Big Bang Theory and Redshift

Study Notes

Big Bang Theory

The Big Bang theory proposes that the universe originated from a singular point, referred to as a singularity, approximately 13.8 billion years ago.
The universe has been expanding since the Big Bang.
The theory is supported by several pieces of evidence:
- Cosmic Microwave Background Radiation (CMB): The faint radiation detected in the universe, considered remnant heat from the hot, dense early universe.
- Redshift: Light from distant galaxies is shifted towards the red end of the spectrum, indicating these galaxies are moving away from us. This supports the expansion of the universe.
- Abundance of Elements: The observed proportion of hydrogen, helium, and other light elements in the universe aligns with predictions from Big Bang nucleosynthesis.

### Redshift

Light from distant galaxies appears shifted towards longer wavelengths (red end of the spectrum), which is known as redshift.
This phenomenon occurs because the universe is expanding, causing light to stretch as galaxies move further apart.
Redshift provides compelling evidence for the expansion of the universe.

Hubble Constant

The Hubble constant (H₀) quantifies the rate of the universe's expansion.
Formula: v = H₀ × d
- v: galaxy's velocity (speed at which it’s moving away)
- H₀: Hubble constant
- d: distance to the galaxy
This constant helps in estimating the age of the universe and understanding its expansion rate.

Life History of Stars

A star's life cycle involves distinct stages:
- Nebula: A cloud of gas and dust
- Protostar: A dense region within a nebula that collapses under gravity, heating up.
- Main Sequence: A stable phase where nuclear fusion occurs (our Sun is in this phase).
- Red Giant/Supergiant: When a star exhausts its hydrogen fuel, it expands.
- End of Life:
  - Low/Medium mass stars evolve into White Dwarfs, eventually cooling into Black Dwarfs.
  - High mass stars explode in a Supernova, forming either a Neutron Star or a Black Hole.

Cosmic Microwave Background Radiation (CMB)

CMB is the faint radiation permeating the universe, considered “echoes” of the Big Bang.
Its uniform distribution supports the idea that the Big Bang was the origin of the universe.

Earth System

Earth's system comprises four primary spheres:
- Atmosphere: The gas layer surrounding the Earth.
- Hydrosphere: All water on Earth (oceans, lakes, rivers, groundwater).
- Lithosphere: Earth's solid outer shell (crust and upper mantle).
- Biosphere: All living organisms and their ecosystems on Earth.

Carbon Cycle

The carbon cycle describes the movement of carbon through Earth's different systems.
It involves processes that release carbon into the atmosphere and processes that remove it.
Key steps:
- Combustion: Burning fossil fuels (coal, oil, gas) releases carbon dioxide (CO₂) into the atmosphere.
- Respiration: Organisms release CO₂ as a byproduct of respiration.
- Decomposition: Decomposing plants and animals release carbon into the soil or atmosphere as CO₂.
- Photosynthesis: Plants absorb CO₂ from the atmosphere and convert it into oxygen and glucose.
- Carbon Storage: Carbon is stored in the atmosphere, oceans, soil, and living organisms.

Greenhouse Effect

Certain gases (greenhouse gases) trap heat in Earth's atmosphere, keeping the planet warm enough for life.
Key greenhouse gases: Carbon dioxide (CO₂), methane (CH₄), water vapor (H₂O), nitrous oxide (N₂O).
Process:
- Solar radiation reaches Earth's atmosphere.
- Some energy is reflected back into space, while the rest gets absorbed by Earth's surface and re-radiated as heat.
- Greenhouse gases trap some of this heat, preventing it from escaping into space, maintaining Earth's warmth.
Enhanced Greenhouse Effect: Human activities like fossil fuel burning and deforestation increase greenhouse gas concentrations, trapping more heat and contributing to global warming.

Description

This quiz covers the fundamentals of the Big Bang theory, including the concept of the universe's expansion and supporting evidence such as Cosmic Microwave Background Radiation and redshift. Dive into how these elements contribute to our understanding of the universe's origins and its ongoing evolution.