1.2 The Big Bang Flashcards

Question

T = 1 second ## Footnote PROPOSED SEQUENCE OF EVENTS

Answer 1

* Universe is still hot, composed of energy, and rapidly moving fundamental particles such as quarks, electrons, photons, and neutrinos * **Quarks collide to form the first protons and neutrons** * **Protons and neutrons are called nucleons as they form the nucleus of an atom**

Answer 2

* Universe has cooled to around 10^8 * Expanded to about 3 light years in diameter * **The first nuclei of hydrogen, helium, and Lithium were formed through nucleosynthesis**

Answer 3

* Expansion allows the universe to cool to around 3000K * At this temperature, *positively charged atomic nuclei could capture negatively charged electrons to form the first atoms*; AKA **Era of Recombination** * After this, the universe would appear dark to our eyes and is sometimes called the "**cosmic dark ages**": as stars have yet to form

Answer 4

Homo sapiens evolved

Answer 5

* 1948 - Alpher and Herman: before Recombination, **the universe was filled with hot and energetic particles, known as plasma** (***unbound*** positive and negative particles), which emitted electromagnetic radiation, including some visible light * Due to the high density of free electrons in the plasma, **this light could not travel far before being scattered by the electrons, creating a hazy orange fog** * *Electrons started attaching to atomic nuclei during recombination*. This would result in a momentary clearer universe * However, because of the universe's expansion, **it would have been stretched from its initial orange colour in the visible spectrum into the microwave frequency band.** * If you point a radio telescope at any point in the sky, you get a persistent microwave interference “static.” In 1964, it was realized that this "static" was the proposed CMB!

Answer 6

* numerous probes have been launched to study and map the CMB and have discovered that **there are tiny differences in the temperature of the CMB radiation**, which are thought to represent very small variations in the density of matter of the early universe.

Answer 7

* 1) **Visible ( (baryonic) Matter**: approximately 5% * 2) **Dark Matter**: approximately 27% * 3) **Dark Energy**: 68%

Answer 8

* We can only infer the existence of dark matter from its gravitational effects * For example, it was expected that stars in the middle of a galaxy should *rotate faster* than those on the outskirts of the galactic mass, yet,*stars move much faster than expected based on the visible matter in the galaxy* * At this velocity, galaxies should have torn themselves apart long ago. * It has been suggested that all galaxies are surrounded by large halos of dark matter (Figure 18) and that the gravitational influence of dark matter helps to hold the galaxies together

Answer 9

* Initially, believed that the universe's expansion was slowing down due to the gravitational attraction of matter. * However, observations of distant supernovae indicated that the universe in the past was expanding at a slower rate than it is today * **Dark Energy is the term used for this unknown force acting in the opposite manner to gravity**, pushing things apart rather than drawing them together.

Answer 10

* Galaxies are arranged in **filament**-like structures throughout the universe, composed of massive clusters of galaxies connected by thin, thread-like gas and dark matter structures (kind of looks like neurons?) * Galaxy Filaments are the largest structures in the universe; form the cosmic web

Answer 11

* Galaxy filaments are believed to have formed through the gravitational collapse of small perturbations in the early universe (as seen in the CMB), eventually growing through mergers with other structures. * Dark matter is thought to gravitationally attract visible (baryonic) matter, forming the filaments that surround the voids.