Almost all of Earth's water is contained in its global ocean, covering 70.8% of Earth's crust. The remaining 29.2% of Earth's crust is landmass, most of which is located in the form of continental landmasses within Earth's land hemisphere.
Most of Earth's land is somewhat humid and covered by vegetation, while large sheets of ice at Earth's polar deserts retain more water than Earth's groundwater, lakes, rivers, and atmospheric water combined.
Earth's crust consists of slowly moving tectonic plates, which interact to produce mountain ranges, volcanos, and earthquakes. Earth has a liquid outer core that generates a magnetosphere capable of deflecting most of the destructive solar winds and cosmic radiations.
The diameter of Earth is 12742 km and it has a dynamic atmosphere, which sustains Earth's surface conditions and protects it from most meteoroids and UV light at entry. It has a composition of primarily nitrogen and oxygen. Water Vapor is widely present in the atmosphere, forming clouds that cover most of the planet.
The water vapor acts as a greenhouse gas and, together with other greenhouse gases in the atmosphere, particularly Carbon dioxide (CO2), creates the conditions for both liquid surface water and water vapor to persist via the capturing of energy from the Sun's light. This process maintains the current average temperature of 14.76 degrees Celsius, at which water is liquid under normal atmospheric pressure.
Differences in the amount of captured energy between geographic regions (as with the equatorial region receiving more sunlight than other polar regions) drive atmospheric and ocean currents, producing a global climate system with different climate regions, and a range of weather phenomena such as precipitation, allowing components such as nitrogen to cycle.
Earth is a round planet shaped like a ball, but it is slightly squished at the poles. It is the biggest and densest of the rocky planets in our solar system. It takes about 365 days for Earth to go around the sun once, and it spins on its own axis in about 24 hours.
The Moon is Earth's only natural satellite and it orbits around the Earth. The Moon's gravity helps to keep Earth steady and causes tides on Earth. Earth formed about 4.5 billion years ago from gas and dust. Life began in the oceans and has changed Earth's atmosphere and surface over time. Humans have lived on the Earth for about 300,000 years and have had a big impact on the planet. But our actions are hurting Earth's environment and threatening the survival of many living things.
The English word "Earth" has its roots in the Old English term "eorðe", which is related to similar words in other Germanic languages. This word was used to describe the ground, soil, dry land, and the planet itself.
Historically, "Earth" was typically written in lowercase. However, as capitalization became more common in English, the name began to appear in uppercase, especially when referring to the planet alongside other celestial bodies. Today, both lowercase and uppercase forms are used, with the choice often depending on the context and style guide.
While "Earth" is the most common name for our planet, there are a few alternative terms:
Several adjectives are derived from "Earth", including;
Increasing solar luminosity will lead to rising temperatures and the loss of oceans. Sun's evolution into a red giant keeps Earth's fate uncertain, but it may be vaporized or swallowed by the Sun.
Earth rotates on its axis, completing one full spin every 24 hours, which we call a day. This spin is slightly longer than it used to be because of the slowing effect of ocean tides. The exact time it takes to rotate relative to distant stars is around 23 hours, 56 minutes, and 4 seconds. This slight difference explains why stars seem to shift a bit each night. As Earth Spins, the sky appears to move from east to west at a steady rate, causing the Sun and stars to rise and set.
Earth orbits the Sun at an average distance of 150 million kilometers, which takes 365.256 days - what we call a year. This is why we add a leap year every four years. Earth moves through space at about 107,000 km/hr. Even though its path is slightly elliptical (not a perfect circle), this difference has little effect on seasons, which are mostly caused by the tilt of the Earth's axis.
Earth's axis is tilted about 23.4 degrees, which is why we have seasons. This tilt means that different parts of Earth receive varying amounts of sunlight throughout the year. During summer, one hemisphere is tilted toward the Sun and receives more sunlight, while the opposite hemisphere is tilted away and experiences winter. Near the poles, there are times of continuous daylight or darkness, depending on the season.
Earth's orbit and tilt lead to other effects, like changes in the length of days, the occurrence of solar and lunar eclipses, and small variations in Earth's rotation, known as the Chandler wobble.
In short, Earth's day-night cycle is due to its rotation, while its yearly journey around the Sun causes the changing seasons.
The Moon is Earth's only natural satellite and is about one-quarter the size of Earth. It is the largest moon in the Solar System compared to the size of its planet. Scientists believe it was formed when a Mars-sized object collided with the early Earth, creating debris that eventually became the Moon. The Moon's composition is very similar to Earth's outer layers.
The gravity between Earth and the Moon causes ocean tides on Earth. Because of this gravitational interaction, the Moon's rotation is "tidally locked" with Earth, meaning we always see the same side of the Moon. As it orbits Earth, the Moon goes through phases based on how much sunlight hits its surface.
The Moon is slowly moving away from Earth - about 1.5 inches each year. Over millions of years, this small movement has caused Earth's days to get slightly longer. For example, around 620 million years ago, a day lasted only 22 hours.
The Moon helps stabilize Earth's tilt, which affects our climate as well. Without this, Earth's tilt might change widely, causing extreme shifts like what happens on Mars.
From Earth, the Moon appears almost the same size as the Sun in the sky because it is much closer to us, even though the Sun is 400 times larger. This is why we can experience solar eclipses.
Earth also has artificial satellites - over 11,000+ as of 2024 - along with space debris, such as old satellites. The largest artificial satellite is the International Space Station (ISS). Additionally, some asteroids sometimes come near Earth and even orbit temporarily.
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