Origins: Fourteen Billion Years of Cosmic Evolution by Donald Goldsmith, Neil deGrasse Tyson Read Free Book Online

and hotter—from the way we find it today. The first direct observations of the CBR therefore put the first nails in the coffin of the steady state theory (though Fred Hoyle never fully accepted the CBR as disproving his elegant theory, going to his grave attempting to explain the radiation as arising from other causes). In 1964, the CBR was inadvertently and serendipitously discovered by Arno Penzias and Robert Wilson at the Bell Telephone Laboratories (Bell Labs, for short) in Murray Hill, New Jersey. Little more than a decade later, Penzias and Wilson received the Nobel Prize for their good luck and hard work.
    What led Penzias and Wilson to their Nobel Prize? During the early 1960s, physicists all knew about microwaves, but almost no one had created the capability of detecting weak signals in the microwave portion of the spectrum. Back then, most wireless communication (e.g., receivers, detectors, and transmitters) rode on radio waves, which have longer wavelengths than microwaves. For these, scientists needed a shorter-wavelength detector and a sensitive antenna to capture them. Bell Labs had one, a king-size, horn-shaped antenna that could focus and detect microwaves as well as any apparatus on Earth.
    If you’re going to send or receive a signal of any kind, you don’t want other signals to contaminate it. Penzias and Wilson were trying to open up a new channel of communication for Bell Labs—so they wanted to pin down how much contaminating “background” interference these signals would experience—from the Sun, from the center of the galaxy, from terrestrial sources, from whatever. They therefore embarked on a standard, important, and entirely innocent measurement, aimed at establishing how easily they could detect microwave signals. Though Penzias and Wilson had some astronomy background, they were not cosmologists but technophysicists studying microwaves, unaware of the predictions made by Gamow, Alpher, and Herman. What they were decidedly not looking for was the cosmic microwave background.
    So they ran their experiment, and corrected their data for all known sources of interference. But they found background noise in the signal that didn’t go away, and they couldn’t figure out how to get rid of it. The noise seemed to come from every direction above the horizon, and it didn’t change with time. Finally they looked inside their giant horn. Pigeons were nesting there, leaving a white dielectric substance (pigeon poop) everywhere nearby. Things must have been getting desperate for Penzias and Wilson: could the droppings, they wondered, be responsible for the background noise? They cleaned it up, and sure enough, the noise dropped a bit. But it still wouldn’t go away. The paper they published in 1965 in The Astrophysical Journal refers to the persistent puzzle of an inexplicable “excess antenna temperature,” rather than the astronomical discovery of the century.
    While Penzias and Wilson were scrubbing bird droppings from their antenna, a team of physicists at Princeton University led by Robert H. Dicke was building a detector specifically designed to find the CBR that Gamow, Alpher, and Herman had predicted. The professors, however, lacked the resources of Bell Labs, so their work proceeded more slowly. The moment that Dicke and his colleagues heard about Penzias and Wilson’s results, they knew that they’d been scooped. The Princeton team knew exactly what the “excess antenna temperature” was. Everything fit the theory: the temperature, the fact that the signal came from all directions in equal amounts, and that it wasn’t linked in time with Earth’s rotation or Earth’s position in orbit around the Sun.
    But why should anybody accept the interpretation? For good reason. Photons take time to reach us from distant parts of the cosmos, so we inevitably look back in time whenever we look outward into space. This means that if the intelligent inhabitants of a galaxy far, far away measured