The next time you get the Halloween season chills -- like hair standing up on the back of your neck as you feel a paranormal presence behind you -- remember Isaac Newton.
A paper published by University of Central Florida professor Costas Efthimiou and his student Sohang Gandhi says the laws of physics debunk most ghost and ghoul stories.
But Gandhi, a UCF graduate now studying at Cornell University, admits he is not completely free of fear.
"I was afraid of ghosts and vampires when I was a child," he confesses. "Even now, if I am walking home from the theatre at night after watching a horror film, I look over my shoulder. I am human, and we all have irrational fears nested deeply in our subconscious.
"However," he continues, "intellectually I know that belief in the existence of goblins and ghouls is just as arbitrary as belief that I can flap my arms and fly."
Using Newton's Laws of Motion, Efthimiou and Gandhi -- who was selected to the USA Today All-Academic Team last year -- demonstrate that ghosts cannot possibly walk through walls. They use basic math to disprove myths of humans turning into vampires after they are bitten.
And if the movie Ghost, starring Patrick Swayze and Demi Moore, made you smile, Efthimiou and Gandhi have some sad news. For ghosts to be able to walk like humans, the paper says, they would need to exert force upon the floor, which would exert an equal and opposite force in return.
But if ghosts can pass through walls and have humans walk right through them, it means they cannot apply any force.
There's bad news for Dracula too. To disprove the existence of vampires, and to debunk the myth of people turning into vampires once bitten, Efthimiou and Gandhi rely on geometric progression, a basic math principle.
If the first vampire swung into action January 1, 1600, when the human population was 536,870,911, Efthimou and Gandhi suppose, and if it needed feeding once a month, there would be two vampires and 536,870,910 humans on February 1. There would be four vampires on March 1 and eight on April 1.
If this continued, all humans would become vampires within two and a half years. And the vampires' food source would disappear.
'In the long run, humans cannot survive under these conditions, even if our population were doubling each month,' Efthimiou was quoted as saying. 'And doubling is clearly way beyond the human capacity of reproduction.'
Gandhi says their paper is only a study, not a research. "The article isn't really based on any research done by myself or my professor. It merely employs basic and well known principles from math and physics to poke fun at popular myths."
But why did they want to bury the myths in the first place?
"It started as a series of themed talks given around Halloween two years ago by my professor," says Gandhi. "He later asked me to help him turn his lecture into an article which we could publish in a journal/magazine aimed at the general public. I came up with many ideas of my own and the article is a synthesis of these and his lectures.
"It was an educational effort designed to promote critical thinking -- which is alarmingly lacking in our society -- in the general public while entertaining," Gandhi adds.
He says children's fears are a normal part of development. The real danger is when people grow up without learning how to examine, think critically, and with reason and evidence before believing in the stories, he points out.
Gandhi never thought of pursuing a career in physics until a lesson on Newton's Laws of Motion inspired him during his senior year of high school.
Gandhi -- a recipient of the Barry M Goldwater Scholarship, a premier award for undergraduates in mathematics, science and engineering -- plans to be a researcher in theoretical, elementary particle physics.
He wants to stay in academia because "the university environment nurtures ideas and is all the richer for it."
Gandhi's parents moved to the United States in the seventies. His father is a retired aerospace engineer, and he has a brother studying engineering at the University of Florida.