Cosmology Review Flashcards

Flashcards about Cosmology

Cosmology

Study of the nature, origin, evolution (change) and fate of the Universe.

Olbers’ Paradox

If the universe is infinite, then every line of sight should end on the surface of a star at some point, making the night sky as bright as the surface of stars.

Solution to Olbers’ Paradox

The visible universe is finite, because if the universe had a beginning, then we can only see light from galaxies that has had time to travel to us since the beginning of the universe.

Homogeneity

On the largest scales, the local universe has the same physical properties.

Isotropy

On the largest scales, the local universe looks the same in any direction that one observes.

Universality

The laws of physics are the same everywhere in the universe.

Hubble Law

Distant galaxies are moving away from our Milky Way, with a recession velocity proportional to their distance.

The Expanding Universe and the Big Bang

Galaxies are moving apart, with velocity proportional to distance, implying a beginning when everything was concentrated in one single point.

Cosmic Microwave Background

The radiation from the very early phase of the universe, discovered in the mid-1960s as blackbody radiation with a temperature of 2.73 K.

Recombination

After a few hundred thousand years, protons can capture electrons, and photons can travel freely through space.

Cosmic Redshift

The wavelength is stretched (red shifted) by cosmic expansion.

Model Universes & Fluctuations in the Cosmic Microwave Background Fate of Universe

Density determines Geometry of Universe. Density determines Geometry, Universe has a flat geometry.

The Big Bang

The Universe evolved from an infinitely dense and hot point

Two Key Pieces of Evidence for The Big Bang

Redshifts of Galaxies (Hubble’s law) and the 3 degree cosmic microwave background

Surprise Discovery About the Universe

Distant Galaxies are FURTHER than Expected.

Measuring the Deceleration of the Universe

By observing Type Ia supernova, astronomers can measure the Hubble relation at large distances.

The Accelerating Universe

Universe is accelerating, caused By Dark Energy.

The Contents of the Universe

Dark Energy: 70%, Dark Matter: 25%, Stars: 0.5%

The Shape of Space and Time

The density of the universe depends on Mass, Universe’s fate depends on density and this determined the geometry. Geometry of Universe - Open, Flat, or Closed