Big Bang Theory - Vocabulary Flashcards

Vocabulary flashcards covering key terms and definitions from the lecture notes on the Big Bang, recombination, CMBR, redshift, and related concepts.

Big Bang Theory

The idea that the universe began from a hot, dense state and has been expanding since.

Photoionization

The process by which photons ionize atoms, ejecting electrons and creating free ions.

Recombination

Epoch when electrons and protons combined to form neutral atoms, allowing photons to travel freely and creating the Cosmic Microwave Background Radiation (CMBR).

Cosmic Microwave Background Radiation (CMBR)

Uniform microwave radiation filling the universe; the afterglow of the Big Bang and key evidence for the theory.

Cosmological Redshift

Stretching of light wavelengths due to the expansion of the universe, shifting light toward the red end of the spectrum.

Hubble’s Law

The relationship between a galaxy’s distance from Earth and its recessional speed—the farther the galaxy, the faster it is moving away.

Doppler Effect

Change in frequency or wavelength of a wave due to the motion of the source relative to the observer (includes light).

Abundance of Light Elements

Observed proportions of hydrogen (~73.9%), helium (~24%), and traces of lithium, supporting Big Bang nucleosynthesis.

Stellar Nucleosynthesis

The process by which stars fuse lighter elements into heavier ones, producing elements heavier than helium.

Electromagnetic Spectrum

The range of electromagnetic radiation from radio waves to gamma rays, categorized by wavelength and energy.

Visible Spectrum

The portion of the electromagnetic spectrum visible to humans, ordered from violet to red.

Neutral Atoms

Atoms formed when electrons and nuclei combine, allowing photons to travel freely.

Evidence for the Big Bang

Cosmological redshift, the Cosmic Microwave Background Radiation (CMBR), and the abundance of light elements.

Penzias & Wilson (CMBR Discovery)

Astronomers who discovered the cosmic microwave background using a radio telescope, identifying it as the Big Bang’s afterglow.

Expansion of Space

The idea that space itself stretches over time, causing photons to be redshifted as they travel.

Opacity of the Early Universe

Before recombination, photons repeatedly scattered off free electrons, preventing transparent travel of light.

Early Universe Temperature (~3000 K at Recombination)

The approximate temperature at which neutral atoms formed and photons began traveling freely, creating the CMBR.

380,000 years old (Recombination Era)

Approximate time after the Big Bang when recombination occurred and the CMBR was released.