The Age of the Earth

• Scientists estimate that the Earth is approximately 4.54 billion years old, based on evidence from radiometric dating techniques and comparative studies with meteorites and moon rocks.

How Do We Determine Earth’s Age?

a. Radiometric Dating

• Decay of radioactive isotopes (e.g., Uranium → Lead) is measured to determine age.
• Half-lives range from 700 million to 100 billion years, making this method highly reliable.

b. Oldest Earth Materials

• Zircon crystals found in Western Australia → 4.3 billion years old.
• These crystals indicate that Earth’s history began much earlier than the rocks’ formation.

c. Moon Rocks & Meteorites

• Moon rocks: 4.4 to 4.5 billion years old.
• Meteorites: Similar ages, confirming the solar system’s formation around the same time.

d. Assumptions About Solar System Formation

• Earth formed alongside other planets in the Solar System, making their ages comparable

Cosmic Context

• Milky Way Galaxy → 11 to 13 billion years old.
• Universe → 10 to 15 billion years old (Big Bang Theory).

Key Discoveries

• Zircon grains (4.4 Ga) → Oldest Earth material found so far.
• Lunar rocks (4.5 Ga) → Provide insights into Earth’s formative period.