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If 3C 273 was racing away from earth, Schmidt realized, the wave length of its light would be lengthened — just as the wave length of sound from a train's whistle lengthens (thereby dropping in pitch) as it speeds away from a listener at the railroad station. Such an effect on light is known to astronomers as a "red shift" because it moves the characteristic lines of spectral light toward the red, longer wave length end of the spectrum.
The effect had already been observed in light from distant galaxies, which are receding from the earth as well as from each other. Furthermore, according to a law described by Astronomer Edwin Hubble in 1929 (and never successfully challenged since), the greater the red shift in a galaxy's spectrum, the faster the galaxy is speeding away, and the further it is out in space.
State of Shock. Acting on his hunch, Schmidt assumed that the lines he saw were really hydrogen lines. He measured the shift and calculated that 3C 273 was moving away at 15% of the speed of light, or about 28,000 miles per second. This meant, according to Hubble's law, that the quasar must be about 1.5 billion light-years from the earth, instead of being a faint, nearby star — as most astronomers had assumed.
The more Schmidt calculated, the more problems he raised. Even a very bright galaxy consisting of billions of stars would be much dimmer at this distance, but starlike 3C 273 can be seen easily with a 6-in. telescope. Clearly, more study was needed.
The strongest of hydrogen's lines, called H-alpha, seemed to be missing entirely from 3C 273's spectrum. If Schmidt's theory was right, the line was not missing but had shifted into the infar-red region of the spectrum, where it would not register on an ordinary photographic plate. Schmidt remembered Astronomer Beverley Oke had already studied the spectrum with an electronic gadget sensitive to invisible infrared. Oke had found a prominent line precisely where Schmidt thought that H-alpha should be, shifted into the infrared. 3C 273 was moving faster than seemed possible; it was farther away than anyone had been prepared to believe, and it was brighter than it should be. Schmidt recalls that he "was in a state of complete shock."
When Schmidt's interpretation and Oke's proof were published in Nature, the world of science also went into a state of shock. Astronomer Greenstein promptly shelved his own unpublished quasar theory, admitting that "if it weren't for Maarten, I could have been caught with my scientific trousers down." Instead, he turned to a spectrogram that he had taken from quasar 3C 48 and — using Schmidt's redshift key — discovered that 3C 48 was re ceding even faster than 3C 273. By Hubble's law it appeared to be some 4 billion light-years away.