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EARTH
EARTH

                                                      Earth

Our home planet is the third planet from the Sun, and the only place we know of so far that’s inhabited by living things and it is known as Earth.

A close-up of the earth

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Moon orbiting around Earth as observed by a NASA satellite from space

Earth is only astronomical object known to harbour and support life. While Earth is only the fifth largest planet in the solar system, it is the only world in our solar system with liquid water on the surface. Just slightly larger than nearby Venus, Earth is the biggest of the four planets closest to the Sun, all of which are made of rock and metal.

Where did the name EARTH come from?

The name of Earth is at least 1,000 years old. All the planets, except for Earth, were named after Greek and Roman gods and goddesses. However, the name Earth is a Germanic word, which simply means “the ground.”

Earth’s Potential for Life

All the conditions on earth are very suitable for life. And to reach favourable conditions for life to exist on earth, it took earth millions of years of transformations. Most notably, Earth is unique in that most of our planet is covered in liquid water since the temperature allows liquid water to exist for extended periods of time. Earth's vast oceans provided a convenient place for life to begin about 3.8 billion years ago.

Some of the features of our planet that make it great for sustaining life are changing due to the ongoing effects of climate change because of uncontrolled exploitation and destruction of earth’s resources.

Size and Distance from the Sun

With a radius of 6,371 kilometres, Earth is the biggest of the terrestrial planets and the fifth largest planet overall.

From an average distance of 150 million kilometres, Earth is exactly one astronomical unit away from the Sun because one astronomical unit (AU), is the distance from the Sun to Earth. This unit provides an easy way to quickly compare planets' distances from the Sun.

It takes about eight minutes for light from the Sun to reach our planet.

Diagram, schematic

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Earth’s revolution around the Sun and changing seasons

Orbit and Rotation of Earth

Earth completes one rotation every 23.9 hours. It takes 365.25 days to complete one trip around the Sun. That extra quarter of a day presents a challenge to our calendar system, which counts one year as 365 days. To keep our yearly calendars consistent with our orbit around the Sun, every four years we add one day. That day is called a leap day, and the year it's added to is called a leap year.

Earth's axis of rotation is tilted 23.4 degrees with respect to the plane of Earth's orbit around the Sun. This tilt causes our yearly cycle of seasons. During part of the year, the northern hemisphere is tilted toward the Sun, and the southern hemisphere is tilted away. With the Sun higher in the sky, solar heating is greater in the north producing summer there. Less direct solar heating produces winter in the south. Six months later, the situation is reversed. When spring and fall begin, both hemispheres receive roughly equal amounts of heat from the Sun.