Origin of Earth
ORIGIN OF EARTH
1. Cosmic Perspective:
- Earth's history is a tiny fraction of the universe's vast timeline.
- Stellar distances are measured in light-years, meaning what we see when looking at stars is light that left them millions of years ago.
- In simple terms, the cosmic perspective on Earth's origin means looking at how our planet was formed and exists in the context of the entire universe. It helps us understand that Earth is just one part of a much bigger cosmic picture, and it encourages us to explore the possibility of life beyond our planet.
2. The Big Bang Theory:
- The universe is approximately 20 billion years old.
- The Big Bang theory explains the origin of the universe, suggesting a singular, massive explosion.
- This explosion led to the expansion of the universe, resulting in a decrease in temperature.
3. Formation of Elements:
- After the Big Bang, hydrogen and helium were the first elements to form.
- Under the influence of gravity, these gases condensed to create galaxies.
- Earth formed around 4.5 billion years ago within the Milky Way galaxy.
- Early Earth had no atmosphere, and its surface was covered with water vapor, methane, carbon dioxide, and ammonia.
- As Earth cooled, UV rays from the sun broke up water into hydrogen and oxygen. Hydrogen escaped, while oxygen combined with ammonia and methane to form water and CO2.
- The ozone layer formed, protecting Earth from harmful radiation.
- As the planet continued to cool, the water vapor in the atmosphere fell as rain, filling depressions and forming oceans.