21 grams: the weight of the soul

What is a soul? Can it be touched? Does it have mass? These questions plagued Duncan McDougall, a physician in Haverhill, Massachusetts, so much that he developed “the 21 Grams” experiment to determine whether souls have physical weight.

The April 1907 issue of American Medicine published an article by Dr. Duncan McDougall describing his experiment in which the beds of dying patients were placed on sensitive scales. Believe it or not, he was trying to weigh the human soul!

Experiment

In 1901, Duncan MacDougall, a physician in Haverhill, Massachusetts, who wanted to scientifically determine whether the soul had weight, identified six nursing home patients whose death was inevitable. Four suffered from tuberculosis, one from diabetes and one from unknown causes.

McDougall specifically chose people who were suffering from conditions that cause physical debilitation, as he needed patients to remain still as they died in order to accurately measure them.

When patients looked as if they were close to death, their entire bed was placed on an industrial scale with sensitivity within 5.6 grams and it was concluded that at the time of death there was a weight loss of about three quarters of an ounce, or 21 grams. Believing that humans have souls and animals do not, McDougall later measured fifteen dogs' weight changes after death.

It is unclear how he got 15 dying dogs in his hands, but he found no weight loss at the time of their death. He wasn't surprised, of course, because he didn't think dogs had souls.

MacDougall had no more breakthroughs regarding his experiments with the human soul. His very soul went to another world in 1920. Despite being dismissed as scientific fact, McDougall's experiment popularized the idea that the soul weighs 21 grams, and the idea has appeared in novels, songs, and films.