Earth’s Moon, Rotation, Translation, and Layers Explained
Our Satellite: The Moon
The Moon lights the Earth’s night sky and is the brightest celestial object after the Sun, as observed from Earth. Its radius is approximately 1238 km, about 0.27 times the Earth’s radius. Its mass is nearly eighty times lower than that of the Earth. Its rotation period is 27.3 days, and its orbital period is also 27.3 days.
Due to the relative positions of the Earth, Moon, and Sun, we observe the Moon in various phases: crescent, waning moon, full moon, and new moon.
Earth’s Rotation
Earth has a direct rotation with a period of 23 hours, 56 minutes, and 4 seconds. It turns around its polar axis at an average speed of 1670 km/h at the Equator. The rotation axis is an imaginary line joining the North and South poles. This axis is inclined at 63 degrees to the ecliptic. The speed is highest at the Equator and decreases to zero at the poles. Every spot on Earth passes alternately through a light and dark cycle.
Earth’s Translation
Earth moves in a slightly elliptical orbit in a forward direction. The plane containing the Earth’s orbit and the Sun is called the ecliptic. The translation period is one year (365 days, 5 hours, 48 minutes, and 46 seconds), with an average speed of 107,000 km/h.
Effects of Earth’s Rotation and Translation
The rotation of the Earth causes day and night. The night period is shorter in summer and longer in winter. This phenomenon is due to the inclination of the Earth’s axis of rotation relative to the plane of the ecliptic. As our planet moves through different orbital positions, the Sun reaches different heights above the horizon at each point on the planet, and the time that illuminates each area of the Earth changes over the year.
Parts of the Earth
- Hydrosphere: The layer of water covering 75% of the Earth’s surface, often called the blue planet.
- Geosphere: The remaining 25% consists of rocks and minerals that build mountains, volcanoes, and so on. This rock composition extends throughout the deep Earth.
- Atmosphere: The gaseous layer that surrounds the Earth and makes life possible.
- Biosphere: The layer formed by all living things (animals, plants, and microorganisms) that dwell on the Earth.
Atmosphere Layers
- Troposphere: The layer closest to the surface (14 km), containing 80% of atmospheric gases. Most meteorological phenomena occur here.
- Stratosphere: Contains the ozone layer, which is crucial for life on Earth.
- Mesosphere: Contains heaps of ice and dust, with no ozone or water vapor (40 km).
- Ionosphere: The top and thickest layer (500-1000 km).
Layers in the Static Model
The cortex (crust) is the outer layer of the Geosphere. It is divided into two parts: the continental crust, with materials of varied composition and age, and the oceanic crust, more homogeneous and composed of relatively young rocks from a geological perspective. Below the crust lies the mantle, which is much more uniform but divided into two distinct areas: the upper mantle, which contains olivine, and the lower mantle, with denser materials such as silicates. Finally, the innermost layer is the core, characterized by its high density due to the presence of iron and nickel alloys. The inner core may be composed of pure iron.
Layers in the Dynamic Model
The outermost layer is the lithosphere, comprising the crust and part of the upper mantle. This layer is considered rigid. The lithosphere rests on the asthenosphere, which is equivalent to the shallow mantle in the static model. It is a plastic layer where temperature and pressure can reach levels that allow the rocks to flow in places. Below is the mesosphere, which is equivalent to the rest of the mantle. The area of contact with the core is called Zone D, where molten materials may exist. The innermost layer is the endosphere, which includes both the inner and outer core.