Our planet is approximately 4.6 billion years old. Scientists have been able to make this estimate through the radioactive dating of meteorites that have crashed onto Earth. These meteorites are significant because they are the remains of the original Supernova that created our solar system and Earth.
Since there is nothing on Earth quite as old as Earth (obviously) or these meteorites, it is pretty hard to imagine what this number means. To help you get a sense of just how old Earth is, consider an analogy (comparison) with 1 World Trade Center.
The 1 World Trade Center is 541 meters, or 54,100 centimeters, since there are 100 centimeters in every meter. The first humans came around 2.5 million years ago. If the birth of the Earth were at the base of the tower, this would mean that the first humans weren't built until 29 centimeters from the very top, or, 54,071 centimeters from the bottom! We humans are just a tiny spec in the grand scheme of the Earth's history!
Scientists believe the Earth was "a hellish, fiery wasteland, a molten planet hostile to life" at its birth, according to Origins: The Earth is Born. Today, the Earth is made up of water, land, life, and an atmosphere. Take a look at the image above to see the transformation!
Earth science is the study of the origin, history, and structure of the Earth. Over the course of the unit, we will gather evidence to explain how Earth began, how Earth has changed, how Earth continues to change, and the impact humans have on Earth!
Earth's parts, or "systems", include all of the rock, water, life, and air on Earth. These systems interact on both microscopic (tiny) and macroscopic (huge) scales. Energy and mass never stop flowing and cycling between these systems. Below is an outline of these systems on Earth:
- Lithosphere (also known as Geosphere) - all of the land on Earth, including the continental and oceanic crust, and the upper part of the mantle; made up of rocks and minerals. **litho = stone**
- Hydrosphere - all of the water on Earth, in all states of matter. **hydro = water**
- Biosphere - all of the life on Earth. **bio = life**
- Atmosphere - all of the gases that surround Earth. **atmo = air**