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The Evolution of the Universe

Nicola Loaring. The Evolution of the Universe. The Big Bang. According to scientists the Universe began ~15 billion years ago in a hot Big Bang. At creation the Universe was infinitely hot and infinitely small. Time started when the Universe began- there is no before the Big Bang!.

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The Evolution of the Universe

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  1. Nicola Loaring The Evolution of the Universe

  2. The Big Bang • According to scientists the Universe began ~15 billion years ago in a hot Big Bang. • At creation the Universe was infinitely hot and infinitely small. • Time started when the Universe began- there is no before the Big Bang!

  3. The early Universe 10-34 seconds : Matter forms Scores of different building block particles - quarks, leptons, photons, and neutrinos flood the universe (the size of a melon). 10-6 seconds : Protons and Neutrons form Quarks combine to form protons and neutrons. Each is made of 3 quarks 3 minutes: Nuclei form Protons and neutrons combine to form the atomic nuclei of the lightest elements hydrogen, helium and lithium. ~ 700,000 years : Atoms form The temperature has fallen to a few 1000K, electrons and protons can hold together to begin forming hydrogen atoms.

  4. The Cosmic microwave background • As the Universe cools sufficiently for all the electrons to be soaked up into atoms the matter and radiation stop interacting • Light is free to travel to us. • We see this as the Cosmic Microwave background radiation.

  5. The cosmic microwave background • The earth is bathed in CMB at a temperature of 2.73K • Very smooth in all directions , temperature variations of only 1 part in 105 -tiny temperature fluctuations WMAP probe currently measuring the CMB

  6. The Universe is expanding: Hubble’s Law • In 1929 Hubble noted that speed of recession of galaxies is proportional to their distance from us

  7. How does structure form?Gravity • Newton realised that a falling apple is attracted to the Earth via a force called gravity. • Newton’s third law states that every force has an equal and opposite reaction – so that every object attracts every other object • Leads to build up of structure F = G m1 m2 r2

  8. Stellar evolution • Stars shine by nuclear burning of fuel • Gravity is balanced by radiation pressure • Evolution depends on initial mass of the star • Initial masses of less than 8 solar masses end their lives by ejecting planetary nebulae (White dwarf remnants) • Initial masses greater than 8 solar masses end their lives by exploding as supernovae. Remnants are neutron stars or black holes Size is the same as the orbit of Mars

  9. Star formation • As Universe cooled further giant molecular clouds formed • Gravity collapses them until they are so dense that nuclei begin to fuse - a star is born

  10. Supernovae • Needed to form very heavy elements • Nuclei thrown into the galaxy and pick up elections forming heavy atoms which are used in next round of star formation • All the atoms in your body except hydrogen were made in a supernova ~5 billion years ago or more

  11. Formation of the solar system • Formed when a cloud of gas and dust in space was disturbed • Gravity pulled the gas and dust together, forming a solar nebula • The cloud began to spin as it collapsed • As the disk got thinner particles began to stick together and form clumps eventually forming planets or moons • As the cloud continued to fall in, the center eventually got so hot that it became a star, the Sun

  12. Galaxies 1pc =3x1013 km = 3.2 light years = 206,000AU • Have billions of stars • Stars gather together by mutual gravitational attraction • Gas and dust are intermixed with the stars • 70% spiral, 30% elliptical • Size ~9kpc M32 - Elliptical galaxy M33 spiral galaxy M83 – Spiral galaxy

  13. Peering at the earliest Galaxies • The further away from the Earth we look, the further back in time we are looking due to the finite speed of light.

  14. The Hubble Space telescope deep field • Distant galaxies as they were nearly 13 million years ago • Still busy forming and interacting

  15. Galaxy clusters • Sizes 1-10 Mpc • Irregular Virgo Galactic Cluster • 50 million light-years from Earth • Contains roughly 2,000 galaxies • The dominant (largest) galaxy is the elliptical M87 (Virgo A)

  16. Super-structures From 2QZ

  17. Simulations of structure formation Virgo consortium simulation

  18. The matter density of the Universe and dark matter • Evidence for dark matter on a range of scales: from galaxy rotation curves • Gravitational lensing • Most of the matter in the Universe is ‘dark’

  19. The fate of the Universe • Dark energy introduced by Einstein, anti-gravity energy to stop collapse • Appears to dominate the total mass-energy content of the Universe • Universe expansion is accelerating at the moment

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