About Planet Earth – Introduction

Earth is the fifth-largest planet in the solar system. Its diameter is about 8,000 miles. And 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.

Scientists have estimated the Earth as being between 4 and 5 billion years old.

Some statistics about Earth, according to NASA:
• Average distance from the sun: 92,956,050 miles (149,598,262 km)
• Perihelion (closest approach to the sun): 91,402,640 miles (147,098,291 km)
• Aphelion (farthest distance from the sun): 94,509,460 miles (152,098,233 km)
• Length of solar day (single rotation on its axis): 23.934 hours
• Length of year (single revolution around the sun): 365.26 days
• Equatorial inclination to orbit: 23.4393 degrees

Earth orbits the sun once every 365 days, or one year.

At all times, half of Earth is lighted by the sun and half is in darkness.

From September to November, the sun shines equally on both hemispheres. The result is fall in the Northern Hemisphere and spring 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 cold (winter) weather in the Northern Hemisphere and warm (summer) weather in the Southern Hemisphere.

Earth has a natural satellite called Moon. Earth’s moon is 2,159 miles (3,474 km) wide, about one-fourth of Earth’s diameter.

About 70% of the earth’s surface is covered with water.

Ninety-seven percent of the water on the earth is salt water. Salt water is filled with salt and other minerals, and humans cannot drink this water. Although the salt can be removed, it is a difficult and expensive process.

Two percent of the water on earth is glacier ice at the North and South Poles. This ice is fresh water and could be melted; however, it is too far away from where people live to be usable.

Less than 1% of all the water on earth is fresh water that we can actually use. We use this small amount of water for drinking, transportation, heating and cooling, industry, and many other purposes.

Earth has a powerful magnetic field, and that is all thanks to the partially molten core. The constant movement of molten iron creates an electrical current inside the planet, and that in turn generates a magnetic field that reaches far out into space.

The magnetic field helps to shield us from harmful solar radiation. If the core of the Earth wasn’t the way it is, there would be no magnetic field, and we would have all sorts of problems to contend with.

Air surrounds Earth and becomes thinner farther from the surface.

Air consists of 78 percent nitrogen, 21 percent oxygen, and trace amounts of argon, carbon dioxide and other gases envelops us. This atmosphere affects Earth’s long-term climate and short-term local weather; shields us from nearly all harmful radiation coming from the sun; and protects us from meteors as well.

Phenomenon’s on Earth – Part I