EARTH

Terre-Erde-Chikyu-Tierra-Terra-Gaia

Earth is a small planet in the vastness of space. It is one of nine planets that travel through space around the sun. The sun is a star -- one of billions of stars that make up a galaxy called the Milky Way. The Milky Way and as many as 100 billion other galaxies make up the universe.

The planet Earth is only a tiny part of the universe, but it is the home of human beings and, in fact, all known life in the universe. Animals, plants, and other organisms live almost everywhere on Earth's surface. They can live on Earth because it is just the right distance from the sun. Most living things need the sun's warmth and light for life. If Earth were too close to the sun, it would be too hot for living things. If Earth were too far from the sun, it would be too cold for anything to live. Living things also must have water to live. Earth has plenty. Water covers most of Earth's surface.

The study of Earth is called geology, and scientists who study Earth are geologists. Geologists study different physical features of Earth to understand how they were formed and how they may have changed over time. Much of Earth, such as the deep interior, cannot be studied directly. Geologists must often study samples of rock and use indirect methods to learn about the planet. Today, geologists can also view and study the entire Earth from space.

Earth ranks fifth in size among the nine planets. It has a diameter of about 8,000 miles (13,000 kilometers). Jupiter, the largest planet, is about 11 times larger in diameter than Earth. Pluto, the smallest planet, has a diameter less than one-fifth that of Earth.

Earth, like all the planets in our solar system, travels around the sun in a path called an orbit. Earth is about 93 million miles (150 million kilometers) from the sun. It takes one year for Earth to complete one orbit around the sun. The innermost planet, Mercury, is only about one-third as far from the sun as Earth and circles the sun in only 88 days. Pluto, the outermost planet, is 40 times as far from the sun as Earth and takes 248 Earth years to circle the sun.

 

Earth: Facts & Figures

Average Distance from the Sun Metric: 149,597,890 km English: 92,955,820 miles Scientific Notation: 1.4959789 x 108 km (1.000 A.U.) Perihelion (closest) Metric: 147,100,000 km English: 91,400,000 miles Scientific Notation: 1.471 x 108 km (0.983 A.U.) Aphelion (farthest) Metric: 152,100,000 km English: 94,500,000 miles Scientific Notation: 1.521 x 108 km (1.017 A.U.) Equatorial Radius Metric: 6,378.14 km English: 3,963.19 miles Scientific Notation: 6.37814 x 103 km By Comparison: 1 x Earth's Equatorial Circumference Metric: 40,075 km English: 24,901 miles Scientific Notation: 4.0075 x 104 km Volume Metric: 1,083,200,000,000 km3 English: 259,900,000 mi3 Scientific Notation: 1.0832 x 1012 km3 By Comparison: 1 x Earth's Mass Metric: 5,973,700,000,000,000,000,000,000 kg Scientific Notation: 5.9737 x 1024 kg Density Metric: 5.515 g/cm3 Surface Area Metric: 510,065,700 km2 English: 196,937,500 square miles Scientific Notation: 5.100657 x 108 km2 Equatorial Surface Gravity Metric: 9.766 m/s2 English: 32.041 ft/s2 Escape Velocity Metric: 40,248 km/h English: 25,009 mph Scientific Notation: 11,180 m/s Sidereal Rotation Period (Length of Day) 0.99726968 Earth days 23.934 hours Sidereal Orbit Period (Length of Year) 1.0000174 Earth years 365.24 Earth days Mean Orbit Velocity Metric: 107,229 km/h English: 66,629 mph Scientific Notation: 29,785.9 m/s Orbital Eccentricity 0.01671022 Orbital Inclination to Ecliptic 0.00005 degrees Equatorial Inclination to Orbit 23.45 degrees Orbital Circumference Metric: 924,375,700 km English: 574,380,400 miles Scientific Notation: 9.243757 x 108 km Minimum/Maximum Surface Temperature Metric: -88/58 (min/max) C English: -126/136 (min/max) F Scientific Notation: 185/331 (min/max) K Atmospheric Constituents Nitrogen, Oxygen Scientific Notation: N2, O2 By Comparison: N2 is 80% of Earth's air and is a crucial element in DNA.

Earth Fact Sheet

Bulk parameters

Mass (1024 kg)                 5.9736
Volume (1010 km3)             108.321   
Equatorial radius (km)	        6378.1    
Polar radius (km)               6356.8         
Volumetric mean radius (km)     6371.0
Core radius (km)                3485
Ellipticity (Flattening)        0.00335      
Mean density (kg/m3)            5515      
Surface gravity (m/s2)          9.798  
Surface acceleration (m/s2)     9.780        
Escape velocity (km/s)         11.186
GM (x 106 km3/s2)               0.3986      
Bond albedo                     0.306  
Visual geometric albedo         0.367
Visual magnitude V(1,0)        -3.86
Solar irradiance (W/m2)         1367.6    
Black-body temperature (K)       254.3    
Topographic range (km)            20
Moment of inertia (I/MR2)       0.3308
J2 (x 10-6)                    1082.63      
Number of natural satellites       1          
Planetary ring system             No 

Orbital parameters

Semimajor axis (106 km)         149.60    
Sidereal orbit period (days)    365.256
Tropical orbit period (days)    365.242    
Perihelion (106 km)             147.09        
Aphelion (106 km)               152.10
Mean orbital velocity (km/s)     29.78        
Max. orbital velocity (km/s)     30.29
Min. orbital velocity (km/s)     29.29
Orbit inclination (deg)           0.000     
Orbit eccentricity                0.0167     
Sidereal rotation period (hrs)   23.9345    
Length of day (hrs)              24.0000
Obliquity to orbit (deg)         23.45     

Earth Mean Orbital Elements (J2000)

Semimajor axis (AU)                  1.00000011  
Orbital eccentricity                 0.01671022   
Orbital inclination (deg)            0.00005  
Longitude of ascending node (deg)  -11.26064  
Longitude of perihelion (deg)      102.94719  
Mean Longitude (deg)               100.46435

North Pole of Rotation

Right Ascension:  0.00 - 0.641T
Declination    : 90.00 - 0.557T
Reference Date : 12:00 UT 1 Jan 2000 (JD 2451545.0)
T = Julian centuries from reference date 

Terrestrial Magnetosphere

Dipole field strength: 0.3076 gauss-Re3
Latitude/Longitude of dipole N: 78.6 degrees N/70.1 degrees W
Dipole offset (planet center to dipole center) distance: 0.0725 Re
Latitude/Longitude of offset vector: 18.3 degrees N/147.8 degrees E

Note: Re denotes Earth radii, 6,378 km

Terrestrial Atmosphere

Surface pressure: 1014 mb
Surface density: 1.217 kg/m3
Scale height: 8.5 km
Total mass of atmosphere:  5.1 x 1018 kg
Total mass of hydrosphere:  1.4 x 1021 kg
Average temperature:  288 K (15 C)
Diurnal temperature range: 283 K to 293 K (10 to 20 C)
Wind speeds: 0 to 100 m/s
Mean molecular weight: 28.97 g/mole 
Atmospheric composition (by volume, dry air): 
    Major      : 78.08% Nitrogen (N2), 20.95% Oxygen (O2), 
    Minor (ppm): Argon (Ar) - 9340; Carbon Dioxide (CO2) - 380
                 Neon (Ne) - 18.18; Helium (He) - 5.24; CH4 - 1.7
                 Krypton (Kr) - 1.14; Hydrogen (H2) - 0.55 
    Numbers do not add up to exactly 100% due to roundoff and uncertainty
    Water is highly variable, typically makes up about 1%

Earth's diameter is just a few hundred kilometers larger than that of Venus. The four seasons are a result of Earth's axis of rotation being tilted more than 23 degrees.

Oceans at least 4 km deep cover nearly 70 percent of Earth's surface. Fresh water exists in the liquid phase only within a narrow temperature span (0 degrees to 100 degrees Celsius). This temperature span is especially narrow when contrasted with the full range of temperatures found within the solar system. The presence and distribution of water vapor in the atmosphere is responsible for much of Earth's weather.

Near the surface, an ocean of air that consists of 78 percent nitrogen, 21 percent oxygen, and 1 percent other ingredients 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 - most of which burn up before they can strike the surface. Satellites have revealed that the upper atmosphere actually swells by day and contracts by night due to solar activity.

Our planet's rapid spin and molten nickel-iron core give rise to a magnetic field, which the solar wind distorts into a teardrop shape. The solar wind is a stream of charged particles continuously ejected from the Sun. The magnetic field does not fade off into space, but has defi- nite boundaries. When charged particles from the solar wind become trapped in Earth's magnetic field, they collide with air molecules above our planet's magnetic poles. These air molecules then begin to glow and are known as the aurorae, or the Northern and Southern Lights.

• North American Plate - North America, western North Atlantic and Greenland 

• South American Plate - South America and western South Atlantic

• Antarctic Plate - Antarctica and the "Southern Ocean"

• Eurasian Plate - eastern North Atlantic, Europe and Asia except for India

• African Plate - Africa, eastern South Atlantic and western Indian Ocean

• Indian-Australian Plate - India, Australia, New Zealand and most of Indian Ocean

• Nazca Plate - eastern Pacific Ocean adjacent to South America

• Pacific Plate - most of the Pacific Ocean (and the southern coast of California)

Concealed within the rocks that make up the Earth's crust lies evidence of over 4.5 billion years of time. The written record of human history, measured in decades and centuries, is but a blink of an eye when compared with this vast span of time. In fact, until the eighteenth century, it was commonly believed that the Earth was no older than a few thousand, or at most, million, years old. Scientific detective work and modern radiometric technology have only recently unlocked the clues that reveal the ancient age of our planet.

Long before scientists had developed the technology necessary to assign ages in terms of number of years before the present, they were able to develop a 'relative' geologic time scale. They had no way of knowing the ages of individual rock layers in years (radiometric dates), but they could often tell the correct sequence of their formation by using relative dating principles and fossils. Geologists studied the rates of processes they could observe first hand, such as filling of lakes and ponds by sediment, to estimate the time it took to deposit sedimentary rock layers. They quickly realized that millions of years were necessary to accumulate the rock layers we see today. As the amount of evidence grew, scientists were able to push the age of the Earth farther and farther back in time. Piece by piece, geologists constructed a geologic time scale, using increasingly more sophisticated methods for dating rock formations. 

Early geologists used the relative positions of rock layers as clues to begin to unravel the complex history of our planet. However, it was not until this century that nuclear age technology was developed that uses measurements of radioactivity in certain types of rocks to give us ages in numbers of years. These ages, usually called radiometric ages, are used in conjunction with relative dating principles to determine at least an approximate age for most of the world 's major rock formations.

The 4.55 billion-year geologic time scale is subdivided into different time periods of varying lengths. All of Earth history is divided into two great expanses of time. The Precambrian began when Earth first formed 4.55 billion years ago and ended about 570 million years ago. The Phanerozoic Eon began 570 million years ago and continues today.

About | Authors | Twitter | Facebook | RSS | Legal

© 2011 Solcomhouse.com. All Rights Reserved.