Teaching Tip

This Day in Science Posted on Sep 1 2010 10:53AM

SEPTEMBER 1
In 1859, a solar flare was observed for the first time by astronomer Richard C. Carrington. He reported his Description of a Singular Appearance seen in the Sun in the Monthly Notices of the Royal Astronomical Society (1860), "While engaged in the ... observation of ... solar spots ... two patches of intensely bright and white light broke out. ... I therefore noted down the time, ... and seeing the outburst to be very rapidly on the increase ... I hastily ran to call some one to witness ... and on returning within 60 seconds,  was mortified to find that it was already much changed and enfeebled. Very shortly afterwards the last trace was gone. In this lapse of 5 minutes, the two patches of light traversed a space of about 35,000 miles.

SEPTEMBER 3
In 2000, NASA data showed the hole at just under 11 million square miles - the biggest it had ever been. Record low temperatures in the stratosphere are believed to have helped the expansion of the ozone hole during the southern hemisphere’s spring season. Antarctic ozone depletion starts in July, when sunlight triggers chemical reactions in cold air trapped over the South Pole during the Antarctic winter. It intensifies during August and September before tailing off as temperatures rise in late November of early December. Depletion of the ozone layer over Antarctica and the Arctic is being monitored because ozone protects Earth from harmful ultraviolet radiation. By 9 Sep 2000, the hole had grown over Chile, exposing a populated city for the first time.  Image, compiled from NASA's Total Ozone Mapping Spectrometer instrument onboard the Earth Probe satellite, reveals how the ozone hole (in deep blue) has extended as far as southern Chile.

SEPTEMBER 5
In 1857, Charles Darwin, now 48 years old, had not yet published his theory of evolution. On this day, he sent a letter to Asa Gray, a Harvard botanist, discussing his theory. The encouragement which followed from Gray and others, and new knowledge that Alfred Wallace had independently developed the same theory, prompted Darwin to end 20 years of indecision and publish his ideas.

SEPTEMBER 7
In 1776, the first U.S. submarine built for wartime use, the American Turtle, was used in New York harbour to attach explosives to the hull of the Eagle, Admiral Howe's flagship. Known as a "torpedo" the weapon was a cask with 150 lbs of black powder and a clockwork time fuse. Because it separated from the ship before it exploded, little damage was done. The submarine, just large enough for one occupant, was operated by Ezra Lee, turning a 24-in diam. two-bladed wooden propeller giving up to3 knots speed. It was built by David Bushnell of Saybrook, Conn., who provided it with a rudder and a second propeller for vertical movement. Water taken in as ballast to submerge was expelled by hand-pump to resurface