Lesson 1: The Origin of the Universe PDF

Lesson 1: THE UNIVERSE AND ITS ORIGIN Baryonic matter- “ordinary” matter consisting of protons, electrons, and neutrons that comprises atoms, planets, stars, galaxies, and other bodies Dark matter- matter that has gravity but does not emit light Dark energy-...

Lesson 1: THE UNIVERSE AND ITS ORIGIN Baryonic matter- “ordinary” matter consisting of protons, electrons, and neutrons that comprises atoms, planets, stars, galaxies, and other bodies Dark matter- matter that has gravity but does not emit light Dark energy- a source of anti-gravity, a force that counteracts gravity and causes the universe to expand Protostar- an early stage in the formation of a star resulting from the gravitational collapse of gases Thermonuclear reaction- a nuclear fusion reaction responsible for the energy produced by stars Main Sequence Stars- stars that fuse hydrogen atoms to form helium atoms in their cores; outward pressure resulting from nuclear fusion is balanced by gravitational forces Light years- a unit of length used to measure astronomical distance THE UNIVERSE -The Universe is at least 13.8 billion years old while the Solar System is at least 4.5-4.6 billions of years old - Comprises all space and time, and all matter and energy in it  Made up of 4.6%baryonic matter(ordinary matter consisting of protons, electrons and neutrons: atoms, planets , stars, galaxies, nebulas, and other bodies)  24% cold dark matter (matter that has gravity but does not emit light) -Dark matter can explain what may be holding galaxies together for the reason that the low total mass is insufficient for gravity alone to do so  71% dark energy(a source of anti-gravity) - Dark energy can explain the observed accelerating expansion of the universe  It is also made up of Hydrogen, helium, and Lithium STARS- (the building block of galaxies) are born out of clouds of gas and dust - Stellar interiors are like furnaces where elements are synthesized or combined/fused together - Most stars such as the Sun belong to the so-called “Main Sequence Stars”, where in their cores, hydrogen atoms are fused through thermonuclear reactions to make helium atoms - Massive main sequence stars burn up their hydrogen faster than smaller stars. - Stars like our Sun burn up hydrogen in about 10 billion years GALAXY- a cluster of billions of stars Superclusters- clusters of galaxies Practicallyan empty space- found between the clusters - Diameter is at least 91 billion light years THEORIES THAT PRECEDED THE BIG BANG THEORY OF THE ORIGIN OF THE UNIVERSE * NON-SCIENTIFIC THOUGHT*  Ancient Egyptians believed in many gods and myths which narrate that the world arose from an infinite sea at the first rising sun.  The Kuba people of Central Africa tell the story of a creator god Mbombo (or Bumba) who, alone in the dark and water- covered Earth, felt an intense stomach pain and then vomited the stars, sun, and moon  In India, there is the narrative that gods sacrificed Purusha, the primal man whose head, feet, eyes, and mind became the sky, earth, sun, and moon respectively.  The monotheistic religions of Judaism, Christianity, and Islam claim that a supreme being created the universe, including man and other living organisms.  STEADY STATE MODEL - Proposed by Bondi, Gould, and Hoyle in 1948 - It maintains that new matter is created as the universe expands thereby maintaining its density.  THE PRIMORDIAL UNIVERSE - Proposed by the Greek Philosopher Anaxagoras. He believed that the original state of the universe was a primordial mixture of all of its ingredients which existed in infinitesimally small fragments of themselves - During this primordial phase, the fundamental forces of nature, such as gravity, electromagnetism, and the strong and weak nuclear forces, were unified into a single force, and the four known forces we observe today gradually separated as the universe expanded and cooled. - As the universe expanded, it underwent various phases, including cosmic inflation, which is a period of rapid exponential expansion  CYCLICAL OR OSCILLATING UNIVERSE  - A cyclical or oscillating universe is a cosmological model that suggests the universe goes through an infinite series of cycles, each consisting of a Big Bang followed by cosmic expansion and then a Big Crunch, in a repeating pattern. In this model, the universe does not have a definitive beginning or end but undergoes a cycle of expansion and contraction indefinitely  PTOLEMAIC UNIVERSE -The Roman-Egyptian Mathematician and astronomer Claudius Ptolemaus Ptolemy) described a geocentric model of the universe based on the theory of Artistotle in which the planets and the rest of the universe orbit a stationary Earth in circular epicycles  EINSTEINIAN UNIVERSE - Albert Einstein assumed the model of the universe a static, stable which was neither expanding or contracting  “ THE BIG BANG THEORY” - formulated by Abbe Georges Edouard Lemaitre - The currently accepted theory of the origin and evolution of the Universe - Postulates that 13.8 billion years ago, the Universe expanded from a tiny, dense and hot mass to its present size and much cooler state. - this theory explains that the universe developed 13.8 billion years ago and started as a very dense and hot “singularity” which eventually cooled and began to form different particles  The Big Bang Theory has withstood the tests for expansion: 1. the redshift 2. abundance of hydrogen, helium, and lithium 3. the uniformly pervasive cosmic microwave background radiation(the remnant heat from big bang)  “ THE RED-SHIFT” -discovered by Edwin Hubble in 1929 -it interprets that galaxies are moving away from each other  Redshift refers to a phenomenon in astronomy where the light emitted by an object in space, such as a star or galaxy, appears to be shifted toward longer wavelengths, which corresponds to the red end of the electromagnetic spectrum.  This is primarily observed in the context of the Doppler effect, which is the change in the frequency or wavelength of a wave as perceived by an observer moving relative to the source of the wave.  In the case of redshift, it usually occurs because an object in space is moving away from an observer (like Earth). As the object moves away, the light it emits is stretched, causing its wavelength to increase.  This stretching of the light waves results in a shift towards the longer-wavelength, lower-frequency, and "redder" part of the spectrum.  “COSMIC MICROWAVE BACKGROUND (CMB)” - A radiation in the universe that was accidentally discovered by Arno Penzias and Robert Woodrow Wilson in 1964 and that made them earned the physics Nobel Prize in 1978 - the faint afterglow of the Big Bang, a remnant of the universe’s early hot and dense phase  Evolution of the Universe according to the Big Bang Theory  From time zero (13.8 billion years ago) until 10ˉ¹³ second later, all matter and energy in the universe existed as a hot, dense, tiny state.  It then underwent extremely rapid, exponential inflation until 10ˉ³² second later after which and until 10 seconds from time zero, conditions allowed the existence of only quarks, hadrons, and leptons.  Then, Big Bang nucleosynthesis took place and produced protons, neutrons, atomic nuclei, and then hydrogen, helium, and lithium until 20 minutes after time zero when sufficient cooling did not allow further nucleosynthesis.  From then on until 380,000 years, the cooling universe entered a matter-dominated period when photons decoupled from matter and light could travel freely as still observed today in the form of cosmic microwave background radiation.  As the universe continued to cool down, matter collected into clouds giving rise to only stars after 380,000 years and eventually galaxies would form after 100 million years  From 9.8 billion years until at present, the universe became dark-energy dominated and underwent accelerating expansion.  At about 9.8 billion years after the Big Bang, the solar system was formed.