We kick off this week’s experiments for our poll with the discovery of a special kind of light: cosmic microwave background. The story of this discovery is a beautiful example of the fortuity of scientific discovery. Abstract. Theories unifying gravity with other interactions suggest temporal and spatial variation of the fundamental “constants” in expanding Universe. The spatial variation can explain fine tuning of the fundamental constants which allows humans (and any life) to appear. We appeared in the area of the Universe where the values of the fundamental constants are consistent with our existence.
In 1948 Ralph Alpher and Robert Herman published a prediction that if indeed the universe were created in a Big Bang, today we would see the glow of light that was released when atoms first formed, when the universe was about 300,000 years old. Since the universe has been expanding for billions of years, the light would have been redshifted by a factor of 1,000, so that it could only be detected today as microwaves. In 1964 Arno Penzias and Robert Wilson of Bell Labs announced they had identified this light, providing the strongest evidence to date in support of the Big Bang theory.
In 1960, Bell Labs built a 20-foot horn-shaped antenna in Holmdel, NJ to be used with an early satellite system called Echo. The intention was to collect and amplify radio signals to send them across long distances, but within a few years, another satellite was launched and Echo became obsolete. Penzias and Wilson were awarded the Nobel Prize for Physics in 1978, for the discovery of the cosmic microwave background radiation.
The science of radio astronomy began in 1928, when AT&T began transatlantic radio communications. In an attempt to reduce the background hiss and crackle that sometimes interfered with the signals, the company hired 22 year-old Karl Jansky to find the source of the bothersome noise.
Sure enough, in 1972, only a few years after the first laser demonstration, Theodor W. Hänsch used laser spectroscopy to measure with unprecedented precision the transition frequency of the Balmer line of atomic hydrogen using a dye laser. However, it was not until the latter part of 1990s, when frequency combs from mode-locked lasers were used for frequency metrology, that truly game-changing precision became available. A frequency comb is a set of equidistant spectral lines that can be used as an optical ruler as long as the comb spacing and the carrier–envelope offset frequency are known and stabilized. Frequency combs can be used to measure frequency and time with extreme precision which has numerous technological applications, such as in gas sensing and optical clocks, but also in fundamental science: they are used for detecting possible variations in universal physical constants, which could challenge our understanding of physics and the universe.