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EXPLORATIONS — a program in Special English by the Voice ofAmerica.
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Today, Richard Rael and Tony Riggs tell the story of Americanastronomer, Edwin Hubble. He changed our ideas about the universeand how it developed.
Edwin Hubble made his most important discoveries in theNineteen-Twenties. Today, other astronomers continue the work hebegan. Many of them are using the Hubble space telescope that isnamed after him.
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Edwin Powell Hubble was born in Eighteen-Eighty-Nine inMarshfield, Missouri. He spent his early years in the state ofKentucky. Then he moved with his family to Chicago, Illinois. Heattended the University of Chicago. He studied mathematics andastronomy.
Hubble was a good student. He was a good athlete, too. He was amember of the University of Chicago championship basketball team inNineteen-oh-Nine. He also was an excellent boxer. Several peopleurged him to train for the world heavyweight boxing championshipafter college. Instead, he decided to continue his studies. He wentto Queen’s College at Oxford, England.
At Oxford, Hubble studied law. Hewas interested in British Common Law, because his family had come toAmerica from England many years before. He spent three years atOxford.
In Nineteen-Thirteen, Hubble returned to the United States. Heopened a law office in Louisville, Kentucky. After a short time,however, he decided he did not want to be a lawyer. He returned tothe University of Chicago. There, once again, he studied astronomy.
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Hubble watched the night sky withinstruments at the university’s Yerkes Observatory. His researchinvolved a major question astronomers could not answer. What arenebulae?
The astronomical term ‘nebulae’, Hubble explained, had come downthrough the centuries. It was the name given to permanent, cloudyareas in the sky outside our solar system. Some astronomers thoughtnebulae were part of our Milky Way Galaxy. Others thought they wereisland universes farther away in space. In his research paper,Hubble said the issue could be decided only by more powerfulinstruments. And those instruments had not yet been developed.
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In Nineteen-Seventeen, the United States was fighting in WorldWar One in Europe. Edwin Hubble joined the American army and servedin France. Earlier, astronomer George Ellery Hale had offered Hubblea position at the Mount Wilson Observatory in southern California.When Hubble returned to the United States after World War One, heaccepted Hale’s offer. Hubble was thirty years old. He was justbeginning the work that would make him famous.
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In his first observations from Mount Wilson, Hubble used atelescope with a mirror one-hundred fifty-two-centimeters across. Hestudied objects within our own galaxy. And he made an importantdiscovery about nebulae.
Hubble said the light that appeared to come from nebulae reallycame from stars near the nebulae. The nebulae, he said, were cloudsof atoms and dust. They were not hot enough — like stars — to giveoff light.
Soon after, Hubble began working with a larger and more powerfultelescope at Mount Wilson. Its mirror was two-hundred-fiftycentimeters across. It was the most powerful telescope in the worldfor twenty-five years. It had the power Hubble needed to make hismajor discoveries.
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From Nineteen-Twenty-Two on, Edwin Hubble began examining moreand more distant objects. His first great discovery was made when herecognized a Cepheid variable star. It was in the outer area of thegreat nebula called Andromeda. Cepheid variable stars are starswhose brightness changes at regular periods.
An astronomer at Harvard College, Henrietta Leavitt, haddiscovered that these periods of brightness could be used to measurethe star’s distance from Earth. Hubble made the measurements. Theyshowed that the Andromeda nebula lay far outside our Milky WayGalaxy.
Hubble’s discovery ended a long dispute. He proved wrong thosewho believed nebulae lay inside the Milky Way. And he proved thatnebulae were galaxies themselves. Astronomers now agree that fardistant galaxies do exist.
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Hubble then began to observe more details about galaxies. Hestudied their shape and brightness. By Nineteen-Twenty-Five, he hadmade enough observations to say that the universe is organized intogalaxies of many shapes and sizes.
As stars differ from one another, he said, so do galaxies. Someare spiral galaxies like the Milky Way and Andromeda. They have acenter, and arms of matter that seem to circle the center like apinwheel. Others are shaped like baseballs or eggs. A few have nospecial shape.
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Hubble proposed a system to describe galaxies by their shape. Hissystem still is used today. He also showed that galaxies are similarin the kinds of bright objects they contain. All galaxies, he said,are related to each other, much as members of a family are relatedto each other.
In the late Nineteen-Twenties, Hubble studied the movement ofgalaxies through space. His investigation led to the most importantastronomical discovery of the Twentieth century — the expandinguniverse.
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Earlier observations about the movement of galaxies had been doneby V. M. Silpher. He discovered that galaxies are moving away fromEarth at speeds between three-hundred kilometers a second andone-thousand-eight-hundred kilometers a second.
Hubble understood the importance of Silpher’s findings. Hedeveloped a plan for measuring both the distance and speed of asmany galaxies as possible. With his assistant at Mount Wilson,Milton Humason, Hubble measured the movement of galaxies. The twomen did this by studying what Hubble called the “red shift.” It alsois known as the “Doppler effect.”
The Doppler effect explains changes in the length of light wavesor sound waves as they move toward you or away from you. Light wavesfrom an object speeding away from you will stretch into longerwavelengths. They appear red. Light waves from an object speedingtoward you will have shorter wavelengths. They appear blue.
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Observations of forty-six galaxies showed Hubble that thegalaxies were traveling away from Earth. The observations alsoshowed that the speed was linked directly to the galaxies’ distancefrom Earth. Hubble discovered that the farther away a galaxy is, thegreater its speed. This scientific rule is called “Hubble’s Law.”
Hubble’s discovery meant a major change in our idea of theuniverse. The universe had not been quiet and unchanging since thebeginning of time, as many people had thought. It was expanding. Andthat, Hubble said, meant it probably began with an explosion ofunimaginable force. The explosion often is called “the big bang.”
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Hubble’s work did not end with this discovery. He continued toexamine galaxies. He continued to gain new knowledge about them.Astronomers from all over the world went to study with him.
Hubble left the Mount Wilson Observatory during World War Two. Hedid research for the United States War Department. He returned afterthe war. Then, he spent much of his time planning a new, much largertelescope in southern California. The telescope was completed inNineteen-Forty-Nine. It had a mirror five-hundred centimetersacross. It was named after astronomer George Ellery Hale.
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Edwin Hubble was the first person to use the Hale Telescope. Hedied in Nineteen-Fifty-Three while preparing to spend four nightslooking through the telescope at the sky.
Hubble’s work led to new research on the birth of the universe.One astronomer said scientists have been filling in the details eversince. And, he said, there is a long way to go.
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ANNOUNCER:
This Special English program was written by Marilyn RiceChristiano. Your narrators were Richard Rael and Tony Riggs. Listenagain next week for another EXPLORATIONS program on the Voice ofAmerica.
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