1 / 63

Chapter 18: Cosmology

Chapter 18: Cosmology. Cosmological red shift Anywhere in the Universe, an observer feels like he/she/it is the at the center. Microwave background (“Echo of the Big Bang”) Our motion through the Cosmic background radiation The four forces of nature, unified.

gitel
Télécharger la présentation

Chapter 18: Cosmology

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Chapter 18: Cosmology

  2. Cosmological red shift Anywhere in the Universe, an observer feels like he/she/it is the at the center. Microwave background (“Echo of the Big Bang”) Our motion through the Cosmic background radiation The four forces of nature, unified. The early history of the universe. Inflation The observable universe. Structure of the early universe. Galaxy formation Stellar birth rates Possible geometries of the universe. The acceleration of the universe. Topics Today:

  3. Expansion explains the cosmological redshift • Hubble’s law shows that the more distant galaxies have higher recessional velocities • Hubble’s law is the same in all directions (called isotropic) • Hubble’s law allows to “play the scenario backwards” and determine an age of the universe • Doppler red shifts are caused by an object’s motion whereas cosmological redshifts are caused by the expansion of spacetime.

  4. Cosmological Redshift

  5. Expanding Cake Analogy Just as all the chocolate chips move apart as the cake rises, all the superclusters of galaxies recede from each other as the universe expands.

  6. The universe probably originated in an explosion called the Big Bang • In the 1940s, based on Hubble’s Law, George Gamow proposed the the universe began in a colossal explosion • In the 1950s, the term BIG BANG was coined by an unconvinced Sir Fred Hoyle • In the 1990s, there was an international competition to rename the BIG BANG with a more appropriate name, but no new name was selected

  7. BIG BANG is a relatively simple idea • If the universe is expanding, it must have been smaller in the past • If it was smaller in the past, then something must have made it begin to expand • This “event” is called the BIG BANG • The age of the universe is simply the separation distance of the most distant galaxies divided by their recessional velocities • Current figures place the age about about 13 billion years

  8. Observable Universe The cosmic light horizon today is about 13.8 billion light-years away in all directions. Inset: ThisHST Deep Field Telescope image shows some of the most distant galaxies we have seen.

  9. If the Big Bang really happened: • Universe should be filled with microwave radiation corresponding to a cool black body (about 3 K) • Predicted by scientists at Princeton in early 1960s, who began building an antenna to detect it. • Discovered by accident by Bell Labs physicists, Penzias and Wilson, working on a communications antenna just a few miles away.

  10. Bell Labs Horn Antenna Arno Penzias (right) and Robert Wilson

  11. Spectrum of the Cosmic Microwave Background

  12. In Search of Primordial Photons Wilkinson Microwave Anisotropy Probe (WMAP) satellite, launched in 2001

  13. In Search of Primordial Photons The balloon-carried telescope BOOMERANG

  14. The Microwave Sky The Doppler shift across the sky is caused by the Earth’s motion through the microwave background.

  15. Our Motion Through the Microwave Background Because of the Doppler effect, we detect shorter wavelengths in the microwave background and a higher temperature of radiation in that part of the sky toward which we are moving.

  16. A period of vigorous inflation followed the Big Bang • PROBLEM: If the universe is at least 26 billion light years across (13 billion in each direction), how could both sides have exactly the same temperature if they couldn’t “communicate?” • SOLUTION: During the first second, the universe underwent a rapid but even expansion, called the inflationary epoch, in which it became many times larger than its original size.

  17. All physical forces in nature were initially unified • Gravitational force - attraction between any two objects with mass • Electromagnetic force - attraction/repulsion between any two charged particles • Strong nuclear force - holds protons in the nucleus of an atom together • Weak nuclear force - governs the radioactive decay of neutrons into protons

  18. Unification of the Four Forces

  19. Early History of the Universe

  20. The Cause of Inflation

  21. Observable Universe Beforeand After Inflation

  22. Pair Production and Annihilation

  23. Evolution of Density

  24. Era of Recombination

  25. Structure of the Early Universe This Wilkinson Microwave Anisotropy Probe (WMAP) image shows temperature variations in the cosmic microwave background. Inset: Tiny temperature fluctuations, observed by BOOMERANG, are related to the large-scale structure of the universe today, indicating where superclusters and voids grew.

  26. Galaxies Forming by Combining Smaller Units This painting indicates how astronomers visualize the burst of star formation that occurred within a few hundred million years after the Big Bang.

  27. Galaxies Forming by Combining Smaller Units Hubble and Keck telescope images of two groups of stars that are believed to be protogalaxies, from which bigger galaxies grew

More Related