Basics: Planet Earth
Image Source: NASA's Earth Observatory, Published: April 4, 2018
Earth is the only solar system planet that is not named after a Greek/ Roman God. It is the largest terrestrial planet in own solar system (in other words: it can be landed on). As of the date of writing this blog, it is still the only celestial object known to have life. The reason there is life on planet earth is due to several conditions. These include:
- Its position in relation to the Sun
- Liquid water in the correct quantity
- The magnetic core of the planet
- The atmosphere which prevents water from freezing
- The level of oxygen
The region within which earth orbits the sun is called the habitable zone. This is relative to the intensity of the Sun. Theoretically any planet in another star system could be habitable if it is within this habitable zone. The distance in relation to the star could be different though, depending on the output of that star. For example, Venus and Mercury are too close and cannot maintain liquid water. Mars is too far.
What makes earth unusual (amongst other things) is the surface liquid water. Many other solar system planets and moons have significant water, but it is not liquid on the surface. It is also believed that some have liquid water under the surface, for example, the moon Europa.
Planets in other star systems are a problem to look at closely due to their distance. It has been theorized that some may be habitable. There are simply no pieces of equipment that can reach them, as of 2022 (and probably for a very long time). Measurements and studies have to be done from a great distance away.
Unlike the neighbouring terrestrial planets, Mercury, Venus and Mars, Earth has a very powerful magnetic core. It is generated by the movement of molten iron in the core of the planet. It serves in multiple ways to protect the planet. This includes:
- Cosmic radiation from the Sun
- Cosmic rays from deep space
- Charged particles omitted by the Sun
This magnetic core also allows for us to navigate with a compass. This has been done by people for hundreds of years.
Our atmosphere is perfect for the needs of the occupants of the planet who breathe air. Fish obviously respire underwater. Note that for life itself to exist, it does not necessarily need a planet identical to Earth.
Earth’s atmosphere is approximately 21% oxygen, 78% nitrogen and 1% other substances. Part of that 1% is carbon dioxide, which is used by plants. Plant life would have existed on earth before the oxygen rich atmosphere. It is plants that are responsible for producing the oxygen.
As well as containing ingredients that help maintain life, the atmosphere also protects the planet. It protects from harmful Sun radiation. Also, it causes meteoroids to break up due to them burning up. They burn up due to the heating effect of the meteor compressing air in front of it. This in turn heats up the object and makes it burn.
Each layer of the atmosphere has a name. They can be summarized, in order from top (closest to outer space):
- A number of other layers
The Earth is the closest planet to the Sun with a moon. It also has the least amount of moons of any planet. Even Pluto (which is a dwarf planet), has more moons. In comparison to the Mars moons, Earth’s moon is large and very spherical looking. The moons of Mars look more like chunks of random looking rock!