Unit 2: Edwin Hubble
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Edwin Hubble, born in 1889, revolutionized our understanding of the universe by proving its vastness and its expansion, laying groundwork for the Big Bang theory. His key discoveries included demonstrating that galaxies exist outside the Milky Way and formulating Hubble's Law, which establishes a correlation between a galaxy's distance and its redshift. Hubble remained a pivotal figure in astronomy, managing the Mount Wilson Observatory and contributing to the design of the Hale Telescope until his death in 1953.
Unit 2: Edwin Hubble
- 2. EVIDENCE FOR AN EXPANDING UNIVERSE EDWIN HUBBLE Born November 20, 1889 Marshfield, Missouri Died September 28, 1953 San Marino, California
- 3. 2 3 In the course of five years, Edwin Hubble twice changed our understanding of the Universe, helping to lay the foundations for the Big Bang theory. First he demonstrated that the Universe was much larger than previously thought, then he proved that the Universe is expanding.
- 4. 4 5 Early life and education Edwin Powell Hubble, the son of an insurance executive, was born in Marshfield, Missouri, on November 20, 1889, and moved to Wheaton, Illinois, a suburb of Chicago, soon after. Growing up, he was more outstanding as an athlete than as a student, although he did earn good grades in every subject (except spelling). He won seven first-places and a third place in a single high school track-and-field meet in 1906. That year he also set the Illinois high school record in the high jump. At the University of Chicago, Hubble studied mathematics, astronomy, and philosophy — and played for the school’s basketball team. He graduated with a bachelor of science in 1910, and then spent 1911 to 1914 earning his mas- ter’s as one of Oxford University’s first Rhodes scholars. Though he studied law and Spanish there, his love of astronomy never diminished. At Yerkes Observatory Moving back to the United States, Hubble enrolled as a graduate student at the University of Chicago and studied the stars at their Yerkes Observatory in Wisconsin. It was here that he began to study the faint nebulae that would be the key to his greatest discoveries. After receiving his doctorate in astronomy from the University of Chicago in 1917, he won an offer to join the staff at the prestigious Mount Wilson Observatory, near Pasadena, California.
- 5. 6 7 At Mount Wilson Observatory Arriving at Mount Wilson in 1919, he joined an astronomy establishment that was just beginning to grasp cosmic distances. The key to that effort was work that had been done studying Cepheid variable stars, roughly a decade earlier, by Henrietta Swan Leavitt at Harvard. These stars brighten and dim in a predictable pattern, and their distance from us can be worked out by measuring how bright they appear to us. Another astronomer at the observatory, Harlow Shapley, built on Leavitt’s findings and shocked the world with his conclusions about the size of the Milky Way. Using the Cepheid variables, Shapley judged that the Milky Way was 300,000 light years across — 10 times bigger than previously thought. Hubble began his work at Mount Wilson just as the new 2.56-meter Hooker Telescope, the most powerful on Earth, was completed. With it, he was able to peer into the sky with greater detail than anyone had previously. After years of observation, Hubble made an extraordinary discovery. In 1923 he spotted a Cepheid variable star in what was known as the Andromeda Nebula. Using Leavitt’s techniques, he was able to show that Andromeda was nearly 1 million light years away and clearly a galaxy in its own right, not a gas cloud. Hubble then went on to discover Cepheids in multiple nebulae, and proved, in a 1924 paper called “Cepheids in Spiral Nebula,” that galaxies existed out- side our own. Overnight, he became the most famous astronomer in the world, and people everywhere had to get used to the fact that the Universe was far vaster than anyone had imagined. Shapley, for one, was shaken by the news. He wrote Hubble, “I do not know whether I am sorry or glad to see this break in the nebular problem. Perhaps both.” In 1926, while developing a classification system for galaxies, Hubble dis- covered an odd fact: Almost every galaxy he observed appeared to be mov- ing away from the Earth. He knew this because the light coming from the galaxies exhibited redshift. Light waves from distant galaxies get stretched by the expansion of the Universe on their way to Earth. This shifts visible light toward the red end of the spectrum. Hubble used the Hooker Telescope at Mount Wilson Observatory for some of his most important discoveries
- 6. 1928 Biologist Alexander Fleming discovers penicillin 1939 Nazi invasion of Poland triggers the start of World War II 1921 Albert Einstein receives the Nobel Prize in physics 1914 World War I begins 1907 Dmitri Mendeleev dies in St. Petersburg, Russia 1903 Marie Curie shares the Nobel Prize in physics with Pierre Curie and Henri Becquerel 1901 The Nobel Prize is founded by Swedish inventor Alfred Nobel During the time of Hubble 1935 Discovers asteroid 1373 Cincinnati 1941–1948 Helps design the Hale Telescope on Mount Palomar in California 1929 Using the work of Vesto Slipher, Hubble and Milton Humason identify Hubble’s Law, proving that the Universe is expanding 1917–1919 Enlists in the U.S. Army, serves in World War I 1919 Joins the staff of the Mount Wilson Observatory 1924 Demonstrates that there are galaxies beyond the Milky Way 1914–1917 Studies astronomy at the Yerkes Observatory; earns a doctorate from the University of Chicago 1906–1910 Attends University of Chicago 1902–1906 Attends Wheaton High School in Illinois 1889 Born in Marshfield, Missouri on November 20 Timeline of Hubble’s life 1890 1900 1910 1920 1930 1940
- 7. 1952 Jonas Salk develops the first effective polio vaccine 1953 Watson, Crick, and Franklin discover the structure of DNA 1945 The United States deploys the atomic bomb; World War II ends 1940 1950 1960 1953 Dies of a heart attack on September 28 in San Marino, California Building on the work of Vesto Slipher, who measured the redshifts associ- ated with galaxies more than a decade earlier, Hubble and his assistant, Milton Humason, discovered a rough proportionality between the distances and redshifts of 46 galaxies they studied. By 1929 they had formulated what became known as Hubble’s Law. Hubble’s Law basically states that the greater the distance of a galaxy from ours, the faster it recedes. It was proof that the Universe is expanding. It was also the first observational support for a new theory on the origin of the Universe proposed by Georges Lemaitre: the Big Bang. After all, an expanding Universe must once have been smaller. Later life Hubble achieved scientific superstardom for his discoveries and is still considered a brilliant observational astronomer. He ran the Mount Wilson Observatory for the rest of his life, popularized astronomy through books and lectures, and worked to have astronomy recognized by the Nobel Prize committee. He also played a pivotal role in the design and construction of the Hale Telescope, on Palomar Mountain, California. At 5.08 meters, the Hale was four times as powerful as the Hooker Telescope and existed as the most advanced telescope on Earth for some time. After its completion in 1948, Edwin Hubble was given the honor of first use. When asked by a reporter what he expected to find, Hubble answered: “We hope to find something we hadn’t expected.”
- 8. 1312 Sources Bryson, Bill. A Short History of Nearly Everything. New York: Broadway Books, 2003. Christianson, Gale E. Edwin Hubble: Mariner of the Nebulae. Chicago: University of Chicago Press, 1995. Image credits Edwin Hubble © SPL / Photo Researchers, Inc. Edwin Hubble © Science Source Hubble using the Hooker Telescope at Mount Wilson Observatory © Emilio Segrè Visual Archives / American Institute of Physics / Photo Researchers, Inc.