Chapter 1 Our Planets Structure Lesson 1 Review Answer

Introduction

Our domicile planet is the third planet from the Sun, and the only place we know of so far that'due south inhabited by living things. While Earth is only the fifth largest planet in the solar system, it is the only earth in our solar system with liquid water on the surface. Simply slightly larger than nearby Venus, Globe is the biggest of the four planets closest to the Dominicus, all of which are fabricated of rock and metallic.

Namesake

The name Globe is at least one,000 years one-time. All of the planets, except for Earth, were named after Greek and Roman gods and goddesses. However, the name Earth is a Germanic give-and-take, which just means "the ground."

Potential for Life

World has a very hospitable temperature and mix of chemicals that take made life abundant here. Virtually notably, World is unique in that most of our planet is covered in liquid water, since the temperature allows liquid water to be for extended periods of time. Earth's vast oceans provided a user-friendly identify for life to begin about 3.eight billion years ago.

Some of the features of our planet that make it dandy for sustaining life are changing due to the ongoing effects of climatic change. To find out more than visit our sis website, climate.nasa.gov.

Size and Distance

Size and Altitude

With a radius of 3,959 miles (6,371 kilometers), Earth is the biggest of the terrestrial planets and the fifth largest planet overall.

From an average distance of 93 million miles (150 million kilometers), World is exactly one astronomical unit away from the Lord's day because one astronomical unit (abbreviated as AU), is the distance from the Sun to Earth. This unit provides an easy way to chop-chop compare planets' distances from the Sun.

It takes nearly 8 minutes for light from the Sun to achieve our planet.

A 3D model of Earth, our home planet. Credit: NASA Visualization Engineering Applications and Development (VTAD) › Download Options

Orbit and Rotation

Equally World orbits the Dominicus, it completes one rotation every 23.9 hours. Information technology takes 365.25 days to complete one trip around the Sun. That extra quarter of a mean solar day presents a challenge to our agenda organization, which counts one twelvemonth as 365 days. To keep our yearly calendars consistent with our orbit effectually the Sun, every 4 years nosotros add one day. That day is called a leap solar day, and the year information technology's added to is chosen a spring year.

Earth's centrality of rotation is tilted 23.4 degrees with respect to the plane of Earth'south orbit effectually the Lord's day. This tilt causes our yearly cycle of seasons. During part of the year, the northern hemisphere is tilted toward the Sun, and the southern hemisphere is tilted away. With the Sun college in the sky, solar heating is greater in the due north producing summer there. Less direct solar heating produces wintertime in the due south. Six months afterward, the state of affairs is reversed. When spring and autumn begin, both hemispheres receive roughly equal amounts of heat from the Lord's day.

Moons

Earth is the only planet that has a single moon. Our Moon is the brightest and nigh familiar object in the night sky. In many ways, the Moon is responsible for making World such a smashing home. It stabilizes our planet's wobble, which has fabricated the climate less variable over thousands of years.

Earth sometimes temporarily hosts orbiting asteroids or big rocks. They are typically trapped by Earth'due south gravity for a few months or years earlier returning to an orbit effectually the Dominicus. Some asteroids will exist in a long "trip the light fantastic" with Globe as both orbit the Sunday.

Some moons are bits of rock that were captured past a planet'south gravity, but our Moon is probable the result of a standoff billions of years ago. When World was a young planet, a large clamper of stone smashed into it, displacing a portion of Earth's interior. The resulting chunks clumped together and formed our Moon. With a radius of 1,080 miles (one,738 kilometers), the Moon is the fifth largest moon in our solar system (after Ganymede, Titan, Callisto, and Io).

The Moon is an average of 238,855 miles (384,400 kilometers) away from World. That ways 30 Globe-sized planets could fit in between Globe and its Moon.

Rings

Earth has no rings.

Formation

When the solar system settled into its current layout about iv.5 billion years agone, Earth formed when gravity pulled swirling gas and dust in to get the third planet from the Sun. Similar its swain terrestrial planets, World has a cardinal core, a rocky pall, and a solid crust.

Cartoon of Earth

Kid-Friendly Globe

Our home planet Earth is a rocky, terrestrial planet. It has a solid and active surface with mountains, valleys, canyons, plains so much more. Earth is special because it is an bounding main planet. Water covers lxx% of Globe'south surface.

Earth'southward temper is made mostly of nitrogen and has plenty of oxygen for us to breathe. The atmosphere also protects us from incoming meteoroids, nearly of which pause up before they tin striking the surface.

Visit NASA Space Identify for more than kid-friendly facts.

NASA Infinite Place: All Nearly Earth ›

Structure

World is composed of iv main layers, starting with an inner core at the planet'due south center, enveloped by the outer core, curtain, and crust.

The inner core is a solid sphere made of iron and nickel metals near 759 miles (1,221 kilometers) in radius. In that location the temperature is as high equally ix,800 degrees Fahrenheit (5,400 degrees Celsius). Surrounding the inner cadre is the outer core. This layer is about i,400 miles (2,300 kilometers) thick, made of iron and nickel fluids.

In between the outer core and chaff is the pall, the thickest layer. This hot, viscous mixture of molten stone is about i,800 miles (2,900 kilometers) thick and has the consistency of caramel. The outermost layer, Earth'due south chaff, goes about xix miles (30 kilometers) deep on average on state. At the lesser of the ocean, the crust is thinner and extends nigh 3 miles (five kilometers) from the seafloor to the top of the mantle.

Surface

Like Mars and Venus, Earth has volcanoes, mountains, and valleys. Globe's lithosphere, which includes the crust (both continental and oceanic) and the upper mantle, is divided into huge plates that are constantly moving. For example, the North American plate moves west over the Pacific Bounding main bowl, roughly at a rate equal to the growth of our fingernails. Earthquakes outcome when plates grind past one another, ride upwardly over one some other, collide to make mountains, or divide and split up.

Earth's global sea, which covers nearly seventy% of the planet's surface, has an average depth of nigh 2.5 miles (4 kilometers) and contains 97% of Globe'south h2o. Almost all of Earth's volcanoes are subconscious under these oceans. Hawaii's Mauna Kea volcano is taller from base to summit than Mountain Everest, but most of it is underwater. World's longest mountain range is besides underwater, at the bottom of the Arctic and Atlantic oceans. It is four times longer than the Andes, Rockies and Himalayas combined.

Temper

Atmosphere

Near the surface, Earth has an atmosphere that consists of 78% nitrogen, 21% oxygen, and 1% other gases such as argon, carbon dioxide, and neon. The temper affects Earth'southward long-term climate and short-term local weather and shields united states of america from much of the harmful radiation coming from the Dominicus. It as well protects us from meteoroids, about of which burn up in the atmosphere, seen equally meteors in the night heaven, before they can strike the surface as meteorites.

Magnetosphere

Our planet'south rapid rotation and molten nickel-iron cadre give rise to a magnetic field, which the solar wind distorts into a teardrop shape in infinite. (The solar wind is a stream of charged particles continuously ejected from the Sun.) When charged particles from the solar air current become trapped in Globe's magnetic field, they collide with air molecules above our planet's magnetic poles. These air molecules and so begin to glow and crusade aurorae, or the northern and southern lights.

The magnetic field is what causes compass needles to point to the North Pole regardless of which manner you turn. But the magnetic polarity of Earth can change, flipping the direction of the magnetic field. The geologic record tells scientists that a magnetic reversal takes identify nearly every 400,000 years on average, merely the timing is very irregular. Every bit far equally we know, such a magnetic reversal doesn't crusade any harm to life on Earth, and a reversal is very unlikely to happen for at least another thousand years. Only when it does happen, compass needles are likely to point in many different directions for a few centuries while the switch is being made. And after the switch is completed, they will all bespeak s instead of n.

Resources

NASA Earth Observatory
NASA's Climate Portal
NASA World Science Division

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Source: https://solarsystem.nasa.gov/planets/earth/in-depth/