Did you know you owe your teeth to a 15th Century emperor? This week marks significant strides in history for dental care, but that's not all.

The week also commemorates the first African-American astronaut—and it's not who you might think. Chemists synthesized one of the world's most important molecules for the first time, and a man made history while traveling the high seas.

What else does "This Week In Science History" hold? Check out the slideshow for all the landmark events.

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  • Brushing History

    On June 26, 1498, the Emperor of China invented the first bristle toothbrush using the coarse hairs from a hog's back. The invention swept the world--even French leader Napoleon Bonaparte brushed his teeth with a silver-handled version (see photo). Now June 26 has become known as National Toothbrush Day.

  • Fluorine Isolated

    French chemist Henri Moissan reported the isolation of elemental fluorine to the Academy of Science in Paris on June 26, 1886. Fluorine (atomic number 9) exists within the Earth's crust and has many uses--from dental care, to pharmaceuticals, to nuclear fuel cells.

  • Scraping The Sky

    Toronto's famed CN Tower opened on June 26, 1976, as the world's tallest free-standing structure. At 1,815.4 feet tall, this epic feat of engineering held onto its title for 34 years until it was surpassed by Dubai's Burj Khalifa skyscraper in 2010.

  • Genetic Blueprint

    President Bill Clinton announced a working draft of the Human Genome Project on June 26, 2000. The 13-year effort aimed to discover all the estimated 20,000-25,000 human genes, making them accessible for further biological study. The project would lead to greater insight into our own genetic makeup.

  • A Sail Around The World

    Joshua Slocum (1844-1909) completed his historic solo voyage around the world on June 27, 1898. Slocum completed his three-year journey around the world aboard his oyster sloop sailboat <em>The Spray</em>. He documented his travels in the book <em>Sailing Alone Around the World</em>.

  • First Atomic Power

    The first civilian nuclear power station started generating power June 27, 1954 in Obninsk, U.S.S.R. It produced about five megawatts using a small graphite reactor. The plant was shut down in 2002.

  • Chemical Breakthrough

    Chlorophyll was first synthesized on June 27, 1960 by organic chemist Robert Burns Woodward at Harvard University. Woodward (1917-1979) pioneered scientific synthesis of organic molecules, and even won a Nobel Prize for his groundbreaking work.

  • iPhone Released

    Steve Jobs (1995-2011) rocked the world on June 29, 2007, when Apple released the first iPhone, shaping smartphone technology in a major way.

  • First African-American Astronaut

    Robert Henry Lawrence, Jr. (1935-1967) became the first black astronaut on June 30, 1967, when he was chosen to begin NASA's astronaut training program. Lawrence, a chemist and test pilot, never made a space trip as he died in a F-104 crash in December 1967. Lawrence paved the way for other African-Americans in NASA, including current Administrator of NASA Charlie Bolden.

  • Space Disaster

    Tragedy struck on June 30, 1971, when the three crew members aboard the Russian capsule Soyuz 11 were killed during their preparations for re-entry into Earth's atmosphere. The cabin of the crew members Vladislav Volkov, Georgi Dobrovolski and Viktor Patsayev, lost pressure. The trio was asphyxiated on the way back from a nearly month-long trip.

  • Wallace-Darwin Theory Published

    On July 1, 1858, the Wallace-Darwin theory of evolution was first published for the Linnean Society in London. This was the precursor to Darwin's <em>On the Origin of Species</em>, which was published the next year. The piece represented very similar theories that were developed by both Darwin and Alfred Russell Wallace.

  • Historic Atomic Bomb Drop

    "Able Day" made history on July 1, 1946 at 9 a.m., when a B-29 airplane dropped a bomb (named 'Able') from the sky, which exploded about 500 feet above the ocean at Bikini Atoll. Able sunk five of the vessels that had been assembled for the test.

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