ORIGIN OF THE UNIVERSE In the beginning, God created the heaven and the earth; and the earth was without form and void; and darkness was upon the face of the deep and the spirit of God moved upon the face of the water. And God said, " Let there be light, " and there was light. And God saw the light, that it was good. Genesis 1:1-3

COSMOLOGY The study of the origin, structure, and evolution of the universe.

Clues about the Origin of the Universe - Cosmic background radiation - Temperature of Space (3 o K) - Cosmological redshift - Presence of light elements

What is cosmic background radiation? This is background microwave radiation that is uniform in all directions and indicates a temperature for the current universe of about 3 degrees Kelvin. This supports the Big Bang theory.

5 An animal, or a human body, for example, emits some infrared radiation that can be detected by an infrared camera Color is related to temperature

6 Long wave- -length Low temperature

7 … by Penzias and Wilson, two physicists from the Bell labs, who got the Nobel prize in 1978 In 1964, this radiation was finally detected, with this antenna … antennaPenziasWilson

8 In fact, the snow that one can see on an untuned TV is also due in part to that radiation emitted by the Universe as it was just 380,000 years old !

9 Original temperature of the radiation : 3000 K Today, it is only 3 K The cooling says how far the light has travelled 13,7 billion years : the age of the Universe

10 In 1992, the COBE satelite (Cosmic Background explorer) gave the first image of the radiation COBE was launched on November 18, 1989

11 In 1992, the COBE satelite (Cosmic Background explorer) gave the first image of the radiation  Before correction of the Earth movement around the Sun  The final image of the microwave Radiation  Before correction of the microwave radiation emitted by our own galaxy

12 In 2003, the WMAP satelite gave a better resolution of the small fluctuations of temperature (WMAP = Wilkinson Microwave Anisotropy Probe) WMAP was launched on June 30, 2001

13 Whereever it looked, WMAP measured the same data. So, the big-bang must have taken place at the same time everywhere

14 But we can also observe small fluctuations of temperature, that may have lead to the formation of the galaxies

What is the cosmological redshift? Photons from distant galaxies are all redshifted. This is a color shift in the radiation spectrum of galaxies. The further away the galaxy the greater its redshift. This redshift is caused by the expansion of the universe - further evidence for a Big Bang. All galaxies are receding from each other as a result of the Big Bang.

16 What are light elements? Helium Deuterium (Hydrogen with 1 neutron) Lithium Beryllium

17 Cosmic Nucleosynthesis During the range from about 100 to 1000 seconds after the big bang, the “cosmic nucleosynthesis” era, nuclear reactions made certain elements, in certain proportions inconsistent with the proportions made currently. At the beginning of this nucleosynthesis era the temperature of the universe was a few billion degrees Kelvin.

18 Hydrogen (deuterium) A hydrogen nucleus is simply a proton Hydrogen = raw material to make other elements. Some of these protons combined with neutrons to form an isotope of hydrogen, deuterium, which contains one proton and one neutron in the nucleus. Prior to the start of the nucleosynthesis era, the universe was too hot and energetic for the deuterium to form and remain stable. Must have occurred slightly afterwards.

19 Helium, Lithium, and Beryllium Helium is made in the core reaction of stars, but not at a rate consistent with the abundance of He in our universe. Approximately 25% of matter is He, much larger than could be produced from star fusion alone. The nuclear reactions to make Lithium and Beryllium do not occur in stars. Heat and pressure of stars would destroy these light elements. However, they do exist, though rare in our universe. They are believed to have been made towards the end of the nucleosynthesis era.

What is the Center of the Universe The universe has no preferred center of expansion. We are not the center of the universe nor is anything else. Every observer, no matter where in the universe will see the universe expanding in the same way.

Age of the Universe Calculations indicate an age of about 13.7 billion years for the age of the universe. No objects older than this have been observed. E.G. the age of the earth is about 4.5 billion years The oldest stars are about billion years.

Gamma Rays Particle Anti- particle Gamma Rays Particle Anti- particle Radiation and Matter: Origin of the Universe

After about 1 microsecond P Universe was hot and dense P Radiation converted into protons and antiprotons plus quarks and anti-quarks and visa versa P Small volume, jammed with quarks and antiquarks annihilating each other by creating radiation, began to expand. P The cooler radiation was no longer hot enough to create quarks and thus most quarks disappeared from the universe.

Radiation and Matter: Origin of the Universe After about 1 microsecond P A few quarks survived and combined to make protons and neutrons. P Without this tiny imbalance in quarks (symmetry breaking) the universe would be void of matter containing only cosmic radiation. P Space was then filled with ordinary matter and radiation and continued to expand.

Radiation and Matter: Origin of the Universe After about 5 seconds P Universe still hot enough to create light particles, electrons and anti-electrons. P Protons and electrons interact to produce neutrons P Universe continues to expand P Universe cools to a few billion degrees and the creation of matter stops.

Radiation and Matter: Origin of the Universe About 3 minutes P Expansion cools the universe to a few hundred million degrees. P Approximately 1/4 of the protons are fused into helium. P All of space is now permeated by helium and hydrogen (about 71% H and 27 % He).

Radiation and Matter: Origin of the Universe About a million years P Expansion cools the universe to about 3000 K P Atoms can now form by nuclei capturing electrons - recombination. P Before recombination, the universe behaved as a single blend of radiation and matter. P After recombination, matter and radiation acted as separate entities.

Radiation and Matter: Origin of the Universe The matter Era P Since matter and radiation are no longer locked together, radiation just expands with the universe to become the 2.7 K cosmic radiation of today. P Clouds of matter condense out to form clumps of matter, galaxies, etc. Formation of galaxies needs dark matter?

Sequence of Events in the Big Bang Event Time Temperature (K) Result Heavy-particle era 10 sec 10 Photons make massive particles Light-particle era 10 sec 10 Photons make light particles Radiation era 10 sec 10 Only a few particles left in a sea of photons Matter era 10 yrs 3000 Radiation & matter decouple Now 10 yrs 3 Current picture of universe Creation 0 infinite ?

Evolution of Forces in the Big Bang Strong nuclear force Gravity Electromagnetic force Weak nuclear force 10 Sec K 10 3 K Now

31 Is the universe “open” or “closed” Open means that it will expand forever Closed means that sometime it will stop expanding and will begin to contract - the Big Crunch. Third possibility is a “flat” universe. This universe just stops expanding at some point and remains at that size. Summary of Big Bang

Nucleosynthesis P Universe begins with “ Big Bang” - plasma of protons & neutrons. P Plasma cools & forms hydrogen nuclei P Gravity pulls hydrogen together to form stars P Collapsing hydrogen heats up (for about 10 million years) & the hydrogen becomes fused into helium, releasing energy.

Summary of Big Bang Nucleosynthesis P Eventually, the star materials fuse into nuclei around iron, releasing energy, and the star uses up its energy. P The larger of these dying stars explode into supernovae. P The explosions release lots of neutrons which fuse with medium weight nuclei makeing heavier elements. P This spreads as dust into the universe eventually forming planets in some cases.

Questions P Dark Matter - missing mass? P Open, closed or flat? P Other universes - other dimensions? P Why is the universe all ordinary matter, i.e. no antimatter? P Why is the cosmic background radiation so smooth?

Review Questions: Why do astronomers believe the universe is expanding ? What is cosmic background radiation and what is its origin? How was helium formed from hydrogen in the early universe? What is the approximate age of the universe? What is dark matter? What is meant by the big bang and the big crunch? What is meant by an open and closed universe?