Overview
This lecture explains the origin of the universe according to the Big Bang Theory, outlining key stages in the early development of matter, atoms, stars, and galaxies.
The Birth of the Universe
- The universe began about 13.7 billion years ago with a massive explosion called the Big Bang.
- The Big Bang started from an extremely hot, dense bubble smaller than a pinhead.
- In a fraction of a second, time, space, and matter were created and the universe expanded rapidly.
- The universe continues to expand even today.
Formation of Matter and Atoms
- As the universe cooled, energy turned into particles of matter and antimatter, which mostly destroyed each other.
- Some matter survived, and after one second, the universe had grown to 100 billion kilometers across.
- The universe cooled enough for stable particles, protons and neutrons, to form.
- Within three minutes, protons and neutrons combined to form the first atom: hydrogen.
The Emergence of Stars and Galaxies
- Millions of years later, hydrogen gas clumped together under gravity to form stars and galaxies.
- Radiation from these new stars turned hydrogen gas into plasma, allowing visible light to travel through space.
Other Concepts & Theories
- The original super-concentrated point before the Big Bang is called the "primeval atom" or "cosmic egg."
- One possible fate of the universe is the "big crunch," where the universe could eventually collapse and potentially start another big bang.
Key Terms & Definitions
- Big Bang — the massive explosion marking the origin of the universe, creating time, space, and matter.
- Antimatter — particles with properties opposite to normal matter; they destroy each other upon contact.
- Proton — a positively charged particle found in atom nuclei.
- Neutron — a neutral particle found in atom nuclei.
- Hydrogen Atom — the simplest atom, consisting of one proton and one electron.
- Primeval Atom/Cosmic Egg — the initial dense point that became the universe after the Big Bang.
- Big Crunch — a possible scenario where cosmic expansion reverses and the universe collapses inward.
Action Items / Next Steps
- Answer the question: How many years ago did the Big Bang occur?