Quiz: Test Your Knowledge of These Debunked Conspiracy Theories

Cruise any 9/11 conspiracy forums and you're bound to run into this one - the idea that the towers just collapsed all at once, in a freefall, something that might point to carefully planned explosives. But it only takes one careful viewing from a still camera to see the reality, that the towers, sadly, collapsed in a time of between 15 and 22 seconds.

It's true that Denver International Airport is a sprawling monstrosity. And there are murals of conflict and death on the premises. However, those bits of evidence don't really seem to prove that the tarmac conceals the headquarters of the New World Order, as some conspiracists believe.

In 2012, an anonymous internet post dropped a bomb on hip hop - revealing that an early '90s meeting between corporate bigwigs where rap album marketers would agree to push hardcore "gangsta" rap, proliferating a lifestyle that was sure to keep private prison business booming. Of course, U.S. prisons haven't needed gangsta rap albums to be profitable.

Your eyes aren't deceiving you - in video of the moon first landing, the flag is indeed flapping. But the fabric isn't waving due to air. The astronauts had trouble extending the flag rod completely and in still pictures this created a ripple effect, making it look as if the flag was waving. In video images it becomes clear that the flag only moved when they were trying to plant it into the moon's surface.

In 1990, retired English soccer player David Icke visited a psychic and the rest is twisted history. He became a one-man conspiracy machine, spouting stories about reptilian beings that were controlling Earth and its inhabitants. His sports fame helped give the ideas traction and he still makes a fortune weaving his fantastic tales.

In 2014, the Anti-Defamation League released a study showing that half of the respondents had never heard of the Holocaust - the systematic murder of Jews and other people during WWII. Of the half who had heard of the murders, one-third believed that the Holocaust was a fiction invented to further political gains of the mid-20th century.

In 1997, Andrew Wakefield, a British surgeon, published a study suggesting that the measles, mumps, rubella (MMR) vaccine sparked autism in English kids. Turns out, the "study" was rife with errors and financial conflicts of interest - and it was retracted by Lancet. Meanwhile, real science has found plenty of evidence that variables for autism often take hold in human physiology long before vaccines are introduced.

In 2016, a white supremacist Twitter account spouted blatantly false information about a "human trafficking" ring involving Hillary Clinton that originated from a pizza parlor in Washington, D.C. About a month later, a deranged man showed up there with a gun to "investigate" the problem, blasting holes into the restaurant's interior. Authorities quickly disproved the conspiracy.

High on heroin, Cobain ended his life with a gun. But not before he scrawled a page-long suicide note, one that ended with childlike pen strokes. Forensics investigators concluded that the writing was in fact Cobain's and that perhaps the overload of drugs in his system (and his extreme emotional distress) caused the deterioration of his penmanship at the end of his missive.