Overview
This lecture uses the "cosmic calendar" to illustrate the immense age and scale of the universe and humanity's brief presence within it.
The Age of the Universe
- Science estimates the universe is about 15 billion years old, beginning with the Big Bang.
- The "cosmic calendar" compresses the universe’s history into one year to visualize time scales.
Cosmic Calendar Highlights
- If the universe began on January 1st, the Milky Way formed in May.
- Other planetary systems may have formed in June to August.
- Our Sun and Earth appeared in mid-September.
- Life on Earth arose shortly after Earth's formation.
Human History on the Cosmic Calendar
- All of human activity is a tiny fraction at the end of the "cosmic year."
- Human ancestors appeared around 10:30 p.m. on December 31st.
- Humans tamed fire at 11:46 p.m.
- Domestication of plants and animals began at 11:59:20 p.m.
- First cities formed at 11:59:35 p.m.
- Recorded human history occurs in the last few seconds of December 31st.
Perspective and Legacy
- Human memory and history cover only the last seconds of the cosmic calendar.
- We are recent products of cosmic evolution—emerging from 15 billion years of development.
- Our actions will determine humanity's future in the next "cosmic year."
Key Terms & Definitions
- Big Bang — The explosive event marking the origin of the universe.
- Cosmic calendar — A scale where the universe's history is compressed into one year for comparison.
- Cosmic Evolution — The process of change and development in the universe from its origin to now.
Action Items / Next Steps
- Reflect on humanity’s role and responsibility in the vast timeline of the universe.