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Baking a universe

Baking a universe. Or, how we came looking like this out of the Big Bang. The Big Bang. All matter, energy and space itself. coalesced at a single point. From that time on,. the universe has been expanding. Everything we see today. resulted from the initial conditions.

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Baking a universe

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  1. Baking a universe Or, how we came looking like this out of the Big Bang

  2. The Big Bang All matter, energy and space itself coalesced at a single point. From that time on, the universe has been expanding. Everything we see today resulted from the initial conditions at that remote epoch. 13.5 billion years ago

  3. How do we know the universe is expanding? • Looking at distant galaxies: • They are all moving away from us and form each other • Their speed is proportional to their distance • Precisely as if they were “carried away” by an expanding universe

  4. How do we use this to understand the present universe? • We mix • Theory of relativity • Gravitation • Thermodynamics • Particle physics We get a “story” … … and some of the scenes can be compared with data As in the theory of evolution, The details of some periods are heatedly discussed But the paradigm is not.

  5. An atom primer Atoms are made of a small nucleus of radius 10-15m Surrounded by an electron cloud of darius 10-10 m The nucleus is made of protons and neutrons Protons and neutrons are made of quarks To date no “parts” of quarks or electrons have been found

  6. The earliest fossils In the earliest times the universe was very hot Up until 100 microseconds protons and neutrons could not form The universe was a soup of quarks, electrons and radiation At 1s, and a temperature of 9 £ 109oK: Protons and neutrons formed At 200s, and a temperature of 8 £ 108oK: Atomic nuclei formed

  7. Electric repulsion High speed (large temp.) But not all nuclei were created! For light nuclei… Electric repulsion • Only • Deuterium • Helium • A bit of Lithium • were “cooked” in the early universe • The amounts are also predicted. High speed (large temp.) CONFIRMED For heavier nuclei…

  8. The earliest light At 1/3 million years, Atoms formed Atoms are neutral They interact little with light From that time on the early-universe radiation has traveled (almost) unimpeded As the universe expands the wavelength of the radiation also expands The current universe is suffused by a uniform bath of microwaves CONFIRMED

  9. If we could see microwaves … • Inhomogeneities in the Early Universe • z • Very faint (about 0.001%) • The seeds of clusters of galaxies • Each has expanded to a region 5£ 109 light years across Antarctica

  10. A mysterious matter • The fate of the universe depends on how much matter it contains: • Too much: it will expand to a maximum size and then re-contract • Too little: it will expand forever • There is a critical value separating these two cases • (about 1 mass of the Moon in every 30 cubic light years) • Luminous matter: about 4% of critical • From counting galaxies and gas clouds • From the synthesis of D, He and Li in the early universe Unless there are othrer contributions … … the universe will expand forever

  11. Another way of measuring matter R = 3.8 £ 105 km Looking at the Moon I can weight the Earth. To go around the Earth takes me T = 27.3 days = 0.07479 years So MEarth = 6 £ 1024 kg

  12. For the planets I get: And I can do the same for a galaxy: Measure the speeds of stars orbiting it. Measure their distance to the center ) get the mass of the galaxy

  13. Rotation curves for near-by galaxies surprise! Can be explained if the force is / 1/r not /1/r2. Are Newton & Einstein wrong? Are we missing matter?

  14. Dark Matter The hypothesis is that the universe has enough of a new kind of matter to explain the rotation curves of galaxies. This new matter is called Dark Matter … … because it does not shine. Then the density should be / 1/r2 and its temperature should be uniform So galaxies would be surrounded by a dark matter halo Stars orbiting the galaxy are plowing through a dark-matter mist

  15. There is other evidence of Dark Matter: If we observe distant galaxies and there is a lot of dark matter in between, we should see a characteristic distortion … … and we do! Images distorted … perhaps by a great deal of dark matter

  16. And then there’s the “bullet” cluster: Two galaxies with few stars and a lot of gas collided Most of the matter is in the form of gas The stars were almost unaffected The gas of each interacts a lot so it stayed in the middle But the strongest gravitational effects are localized near the stars … not the gas! Matches perfectly the Dark Matter hypothesis Hard to explain with other hypotheses

  17. Update on the cosmic census Ordinary matter: 4% of critical Dark Matter: 23% of critical If there is Dark Matter, Can we detect it in some way? Is there only one kind? Could it be that Dark Matter cosmologists are wondering what that annoying 4% is all about? Could it be something else?

  18. Another mystery The rate of expansion is increasing The universe is accelerating … why? The best current hypothesis: There is a new form of energy causing this … dark energy If so then it gives about 73% of critical

  19. The decade of cosmology Over the next 10-15 years The nature of Dark Matter will be understood The nature of Dark Energy will be understood Or else We’ll have to revise our understanding of space matter and gravitation

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