The Earth
The earth is the third planet from the sun and the only astronomical object known to harbour life.
About 29% of earth surface id land consisting of continents and islands
The remaining 71% is covered with water mostly by oceans but also Lakes, Rivers and other fresh water.
- Total Water Area (382,672,000 sq. km)
- Type of Water (97% salt), (3% fresh)
- Circumference at the equator (40,066 km)
- Circumference at the poles (39, 992 km)
- Diameter at the equator (12,753 km)
- Diameter at the poles (12,710 km)
- Radius at the equator (6,376 km)
Planet Earth is a rocky, terrestrial planet. It has a solid and active surface with mountains, valleys, canyons, plains and so much more. Earth is special because it is an ocean planet. Water covers 70% of Earth's surface.
Our atmosphere is made mostly of nitrogen and has plenty of oxygen for us to breathe. The atmosphere also protects us from incoming meteoroids, most of which break up in our atmosphere before they can strike the surface as meteorites.
Structure and Surface
Earth is a terrestrial planet. It is small and rocky.
Earth's atmosphere is the right thickness to keep the planet warm so living things like us can be there. It’s the only planet in our solar system we know of that supports life. It is mostly nitrogen, and it has plenty of oxygen for us to breathe.
Time on Earth
A day on Earth lasts a little under 24 hours.
One year on Earth lasts 365.25 days. That 0.25 extra means every four years we need to add one day to our calendar. We call it a leap day (in a leap year).
Earth’s Neighbours
Earth has just one Moon. It is the only planet to have just one moon.
Earth has lots of spacecraft watching it. There is still a lot we can learn about our home planet.
Earth is the third planet from the Sun in our solar system. That means Venus and Mars are Earth’s neighbouring planets.
ATMOSPHERE
The atmosphere is a layer of gas surrounding the Earth that is some 700 km (400 miles) thick. It is made up of nitrogen (78 per cent) and oxygen (21 per cent), plus traces of other gases. Tiny droplets of water vapour form the clouds we see.
OCEANS
Oceans cover 70.8 per cent of the Earth’s surface, to an average depth of 3.5 km (2 miles). The hydrosphere (watery zone) also includes freshwater rivers and lakes, but these make up less than 1 per cent of Earth’s water.
LAND
Dry land occupies 29.2 per cent of the Earth’s surface, where the lithosphere (rocky crust) rises above sea level to form seven continents and countless smaller islands. Land can be categorised into biomes – major habitats such as forests, grasslands, and deserts.
ICE AND SNOW
The cryosphere (frozen zone) includes snow and glaciers on high mountains, sea ice, and the huge ice caps that cover the landmasses of Greenland and the Antarctic. In the past, during long cold eras called ice ages, ice covered much more of Earth’s surface than it does today.
EARTH SCIENCE
Meteorology, the study of Earth’s atmosphere, is one of the Earth sciences. Earth scientists study Earth’s physical characteristics, from raindrops to rivers and the rocks beneath our feet. Other branches of study include geology (rocks), hydrology, (oceans and freshwater), and ecology (living things and the environment).
BIOSPHERE
The biosphere is the part of Earth that contains what is needed for living things. This zone extends from the ocean floor to top of the troposphere (lower atmosphere). Tiny organisms can survive deep in the Earth’s crust, but most forms of life are found from a few hundred metres below sea level to about 1,000 m (3,300 ft) above sea level.
THE LIFE ZONE
Ozone is a gas spread thinly through the atmosphere. It filters harmful ultraviolet (UV) rays from sunlight, while allowing visible light (the light we can see) to pass through. Other gases in the atmosphere trap the Sun’s heat when it is reflected from the Earth’s surface, providing additional warmth for living things.
AXIS
The ground beneath our feet may seem still, but in fact the Earth is spinning like a top as it orbits the Sun. The Earth takes 24 hours to rotate about its axis, an imaginary line running from the North Pole to the South Pole through the centre of the Earth. The Earth’s axis is not at a right-angle to the path of its orbit, but tilts at an angle of 23.5°. The angle between each region of Earth and the Sun’s rays alters through the year, producing seasonal changes in temperature and day length. These are most noticeable in regions next to the poles, which are most distant from the Equator.
DAY AND NIGHT
As Earth turns about its axis, one half is bathed in sunlight and experiences day, while the other half is plunged into darkness and has night. The Earth always rotates eastward, so the Sun and stars appear to rise in the east and set in the west. The tilt of the planet means that at any time, one hemisphere (half of the Earth, as divided by the Equator) leans toward the Sun and experiences summer, while the other leans away and has winter.DAY AND NIGHT
As Earth turns about its axis, one half is bathed in sunlight and experiences day, while the other half is plunged into darkness and has night. The Earth always rotates eastward, so the Sun and stars appear to rise in the east and set in the west. The tilt of the planet means that at any time, one hemisphere (half of the Earth, as divided by the Equator) leans toward the Sun and experiences summer, while the other leans away and has winter.
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