ASTR Fall Semester Joel E. Tohline, Alumni Professor Office: 247 Nicholson Hall [Slides from Lecture23]

Chapter 26: Cosmology and Chapter 27: Exploring the Universe

Implications of Big Bang Era of “recombination” and “Cosmic Microwave Background (CMB)” Origin of the Elements Non-uniformities in the Early Universe and the Origin of Galaxies

At the time of recombination, the temperature was a few thousand degrees everywhere! But from our point of view “now,” this radiation has been significantly redshifted (due to expansion of the universe) so the spectrum should look like a “black-body” of a much cooler temperature.

Remember “Black body spectrum” from Chapter 5

At the time of recombination, the temperature was a few thousand degrees everywhere! But from our point of view “now,” this radiation has been significantly redshifted (due to expansion of the universe) so the spectrum should look like a “black-body” of a much cooler temperature. From Einstein’s theory, Dicke & Peebles (Princeton University) predict T = 3 K.

At the time of recombination, the temperature was a few thousand degrees everywhere! But from our point of view “now,” this radiation has been significantly redshifted (due to expansion of the universe) so the spectrum should look like a “black-body” of a much cooler temperature. From Einstein’s theory, Dicke & Peebles (Princeton University) predict T = 3 K.

Remember “Black body spectrum” from Chapter 5 What would a 3 K spectrum look like?

Penzias & Wilson discover CMB radiation; awarded 1978 Nobel Prize

Uniformity of CMB COBE satellite measurements (which improved on discovery of Penzias & Wilson) show … –CMB temperature is K –Exactly the same temperature no matter which direction you look in the sky!  at the time of recombination, the universe was extremely uniform –Slight Doppler shift due to Earth’s motion through space –Otherwise, only very tiny fluctuations; smaller than 200 micro-Kelvin (  K)

Uniformity of CMB COBE satellite measurements (which improved on discovery of Penzias & Wilson) show … –CMB temperature is K –Exactly the same temperature no matter which direction you look in the sky!  at the time of recombination, the universe was extremely uniform –Slight Doppler shift due to Earth’s motion through space –Otherwise, only very tiny fluctuations; smaller than 200 micro-Kelvin (  K)

Uniformity of CMB COBE satellite measurements (which improved on discovery of Penzias & Wilson) show … –CMB temperature is K –Exactly the same temperature no matter which direction you look in the sky!  at the time of recombination, the universe was extremely uniform –Slight Doppler shift due to Earth’s motion through space –Otherwise, only very tiny fluctuations; smaller than 200 micro-Kelvin (  K)

Uniformity of CMB COBE satellite measurements (which improved on discovery of Penzias & Wilson) show … –CMB temperature is K –Exactly the same temperature no matter which direction you look in the sky!  at the time of recombination, the universe was extremely uniform –Slight Doppler shift due to Earth’s motion through space –Otherwise, only very tiny fluctuations; smaller than 200 micro-Kelvin (  K)

Uniformity of CMB COBE satellite measurements (which improved on discovery of Penzias & Wilson) show … –CMB temperature is K –Exactly the same temperature no matter which direction you look in the sky!  at the time of recombination, the universe was extremely uniform –Slight Doppler shift due to Earth’s motion through space –Otherwise, only very tiny fluctuations; smaller than 200 micro-Kelvin (  K) – confirmed by WMAP spacecraft

Implications of Big Bang Era of “recombination” and “Cosmic Microwave Background (CMB)” Origin of the Elements Non-uniformities in the Early Universe and the Origin of Galaxies

Implications of Big Bang Era of “recombination” and “Cosmic Microwave Background (CMB)” Origin of the Elements Non-uniformities in the Early Universe and the Origin of Galaxies

Origin of the Elements Looking back even further in time – before recombination – the universe was even hotter At a sufficiently early epoch it was too hot for any atomic nuclei heavier than Hydrogen to have existed! When did the first elements form; and which ones were able to form? ANS: In the “first 3 minutes”; and only Helium!

Origin of the Elements Looking back even further in time – before recombination – the universe was even hotter At a sufficiently early epoch it was too hot for any atomic nuclei heavier than Hydrogen to have existed! When did the first elements form; and which ones were able to form? ANS: In the “first 3 minutes”; and only Helium!

Origin of the Elements Looking back even further in time – before recombination – the universe was even hotter At a sufficiently early epoch it was too hot for any atomic nuclei heavier than Hydrogen to have existed! When did the first elements form; and which ones were able to form?

Origin of the Elements Looking back even further in time – before recombination – the universe was even hotter At a sufficiently early epoch it was too hot for any atomic nuclei heavier than Hydrogen to have existed! When did the first elements form; and which ones were able to form? ANS: In the “first 3 minutes”; and only Helium!

How Do We Measure  0 ? Measure (count up) all the matter density in the universe (  0 ) and compare the value to  c. Measure distances and redshifts of even more distant galaxies and look for deviations in the Hubble diagram.

Modern Hubble Law implies:  0 =  m +  