Physics Lecture 11 - Big Bang & Steady State

Big Bang Theory

The theory that the universe had a definite beginning, evolving and expanding over time.

Steady State Theory

The theory that the universe is eternal and expands with continuous creation of matter, having no beginning or end.

Galaxy Age Distribution (Big Bang)

Predictions that distant galaxies should be younger as they are seen earlier in the history of the universe.

Galaxy Age Distribution (Steady State)

Predictions that galaxies of all ages are evenly spread throughout the universe.

Cosmic Microwave Background (CMB)

Predicted by the Big Bang theory; it is the radiation that is a remnant of the early universe.

Recombination

The process occurring about 300,000 years after the Big Bang when the universe cooled enough for electrons and nuclei to combine into neutral atoms.

Transparency of the Universe After Recombination

Prior to recombination, photons scattered off electrons making the universe opaque; after recombination, photons could travel freely, making it transparent.

Stellar Nucleosynthesis

The process through which elements heavier than helium are formed in stars.

Supernova

An explosive event resulting from the collapse of a massive star, creating heavy elements and potentially leaving a neutron star or black hole.

Protostar

The early stage of star formation when a collapsing gas cloud becomes hot before nuclear fusion starts.

Brown Dwarf

A 'failed star' with too low a mass (less than 0.08 solar masses) to initiate fusion.

Red Giant

An aging star that expands after depleting hydrogen in its core and starts fusing helium into heavier elements.

White Dwarf

The hot, dense core remnant of a low-mass star after it has shed its outer layers.

Neutron Star

An extremely dense remnant of a supernova, primarily made up of neutrons.

Pulsar

A rapidly spinning neutron star that emits beams of electromagnetic radiation, observable as regular pulses.

Evidence of Accelerating Universe Expansion from Supernovae

Observations showing distant supernovae are dimmer than expected, suggesting the universe's expansion is accelerating.

Equilibrium Radiation (Blackbody Radiation)

Radiation emitted by an object in thermal equilibrium; the CMB is a specific form of this.

Fred Hoyle

The scientist who formulated the stellar nucleosynthesis theory.

Ralph Alpher and Robert Herman

Scientists who first predicted the Cosmic Microwave Background in 1948.

Arno Penzias and Robert Wilson

The first scientists to observe the Cosmic Microwave Background in 1967.

John Mather and George Smoot

Researchers who proved the CMB is a form of equilibrium radiation, recognized with the Nobel Prize in 2006.