figure 3

Red is the longest wavelength in the visible spectrum so a shift in the Fraunhofer lines toward the red meant that the star was moving away from the earth. The Huggins were able to calculate in 1868 that the redshift in the spectrum of the star Sirius meant that it was moving away from the earth at a speed of 45 kilometers per second. By 1912 with improved telescopes and spectroscopes and faster photographic plates it was possible with long exposures to measure the spectral shift of nebulae. By the time Hubble had measured the incredible distance to Andromeda, many astronomers had shown that nearly all galaxies had redshifts indicating that they were rushing away from us at incredible speeds.

Hubble and Minnesotan Milton Humason decided to use the 100-inch telescope to couple the new method for measuring the distance to galaxies with measurements of the red shift. In 1929 Hubble's plot of the result for 20 galaxies showed that the degree of redshift predicted the distance! In 1931, after further measurements in eight more galaxies much more distant, Hubble and Humason confirmed their prediction. The universe is indeed expanding and at no small rate. Extrapolating backward in time Hubble calculated that the furthest galaxies must have been concentrated in a very small volume about 1.8 billion years ago. With more observations from better telescopes along with other considerations this calculation is currently revised to 13.7 billion years. Nevertheless, Hubble and Humason had produced solid evidence that the universe has been expanding for a very long time.

Einstein visited Hubble and Humason at the 100-inch telescope in 1931 and saw their photos for himself. Afterward, he publicly admitted that he had been wrong about his cosmological constant and a stable universe. Friedmann and Lemaître were fully vindicated.

Page 5
Next Page

Page 1 • Page 2 • Page 3 • Page 4 • Page 5 • Page 6 • Page 7 • Page 8 • Page 9 • Page 10