The Big Bang Theory

Overview

• Almost all astronomers support the Big Bang Theory.
• Universe is expanding with galaxies moving away from us.
• 13.8 billion years ago, everything started from a single point in space.

Evidence for the Big Bang Theory

1. Distant Galaxies Moving Away

• Vesto Slipher (1912): Measured speed and direction of spiral nebulae, found most moving away.
• Edwin Hubble (1924): Discovered these spiral nebulae are actually galaxies outside the Milky Way.
  • Used variable stars to calculate distances of these galaxies.
  • Suggests the Universe was once in a single point.

2. Abundance of Elements

• Big Bang Nucleosynthesis: Early Universe had high heat and pressure, fusing hydrogen into helium and other elements.
• Current ratios of elements in the Universe match theoretical predictions from this process.

3. Cosmic Microwave Background Radiation

• Penzias and Wilson (1960s): Discovered background radio emission consistent across the sky.
• The radiation corresponds to predictions of a huge release of radiation post-Big Bang, shifted to microwave range.

4. Formation of Galaxies and Large Scale Structure

• About 10,000 years post-Big Bang, the Universe cooled, allowing gravitational attraction to dominate.
• Matter collected into first stars and galaxies.

Additional Lines of Evidence

• Fluctuations in cosmic microwave background radiation.
• No stars older than 13.8 billion years.
• Discoveries of dark matter and dark energy.
• Observations of light curves from distant supernovae.

Conclusion

• While labeled a theory, the Big Bang Theory is well-supported like gravity and evolution.
• Ongoing research will refine our understanding and explanations of the Universe's origins.