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TIL roller coasters use three sets of wheels to keep the trains on the track. Running wheels which are on top of the rails, side friction wheels which are on the side of the rails, and up-stop wheels which are under the rails. This is why inversions and negative-g moments are possible.

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e0JV4 TIL that putting live birds in a pie was a form of entertainment in the 16th century. An Italian recipe book of 1549 described how to make a pie so that the birds survived and 'flew out' when it was cut open. This practice was also found in 1725 in a cookery book by John Nott.
WkxLA TIL Mark Zuckerberg attempted to buy Snapchat for 3 billion dollars in November of 2013 but was rejected. Almost 3 years later, Instagram cloned Snapchat’s main features and launched ‘Instagram Stories’.
b9vVE TIL of Vivien Thomas, An African-American surgical technician that developed the procedures used to treat blue baby syndrome ( a fatal heart condition in infants) in the 1940s. He was offered the position of Chief of Surgery at Johns Hopkins (his alma mater) in 1941.
lw0a TIL Brian May’s dad helped him build his famous guitar, but was upset when Brian abandoned his PhD program to join Queen. Brian went on to write “We Will Rock You”, “Fat Bottomed Girls"—and eventually "A Survey of Radial Velocities in the Zodiacal Dust Cloud”, the thesis he finished 36 years later.
grdab TIL Tonic water was initially marketed for its quinine (known to treat Malaria) but due to its bitter taste, British soldiers in India added Gin (which was rationed to them), thus creating the Gin and Tonic