Lois & Clark Forums Forums General Discussion Off Topic The Big Bang and the Universe, part 8: What's that noise in our antenna?

In 1964, Arno Penzias and Robert Woodrow Wilson were hired by Bell Labs to build a radio antenna that would detect radio waves bounced off echo balloon satellites.



Penzias and Wilson and their antenna.

Penzias and Wilson did everything they could to protect their antenna from unwanted interference from other radio sources. They came up with ways to avoid picking up radar and radio broadcasting, made sure they never pointed their antenna at known radio sources like the Sun and the center of the Milky Way, and they meticulously cleaned their antenna to remove bird droppings from it, too!



Penzias and Wilson would have none of this in their antenna!

But for all their efforts, there remained a low, steady noise in their antenna. It didn't change when they pointed their antenna in different directions, and it remained the same day and night. Nothing changed it. It turned out that this radiation corresponded to a mysterious something filling the observable sky and corresponding to a temperature of 2.725 degrees Kelvin, that is, 2.725 degrees above absolute zero.



A so called "blackbody curve" of the radiation that Penzias and Wilson detected. As astronomical observations go, the fit between the predicted blackbody curve of an object radiating at 2.725 degrees Kelvin and an object or a gas actually emitting at that temperature is extremely good. And as even more sensitive instruments have been used to measure the radiation detected by Penzias and Wilson, the fit between the predicted and the actually measured blackbody curve of the radiation has become even better.

Penzias and Wilson didn't know what to make of their discovery, particularly since they were not astronomers themselves. But a group of people who were astronomers, led by Robert H. Dicke, Jim Peebles, and David Wilkinson at Princeton University, had just been planning to start looking for signs of an echo of the Big Bang. If such an echo existed, they theorized, it ought to fill the entire universe, be the same in all directions, and be a thin, thin gas with a tempereature of a few degrees above absolute zero.

But Dicke, Peebles and Wilkinson never started to look for the echo of the Big Bang on their own. When they heard about what Penzias and Wilson had discovered, they concluded that this was it.

The echo of the Big Bang had been found.



The Big Bang.



The echo of it.

Ann

Oh, and by the way, what about the white noise on an old-fashioned TV? That is frankly nothing less than the TV picking up the echo of the Big Bang. That's really it. A TV showing white noise is in fact broadcasting the all-pervasive echo of the Big Bang, the so called cosmic microwave background ratiation.



Anyone up for watching the echo of the Big Bang on TV?

Ann

The discovery of the cosmic microwave background radiation (the echo of the Big Bang) led to the general acceptance of the Big Bang theory, certainly in the astronomical community. There were still opponents of the Big Bang, like Fred Hoyle who was the one who had coined the term "Big Bang" in the first place in order to ridicule the idea of an explosive "cosmic birth", but most astronomers by far were now convinced that the Big Bang had happened.

You can say that the discovery of the cosmic microwave background radiation did for the Big Bang theory what Hubble's discovery of Cepheid variables in the Andromeda galaxy did for the idea that there exist other galaxies.

Ann

I should add, now that I've brought up the cosmic microwave background radiation, that many astronomers regard the tiny temperature variations in this all-pervasive thin cool gas as the "seeds" that were necessary for the growth of galaxies in the universe.



The cosmic microwave background, with tiny temperature differences shown as small "cells" of different colors.



The large-scale structure of galaxies and galaxy clusters in the universe. The brighter areas correspond to regions of space where there are many galaxies. Because of the mutual attraction of gravity between galaxies, inhomogenities have grown in the universe since matter started to clump together to form galaxies.

Ann