars was simply an optical illusion -- but some diehard conspiracy theorists insist it's a NASA cover-up.
19 Jews Are Bent on Dominating the World
For centuries, Jews have been the target of a wide range of conspiracy theories, typically accusing them of manipulating the world financial system, the media, and political leaders at the expense of those of other religions. Possibly the first modern conspiracy theory was that of the 19th century "Protocols of the Elders of Zion," a forged book that supposedly detailed the plans of Jews to take over the world. Throughout history, hate mongers used such suspicions about the minority group to justify stripping Jews of rights, property, and their lives -- culminating in the horrors of the Holocaust. Pictured: a poster for a Nazi anti-Semitic propaganda film.
20 Martin Luther King Was Killed by the Government
Conspiracy theorists say the civil-rights leader wasn't killed by lone gunman James Earl Ray but by government agencies who thought he was a communist or a destabilizing force for America.
21 James Earl Ray Didn't Pull the Trigger on Martin Luther King
James Earl Ray, King's convicted killer, said that he was drawn into a conspiracy with his brother and a mysterious man named Raoul. He claimed he didn't actually shoot the civil-rights leader himself, and that he pleaded guilty only to avoid the death sentence.
22 The Council on Foreign Relations Wants to Install a World Dictatorship
A bipartisan and well-respected Washington, D.C., think tank that focuses on world diplomatic affairs, you'd think the CFR would get a little slack from conspiracy theorists. But many, including the John Birch Society, believe that its ultimate goal is to create a single government to rule the entire world. Pictured: President Bill Clinton addresses the CFR in 1998
23 The Trilateral Commission Is Taking Over the World
Much like its counterpart the CFR, the Trilateral Commission -- founded in 1973 to foster better relations between the U.S., Europe, and Japan -- is seen as yet another group trying to create a one-world government. Pictured: Russian Foreign Minister Sergey Lavrov (second from the left) welcomes the members of Trilateral Commission -- the former British ambassador to Russia Roderick Lyne (second from right), Brooklyn Institute president Strobe Talbot (left) and former Japanese ambassador to Russia Koji Watanabe --- during their 2006 meeting in Moscow.
24 Big Business Wants Marijuana Outlawed
Conspiracy theorists say that the real reason marijuana is against the law is because the hemp plant is so useful that it threatens the paper, rope, pharmaceutical, and cloth industries.
25 Black Helicopters Watch Our Every Move
According to militia groups' conspiracy theorists, there's a shadow government already in power in the U.S. (and possibly the rest of the world), and it exercises its power with ubiquitous black helicopters that act as the eyes and ears of the people secretly in power.
26 The Vatican Secretly Governs the World
It's been around for a long, long, long time, so it's no wonder that the Vatican has plenty of conspiracy theories surrounding it -- mostly that the Catholic Church's inner circle is the world's puppeteers. In the U.S., many Americans feared that the Vatican was trying to take control of the White House when Catholic candidates like Al Smith and John Kennedy ran for the highest office. Pictured: Pope Benedict XVI leaves St. Peters's square at the Vatican on June 24, 2009.
27 The Royal Family Had Princess Diana Killed
When investigators concluded that the 1997 death of Princess Diana and her boyfriend, Dodi Fayed, was caused by a drunk driver and reckless driving, conspiracy theorists -- including Fayed's powerful father -- begged to differ. They said they knew that it was in fact the British royal family who had MI6 kill Di because she was pregnant with a Muslim man's baby.
28 'The Da Vinci Code' Conspiracy Is True
Dan Brown's bestselling novel "The Da Vinci Code" posits that the Mona Lisa was part of a centuries-long conspiracy to cover up the fact that Jesus Christ fathered a child with Mary Magdalene. It's technically a work of fiction, but there are conspiracy theorists who believe some of the ideas in the book are perfectly valid.
29 The Jesuits Are a Rogue Organization Bent on World Domination
The first conspiracy theories about the Jesuit order actually began with the Catholic Church itself -- the Inquisition was particularly irked by the clannish but well-funded group. Modern conspiracy theories claim that the Jesuits have imposed their philosophies on the Church and various governments from within, started wars throughout the Western hemisphere to gain power, and -- yep, you guessed it -- form a one-world government. Pictured: Jesuits attend the general congregation of the Society of Jesus in Rome.
30 The Sept. 11 Attacks Were an Inside Job
A distressing number of people around the world believe that the terrorist attacks of Sept. 11, 2001 were the work of the George W. Bush administration. The motive: an excuse to clamp down on civil liberties inside the United States and launch wars around the world.
31 Airplane Contrails Are Actually Chemicals Being Sprayed
It's perfectly normal for aircraft to have contrails -- trails of water vapor that follow the hot exhaust of the engine. For conspiracy theorists, though, some contrails are actually chemtrails -- the secret spraying of various chemicals onto populations and crops to further the purposes of government scientists or various evil organizations.