There is no such thing as a failed experiment, only experiments with unexpected outcomes.
 

RICHARD BUCKMINSTER-FULLER (1895–1983)

Experiments

Sanctorius Sanctorius


Sanctorius Sanctorius was a 16th-century professor in Padua who for 30 years weighed himself, the food he ate, and his excretions. To weigh himself he sat in a weighing platform suspended from his ceiling. He often ate, worked and slept on the scale.

He found that his urine and faeces weighed only a fraction of what his food weighed but that he nonetheless stayed the same weight. From this, he deduced that the rest of the weight of his food must be lost through 'insensible perspiration' i.e. it was sweated out of his skin. He therefore believed it was vital not to obstruct the body's pores, so the poisonous waste could evaporate freely.
 
Sanctorius was wrong, but importantly he used real observation and measurement, rather than just thought experiments. Faeces weigh less than the food we eat because much of our food is burned by the body to keep us alive. Human faeces are normally about three-quarters liquid to one-quarter solid, and 30% of the dry weight is dead bacteria.

Sanctorius also invented the mouth thermometer with his friend Galileo.

Dubious Experiments 


In 1938, American psychologists conducting a study into ‘Egocentricity in Adult Conversation’ wanted to find out how frequently people referred to themselves in conversation, but without people knowing they were being studied. Hence, they concealed themselves under beds in students' dormitories and recorded their conversations, as well as eavesdropping in smoking rooms and wash-rooms, and listening to telephone conversations. The results showed that 40% of people's remarks tended to be about themselves.
 
The history of scientific experimentation is rife with dubious or downright dishonest experimenters. One researcher called Mortimer Sullivan wanted to investigate the enlisting process, so he joined the air force, then re-enlisted with a different name, appearance and mannerisms. Another, Eugene D. Webb, recommended setting up a microphone in a fake hearing aid to record people's voices, saying 'it works extremely well in inducing the subject to lean over and shout directly into the recording apparatus.’
 
Middlemist, Knowles and Matter’s 1976 study into ‘Personal Space Invasion in the Men’s Restroom’ involved concealing a camera in a stack of books on the floor of one of the cubicles in the Gents, and filming a row of urinals from under the partition.
 
In 1942, psychologist Lawrence LeShan tried to use sleep-learning at a summer camp to cure some boys of nail-biting. He recorded the phrase 'My fingernails taste terribly bitter' on a phonograph which played the phrase 300 times a night. One boy appeared to respond positively, but after five weeks the phonograph broke. To keep the experiment running, LeShan stood in the boys' dormitory through the night and repeated the phrase himself. This seemed to be much more effective, and LeShan claimed it as a success. However, these days, it is thought that the boys were just awake and freaked out by the experience, concluding that the only way to get LeShan to leave them alone was to stop biting their nails.

In the 1900s, a scientist decided to test the idea of ‘crocodile tears’ by rubbing onion into crocodiles' eyes.

King Charles II and Isaac Newton both conducted alchemical experiments.

ERNEST RUTHERFORD (1871–1937)

If your experiment needs statistics, you ought to have done a better experiment.

100 Defecated Ants


In 2012 Professor Volker Sommer was studying the behaviour of Nigerian chimps that used ‘dipping wands’ to eat army ants (Dorylus rubellus). The ‘wands’ - short sticks - were dipped into ants’ nests and removed once the chimp decided that enough ants had climbed onto them. 

To see how effective this technique was, Volker used discarded wands to measure how fast ants ran up the stick, how many ants were harvested in a single dip, and the typical weight of those ants. However, the question he couldn’t answer was how much nutrition the chimps got from the ants. Measuring the difference between (a) what goes into a chimp and (b) what comes out would require a high degree of control that would interfere with the animals’ natural behaviour. So Sommer volunteered himself instead.

On each occasion the test was run, Sommer ate 100 Dorylus worker (after immobilising them in whisky). Over the subsequent three days, he detected 10.1% of ingested ant heads in his excreta. This enabled him to work out how many ants the chimps were eating, and his conclusion was that the number was too small for them to be serving any nutritional purpose. The chimps were obviously eating the ants for another reason.  Sommer suggests that it was as a cultural identifier:

'What you're eating and what you're not eating helps create your social identity, and that's what I believe these chimpanzees are doing. They are eating these ants - they taste horrible - and by doing so they are saying, "Look, if you want to be a proper member of our group, you have to eat ants."'

HENRI POINCARE (1854–1912)

It is often said that experiments should be made without preconceived ideas. That is impossible.

Self Experimentation


Article 5 of the Nuremberg Code prohibits the use of human subjects for medical experiments when there is an ‘a priori risk of death’. The only exception to this rule is if the subject is one of the experimentors. Nobel laureate Gerhard Domack, for instance, once injected cancer cells into his own body to prove it was not an infectious disease.
 
Werner Forssmann was the first person to insert a catheter into someone’s heart (a catheter is a tube inserted into the body to drain it). It was his own heart. After inserting the tube through his arm and into his heart, he walked up to the X-ray department and took a picture to prove what he’d done. The experiment lost him his job, but won him the 1956 Nobel Prize for Medicine.
 
Conventional wisdom in the 1940s was that the human body could not stand G-forces of over 18g. John Paul Stapp proved that this was not the case by sitting in his own rocket-sled, speeding up to close to the speed of sound, then stopping abruptly; he subjected himself to over 35g and survived.

Isaac Newton tested the effect of the shape of the human eye by inserting a knife between his eyeball and its socket.