01:750:109 Chapter Notes - Chapter 13.2: Astronomical Object, Bell Labs, Wilkinson Microwave Anisotropy Probe
Evidence for the Big Bang
●The Big Bang theory gained wide scientific acceptance for 2 key reasons:
○It predicts that the radiation that began to stream across the universe at the end of the
era of nuclei should still be present today
■Sure enough, we find that the universe is filled with cosmic microwave
background
○It predicts that some of the original hydrogen in the universe should have fused into
helium during the era of nucleosynthesis
■Observations of the actual helium content of the universe closely match the
value predicted by the Big Bang theory
How do observations of the cosmic microwave background support the Big Bang theory?
●Cosmic microwave background announced in 1965. Arno Penzias and Robert Wilson, two
physicists working at Bell Laboratories in NJ, were calibrating a sensitive microwave antenna
designed for satellite communications but they kept on finding unexpected noise in every
measurement they made
○Noise where in every directions meaning it came from all directions in the sky ruling out
the possibility that it came from any particular astronomical object or from any place on
Earth
●Partnered w physicists from Princeton University and compared notes and realized that the
"noise" from the Bell Labs antenna was the predicted cosmic microwave background-- the first
strong evidence that the Big Bang really did happen
Origin of the Cosmic Microwave Background
●Consists of microwave photons that have traveled through space since the end of the era of
nuclei, when most of the electrons in the universe joined w nuclei to make neutral atoms. W
very few free electrons left to block them, most of the photons from that time have traveled
unobstructed through the universe ever since
●When observing cosmic microwave background, basically seeing back to the end of the era of
nuclei when the universe was only 380,000 yrs old, aka we are studying light from the most
distant observable region of the universe
●Cosmic microwave background represents a limit on how far back we can see in time
○Universe filled w hella fog of light before radiation released, so cannot see light from
earlier times
○BUT provides clues about earlier times bc conditions in the universe at the time of the
background radiation was released were determined by events that occurred even
earlier in time
Characteristic of the Cosmic Microwave Background
●Cosmic microwave background should have an essentially perfect thermal radiation spectrum bc
it came from the heat of the universe itself
Document Summary
The big bang theory gained wide scientific acceptance for 2 key reasons: It predicts that the radiation that began to stream across the universe at the end of the era of nuclei should still be present today. Sure enough, we find that the universe is filled with cosmic microwave background. It predicts that some of the original hydrogen in the universe should have fused into helium during the era of nucleosynthesis. Observations of the actual helium content of the universe closely match the value predicted by the big bang theory. Arno penzias and robert wilson, two physicists working at bell laboratories in nj, were calibrating a sensitive microwave antenna designed for satellite communications but they kept on finding unexpected noise in every measurement they made. Noise where in every directions meaning it came from all directions in the sky ruling out the possibility that it came from any particular astronomical object or from any place on.
