Our Planet Earth: Structure, Solar System Position, and Dynamic Movements

Our Planet Earth: Its Place in the Universe

The Earth is a planet in our Solar System. It is part of a single galaxy called the Milky Way, but there are many galaxies in the universe.

The Earth in the Solar System

Components of the Solar System

The Solar System is formed by the Sun, 8 planets, 3 principal dwarf planets, and a series of other celestial bodies.

Planets

Planets are celestial bodies that orbit the Sun and do not have their own light. Earth is one of the planets belonging to the Solar System. Some planets also have satellites that orbit around them.

Planets and their satellites have movements: they rotate on their own axis and also revolve around the Sun, following paths called orbits.

Each celestial body orbits its sun at different times and speeds. The planets follow an almost elliptical orbit.

According to their distance from the Sun, planets are divided into two groups, separated by the asteroid belt, which consists of small rocky bodies.

Inner Planets

Mercury, Venus, Earth, and Mars are closer to the Sun. They are rocky planets and have few satellites.

Outer Planets

Jupiter, Saturn, Uranus, and Neptune are further from the Sun. They are gaseous planets and have many satellites.

Dwarf Planets

Pluto, Eris, and Ceres are part of a new category of planets established by astronomers in 2006.

They are distinguished from other planets because their main orbit around the Sun is not very precise, which suggests they might have a different origin from the rest of the planets.

Our Blue Planet: Earth's Characteristics

Artificial satellites have allowed us to capture photos of our planet, leaving no doubt about its shape and dimensions.

The Shape of the Earth

The Earth is not a perfect sphere; it is slightly flattened at the poles. This shape is called a geoid.

If our planet were cut by the Equator, it would be divided into two equal hemispheres:

• Northern Hemisphere: Also known as the Continental Hemisphere.
• Southern Hemisphere: Also known as the Sea Hemisphere.

Earth's Rotation: Day and Night Cycle

The Earth revolves around its own imaginary axis of rotation. This movement, called rotation, completes one full turn in approximately 24 hours.

The Earth's rotation causes the succession of days and nights.

The cycle of days and nights helps regulate Earth's temperatures, preventing them from becoming extreme, which is crucial for the life of people and animals.

Earth's Revolution: Seasons and Leap Years

The Earth's movement around the Sun is called revolution. Earth traces an elliptical orbit and takes approximately one year (365 days, 6 hours, and 9 minutes) to complete it.

The accumulated six hours every year result in an extra day every four years, which is added to February, creating a leap year.

Earth's Axial Tilt and Seasons

The Earth's axis of rotation is not perpendicular to its orbital plane. This axial tilt is responsible for the succession of the seasons.

Due to this tilt, different parts of the Earth are alternately exposed to the Sun, and the area of maximum insolation shifts throughout the tropical year, moving between the Tropic of Cancer and the Tropic of Capricorn.