The discovery of the cosmic background radiation

The discovery of the cosmic background radiation

Fate is sometimes really bizarre.

It all began in 1941, when Adams measured the absorption lines of the cyanogen molecule (CN) and McKeller estimated an excitation temperature of about 2.3 K. Seven years later, in 1948, Gamow, Alpher and Herman wrote a fundamental article, with hindsight, for the cosmology, which spoke of the initial nucleosynthesis of the lighter atoms, also hypothesizing the emission of a large amount of electromagnetic radiation that, at the time of writing of the article, the authors had estimated equal to about 5 K. This result was however forgotten…

Two years earlier, in 1946, Robert Dicke of Princeton had studied the microwave emission of the atmosphere, establishing that the cosmic radiation had to have a maximum temperature of about 20 K. In the following years, other measurements followed by different scientists, but nobody can guess the epochal discovery that was right in front of their eyes.

So we arrive at 1961. At Bell Laboratories, engineers were building an antenna to test NASA‘s new communications satellite, Echo.

Ed Ohm, calibrating the antenna, found an excess temperature of about 3.3 K but that eventually erroneously attributed to the antenna itself and not to the sky. Two Russian cosmologists, Doroshkevich and Novikov, who became aware of the fact, attributed the disturbance to the sky. The list of people who could change their lives with this discovery was stretching out of all proportion!

But of course, sooner or later someone had to come enlightenment. The year was 1964, and two young scientists hired by the Bell Laboratories, Arno Penzias and Robert Wilson, began to work on the antenna, always finding the same excess temperature of 3.3 K. But they noticed something else: it came from all over the sky, from any direction. The two understood that this disturbance was not due either to the antenna or to the atmosphere, but it came homogeneously from the whole Universe. So it was that two young scientists happened to find one of the cosmological discoveries of the century and received the Nobel Prize in Physics.

In the same identical period, Dicke, having perhaps guessed the truth, had begun a series of measurements of this radiation. Upon learning of having just been beaten on time, I pronounce the famous phrase:

Well boys, we’ve been scooped!

Since then, scientists have developed increasingly powerful and precise instruments, which have allowed us to obtain a map of the Universe just 380,000 years after its birth. For example, NASA‘s COBE satellite in 1989, NASA’s WMAP satellite in 2001 and the most recent of these, ESA‘s Planck satellite, allowed to obtain a map of the primordial Universe with a resolution never seen before.

The discovery of the cosmic background radiation

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