Earth's lithosphere is divided into several rigid tectonic plates that migrate across the surface over periods of many millions of years. About 71% of Earth's surface is covered with water, mostly by its oceans.[29] The remaining 29% is land consisting of continents and islands that together have many lakes, rivers and other sources of water that contribute to the hydrosphere. The majority of Earth's polar regions are covered in ice, including the Antarctic ice sheetand the sea ice of the Arctic ice pack. Earth's interior remains active with a solid iron inner core, a liquid outer core that generates the Earth's magnetic field, and a convecting mantle that drives plate tectonics.
SOLAR SYSTEM 101 How was our solar system born? Join scientists as they embark on a journey into the mesmerizing mysteries of space. Hear their expert theories, then decide for yourself.
Viewing Earth from the unique perspective of space provides the opportunity to see Earth as a whole. Various satellites and spacecraft, including the Mars Rover and Cassini, which hails from Saturn, provide perspectives of the planet from the others in the solar system.
EARTH: FAST FACTS
Earth is the third planet from the sun and the fifth largest in the solar system.
Earth is 92,955,820 miles (149,597,891 kilometers) away from the sun.
At 7,917.5 miles (12,742 km), 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.
The length of a year on Earth is 365 days, 6 hours, and 16 minutes.
The length of a day on Earth is 23 hours and 56 minutes.
Oceans at least 2.5 miles (4 kilometers) deep cover nearly 70 percent of Earth's surface.
The minimum weather temperature on Earth is -126 degrees Fahrenheit (-87.8 degrees Celsius) and the maximum weather temperature on Earth is 136 degrees Fahrenheit (57.8 degrees Celsius).
Fresh water exists in the liquid phase only within a narrow temperature span (32 to 212 degrees Fahrenheit/0 to 100 degrees Celsius). This temperature span is especially narrow when contrasted with the full range of temperatures found within the solar system (from -400 to 900 degrees Farenheit/-300 to 500 degrees Celcius).
The presence and distribution of water vapor in the atmosphere is responsible for much of Earth's weather.
PROTECTIVE ATMOSPHERE
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 meteorsas well. 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 definite boundaries.
VIEW IMAGES
The silhouette of a woman is seen on a Norwegian island beneath the Northern Lights (aurora borealis).
PHOTOGRAPH BY GARCIA JULIEN, GETTY IMAGES
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.
Planet Profile
orbit: 149,600,000 km (1.00 AU) from Sun diameter: 12,756.3 km mass: 5.972e24 kg
History of Earth
Earth is the only planet whose English name does not derive from Greek/Roman mythology. The name derives from Old English and Germanic. There are, of course, hundreds of other names for the planet in other languages. In Roman Mythology, the goddess of the Earth was Tellus - the fertile soil (Greek: Gaia, terra mater - Mother Earth).
It was not until the time of Copernicus (the sixteenth century) that it was understood that the Earth is just another planet.
Earth, of course, can be studied without the aid of spacecraft. Nevertheless it was not until the twentieth century that we had maps of the entire planet. Pictures of the planet taken from space are of considerable importance; for example, they are an enormous help in weather prediction and especially in tracking and predicting hurricanes. And they are extraordinarily beautiful.
The Earth is divided into several layers which have distinct chemical and seismic properties (depths in km):
The crust varies considerably in thickness, it is thinner under the oceans, thicker under the continents. The inner core and crust are solid; the outer core and mantle layers are plastic or semi-fluid. The various layers are separated by discontinuities which are evident in seismic data; the best known of these is the Mohorovicic discontinuity between the crust and upper mantle.
Most of the mass of the Earth is in the mantle, most of the rest in the core; the part we inhabit is a tiny fraction of the whole (values below x10^24 kilograms):
The core is probably composed mostly of iron (or nickel/iron) though it is possible that some lighter elements may be present, too. Temperatures at the center of the core may be as high as 7500 K, hotter than the surface of the Sun. The lower mantle is probably mostly silicon, magnesium and oxygen with some iron, calcium and aluminum. The upper mantle is mostly olivene and pyroxene (iron/magnesium silicates), calcium and aluminum. We know most of this only from seismic techniques; samples from the upper mantle arrive at the surface as lava from volcanoes but the majority of the Earth is inaccessible. The crust is primarily quartz (silicon dioxide) and other silicates like feldspar. Taken as a whole, the Earth's chemical composition (by mass) is:
The Earth is the densest major body in the solar system.
The other terrestrial planets probably have similar structures and compositions with some differences: theMoon has at most a small core; Mercury has an extra large core (relative to its diameter); the mantles ofMars and the Moon are much thicker; the Moon and Mercury may not have chemically distinct crusts; Earth may be the only one with distinct inner and outer cores. Note, however, that our knowledge of planetary interiors is mostly theoretical even for the Earth.
Unlike the other terrestrial planets, Earth's crust is divided into several separate solid plates which float around independently on top of the hot mantle below. The theory that describes this is known as plate tectonics. It is characterized by two major processes: spreading and subduction. Spreading occurs when two plates move away from each other and new crust is created by upwelling magma from below. Subduction occurs when two plates collide and the edge of one dives beneath the other and ends up being destroyed in the mantle. There is also transverse motion at some plate boundaries (i.e. the San Andreas Fault in California) and collisions between continental plates (i.e. India/Eurasia). There are (at present) eight major plates:
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!)
There are also twenty or more small plates such as the Arabian, Cocos, and Philippine Plates. Earthquakes are much more common at the plate boundaries. Plotting their locations makes it easy to see the plate boundaries.
The Earth's surface is very young. In the relatively short (by astronomical standards) period of 500,000,000 years or so erosion and tectonic processes destroy and recreate most of the Earth's surface and thereby eliminate almost all traces of earlier geologic surface history (such as impact craters). Thus the very early history of the Earth has mostly been erased. The Earth is 4.5 to 4.6 billion years old, but the oldest known rocks are about 4 billion years old and rocks older than 3 billion years are rare. The oldest fossils of living organisms are less than 3.9 billion years old. There is no record of the critical period when life was first getting started.
71 Percent of the Earth's surface is covered with water. Earth is the only planet on which water can exist in liquid form on the surface (though there may be liquid ethane or methane on Titan's surface and liquid water beneath the surface of Europa). Liquid water is, of course, essential for life as we know it. The heat capacity of the oceans is also very important in keeping the Earth's temperature relatively stable. Liquid water is also responsible for most of the erosion and weathering of the Earth's continents, a process unique in the solar system today (though it may have occurred on Mars in the past).
The Earth's atmosphere is 77% nitrogen, 21% oxygen, with traces of argon, carbon dioxide and water. There was probably a very much larger amount of carbon dioxide in the Earth's atmosphere when the Earth was first formed, but it has since been almost all incorporated into carbonate rocks and to a lesser extent dissolved into the oceans and consumed by living plants. Plate tectonics and biological processes now maintain a continual flow of carbon dioxide from the atmosphere to these various "sinks" and back again. The tiny amount of carbon dioxide resident in the atmosphere at any time is extremely important to the maintenance of the Earth's surface temperature via the greenhouse effect. The greenhouse effect raises the average surface temperature about 35 degrees C above what it would otherwise be (from a frigid -21 C to a comfortable +14 C); without it the oceans would freeze and life as we know it would be impossible. (Water vapor is also an important greenhouse gas.)
The presence of free oxygen is quite remarkable from a chemical point of view. Oxygen is a very reactive gas and under "normal" circumstances would quickly combine with other elements. The oxygen in Earth's atmosphere is produced and maintained by biological processes. Without life there would be no free oxygen.
The interaction of the Earth and the Moon slows the Earth's rotation by about 2 milliseconds per century. Current research indicates that about 900 million years ago there were 481 18-hour days in a year.
Earth has a modest magnetic field produced by electric currents in the outer core. The interaction of the solar wind, the Earth's magnetic field and the Earth's upper atmosphere causes the auroras (see the Interplanetary Medium). Irregularities in these factors cause the magnetic poles to move and even reverserelative to the surface; the geomagnetic north pole is currently located in northern Canada. (The "geomagnetic north pole" is the position on the Earth's surface directly above the south pole of the Earth's field.)
The Earth's magnetic field and its interaction with the solar wind also produce the Van Allen radiation belts, a pair of doughnut shaped rings of ionized gas (or plasma) trapped in orbit around the Earth. The outer belt stretches from 19,000 km in altitude to 41,000 km; the inner belt lies between 13,000 km and 7,600 km in altitude.
Earth's Satellite
Earth has only one natural satellite, the Moon. But
thousands of small artificial satellites have also been placed in orbit around the Earth.
Asteroids 3753 Cruithne and 2002 AA29 have complicated orbital relationships with the Earth; they're not really moons, the term "companion" is being used. It is somewhat similar to the situation with Saturn's moons Janus and Epimetheus.
Lilith doesn't exist but it's an interesting story.
Distance Radius Mass
Satellite (000 km) (km) (kg)
--------- -------- ------ -------
Moon 384 1738 7.35e22
Our knowledge of the interior of the Earth is derived almost entirely from highly indirect evidence. How can we get more information?
How fast is Earth's core growing?
Despite substantial increases in the solar "constant" the average temperature on the surface of the Earth has remained very stable for several billion years. The best theory is that this has been accomplished by varying the amount of carbon dioxide in the atmosphere to regulate the greenhouse effect. But just how is this done? The Gaia Hypothesis asserts that the biosphere actively regulates it. More detailed information about Venus and Mars may provide clues.
How much more carbon dioxide can we dump into the Earth's atmosphere before it ends up like Venus?
भारत एक कृषि प्रधान देश है । 70% भारतीय लोग किसान हैं। वे भारत देश के रीढ़ की हड्डी के समान है। खाद्य फसलों और तिलहन का उत्पादन करते हैं। वे वाणिज्यिक फसलों के उत्पादक है। वे हमारे उद्योगों के लिए कुछ कच्चे माल का उत्पादन करते इसलिए वे हमारे राष्ट्र के जीवन रक्त है। भारत अपने लोगों की लगभग 60 % कृषि पर प्रत्यक्ष या पपरोक्ष रूप से निर्भर भारतीय किसान पूरे दिन और रात काम करते है। वह बीज बोते है और रात में फसलों पर नजर रखते भी है। वह आवारा मवेशियों के खिलाफ फसलों की रखवाली करते। वह अपने बैलों का ख्याल रखते है। आजकल, कई राज्यों में बैलों की मदद से खेती करने कि संख्या लगभग खत्म हो गई हैं और ट्रैक्टर की मदद् से खेती कि जाती है। उनकी पत्नीय़ॉ और बच्चों उनके काम में उनकी मदद करते है। भारत गांवों का देश है । भारत की आत्मा गांवों और किसानों में बसती है । इसलिए भारत एक कृषि प्रधान देश भी कहलता है । यहां की 70-80 प्रतिशत जनता प्रत्यक्ष और अप्रत्यक्ष रूप से कृषि पर निर्भर करती है । किसान हमारे लिए अन्न, फल, सब्दिया आदि उपजाता है । वह पशुपालन भी करता है । लेकिन भारतीय किसान की आर...
प्री-बुकिंग के पहले दिन रिलायंस जियो ने जियो फोन के सारे स्पेसिफिकेशन से पर्दा उठा लिया है। Jio Phone के सारे स्पेसिफिकेशन कंपनी की वेबसाइट पर सार्वजनिक किए गए हैं। इस फोन के ज़रिए कंपनी की कोशिश 2जी फीचर फोन यूज़र को अपने नेटवर्क से जोड़ने की है। कंपनी एक तरह से हैंडसेट को मुफ्त में दे रही है। हालांकि, शुरुआत में ग्राहकों को सिक्योरिटी डिपॉजिट के तौर पर 1,500 रुपये की राशि देनी होगी। स्पेसिफिकेशन की सूची से एक बार फिर रिलायंस जियो के कई दावों की पुष्टि हुई है। हमें अब हैंडसेट के स्टोरेज, माइक्रोएसडी कार्ड सपोर्ट, प्रोसेसर और हॉटस्पॉट फीचर के बारे में स्पष्ट जानकारी मिल गई है। Jio Phone के स्पेसिफिकेशन एक सिम वाले जियोफोन में 2.4 इंच का क्यूडब्ल्यूवीजीए (240x320 पिक्सल) डिस्प्ले है। इसमें 1.2 गीगाहर्ट्ज़ स्प्रेडट्रम SPRD 9820A/QC8905 डुअल कोर प्रोसेसर का इस्तेमाल हुआ है। माली-400 जीपीयू इंटिग्रेटेड है। साथ में मौज़ूद है 512 एमबी रैम। इनबिल्ट स्टोरेज 4 जीबी है और आप 128 जीबी तक का माइक्रोएसडी कार्ड इस्तेमाल कर पाएंगे। पिछले हिस्से पर 2 मेगापिक्सल का कैमरा है। और फ्...
Earth is the third planet from the Sun and the only object in the Universe known to harbor life. According to radiometric dating and other sources of evidence, Earth formed over 4 billion years ago.[24][25][26] Earth's gravity interacts with other objects in space, especially the Sun and the Moon, Earth's only natural satellite. Earth revolves around the Sun in 365.26 days, a period known as an Earth year. During this time, Earth rotates about its axis about 366.26 times.[n 5]
71 Percent of the Earth's surface is covered with water. Earth is the only planet on which water can exist in liquid form on the surface (though there may be liquid ethane or methane on Titan's surface and liquid water beneath the surface of Europa). Liquid water is, of course, essential for life as we know it. The heat capacity of the oceans is also very important in keeping the Earth's temperature relatively stable. Liquid water is also responsible for most of the erosion and weathering of the Earth's continents, a process unique in the solar system today (though it may have occurred on Mars in the past).
The Earth's atmosphere is 77% nitrogen, 21% oxygen, with traces of argon, carbon dioxide and water. There was probably a very much larger amount of carbon dioxide in the Earth's atmosphere when the Earth was first formed, but it has since been almost all incorporated into carbonate rocks and to a lesser extent dissolved into the oceans and consumed by living plants. Plate tectonics and biological processes now maintain a continual flow of carbon dioxide from the atmosphere to these various "sinks" and back again. The tiny amount of carbon dioxide resident in the atmosphere at any time is extremely important to the maintenance of the Earth's surface temperature via the greenhouse effect. The greenhouse effect raises the average surface temperature about 35 degrees C above what it would otherwise be (from a frigid -21 C to a comfortable +14 C); without it the oceans would freeze and life as we know it would be impossible. (Water vapor is also an important greenhouse gas.)
The presence of free oxygen is quite remarkable from a chemical point of view. Oxygen is a very reactive gas and under "normal" circumstances would quickly combine with other elements. The oxygen in Earth's atmosphere is produced and maintained by biological processes. Without life there would be no free oxygen.
Earth, of course, can be studied without the aid of spacecraft. Nevertheless it was not until the twentieth century that we had maps of the entire planet. Pictures of the planet taken from space are of considerable importance; for example, they are an enormous help in weather prediction and especially in tracking and predicting hurricanes. And they are extraordinarily beautiful.
Earth, of course, can be studied without the aid of spacecraft. Nevertheless it was not until the twentieth century that we had maps of the entire planet. Pictures of the planet taken from space are of considerable importance; for example, they are an enormous help in weather prediction and especially in tracking and predicting hurricanes. And they are extraordinarily beautiful.
Geomagnetism FAQ
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