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PHYSICAL COSMOLOGY

PHYSICAL COSMOLOGY. Assuming that the universe is 12-15 Billion years old. In physical cosmology , the Big Bang is the scientific theory that the universe emerged from an enormously dense and hot state about 13.7 billion years ago.

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PHYSICAL COSMOLOGY

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  1. PHYSICAL COSMOLOGY Assuming that the universe is 12-15 Billion years old

  2. In physical cosmology , the Big Bang is the scientific theory that the universe emerged from an enormously dense and hot state about 13.7 billion years ago. The Big Bang theory is based on the observed Hubble's law redshift of distant galaxies. Extrapolated into the past, these observations show that the universe has expanded from a state of singularity.

  3. THE SINGULARITY • All the matter and energy in the universe was at an immense temperature and density. • The term Big Bang is used in a narrow sense to refer to a point in time when the observed expansion of the universe (Hubble's law) began.

  4. OBSERVATIONAL EVIDENCE • Hubble type expansion seen in the redshifts of galaxies • Detailed measurements of the cosmic microwave background. • The abundance of light elements such as hydrogen and helium. • The observed correlation function of large-scale structure of the cosmos fits well with standard Big Bang theory.

  5. COSMIC BACKGROUND

  6. WHAT IS THE SHAPE OF THE UNIVERSE? • The Universe will keep on expanding forever Ω<1 • The expansion will gradually slow down and approach a limit in size Ω=1 • The universe will stop expanding and start to fall back on itself Ω>1 • It all depends on THE MASS DENSITY.

  7. THE HORIZON PROBLEM • According to observation of the CBR, all regions of the universe, whose horizons have always been separate, have the same temperature. • In order for things to have the same temperature, they must have been able to interact with each other in some way. • The classic big bang theory has regions of the universe permanently separate from each other and as such, unable to interact.

  8. THE FLATNESS PROBLEM • All current observations indicate the universe is flat (matter/energy = critical density). • This implies that the early universe had a density exactly equal to one. • Even if the density were slightly more or less in the early stages, it would be enormously magnified by the expansion of the universe.

  9. COSMIC INFLATION • When the universe was enormously dense, its energy was carried by a Higgs field far from its lowest point. • The field created enormous negative pressure, causing a gigantic gravitational repulsion. • This caused the universe to inflate from a tiny speck to almost its current size in less than 10^-35 seconds.

  10. LIKE SCALING UP A DNA MOLECULE

  11. TO THE SIZE OF THE MILKY WAY

  12. DARK ENERGY • Current observations indicate the expansion of the universe is accelerating. • The cause of this acceleration is an exotic form of energy called Dark Energy. • DE exerts negative pressure and thus causes repulsive gravity which drives the expansion faster and faster.

  13. DARK MATTER • Calculation of the masses of galaxies and the actual counting of stars indicate a big discrepancy. • There is more mass in galaxies than can be seen and counted. • This missing mass is called Dark Matter.

  14. ATOMS • Ordinary matter (Baryonic) is the stuff we are made of and all that we can observe. • This observable matter and the positive energy makes up only four percent of the universe.

  15. THE FATE OF THE UNIVERSE The Big Freeze, Heat Death, Big Rip, or the Big Crunch?

  16. The Big Freeze • Continued expansion results in a universe that is too cold to sustain life. • It could occur under a flat or hyperbolic geometry, because such geometries are a necessary condition for a universe that expands forever.

  17. The Heat Death • The universe goes to a state of maximum entropy in which everything is evenly distributed. • There are no gradients - which are needed to sustain information processing, one form of which is life.

  18. The Big Rip • Dark energy causes the rate of expansion of the universe to accelerate. • Taken to the extreme, an ever-accelerating expansion means that all material objects in the universe, starting with galaxies and eventually all life forms, no matter how small, will disintegrate into unbound elementary particles.

  19. The Big Crunch • The Big Crunch theory is a symmetric view of the ultimate fate of the universe. • Just as the Big Bang started a cosmological expansion, this theory postulates that the average density of the universe is enough to stop its expansion and begin contracting. • The universe collapses into a dimensionless singularity.

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