01:750:109 Chapter Notes - Chapter 14.2: Accelerating Expansion Of The Universe, Cosmological Principle
Gravity versus Expansion
How did structures like galaxies form?
Formation of Galaxies and Galaxy Clusters
●Most dark matter is located at large distances from the center of galaxies
Large-Scale Structures
●Cosmological principle
○On very large scaled, the universe looks the same everywhere
Will the universe continue expanding forever?
●The universe is accelerating with time
●Repulsive force that is counteracting w gravity is dark energy
Four Expansion Models
●Recollapsing universe:
○Extremely strong gravitational attraction and no repulsive force, expansion continue and
then slow down w time and eventually stop and reverse
○Final state look like the state in which the universe began in the Big Bang
●Critical universe:
○Gravitational attraction not strong enough to reverse expansion in the absence of a
repulsive force, expansion decelerate forever
○Critical universe bc it’s what we would expect if the total density of the universe were
the critical density and only matter contributed to this density
●Coasting universe:
○Weak gravitational attraction and no repulsive force, galaxy would move apart at same
speed
○No forced acted to change the expansion rate
●Accelerating universe:
○Repulsive force strong enough to overpower gravity
○Galaxies recede from one another w ever-increasing speed
The Fate of the Universe
●Ordinary and dark matter is 30% of critical density
Document Summary
Most dark matter is located at large distances from the center of galaxies. On very large scaled, the universe looks the same everywhere. Repulsive force that is counteracting w gravity is dark energy. Extremely strong gravitational attraction and no repulsive force, expansion continue and then slow down w time and eventually stop and reverse. Final state look like the state in which the universe began in the big bang. Gravitational attraction not strong enough to reverse expansion in the absence of a repulsive force, expansion decelerate forever. Critical universe bc it"s what we would expect if the total density of the universe were the critical density and only matter contributed to this density. Weak gravitational attraction and no repulsive force, galaxy would move apart at same speed. No forced acted to change the expansion rate. Repulsive force strong enough to overpower gravity. Galaxies recede from one another w ever-increasing speed.
