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16/09/2024 MODULE 2: Composition, Origin, and Evolution of the Physical World SEPTEMBER 5, 2024...

16/09/2024 MODULE 2: Composition, Origin, and Evolution of the Physical World SEPTEMBER 5, 2024 27 27 THEORIES ON THE UNIVERSE Big Bang Theory Split-second of exponential expansion Inflation and start of big bang 28 28 1  16/09/2024 THEORIES ON THE UNIVERSE Big bounce ⚬ current universe is the latest in a long and potentially infinite expanding and contracting cosmos String theory ⚬ Tiny vibrating strings within an eleven-dimensionality reality of hyperspace 29 29 BEGINNING OF THE UNIVERSE Max Planck ⚬ Planck temperature - 1.42 × 10 Kelvin ⚬ Planck length - 1.62 × 10 m ⚬ Planck’s constant ⚬ Planck time - 5.39 × 10 s 13.8 billion years ago the universe began Going back in time, the observable part of the universe shrinks and becomes more compact 30 30 2  16/09/2024 PLANCK ERA Planck Era General Relativity ⚬ first ten-tredecillionth of a second ⚬ Gravity as the curvature of spacetime (10^-42) ⚬ Gravity was the first to manifest Four forces ⚬ Strong force ⚬ Weak force ⚬ Electromagnetic ⚬ Gravity 31 31 PLANCK ERA Back then the size of the universe is smaller than a proton Quantum physics ⚬ Fundamental particles ⚬ the very act of observing changes the outcome 32 32 3  16/09/2024 PLANCK ERA 33 33 PLANCK ERA Quantum mechanics and general relativity are incompatible ⚬ Time ⚬ Cause and Effect Bubbling and dynamic quantum foam ⚬ Dynamical and unpredictable interactions 34 34 4  16/09/2024 GRAND UNIFICATION EPOCH First undecillionth of a second (10^-36) Electroweak Force ⚬ weak and electromagnetic force Electrostrong Force ⚬ strong and electroweak force Grand Unification ⚬ ultimate unification of three of the major fundamental forces 35 35 GRAND UNIFICATION EPOCH Inconsistencies from GR and QM on the presence of gravity Current best theory on the workings of the universe after the Planck Era Million of times longer than the previous as the universe expanded and cooled 36 36 5  16/09/2024 GRAND UNIFICATION EPOCH The universe is still smaller than a quark, the smallest particle known today Due to the large density compressed into such a small space, the temperature reached a trillions of Kelvin During this time particles undergo a series of rapid changes ⚬ Photons transform and decay ⚬ quarks to leptons, matter to antimatter, and vice versa 37 37 GRAND UNIFICATION EPOCH Strong force breaks free from the grand unification It cannot predict how the universe will come to be in the future 38 38 6  16/09/2024 WHAT IS HAPPENING IN THE UNIVERSE? First picosecond (10^-12) The deeper we peer into space, the farther back in time we are looking At distances corresponding to 200 million years ago, the James Webb telescope was able to detect galaxies 39 39 40 40 7  16/09/2024 FLATNESS PROBLEM General Theory of Relativity ⚬ Massive objects creates curves in spacetime Universe shapes ⚬ Positively curved - overall density is high ⚬ Negatively curve - overall density is lower Flatness Problem 41 41 HOMOGENEITY PROBLEM Homogeneity/Horizon Problem ⚬ The average temperature at any direction is the same, 2.7 K everywhere in the universe ⚬ Thermal homogeneity now also means thermal homogeneity in the universe’s earliest moment 42 42 8  16/09/2024 COSMIC EXPANSION Exponential expansion of the universe ⚬ What we see is only a bubble of observable universe ⚬ 93 billion years in diameter Thermal homogeneity ⚬ Our observable universe was in thermal equilibrium with itself before inflation Flat Spacetime ⚬ Only a matter of perspective Monopoles ⚬ Although they existed in the early universe, expansion may have spread them far apart 43 43 THE ELECTROWEAK EPOCH A very large drop in energy levels Although three major forces already exist at this time, the temperature is still to high for them to largely impact the behavior of particles 44 44 9  16/09/2024 QUARK ERA First billionth of a second (10^-9) There are still some flaws The universe is symmetrical The four fundamental forces have finally split apart 45 45 QUARK ERA Particle accelerators ⚬ To discover smaller and smaller particles, the outcome of those collisions is examined 46 46 10  16/09/2024 47 47 48 48 11  16/09/2024 49 49 50 50 12  16/09/2024 51 51 52 52 13  16/09/2024 53 53 The Standard Model of Particle Physics 54 54 14  16/09/2024 The Standard Model of Particle Physics 55 55 HADRON EPOCH 10^-10 of a second Gluons and quarks are able to interact with each other 56 56 15  16/09/2024 LEPTON EPOCH The continues annihilations of particles left only a small amount of matter in the universe compared to how it began More positively charged protons were made 57 57 BIG BANG NUCLEOSYNTHESIS Around 17 minutes after the Big Bang Protons and neutrons fuse together to form hydrogen, helium, and other light elements 58 58 16  16/09/2024 BIG BANG NUCLEOSYNTHESIS It eventually gets too cold for fusion Over the next thousand years, hydrogen and helium nuclei gather together due to gravity 59 59 RECOMBINATION After 377,000 years The universe cools down enough for electrons to combine with nuclei to form neutral atoms 60 60 17  16/09/2024 LIGHT 61 61 OUR CURRENT UNIVERSE 62 62 18  16/09/2024 EVIDENCES FOR THE BIG BANG Expanding universe by Edwin Hubble ⚬ redshift values from the emission spectra for many galaxies ⚬ Doppler Shift/Doppler Effect ￭ For example we have a source of waves that is in motion with respect to our frame of reference 63 63 64 64 19  16/09/2024 65 65 66 66 20  16/09/2024 67 67 EVIDENCES FOR THE BIG BANG Cosmic Microwave Background Radiation (CMB) ⚬ Microwave antenna ⚬ a uniform background noise in every single direction ⚬ leftover heat after the big bang (2.7K) Primordial elements ⚬ The ratio of elements in the universe 68 68 21  16/09/2024 EVIDENCES FOR THE BIG BANG The night sky is dark ⚬ How can the night sky be so dark if the universe is infinite? 69 69 70 70 22