Earth is our home planet. Scientists believe that the Earth and its moon formed around the same time as the rest of the solar system. They think that was about 4.5 billion years ago. Earth is the fifth largest planet in the solar system. Its diameter is about 8,000 miles. Earth is the third closest planet to the sun. Its average distance from the sun is about 93 million miles. Only Mercury and Venus are closer.
On Earth, everything is perfectly suited to the existence of life. It is warm, but not very warm. And there is water in it, but not large quantities of water.
Earth is the only planet known to have large quantities of liquid water. Liquid water is essential for life. Earth is the only planet known to have life on.
What does the earth look like?
From space, the Earth looks like a blue marble with white swirls and areas of brown, yellow, green and white.
1. Blue is water that covers about 71 percent of the Earth’s surface.
2. White swirls are clouds.
3. The brown, yellow and green spaces are land.
4. White areas have snow and ice.
It is an imaginary circle that divides the Earth into two halves. The northern hemisphere is called the northern hemisphere. The southern hemisphere is called the southern hemisphere. The northernmost point on Earth is called the North Pole. The southernmost point on Earth is called the South Pole.
How do we know that the Earth is round?
Humans have known that the Earth is round for more than 2000 years! The ancient Greeks measured shadows during the summer solstice and calculated the circumference of the Earth as well. They used the positions of the stars and constellations to estimate distances on Earth. They can even see the planet’s circular shadow on the moon during a lunar eclipse. (We still see this during a lunar eclipse.)Today, scientists use geodesy, which is the science of measuring the shape of the Earth, gravity and rotation. Geodesy provides accurate measurements that show that the Earth is round. Using the Global Positioning System (GPS) and other satellites, scientists can measure the size and shape of the Earth to within a centimeter. Pictures from space also show that the Earth is round like the moon.
Although our planet is spherical, it is not a perfect sphere. Because of the force that occurs when the Earth rotates, the North and South poles are slightly flat. The rotation of the Earth, wobbling motion and other forces make the planet change shape very slowly, but still rotate.
How does the Earth move?
_ The earth revolves around the sun once every 365 days or one year. The shape of its orbit is not quite a perfect circle. It is more like an oval, which causes the distance between the earth and the sun to vary during the year.
_ The Earth is closest to the sun, or at perihelion, in January when it is about 91 million miles away.
_ The Earth is farthest from the sun, or at “apogee”, in July when it is about 95 million miles away.
_ At the equator, the Earth is rotating at a speed of just over 1,000 miles per hour.
_ The Earth rotates around its axis completely once every 24 hours, or in a single day.
_ The axis is an imaginary line that passes the center of the planet from the north pole to the south pole.
_ Instead of straightening up and down, the Earth’s axis is tilted at an angle of 23.5 degrees.
Night and day .
At all times, half of the Earth is lit by the sun and the other half in the dark. Areas facing the sun pass during the day. Areas facing away from sunlight pass through at night.
When the planet orbits, most places on Earth revolve during the day and at night once every 24 hours.
The Arctic and Antarctica are characterized by constant daylight or darkness, depending on the time of year.
The reason for the Earth’s seasons.
Earth has seasons because its axis is tilted. Hence, the sun’s rays strike different parts of the planet more directly depending on the time of year.
▪️ From June to August, the sun’s rays hit the northern hemisphere more directly than the southern hemisphere. The result is warm (summer) weather in the northern hemisphere and cool (winter) weather in the southern hemisphere.
▪️ From December to February, the sun’s rays hit the northern hemisphere less directly than the southern hemisphere. The result is cool (winter) weather in the northern hemisphere and warm (summer) weather in the southern hemisphere.
▪️ From September to November, the sun shines evenly over both hemispheres. The result is a fall in the northern hemisphere and a spring in the southern hemisphere.From March to May, the sun also shines evenly over both hemispheres. The result is spring in the northern hemisphere and autumn in the southern hemisphere.
Different parts of the earth.
Earth is made up of (earth, air, water, and life).
The land contains (mountains, valleys and flat areas).
Air consists of various gases, mainly nitrogen and oxygen.
The waters include oceans, lakes, rivers and streams, rain, snow and ice.
Life consists of people, animals, and plants.
There are millions of species, or types of life, on Earth. They range in size from very small to very large.
Underground are layers of rocks and minerals. Temperatures increase with depth, until they reach about 12,000 degrees Fahrenheit in the Earth’s inner core.
Parts of the Earth were once thought to be largely separate from one another. But now they are seen together as the “Earth System”. Every part communicates and affects every other part.
Clouds in the air drop rain and snow on the ground.Water gives life to plants and animals.Volcanoes on Earth send gas and dust into the air.People are breathing air and drinking water.Earth system science is the study of the interactions between the different parts of the Earth.
How was the Earth formed?
Currently, two theories are competing for Earth’s formation.
The first and most widely accepted theory, core accretion, works well with terrestrial planet formation such as Earth but has problems with giant planets.
The second method, disk instability method, may be responsible for the formation of these giants.
Scientists continue to study planets inside and outside the solar system in an effort to better understand these more accurate methods.
Basic Accumulation Model.
Roughly 4.6 billion years ago, the Solar System was a cloud of dust and gas known as a solar nebula.
Gravity collapsed in on itself when it began to spin, forming the Sun at the center of the nebula.As the sun rose, the remaining materials began to agglomerate. Small particles clump together, bound together by the force of gravity, into larger particles. The solar winds washed away the lighter elements, such as hydrogen and helium, from nearby regions, leaving only the heavy rocky materials to create smaller Earth-like worlds. But further away, the solar wind had less effect on the lighter elements, allowing it to coalesce into gas giants. In this way, asteroids, comets, planets and moons were formed.
The rocky core of Earth formed first, with heavy elements colliding and bonding together. The dense material sank in the center, while the lighter material formed the crust. The planet’s magnetic field may have formed around this time. Gravity has captured some of the gases that were forming the planet’s early atmosphere.
Early in its development, Earth suffered the impact of a large object that pushed pieces of the young planet’s mantle into space. Gravity caused many of these pieces to come together and form the moon, which took on an orbit around its Creator.
The flow of the mantle under the crust causes the movement of tectonic plates, which is the movement of large plates of rocks on Earth’s surface. Collisions and friction gave rise to mountains and volcanoes, which began to release gases into the atmosphere.
Flint Wild (5-10-2017), “What Is Earth?”، www.nasa.gov
Nola Taylor Redd (31-10-2016), “How Was Earth Formed?”، www.space.com