Earth Science

Planet Earth Poster
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Earth is the third closest planet to the Sun. It has an atmosphere made up of many different gases, mainly nitrogen and oxygen. Earth is the only planet in the solar system that can have eclipses of the Sun. It takes one year to go completely around the Sun. The Earth also rotates, or spins, on its axis once per day. The Earth's axis is not straight up and down relative to the orbit, but is tilted a little bit. This tilt is responsible for the seasons. Otherwise, the temperature would be pretty much the same all year long. It has one natural satellite, the Moon.

93.3 million miles from sun
Diameter: 7,926 miles
Moons: 1.
Length of year: 365.25 days.

Earth is the third closest planet to the Sun. Perhaps Earth's most distinguishing factor, at least from our point of view, is the presence of water, which contributed to the formation of life some 3,000 million years ago. Earth's unique atmosphere is made up of many different gases, mainly nitrogen and oxygen.

Our home in the Universe is a large ball of rock spinning through space. This is the Earth, one of the eight planets circling around the sun. It is the third in distance from the sun and the fifth largest of the planets in diameter. It's the third largest of the four inner, terrestrial planets. The average surface temperature of 55 ° F (13 ° C) makes it suitable for life. It is the only planet known to support life, although some of the other planets have atmospheres and contain water. The mean distance of the earth from the sun is 149,503,000 km (92,897,000 mi). The earth has one natural satellite, the moon.

Earth's Structure
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The Earth has oxygen in its atmosphere (the air we breathe), and water in the seas - both of which are essential for life. More than two thirds of the Earth's surface is covered with water. The Earth is just the right distance from the Sun to be neither too hot nor too cold for us to live..

The change of seasons is caused by the tilt (23.5�) of the earth's equator to the plane of the orbit. The earth is surrounded by an envelope of gases, mostly oxygen and nitrogen, called the atmosphere. Gravitational forces have molded the earth into a spherical shape that bulges slightly at the equator (equatorial diameter: c.7,926 mi/12,760 km; polar diameter: 7,900 mi/12,720 km).

Studies indicate that the earth consists of concentric layers that differ in size, chemistry, and density. The outer shell, or crust, consists of the continents and the ocean basins. The thin, outermost layer of lighter rock is the crust, varying in depth from between 30mi (50km) - the thickest continental crust - to 3 mi (5km) - the thinnest oceanic crust.

Like all the terrestrial planets, there is a dense core rich in iron and nickel, surrounded by a mantle of silicate rocks. The crust and the uppermost mantle together form the lithosphere, consisting of tightly fitting slabs called plates. The crust is broken into vast plates that slide around or float on a plastic zone, or semi-molten layer of mantle called the asthenosphere, within the middle shell, or mantle. These interactions are known as plate tectonics.

At the center of the earth is an outer core, believed to be liquid, and an inner, solid core. The solid inner core rotates at a differenct rate than the molten outer layers, and this causes the Earth's magnetic field.

The earth is estimated to be 4.5-5 billion years old, and its origin is a controversial subject.

The Earth, by Greg Goebels

Of all the planets in the solar system, the Earth is so familiar that it almost seems uninteresting. However, it is a unique world in the solar system, a "bioplanet" covered with a network of living organisms, and also makes a good starting point for the discussion of other worlds in the solar system. This document provides a short description of the Earth and its place in the solar system.