Unit 8 Cosmology Cosmology Study of the structure

Unit 8 Cosmology

Cosmology Study of the structure and evolution of the entire universe

• The frontier of astronomy • More questions than answers • Origin, history, fate, age

• No special place in the universe • No center or edge

Hubble’s Law The space-time volume of the observable universe is expanding (from a smaller past to a larger future)

• All objects observed in deep space have a doppler shift observable relative velocity to Earth, and to each other • The velocity of galaxies receding from the Earth is proportional to their distance from the Earth and all other interstellar bodies.

Doppler Effect • http: //www. explorelearning. com/index. cfm? method=c. Resource. dsp. Detail&Resource. ID=18

Expanding universe

Georges Lemaître

Big Bang Theory

History • Early 20 th century Einstein and almost all scientists thought. . . Universe is static, unchanging, not expanding then…

• Einstein's field equations: (General Relativistic version of Newton's Equations of Motion) • Cosmological constant: Universe is expanding!

• Hubble (1930's): Discovers galaxies are receding from us Measures the expansion

• Einstein claims cosmological constant was the biggest blunder of his life • But recent evidence indicates he might have been right after all

Big Bang Theory Assumptions: • homogeneous, isotropic Universe • no edge, no center • every part looks the same (on average)

• initial `singularity' (beginning) • expansion • evolution cooling, transformation of energy matter, formation of structure

• http: //imagine. gsfc. nasa. gov/Videos/news/ex panding_univ. mov

Galaxy Formation Galaxies form from the primordial density fluctuations that arise after the big bang and grow under inflation. These density fluctuations form filaments, and galaxies form in knots along the filaments.

• microwave background radiation remnant of a primordial explosion Penzias and Wilson (1964) Bell Labs (ATT), New Jersey

The 20 foot Horn-Reflector

• The expansion history of the Universe is determined by the combination of: – matter – density – curvature

• A universe with less than the critical density is “open”, it will expand forever

• A universe with more than the critical density is “closed”, it will eventually recollapse

• A universe with exactly the critical density is “flat”, will expand forever

Multiverse Theory • Hypothetical set of multiple possible universes (including the historical universe we consistently experience) • Together comprise the entirety of space, time, matter, and energy • Also the physical laws that describe them.

M-Theory • Extension of string theory in which 11 dimensions are identified

Theory of Everything • • Scientific Understanding of the Universe All Matter & Forces in the Universe Unified by String Theory 6 extra dimensions of String Theory are very small 1 x 10 -33 cm in length

Ed Witten • Simplest M theory model contain two 9 dimensional surfaces (9 -branes) separated by the new spatial direction—one of which contains our universe. • More complicated models can contain more 9 dimensional surfaces moving between the 2 fixed branes.

• M Theory implies the existence of a Multiverse that contains 10500 universes • Each universe is brought about by its own Big Bang/Inflation • Contain vastly differing physical laws. • Some universes may have carbon-based life forms • Others vastly different life forms. • Majority may not allow for any life forms whatsoever