The moon landing was fake
Reality Check: Believers of this particular conspiracy theory have painstakingly dissected video and photos from the Apollo 11 moon landing looking for evidence that it was faked. For example, some have pointed out that the American flag Neil Armstrong planted on the moon appears to be flapping "in a breeze" in videos and photographs.
But, as spaceflight historian Roger Launius of the Smithsonian's National Air and Space Museum in Washington D.C., explained on the 40th anniversary of the first moon landing, "The video you see where the flag's moving is because the astronaut just placed it there, and the inertia from when they let go kept it moving."
Bigfoot is real
Reality Check: Despite several attempts to prove Bigfoot exists, no one has presented evidence that has withstood scientific scrutiny. Indeed, many such "proofs" have turned out to be outright hoaxes. In 2008, two men claimed to have found a two-metre tall, 230-kilogram Bigfoot corpse in the woods of northern Georgia, but the body was later revealed to be a rubber ape costume.
Another group claimed they had done DNA tests that proved the "North American Sasquatch is a hybrid species, the result of males of an unknown hominin species crossing with female Homo sapiens." The researchers touted the fact that their study was published in a scientific journal called DeNovo—but it seems the publication was created especially for that Bigfoot study.
While Bigfoot is likely just a myth, that's not to say that no new, close relatives of humans have ever been found—it's just that all of them are long extinct. For example, in 2010, scientists announced that a 40,000-year-old pinkie bone found in a Siberian cave belonged to a previously unknown species of ancient human called Denisovans.
Global warming is a hoax
Reality Check: Numerous scientific studies have confirmed that the Earth is warming and that the rate of warming is increasing. Average temperatures have climbed 0.8°C around the world since 1880. Much of the temperature increase happened in recent decades, coinciding with a spike of carbon dioxide and other greenhouse gases emitted into the atmosphere as a result of human activity.
The effects of global warming on the natural world are equally well documented: Arctic sea ice is now thawing at historic rates, flowers are blooming earlier, and the migration patterns of birds and other animals are changing.
Reality Check: It hasn't always been the case, but many astronomers today are open to the idea of life existing elsewhere in the universe—and even to the possibility of intelligent alien life. That's thanks in large part to the relatively recent discoveries of hundreds of so-called exoplanets—worlds beyond our solar system—and thousands of planet candidates. Most scientists think it's only a matter of time before a habitable, rocky, Earth-like twin is discovered.
Even our own solar system might contain evidence of alien life. NASA's Curiosity rover recently discovered tantalizing evidence of clays and minerals that scientists say could only have formed in water. The implication: Ancient Mars had the conditions and ingredients necessary to support life.
As for UFOs, most sightings are eventually linked to more mundane causes. For example, a video by Russell Crowe purportedly capturing a UFO outside his office was likely reflected sunlight from a plane passing near sunset.
Childhood vaccines are linked to autism
Reality Check: A recent government study confirmed what many scientists have been saying all along: There is no connection between the number of vaccines a child receives and his or her risk of developing autism.
The study, published last month in The Journal of Pediatrics, also found that even though kids are getting more vaccines these days, those vaccines contain fewer substances that provoke an immune response.