The Big Bang Theory and Its Proofs; #1 the Doppler Effect

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<Picture 1, The Big Bang Theory(sitcom)>

1. The First Proof of the Big Bang Theory; The Doppler Effect

  I'm obsessively addicted to something very easily. One of the most addictive shows for me was 'Big Bang Theory' which is very popular sitcom in America. The show is primarily centered on five characters living in Pasadena, California: Leonard Hofstadter and Sheldon Cooper, both physicists at Caltech, who share an apartment; Penny, a waitress and aspiring actress who lives across the hall; and aerospace engineer Howard Wolowitz and astrophysicist Raj Koothrappali. Actually, Sheldon gave me some interests in Physics. By the way, Why is the name of the show Big Bang Theory? What is the Big Bang Theory? In the series of posts, we're gonna talk about the Big Bang Theory and its proofs. Today's post is about the first proof of the Big Bang Theory; The Doppler Effect.
    
 

2. The Doppler Effect for Sounds

    We can find the Doppler Effect in our lives. Suppose that an automobile driver speeding by us blows his horn. Inside the car, the driver hears a steady blare at a fixed pitch. But outside the car, we hear a characteristic change in pitch. We hear a high-pitched sound when the car is approaching and a low-pitched sound when the car goes away.

<Picture 2, the Doppler Effect for Sounds>

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  The sound is a wave. The shorter the wave is, the higher the pitch goes. According to the Picture 2, If the car is approaching, then the pitch goes higher because the wave became shorter.

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3. The Doppler Effect for Light

<Picture 3, the Doppler Effect for Light>

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   Light is also a wave. The Doppler effect works here as well. If instead of sound the automobile were emitting a beam of pure yellow light front and back, the frequency of the light would increase slightly as the car approached and decrease slightly as the car receded. At ordinary speeds the effect would be imperceptible. However, If the car were traveling at a good fraction of the speed of light, we would be able to observe the color of the light changing toward lower frequencies, that is, toward red, as the car receded from us. An object apporoaching us at very high velocities is perceived to have the color of its spectral lines blue-shifted. An object receding from us at very high velocities has its spectral lines red-shifted. This red shift, observed in the spectral lines of distant galaxies and interpreted as a Doppler effect, is the key to cosmology.

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4. Discovery of the Big Bang Theory

 

 

 <Picture 2, Edwin Hubble, the Astronomer>

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   After World War Ⅰ, Edwin Hubble came to Mount Wilson to work on the world's largest telescope in the early years of 20C. He was a brilliant, polished, gregarious astronomer. He worked with a scientist named Milton Humason. Soon They found, to their amazement, that the spectra of all the distant galaxies are red-shifted and, still more startling, that the more distant the galaxy was, the more red-shifted were its spectral lines. The most resonable explanation of the red shift was the Doppler effect. It means that the Galaxies were receding from us and that the more distant the galaxy the greater its speed of recession. It seemed that the universe itself was expanding, carrying the galaxies with it. Humason and Hubble, it gradually became clear, had discovered the Big Bang Theory.

  But in fact, the Doppler effect is not the only one supporting the Big Bang theory. So, in the next post, I'm gonna tell you about another proofs of the theory, The Cosmic Background Radiation. 

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Bibiology

 

Sagan, C. E., 1980, Cosmos(1st ed.), New York: Random House.

 

 2016.02.10 Han Kwang Hee