"Even the notion of the Big Bang is quite a recent one. The idea had been kicking around since the 1920s when Georges Lemaitre, a Belgian priest-scholar, first tentatively proposed it, but it didn't really become an active notion in cosmology until the mid-1960s, when two young radioastronomers made an extraordinary and inadvertant discovery.
Their names were Arno Penzias and Robert Wilson. In 1965, they were trying to make use of a large communications antenna owned by Bell Laboratories at Holmdel, New Jersey, but they were troubled by a persistent background noise - a steady, steamy hiss that made any experimental work impossible. The noise was unrelenting and unfocused. It came from every point in the sky, day and night, through every season. For a year the young astronomers did everything they could think of to track down and eliminate the noise. They tested every electrical system. They rebuilt instruments, checked circuits, wiggled wires, dusted plugs. They climed into the dish and placed duct tape over every seam and rivet. They climbed back into the dish with brooms and scrubbing brushes and carefully swept it clean of what they referred to in a later paper as "white dielectric material", or what is known more commonly as bird shit. Nothing they tried worked.
Unknown to them, just 50 kilometres away at Princeton University a team of scientists led by Robert Dicke was working on how to find the very thing they were trying so diligently to get rid of. The Princeton researchers were persuing an idea that had been suggested in the 1940s by the Russian-born astrophysicist George Gamow: that if you looked deep enough into space you should find some cosmic background radiation left over from the Big Bang. Gamow calculated that by time it had crossed the the vastness of the cosmos the radiation would reach Earth in the form of microwaves. In a more recent paper he had even suggested an instrument that might do the job: the Bell antenna at Holmdel. Unfortunately, neither Penzias and Wilson, nor any of the Princeton team, had read Gamow's paper.
The noise that Penzias and Wilson were hearing was, of course, the noise that Gamow had postulated. They had found the edge of the universe, or at least the visible part of it, 90 billion trillion miles away. They were "seeing" the first photons - the most ancient light in the universe - though time and distance had converted them to microwaves, just as Gamow had predicted. In his book The Inflationary Universe, Alan Guth provides an analogy that helps to put this finding in perspective. If you think of peering into the depths of the universe as looking down from the hundredth floor of the Empire State Building (with the hundreth floor representing now and the street level representing the moment of the Big Bang), at the time of Wilson and Penzias's discovery the most distant galaxies anyone had ever detected were on about the sixtieth floor and the most distant things - quasars - were on about the twentieth. Penzias and Wilson's findings pushed our aquaintance with the visible universe to within half an inch of the lobby floor.
Still unaware of what caused the noise, Wilson and Penzias phoned Dicke at Princeton and described their problem to him in the hope that he might suggest a solution. Dicke realised at once what the two young men had found. "Well, boys, we've just been scooped," he told his colleagues as he hung up the phone.
Soon afterwards the Astrophysical Journal published two articles: one by Penzias and Wilson describing their experience with the hiss, the other by Dicke's team explaining its nature. Although Penzias and Wilson had not been looking for cosmic background radiation, didn't know what it was when they found it, and hadn't described or interpreted its character in any paper, they received the 1978 Nobel Prize in Physics. The Princeton researchers got only sympathy. According to Dennis Overbye in Lonely Hearts of the Cosmos, neither Penzias nor Wilson altogether understood the significance of what they had found until they read about it in the New York Times.
Incidently, disturbance from cosmic background radiation is something we have all experienced. Tune your television to any channel it doesn't receive and about 1 per cent of the dancing static you see is accounted for by this ancient remant of the Big Bang. The next time you complain that there is nothing on, remember that you can always watch the birth of the universe."
No comments:
Post a Comment