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The 21 Grams Theory

Weight scale

Does the soul weigh 21 grams?

On 10 April 1901, an unusual experiment was conducted in Dorchester, Massachusetts.  Dr. Duncan MacDougall was going to prove that the human soul had mass, and was therefore, measurable.

Dr. MacDougall conducted this experiment on six dying patients who were placed on specially made Fairbanks weight scales just prior to their deaths.  Dr. MacDougall’s intention was to weigh each body before and after death to determine any differences measured by the delicate scales.  The patients were selected based upon their imminent death.  Two patients were suffering from tuberculosis, 5 were men and one was a woman.

In the company of four other doctors, Dr. MacDougall carefully measured the weight of his first patient prior to his death.  Once the patient died, an interesting event occurred.

“Suddenly, coincident with death,” wrote Macdougall, “the beam end dropped with an audible stroke hitting against the lower limiting bar and remaining there with no rebound. The loss was ascertained to be three-fourths of an ounce.”

The experiment continued on the next patient with the same results.  Dr. MacDougall felt he was on to something extraordinary.  A quote from the 11 March 1907 New York Times article captures the historic moment:

“ The instant life ceased the opposite scale pan fell with a suddenness that was astonishing – as if something had been suddenly lifted from the body.  Immediately all the usual deductions were made for physical loss of weight, and it was discovered that there was still a full ounce of weight unaccounted for”.

All five doctors took their own measurements and compared their results.  Not all the patients lost the same weight, but they did lose something that could not be accounted for.  Unfortunately, only four of the six patient’s results could be counted due to mechanical failures or the patient dying prior to the test equipment being in place.

But what about the consistent weight loss?  Everything was taken into account, from the air in the lungs to bodily fluids.  It still could not be explained.  An interesting variation occurred on the third patient, who maintained his same weight immediately upon death.  But after one minute, he lost about an ounce of weight.  Dr. MacDougall explained this discrepancy as follows:

“ I believe that in this case, that of a phlegmatic man slow of thought and action, that the soul remained suspended in the body after death, during the minute that elapsed before its freedom.  There is no other way of accounting for it, and it is what might be expected to happen in a man of the subject’s temperament”.

Following the experiment and consulting with the other attending physicians, it was determined that the average weight loss of each person was ¾ of an ounce.  Dr. MacDougall concluded that a human soul weighed 21 grams.

Dr. MacDougall conducted the same experiment on 15 dogs.  The experiments showed no change in weight following their death.  MacDougall concluded that this may signify only humans have souls.

H. LaV. Twining, a physics teacher at Los Angeles Polytechnic High School, attempted the same experiment on mice in 1917.  His conclusion was in line with that of Dr. MacDougall.  There was no deviation of weight when the mice died.

Dr. MacDougall was a respected physician of Haverhill and the head of the Research Society that was conducting work in this field for six years prior to the experiment.  Although this experiment would be considered unethical in modern times, it is still a peculiarity that sparks a lot of criticism, ranging from the methodology used to various religious implications

Dr. MacDougall admitted that more research needed to be done, but following these experiments, Dr. MacDougall diverted his attention to obtaining the ability to photograph the soul as it left the human body.  Unfortunately, following his soul weight experiments, Dr. MacDougall failed to establish any further scientific breakthroughs.  Dr. Duncan MacDougal passed away in 1920.

Of Note:  A great movie titled “21 Grams” made in 2003 references Dr. MacDougall’s experiments.  Click here for more details.

References: Snopes, Dr. Duncan MacDougall on Wikipedia, A Soul’s WeightNew York Times archived article, March 11, 1907

About Jim Heddlesten

Jim Heddlesten
Jim was born and raised in Naples, Italy. He created this website in December 2009 because of his fondness for historical mysteries. Since creating the website, Historic Mysteries has grown incredibly fast and over 300 mysteries are now documented on this site. Thank you for visiting and please bookmark this site.


  1. it is really weird , that with all the technology available nowadays , these tests have not been carried out in totally controlled circumstances , where there would be absolutely no doubt , regarding credibility … thousands on people donate their bodies for scientific research , and given the modern equipment capabilities of measuring quantum values etc , this whole question could be answered once and for all with 100 % certainty…i am pretty sure ,that such experiments have been carried out with modern technology ,but in secret . Probably the results were discouraging .. :(

  2. So this is the meaning behind the title of the movie, 21 GRAMS?

  3. I find this quite fascinating and further evidence that the essence of who we REALLY are is eternal. Having had a near death experience myself; I was actually more ME than I am in real life, at the moment of seeming death.

  4. I love reading about all the things that are unexplained to the world and hope more items of such are added to this page thank you again for your info

  5. According to the law of Conservation of energy, where does this "some kind of magnetic energy" goes then?

  6. Unless you have some evidence to the contrary you are just talking out of your ass, aren't you? I am not religious but I am a spiritual man and I consider myself to be a realist. It is ignorant to discount anything that you have no evidence for in either direction… Try shutting your mouth and opening your mind.

  7. Jose Soundwave Valdés

    So, dogs don't have soul but humans do? How convenient. It fits exactly the beliefs at the time. What we know today is that we are not that different. We just enjoy different levels of complexity in our conscience, but the experience is basically the same.

  8. Just Had a thought. If the soul exists and is made up of some kind of magnetic energy then when the soul leaves the body that extra magnetism is lost and gravity itself has less of a pull on you. Just food for thought. Perfect answer for the 21 gram theory!

  9. It was a hoax, there is no soul, there is no skygod, it is all crap! Religious people fall for this kind of stuff since they are so gullible, but not realists who can think for themselves.

  10. although very interesting these things should be left alone. this “happening” is your very private journey to meet your maker.

  11. The Souls wieghs more than its body.
    The loosing of wieght after death is the air supply being stoped in the body.
    When there is no air then there might be a slight change in the body’s mass..
    So If telling that, the soul weighs 21 or 28 gram is based on ambiguity.

  12. i wouldnt call it a hoax unless proved to be so, since its almost legally impossible to experiment with something like this and even so many regard it as unethical and wouldnt allow it on their loved ones

  13. In a book by Dan Brown -”The Lost symbol”, one of the main character is used to test the souls of human beings before and after death. But in that case, it wont be 21 grams or any nearer value.. it will be far less like 0.000164 something…

  14. I don’t want to offend anyone, but the Nazis had a golden opportunity to test this. It wasn’t like they were gonna live.

  15. A research that was conducted on only four patients is hardly reliable.

  16. The only real mystery here is why nobody since then can repeat this. Maybe because it was a hoax?

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