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TIL about Leonhard Euler (1707-1783) who not only popularised the use of lower case Pi to denote the ratio of a circle's circumference to it's diameter, but was also the first to use "i" to denote the square root of -1. The constant "e", the base number in a natural logarithm is the Euler Number

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gMd4b TIL: In 2015, researchers testing the efficiency of mosquito repellents used a Victoria’s Secret perfume because they thought the floral fragrance would attract mosquitoes. To their surprise, they found it repels mosquitoes better than a range of mosquito deterrents.
rWge TIL that Claudette Colvin was the first African American woman to refuse to move to the back of a bus nine months before Rosa Parks did, but the NAACP did not want to use her to represent their organization because she was 15 years old and pregnant.
epNO6 TIL philosopher Joseph Levine’s 1983 paper introduced the “explanatory gap” noting while “Pain is the firing of C fibers” is physiologically valid, it doesn’t make us understand how pain feels. Showing the challenge physicalists face in connecting physical properties to subjective experiences.
xVJy7 TIL The last two remnants of the virus known to cause smallpox, which are kept in tightly controlled government laboratories in the United States and Russia. In 2013, cloned variola major (smallpox) DNA fragments were found in a South African laboratory.
ajAJ TIL that despite earning $967 million in global revenue, the theatrical release of Harry Potter and the Order of the Phoenix fell short of being profitable by $167 million.