On this day:
1946 – The 8.6 Mw Aleutian Islands earthquake shakes the Aleutian Islands with a maximum Mercalli intensity of VI (Strong).
A destructive tsunami reaches the Hawaiian Islands resulting in dozens of deaths, mostly in Hilo, Hawaii.The 1946 Aleutian Islands earthquake occurred near the Aleutian Islands, Alaska on April 1. The shock had a moment magnitude of 8.6 and a maximum Mercalli intensity of VI (Strong). It resulted in 165–173 casualties and over $26 million in damage. The seafloor along the fault was elevated, triggering a Pacific-wide tsunami with multiple destructive waves at heights ranging from 45–130 ft. The tsunami obliterated the Scotch Cap Lighthouse on Unimak Island, Alaska among others, and killed all five lighthouse keepers. Despite the destruction to the Aleutian Island Unimak, the tsunami had almost an imperceptible effect on the Alaskan mainland. The wave reached Kauai, Hawaii 4.5 hours after the quake, and Hilo, Hawaii 4.9 hours later. These Hawaiian natives were caught completely off-guard by the onset of the tsunami due to the inability to transmit any warnings from the destroyed posts at Scotch Cap. The effects of the tsunami also reached the West Coast of the United States.
The tsunami was unusually powerful for the size of the earthquake. The event was classified as a tsunami earthquake due to the discrepancy between the size of the tsunami and the relatively low surface wave magnitude. The large-scale destruction prompted the creation of the Seismic Sea Wave Warning System, which later became the Pacific Tsunami Warning Center in 1949.
Born on this day:
1640 – Georg Mohr, Danish mathematician and academic (d. 1697)
Jørgen Mohr (Latinised Georg(ius) Mohr; 1 April 1640 – 26 January 1697) was a Danish mathematician, known for being the first to prove the Mohr–Mascheroni theorem, which states that any geometric construction which can be done with compass and straightedge can also be done with compasses alone.
Mohr was born in Copenhagen, the son of a tradesman named David Mohrendal. Beginning in 1662 he traveled to the Netherlands, to study mathematics with Christiaan Huygens. In 1672 he published his first book, Euclides Danicus, simultaneously in Copenhagen and Amsterdam, in Danish and Dutch respectively. This book, proving the Mohr–Mascheroni theorem 125 years earlier than Lorenzo Mascheroni, would languish in obscurity until its rediscovery in 1928. Mohr served in Franco-Dutch War in 1672–1673, and was taken prisoner by the French. By 1673, he had published his second book, Compendium Euclidis Curiosi. A third book was later mentioned by Mohr’s son; for many years this was believed to be the Gegenübung auf Compendium Euclidis Curiosi but Andersen & Meyer (1985) argue that it must be a different book, and that the Gegenübung has a different author. As well as his work on geometry, Mohr contributed to the theory of nested radicals, with the aim of simplifying Cardano’s formula for the roots of a cubic polynomial.
While in the Netherlands, Mohr became a friend of Ehrenfried Walther von Tschirnhaus. The two visited Gottfried Wilhelm Leibniz in France and John Collins in England together. Mohr returned to Denmark in 1681; he had dedicated Euclides Danicus to Christian V and hoped for a position in exchange, but was offered only a position as a shipyard supervisor, which he declined. He married Elizabeth von der Linde of Copenhagen on July 19, 1687, and soon after returned to Holland; their son, Peter Georg Mohrenthal, eventually settled in Dresden as a bookseller and publisher. In 1695 he took a job with Tschirnhaus, and spent his last few years as a guest in Tschirnhaus’s house. He died in Kieslingswalde near Görlitz, Germany.
The Danish Mathematics competition is named in honour of Mohr.