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Irreversible Time and the Big Bang

Irreversible Time and the Big Bang. The Main Point. The expansion of the early universe, that followed the Big Bang, played a major part in creating the “ arrow of time .”. The Arrow of Time. We instinctively know that this movie is wrong!. Statistical Mechanics.

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Irreversible Time and the Big Bang

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  1. Irreversible Time and the Big Bang Henri Bergson Conference at UC Berkeley

  2. The Main Point • The expansion of the early universe, that followed the Big Bang, played a major part in creating the “arrow of time.” Henri Bergson Conference at UC Berkeley

  3. The Arrow of Time We instinctively know that this movie is wrong! Henri Bergson Conference at UC Berkeley

  4. Statistical Mechanics However, if we zoom in on the individual atoms in the flower, we will find nothing wrong with their behavior. The individualatomsbehave (almost) exactly the way we expect them to, according to the laws of physics! – They are not the reason for the arrow of time. So why does the movie seem strange? It is just that to grow back into a bud, the motion of the atoms in the flower will have to be correlated in a precise way. This is highly improbable. Henri Bergson Conference at UC Berkeley

  5. Irreversible Processes We observe “irreversible processes” – processes that follow the arrow of time – in systems that are not in thermodynamic equilibrium. Let’s see what is “thermodynamic equilibrium.” Henri Bergson Conference at UC Berkeley

  6. Thermodynamic Equilibrium Over time, an isolated system with a large number of interacting particles reaches thermodynamic equilibrium: • Uniform density; (usually) • Homogeneous composition; (usually) • Uniform temperature; Theoretical problem: Why are we not in equilibrium? Henri Bergson Conference at UC Berkeley

  7. Large Scale Structure In fact, this problem is much bigger … Our Universe now looks like this: Hubble Ultra Deep Field Credit: S. Beckwith & the HUDF Working Group (STScI), HST, ESA, NASA Taken from http://antwrp.gsfc.nasa.gov/apod/ap040309.html Henri Bergson Conference at UC Berkeley

  8. History of the Universe How did the universe get to be like this, with matter clumped in galaxies and almostnothingin between? What did our universe look like in the past? Henri Bergson Conference at UC Berkeley

  9. Structure Formation Computer simulation demonstrating how structure could form by gravitational attraction in the early universe. Still not homogeneous! Credit: F. Summers (Princeton), D. Cox, R. Patterson, E. Wesselak, and B. Sanders (NCSA), L. Carpenter (Pixar), GC3, Cosmic Voyage, Smithsonian http://antwrp.gsfc.nasa.gov/apod/ap970614.html Henri Bergson Conference at UC Berkeley

  10. And even earlier … The early universe at a temperature of about 10,000°C We see by sensing light that is emitted from objects. Similarly, we can “see” the early universe by detecting the radiation that it emitted. Inferred from theCosmic Microwave Background. Lighter regions are about0.01%hotter than the average. Credit: WMAP Science Team, NASA http://antwrp.gsfc.nasa.gov/apod/ap040711.html Still, not quite homogeneous! Henri Bergson Conference at UC Berkeley

  11. Initial Fluctuations How did these0.01%density fluctuations form? We cannot “see” anything earlier than the CMB. But we have several promising theoretical ideas. • This is one of the mostactiveareas of research nowadays. • We believe that a completely satisfactory answer will require a successful merger of gravity with quantum mechanics and particle physics – agrand unified theory! Henri Bergson Conference at UC Berkeley

  12. Big Bang Theory The Big-Bang theory combines formulas of: • General relativity, • Particle and Nuclear Physics, • Quantum Mechanics, • Statistical theory and Thermodynamics. The universe is expanding! Henri Bergson Conference at UC Berkeley

  13. Expansion of the Universe • The expansion sets an arrow of time. • It also allows the early universe to evade reaching an equilibrium. • By a complicated process – a leading theory holds – the expansion played a major role in forming those initial 0.01% fluctuations. (The theory of “inflation.”) Henri Bergson Conference at UC Berkeley

  14. Summary • Irreversibility of time, departure from thermal equilibrium, and the lack of homogeneity in the universe are all related to each other. • They are largely a consequence of the expansion of the early universe, following the big bang. • However, to fully understand the early universe requires a complete theory of high energy physics – a grand unified theory. The search continues … Henri Bergson Conference at UC Berkeley

  15. Fin Henri Bergson Conference at UC Berkeley

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