Earth is the third planet from the Sun and the only planet known to have life. It is 12,756 km wide, about 150 million km from the Sun, and takes 365.25 days to orbit it. Its 23.4-degree tilt gives us seasons. Oceans cover about 70% of its surface, and Earth formed about 4.5 billion years ago.
Earth quick facts
- Earth is the third planet from the Sun.
- Sunlight takes about 8 minutes and 20 seconds to reach Earth.
- Oceans cover about 70% of Earth’s surface.
- Only about 2.5% of Earth’s water is fresh water.
- Earth formed about 4.5 billion years ago.
What is Earth?
Earth is our home planet. NASA says it is the third planet from the Sun, and the only planet we know of where living things can survive.
Earth is a rocky planet, with land, oceans, air and one moon. It has just the right mix of warmth, water and air for plants, animals and people to live.
Earth is not the biggest planet. NASA says it is only the fifth-largest planet in the solar system. Giant Jupiter is about 11 times wider.
| Earth at a glance | |
|---|---|
| Position | third planet from the Sun |
| Distance from the Sun | about 150 million km (93 million miles) |
| Width at the equator | 12,756 km (7,926 miles) |
| One day | about 23.9 hours |
| One year | 365.25 days |
| Tilt | 23.4 degrees |
| Moons | 1 |
| Age | about 4.5 billion years |
Where is Earth?
Earth travels around the Sun along with seven other planets. Mercury and Venus are closer to the Sun than Earth, and Mars, Jupiter, Saturn, Uranus and Neptune are further away.
NASA says Earth is about 150 million km (93 million miles) from the Sun on average. Astronomers call this distance one astronomical unit, or 1 AU, and use it to measure distances across the solar system.
Light is the fastest thing in the universe, but even light takes time to cross that distance. NASA says sunlight takes about 8 minutes and 20 seconds to reach Earth. So when you look at the Sun, you are seeing it as it was eight minutes ago. Never look straight at the Sun, though, because it can damage your eyes.
How big is Earth?
NASA says Earth is 12,756 km (7,926 miles) wide at the equator, the imaginary line around its middle.
That is big to us, but small next to the Sun and the giant planets. Earth is still the biggest of the four rocky planets, which are Mercury, Venus, Earth and Mars.
Days, years and seasons
Earth spins like a top as it travels around the Sun. NASA says one full spin takes about 23.9 hours, just under a day. As Earth spins, different parts face the Sun, giving us day and night.
NASA says one trip around the Sun takes 365.25 days, which is one year. We cannot have a quarter of a day on a calendar, so we add an extra day, 29 February, every four years. This is called a leap year.
Earth is tilted. NASA says it leans over by 23.4 degrees. This tilt gives us the seasons.
For part of the year, the northern half of Earth leans towards the Sun. It gets more direct sunlight and longer days, so it has summer. At the same time, the southern half leans away and has winter. Six months later, it is the other way round.
The air we breathe
Earth is wrapped in a blanket of air called the atmosphere. NASA says it is about 78% nitrogen and 21% oxygen, with 1% of other gases.
NASA’s Space Place says the atmosphere is just the right thickness to keep the planet warm enough for life. It also protects us from harmful rays from space.
Where does our oxygen come from? NOAA says about half of Earth’s oxygen comes from the ocean. It is made by tiny drifting living things called plankton, which use sunlight to make food.
One tiny ocean bacterium, called Prochlorococcus, is a star performer. NOAA says it may make up to 20% of all the oxygen in the living world, more than all the tropical rainforests put together.
Seeing Earth from space
From space, Earth looks like a blue marble floating in the dark. At night, the lights of cities sparkle across the land, as astronauts on the International Space Station can see.
One of the most famous photos of Earth was taken in December 1968. NASA says astronaut Bill Anders took the Earthrise photo from Apollo 8, the first mission to carry people around the Moon. It shows Earth rising over the Moon’s grey surface.
Today, satellites watch Earth all the time. NASA says a satellite has photographed the whole of Earth from about 1.6 million km (one million miles) away.
NASA’s Earth science team runs more than 20 satellites that study our planet. NASA says it has been collecting information about Earth’s land, water, air and climate for more than 50 years.
What is inside Earth?
Earth is made of layers, a bit like a peach. We live on the thin outer skin, called the crust.
NASA says the crust is about 30 km (19 miles) thick under the land, but only about 5 km (3 miles) thick under the oceans.
Below the crust is a thick layer of hot rock called the mantle. NASA says it is about 2,900 km (1,800 miles) thick.
Next comes the outer core, a layer of liquid metal about 2,300 km (1,400 miles) thick. In the very middle is the solid inner core. NASA says it has a radius of 1,221 km (759 miles), and its temperature can reach 5,400 °C (9,800 °F).
Earth’s crust is broken into huge pieces that slowly move, called tectonic plates. Learn more about each layer in our layers of the Earth facts.
A giant magnet
Earth acts like a giant magnet, with a magnetic north and south. This is why a compass needle points north.
Earth’s magnetic field sometimes flips, so that north and south swap places. NASA says this happens on average about every 300,000 years, but not on a regular timetable.
The water planet
Earth is sometimes called the blue planet. NASA says oceans cover about 70% of its surface. NOAA says the ocean covers about 360 million sq km (139 million square miles).
The ocean is very deep. NOAA says it is about 3,682 m (12,080 feet) deep on average, which is more than 3.5 km.
The deepest known place is the Challenger Deep, in the Mariana Trench in the Pacific Ocean near Guam. NOAA says it is about 10,935 m (35,876 feet) deep. It is named after the British ship HMS Challenger, whose crew first measured the trench in 1875.
The United States Geological Survey says the oceans hold about 1.34 billion cubic km of water. That is almost all of Earth’s water.
Very little fresh water
Most of Earth’s water is salty sea water. The United States Geological Survey says only about 2.5% of Earth’s water is fresh water, the kind we can drink.
And most of that fresh water is frozen. The USGS says about 68.6% of it is locked up in ice caps, glaciers and permanent snow, such as the ice that covers Antarctica.
Rivers hold only a tiny amount of water. The USGS says rivers hold about 0.0002% of all Earth’s water, yet people get much of their water from them. The air holds about 0.001%, as water vapour and clouds.
That is why it is so important not to waste fresh water, and to keep rivers and lakes clean.
The unexplored ocean
We know more about some other planets than about the bottom of our own ocean. NOAA says that, as of April 2026, only 28.7% of the seafloor had been mapped in high detail.
People have seen even less of it with their own eyes. NOAA says we have seen less than 0.001% of the deep seafloor, an area about the size of Rhode Island.
NOAA says more than 90% of the ocean is deep ocean, deeper than 200 m (656 feet). Scientists think 700,000 to 1 million kinds of living things live in the ocean, and about two-thirds of them have not even been described yet.
Earth’s Moon
Earth has one moon. NASA’s Space Place says Earth is the only planet in our solar system with exactly one moon.
NASA says the Moon has a radius of 1,738 km (1,080 miles), and it is about 384,400 km (238,855 miles) from Earth. Earth has no rings.
How old is Earth?
Earth is very old. NASA says it formed about 4.5 billion years ago, when gravity pulled together a swirling cloud of gas and dust.
Life began surprisingly early. NASA says the first life on Earth appeared about 3.8 billion years ago. For most of Earth’s history, the only living things were tiny and simple. Plants, animals and people came much later.
Three things people get wrong
A day is not exactly 24 hours. One spin of Earth takes about 23.9 hours.
Most fresh water is not in rivers and lakes. Most of it is frozen in ice or hidden underground.
Earth is not the biggest planet. It is only the fifth-largest in the solar system.
Did you know? About half of Earth’s oxygen is made by tiny living things drifting in the ocean.
Try it
Shine a torch at a tilted ball as you walk it around a lamp. See how the tilt changes which half gets the most light, making seasons.
Knowledge check
What gives Earth its seasons?
Show answer
Earth’s tilt of 23.4 degrees.
What is the deepest known point in the ocean?
Show answer
The Challenger Deep in the Mariana Trench.
Frequently asked questions
How far is Earth from the Sun?
NASA says Earth is about 150 million km (93 million miles) from the Sun on average. Sunlight takes about 8 minutes and 20 seconds to reach us.
How big is Earth?
Earth is 12,756 km (7,926 miles) wide at the equator. It is the fifth-largest planet and the biggest of the four rocky planets.
Why does Earth have seasons?
Earth is tilted 23.4 degrees. As it orbits the Sun, each half takes turns leaning towards the Sun, giving summer, and away from it, giving winter.
How much of Earth is covered by water?
Oceans cover about 70% of Earth’s surface. But only about 2.5% of Earth’s water is fresh, and most of that is frozen.
What is inside Earth?
Earth has a thin rocky crust, a thick mantle of hot rock, a liquid metal outer core and a solid inner core that can reach 5,400 °C.
How old is Earth?
NASA says Earth formed about 4.5 billion years ago from a cloud of gas and dust. Life began about 3.8 billion years ago.
Sources
- NASA: Earth facts — size, distance, day and year, tilt, atmosphere, layers, oceans, Moon, age and magnetic field
- NASA Space Place: all about Earth — position, life, leap days, the atmosphere and the Moon
- USGS Water Science School: where Earth’s water is — ocean water, fresh water, ice, rivers and the air
- NOAA Ocean Exploration: how much of the ocean have we explored? — ocean area, seafloor mapping, the deep ocean and ocean species
- NOAA Ocean Service: how deep is the ocean? — average depth and the Challenger Deep; NOAA’s page on ocean oxygen was also used
- NASA: Apollo 8 Earthrise — the 1968 Earthrise photograph; NASA’s Earth science pages were also used
