1 / 8

4.3 21 st century cosmology

4.3 21 st century cosmology. 21 st Century Cosmology. By 1980, accumulating evidence had made the Big Bang theory widely accepted by cosmologists, but it faced two problems leading to the development of a new theory  a “revised” Big Bang with an important addition.

malha
Download Presentation

4.3 21 st century 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. 4.321st century cosmology

  2. 21st Century Cosmology • By 1980, accumulating evidence had made the Big Bang theory widely accepted by cosmologists, but it faced two problems leading to the development of a new theory  a “revised” Big Bang with an important addition. • Flatness Problem: the properties of the universe are close to the dividing line between an open and closed universe … meaning the geometry seems nearly flat (ρ ~ ρc). • Horizon Problem: related to the observed isotropy of the CMB … how did every part of the entire Big Bang universe get to be so nearly the same temperature at the time of recombination?

  3. 21st Century Cosmology • The key to these problems seems to be found in the hypothesis called the inflationary universe. • It is believed there was a period of sudden expansion during the early evolution of the universe known as inflation. • Triggered by the sudden energy release from the decoupling of the strong and electroweak forces. • New theories unifying the electroweak force with the strong force at high energies are called grand unified theories(GUTs).

  4. The Cosmological Constant • In 1916, to balance the attractive force of gravity, Einstein added a constant to his equations called the cosmological constant, represented by an uppercase lambda (Λ). • This represents a force of repulsion balancing the gravitational attraction between galaxies so the universe would not contract or expand. • 13 years later, Edwin Hubble announced his observations the universe was expanding. • Einstein said introducing the cosmological constant was his biggest blunder • Modern cosmologists think he may have been right after all!

  5. The Cosmological Constant • One explanation for the acceleration of the universe is that there is, after all, a cosmological constant representing a type of antigravity force comprising part of the fabric of space-time. • Causes a continuing acceleration in the expansion of the universe. • Cosmological CONSTANT  the universe would have experience this acceleration throughout history. • Another solution is to suppose totally empty space, the vacuum, contains energy driving the acceleration. • Cosmologists label a universal vacuum energy as quintessence. • Unlike the cosmological constant, quintessence would not necessarily remain constant over time.

  6. Dark Energy • The observed acceleration of the universe’s expansion is evidence that a type of unknown energy is spread throughout space, referred to as dark energy. • However, it does not contribute to the formation of starlight or the Cosmic Microwave Background (CMB) radiation.

More Related