Merriam-Webster defines a conspiracy theory as: "a theory that explains an event or situation as the result of a secret plan by usually powerful people or groups."

In other words, a conspiracy theory is a theory that certain circumstances did not occur due to chance, but were plotted out or created by a powerful group of schemers. These groups are typically thought to be wealthy and influential people of the world.

Although I have a hard time believing most conspiracy theories, listed below are five conspiracy theories that I found to be particularly compelling and interesting - as well as insight into why humans are so likely to believe them.

1.The Mandela Effect (parallel realities)

The Mandela Effect is a theory named after the phenomenon of people claiming to remember certain events or occurrences that do not match up with reality. For example, a large number of people believe that Nelson Mandela died in 1980 while in prison, even remembering the news reports of his death, giving the theory its name. Nelson Mandela did not die until December of 2013. One other example of this theory is that a large number of people claim to remember the popular children's book series and television show "The Berenstain Bears" to be called "The Berenstein Bears", although all previous copies of the books and movies feature the name "Berenstain". Since our human memories are so concrete to us, it may be easier to accept that the universe is incorrect rather than our faulty memories.

2. CERN will end the world

CERN stands for "Conseil Europeen pour la Recherche Nucleaire" which translates to "European Council for Nuclear Research" in English. CERN's Large Hadron Collider has been a subject of conspiracy for some Internet users and bloggers. Many conspiracy theorists believe that the collider will create a black hole that will swallow the earth. One blogger in particular seems to think that CERN is working to summon Osiris, the Egyptian god of the dead, since there is a Shiva statue near the entrance of the collider. Shiva is historically documented to be the god of destruction. CERN describes it as a "powerful particle accelerator" that engineers and physicists are using to "probe the fundamental structure of the universe".

3. There is no gold at the Fort Knox US Bullion Depository in Kentucky

Fort Knox is one of the world's most secure vaults, encased in granite and cement. Completed in 1936, Fort Knox has a vault door that weights 22 tons and can resist drills, torches, and explosives. The roof of the building is even said to be bulletproof. Cameras, electric fences, minefields, and guards serve as additional security, as well as that fact that the depository is on a large U.S. army post. Such security is necessary to protect 5,000 metric tons of gold that is tucked away inside of the vault. However, skeptics say that this depository is empty. Other conspiracy theorists think that there may be something else of higher importance of gold being protected at Fort Knox, such as weapons or very expensive artifacts. "America's Book of Secrets", a documentary series television show, featured an episode covering the Fort Knox conspiracies in 2012. (Watch here. This episode is also available on Netflix.)

4. The 27 Club

"The 27 Club" describes the coincidence that many musicians die at age 27. This reference caught on widely after Kurt Cobain's death in 1994. Fans realized that his age of death was the same as Jimi Hendrix, Janis Joplin, Jim Morrison, and many other notorious musicians. The "curse" also expands to a large number of actors and artists who have died at age 27, such as Star Trek actor Anton Yelchin. Some theories include that this may be due to drug decay or a satanic pact that expires at age 27.

5. "The Simpsons" can predict the future.

Coincidence or not, many events that have occurred in the highly popular television show "The Simpsons" have later happened in reality. Some "prediction" examples include Donald Trump's candidacy for president of the U.S., cell phones with video chat capabilities, the 9/11 terrorist attacks, and the 2014 Ebola virus epidemic.

According to the research journal "Applied Cognitive Psychology," findings and studies show that those who believe in conspiracy theories may tend to feel out of control when it comes to their own lives.

After uncertain or frightening events occur in reality, a large number of conspiracy theories begin to circulate. Psychologically, this is due to individuals trying to make sense or find solutions to instances in which they have no control over, especially if they are particularly devastating.

In a 2015 interview with TIME Magazine, Jan-Willem can Proojen, a VU University Amsterdam associate professor in Social and Organizational Psychology (and research member of the study) said, “When I started this research, one of the things that I really found astonishing was how many people believe in certain conspiracy theories,” said Proojen. “The more that people feared the millennium bug in 1999, the more likely they were inclined to believe in other conspiracy theories, ranging from Kennedy to the government hiding evidence of the existence of UFOs."

Therefore, if an individual believes in one conspiracy theory, they are more likely to believe in alternate conspiracies. Van Proojen also added that this is a natural phenomenon in society. “There are no doubt cultural variables influencing it,” he says. “But the essence of conspiracy theorizing is, I think, universal in human beings. People have a natural tendency to be suspicious of groups that are powerful and potentially hostile.”

Many conspiracy theories have also turned out to be true. To read which conspiracies have really happened, click here.