Archive · 13 Aug 2025
Big Bang: Hubble's Redshift and the Expanding Universe
Imagine the universe as a balloon being blown up.
Galaxies are like dots on the balloon's surface, all moving away from each other as the balloon expands.
Edwin Hubble noticed that light from galaxies is stretched, like the sound of a siren getting lower as it moves away.
This is called redshift, and it means galaxies are moving away from us.
The farther away a galaxy is, the faster it's moving.
This led scientists to the Big Bang theory, where everything started from a tiny point.
We even have proof in the form of the cosmic microwave background, a faint glow left over from the beginning.
The universe is still expanding and has been for billions of years!
Edwin Hubble observed redshift in galaxies, indicating they are moving away from us.
Redshift increases with distance, showing the universe is expanding.
The Big Bang theory proposes the universe began from a single, dense point.
The cosmic microwave background (CMB) provides evidence of the Big Bang.
The expansion of the universe continues and is accelerating, driven by dark energy.
- Who
- Scientists like Edwin Hubble, Georges Lemaître, Arno Penzias, and Robert Wilson contributed to the theory.
- What
- The universe is expanding from an initial point, called the Big Bang.
- When
- The Big Bang occurred billions of years ago.
- Where
- The expansion is happening everywhere in the universe.
- Why
- The universe's expansion explains redshift, the CMB, and the abundance of light elements.
Initial Theories
Big Bang Theory
Steady State vs. Big Bang
Initial Theories
Proposed an eternal and unchanging universe.
Big Bang Theory
Proposed that the universe had a beginning.
- Hubble's Observation
- Galaxies exhibit redshift, indicating expansion.
- Hubble–Lemaître law
- The farther a galaxy, the greater its redshift.
- Big Bang Theory
- The universe began from a dense point.
- Cosmic Microwave Background (CMB)
- Fossil light from early universe.
- First Elements
- Hydrogen, Helium, and traces of Lithium
- Current Expansion
- Accelerating due to dark energy