Earth

For descriptions of the Earth in (science) fiction, see Earth in fiction. The heart may also be illustrated as an icon (♥), symbolizing love. See Spaceship Earth and Gaia theory.. It can vary from one to four chambers (2 atria and 2 ventricle). Earth has also been described as a massive spaceship, with a life support system that requires maintenance, or as having a biosphere that forms one large organism. Different species have different heart chambers. A photo taken of Earth by Voyager 1 inspired Carl Sagan to describe the planet as a "Pale Blue Dot". It resembles venison in structure and taste.

The technological developments of the latter half of the 20th century are widely considered to have altered the public's perception of the Earth. They are counted among offal, but being a muscle, the taste of heart is much more like regular meat than that of other offal. Surveying, the determination of locations and distances, and to a somewhat lesser extent navigation, the determination of position and direction, have developed alongside cartography and geography, providing and suitably quantifying the requisite information. The hearts of cattle, sheep, pigs and certain fowl are consumed as food in many countries. Cartography, the study and practice of mapmaking, and vicariously geography, have historically been the disciplines devoted to depicting the Earth. The earthworm has a series of multiple primitive hearts. Prior to the introduction of space flight, this belief was countered with deductions based on observations of the secondary effects of the Earth's shape and parallels drawn with the shape of other planets. The Gray Whale's heart beats 9 times per minute, Harbour Seal 10 when diving, 140 when on land, elephant 25, human 70, sparrow 500, shrew 600, and hummingbird 1,200 when hovering.

In the past there were varying levels of belief in a flat Earth because of this, but ancient Greek philosophers and, in the Middle Ages, thinkers such as Thomas Aquinas knew that the Earth was a sphere. See "Early development" above for information about the early human heart rates. Since Earth is rather large, it is not immediately obvious to the naked eye viewing from the surface that it is an oblate spheroid, bulging slightly at the equator and slightly flattened at the poles. This is evident within a species as well, as the young beat their hearts faster than the adults. In Norse mythology, the Earth goddess Jord was the mother of Thor and the daughter of Annar. Smaller animals have faster heartbeats. As the patroness of fertility, her element is Earth. Birds and mammals show complete separation of the heart into two pumps, for a total of four heart chambers; it is thought that the four-chambered heart of birds evolved independently of that of mammals.

The Chinese Earth goddess Hu-Tu is similar to Gaia, the deification of the Earth. The blood from the single ventricle is then pumped to both the lungs and the body tissues, an type of double circulation. Earth has often been personified as a deity, in particular a goddess (see Gaia and Mother Earth). Blood from both the body and the lungs is pumped into the single ventricle, where unoxygenated and oxygenated blood may mix. The United Nations is primarily an international discussion forum with only limited ability to pass and enforce laws. Amphibians and reptiles have a three-chambered heart: two atria and one ventricle. There is a worldwide general international organization, the United Nations. The blood pumps through the gills and on to the the body tissues without returning to the heart.

Independent sovereign nations claim all of the land surface except for some segments of Antarctica. In fish, the system has only one circuit. Earth does not have a sovereign government with planet-wide authority. The heart of fish have only two chambers: one atrium and one ventricle. There are 267 administrative divisions, including nations, dependent areas, other, and miscellaneous entries. If an automated external defibrillator is available, this device may automatically administer defibrillation if this is indicated. The southernmost is the Amundsen-Scott South Pole Station, in Antarctica, almost exactly at the South Pole. If a person is encountered in cardiac arrest (no heartbeat), cardiopulmonary resuscitation (CPR) should be started, and help called.

The northernmost settlement in the world is Alert, Ellesmere Island, Canada. See cardiac arrest for emergencies involving the heart. See also space colonization. See also: Cardiology diagnostic tests and procedures. Out of those only twelve humans have ever walked on a world other than Earth: the men of Apollo 11, 12, 14, 15, 16 and 17, who walked on the Moon between 1969 and 1972. The transplant team was headed by Christiaan Barnard. In total, about 400 people have been outside Earth (in space) as of 2004. At Groote Schuur Hospital in Cape Town, South Africa, 53-year-old Louis Washkansky on December 3, 1967 became the first human to receive a heart transplant (however he died 18 days later from double pneumonia).

During the exchange there are more, and sometimes others are also traveling briefly above the atmosphere. Nitroglycerin and other compounds that give off nitric oxide are used to treat heart disease as they cause the dilation of coronary vessels. The station crew is replaced with new personnel every six months. Beta blockers are drugs that lower the heart rate and blood pressure and reduce the heart's oxygen requirements. Two humans are presently in orbit around Earth on board the International Space Station. If a coronary artery is blocked or narrowed, the problem spot can be bypassed with coronary artery bypass surgery or it can be widened with angioplasty. Coastal areas constitute the highest density. Important diseases of the heart include:.

It is estimated that only 1/8th of the surface of the Earth is suitable for humans to live on - 3/4 is covered by oceans, and half of the landmass is unsuitable, being desert, high mountain, etc. The study of diseases of the heart is known as cardiology. Nearly all humans currently reside on Earth: 6,411,000,000 inhabitants (January 5, 2005 est.). The heart also secretes ANF (atrial natriuretic factor), a powerful peptide hormone, that affects the blood vessels, the adrenal glands, the kidneys and the regulatory regions of the brain to regulate blood pressure and volume. Most of the growth is expected to take place in developing nations. In the event of severe pathology, the Purkinje fibers can also act as a pacemaker; this is usually not the case because their rate of spontaneous firing is considerably lower than that of the other pacemakers and hence is overridden. On 25 February 2005 the United Nations Population Division issued revised estimates and projected that the world's population will reach 7 billion by 2013 and swell to 9.1 billion in 2050. The time taken for the wave to reach this node from the sinoatrial nerve creates a delay between contraction of the two chambers and ensures that each contraction is coordinated simultaneously throughout all of the heart.

Long-term climate alteration due to enhancement of the greenhouse effect by human industrial carbon dioxide emissions is an increasing concern, the focus of intense study and debate. Once the wave reaches the atrioventricular node, situated in the lower right atrium, it is conducted through the bundles of His and causes contraction of the ventricles. Large areas are subject to man-made pollution of the air and water, acid rain and toxic substances, loss of vegetation (overgrazing, deforestation, desertification), loss of wildlife, species extinction, soil degradation, soil depletion, erosion, and introduction of invasive species. The sinoatrial node, often known as the cardiac pacemaker, is located in the upper wall of the right atrium and is responsible for the wave of electrical stimulation (See action potential) that initiates atria contraction. Many places are subject to earthquakes, landslides, tsunamis, volcanic eruptions, tornadoes, sinkholes, floods, droughts, and other calamities and disasters. The rhythmic sequence of contractions is coordinated by the sinoatrial and atrioventricular nodes. Large areas are subject to extreme weather such as (tropical cyclones), hurricanes, or typhoons that dominate life in those areas. The heart's rhythmic contractions occur spontaneously, although the frequency or heart rate can be changed by nervous or hormonal influences such as exercise or the perception of danger.

Irrigated land: 2,481,250 km² (1993 est.). This is in contrast with skeletal muscle, which requires either conscious or reflex nervous stimuli. The exploitation of non-renewable resources by human civilization has become a subject of significant controversy in modern environmentalism movements. Cardiac muscle is self-exciting. Some of these resources, such as mineral fuels, are difficult to replenish on a short time scale, called non-renewable resources. Finally complete cardiac diastole involves relaxation of the atria and ventricles in preparation for refilling with circulating blood. Elevation extremes: (measured relative to sea level). The ventricular systole consists of the contraction of the ventricles and flow of blood into the circulatory system. Again, once all the blood empties from the ventricles, the pulmonary and aortic semilunar valves close.

Ocean currents, particularly the spectacular thermohaline circulation which distributes heat energy from the equatorial oceans to the polar regions, are important determinators of climate. It is the closing of the valves that produces the familiar beating sounds of the heart, commonly referred to as the "lub-dub" sound due to the closing of the semilunar and atrioventricular valves. Precipitation patterns vary widely, ranging from several metres of water per year to less than a millimetre. This prevents any backflow into the atria. Two large areas of polar climates separated by two rather narrow temperate zones from a wide equatorial band of tropical to subtropical climates. Once the blood has fully left the atria, the atrioventricular valves, which are situated between the atria and ventricular chambers, close. Terrestrial biomes lying within the Arctic and Antarctic Circles are relatively barren of plant and animal life, while most of the more populous biomes lie near the Equator. Every single beat of the heart involves a sequence of events known as the cardiac cycle, which consists of three major stages: atrial systole, ventricular systole and complete cardiac diastole. The atrial systole consists of the contraction of the atria and the corresponding influx of blood into the ventricles.

On land, biomes are separated primarily by latitude. The function of the heart is to pump blood around the body. The biosphere is divided into a number of biomes, inhabited by broadly similar flora and fauna. See main page cardiac cycle. This biosphere is generally believed to have begun evolving about 3.5 billion (3.5×10⁹) years ago. The blood supply to the heart itself is supplied by the left and right coronary arteries, which branch off from the aorta. The planet's lifeforms are sometimes said to form a "biosphere". The endocardium is a further layer of flattened epithelial cells and connective tissue which lines the chambers of the heart.

Earth is the only place in the universe where life is absolutely known to exist, and some scientists believe that biospheres might be rare. Beneath this is a much thicker myocardium made up of cardiac muscle. Maritime claims: see United Nations Convention on the Law of the Sea. The first is the outer epicardium which is composed of a layer of flattened epithelial cells and connective tissue. Coastline: 356,000 km. The heart wall is made of three distinct layers. Land boundaries: the land boundaries in the world total 251,480 km (not counting shared boundaries twice). The contractile nature of the heart is due to the presence of cardiac muscle in its wall which can work continuously without fatigue.

Area:. Even though the ventricles lie below the atria, the two vessels through which the blood exits the heart (the pulmonary artery and the aorta) leave the heart at its top side. Continents, Oceans. As the right ventricle needs to pump blood only to the lungs, it requires less muscle. Biggest geographic subdivision. The left ventricle is much more muscular (1.3 - 1.5 cm thick) than the right (0.3 - 0.5 cm thick) as it has to pump blood around the entire body, which involves exerting a considerable force to overcome the vascular pressure. Time Zones, Coordinates. Even the lungs take some of the blood supply from the aorta via bronchial arteries.

Map references:. The left ventricle then pumps the blood through the aorta to the entire body. Earth also has at least one co-orbital asteroid, 3753 Cruithne. From the left atrium this newly oxygenated blood passes through the mitral valve to enter the left ventricle. This hypothesis explains (among other things) the Moon's relative lack of iron and volatile elements, and the fact that its composition is nearly identical to that of the Earth's crust. The oxygenated blood then flows through pulmonary veins to the left atrium. The most widely accepted theory of the Moon's origin, the giant impact theory, states that it was formed from the collision of a Mars-size protoplanet with the early Earth. In the lungs gaseous exchange takes places and the blood releases carbon dioxide into the lung cavity and picks up oxygen.

This allows total eclipses and annular eclipses to occur on Earth. The right ventricle pumps the deoxygenated blood to the lungs, through the pulmonary artery. The Moon is just far enough away to have, when seen from Earth, very nearly the same apparent angular size as the Sun (the Sun is 400 times larger, but the Moon is 400 times closer). The blood then passes through the tricuspid valve to the right ventricle. This remains a controversial subject, however, and further studies of Mars—which shares Earth's rotation period and axial tilt, but not its large moon or liquid core—may provide additional insight. Oxygen-depleted or deoxygenated blood from the body enters the right atrium through two great veins, the superior vena cava which drains the upper part of the body and the inferior vena cava that drains the lower part. Planetary scientists who have studied the effect claim that this might kill all large animal and higher plant life. On both sides, the lower ventricles are thicker than the upper atria.

One pole would be pointed directly toward the Sun during summer and directly away during winter. The left side (see left heart) collects oxygenated blood from the lungs and pumps it out to the body. If Earth's axis of rotation were to approach the plane of the ecliptic, extremely severe weather could result, as this would make seasonal differences extreme. this happens through a process called diffusion. Some theorists believe that, without this stabilization against the torques applied by the Sun and planets to the Earth's equatorial bulge, the rotational axis might be chaotically unstable, as it appears to be with Mars. The function of the right side of the heart (see right heart) is to collect deoxygenated blood from the body and pump it into the lungs so that carbon dioxide can be dropped off and oxygen picked up. Paleontological evidence and computer simulations show that Earth's axial tilt is stabilised by tidal interactions with the Moon. Finally complete cardiac diastole involves relaxation of the atria and ventricles in preparation for refilling with circulating blood.

The Moon may dramatically affect the development of life by taming the weather. Again, once all the blood empties from the ventricles, the pulmonary and aortic semilunar valves close. As the Moon orbits Earth, different parts of its face are illuminated by the Sun, leading to the lunar phases: The dark part of the face is separated from the light part by the solar terminator. Valves between the atria and ventricles (atrioventricular valves) maintain coordinated unidirectional flow of blood from the atria to the ventricles.The ventricular systole consists of the contraction of the ventricles and flow of blood into the circulatory system. As a result, it always presents the same face to the planet. A septum divides the right atrium and ventricle from the left atrium and ventricle, preventing blood from passing between them. The same effect on the Moon has led to its tidal locking: Its rotation period is the same as the time it takes to orbit the Earth. It consists of four chambers, the two upper atria (singular: atrium) and the two lower ventricles.

The gravitational attraction between the Earth and Moon cause the tides on Earth. In normal adults, its mass is 250-350 g, but extremely diseased hearts can be up to 1000 g in mass. The natural satellites orbiting other planets are called "moons", after Earth's Moon. A stethoscope can be placed directly over the apex and count the beats. With the exception of Pluto's Charon, it is the largest moon in the Solar system relative to the size of its planet. The apex is the blunt point at the base of the heart. The Moon, sometimes called 'Luna', is a relatively large terrestrial planet-like satellite, whose diameter is about one-quarter of the Earth's. It is enclosed by a sac known as the pericardium and is surrounded by the lungs.

. In the human body, the heart is normally situated slightly to the left of the middle of the thorax, underneath the sternum (breastbone). The Earth is sometimes referred to as the Third Planet from the Sun because, of the nine planets of our solar system, Earth is the third closest planet to the sun. [2]. For other eras, see precession and Milankovitch cycles. There is no difference in male and female heart rates before birth. In modern times, Earth's perihelion is always about January 3, and aphelion is about July 4 (near the winter and summer solstices, which are on about December 21 and June 21, respectively). After the 15th week the deceleration slows reaching an average rate of about 145 (+/-25 bpm) bpm at term.

Also, the rotational velocity varies, a phenomenon known as length of day variation. After peaking at about 9.2 weeks after the LMP, it decelerates to about 150 bpm (+/-25 bpm) during the 15 week after the LMP. The polar motion is quasi-periodic, containing an annual component and a component with a 14-month period called the Chandler wobble. [1]. In a reference frame attached to the solid body of the Earth, its rotation is also slightly irregular due to polar motion. This acceleration is approximately 3.3 bpm per day, or about 10 bpm every three days, an increase of 100 bpm in the first month. These motions are caused by the differential attraction of Sun and Moon on the Earth's equatorial bulge, due to its oblateness. It then accelerates linearly for the first month of beating, peaking at 165-185 bpm during the early 7th week, (early 9th week after the LMP).

In an inertial reference frame, the Earth's axis undergoes a slow precessional motion with a period of some 25,800 years, as well as a nutation with a main period of 18.6 years. The human heart begins beating at a rate near the mother’s, about 75-80 beats per minute (bpm). The Hill sphere (sphere of influence) of the Earth is about 1.5 Gm (930 thousand miles) in radius, within which one natural satellite (the Moon) comfortably orbits. The human embryonic heart (EHR) begins beating at approximately 21 days after conception, or five weeks after the last normal menstrual period (LMP), which is the date normally used to date pregnancy. The orbital and axial planes are not precisely aligned: Earth's axis is tilted some 23.5 degrees against the Earth-Sun plane (which causes the seasons); and the Earth-Moon plane is tilted about 5 degrees against the Earth-Sun plane (otherwise there would be an eclipse every month). . Viewed from Earth's north pole, the motion of Earth, its moon and their axial rotations are all counterclockwise. The term cardiac means "related to the heart", from the Greek kardia (καρδια) for "heart".

When combined with the Earth-Moon system's common revolution around the Sun, the period of the synodic month, from new moon to new moon, is 29.53 days. The heart (Latin cor) is a hollow, muscular organ that pumps blood through the blood vessels by repeated, rhythmic contractions. Earth has one natural satellite, the Moon, which revolves with the Earth around a common barycenter, from fixed star to fixed star, every 27.32 days. Congenital heart defects. The orbital speed of the Earth averages about 30 km/s (108,000 km/h), which is enough to cover one Earth diameter (~12,700 km) in 7 minutes, and one distance to the Moon (384,000 km) in 4 hours. It is sometimes treated by implanting an artificial pacemaker. From Earth, this gives an apparent movement of the Sun with respect to the stars at a rate of about 1 °/day, i.e., a Sun or Moon diameter every 12 hours, eastward. Cardiac arrhythmia is an irregularity in the heartbeat.

Earth orbits the Sun every 365.2564 mean solar days (1 sidereal year). Endocarditis and myocarditis are inflammations of the heart. From Earth the main apparent motion of celestial bodies in the sky (except meteors which are within the atmosphere and low-orbiting satellites) is the movement to the west at a rate of 15 °/h = 15'/min, i.e., a Sun or Moon diameter every two minutes. Congestive heart failure is the gradual loss of pumping power of the heart. It takes the Earth 23 hours, 56 minutes and 4.091 seconds (1 sidereal day) to rotate around the axis connecting the north pole and the south pole. A heart attack occurs when heart muscle cells die because blood circulation to a part of the heart is interrupted.
. Coronary heart disease is the lack of oxygen supply to the heart muscle; it can cause severe pain and discomfort known as Angina.

The geologic component layers of the Earth are located at the following depths below surface:.
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The biosphere is a tiny layer in this composition and is usually not considered part of the physical layers of the Earth. Its components are the atmosphere, the hydrosphere, the crust, the mantle, and its core. The Earth consists of several atmospheric, hydrologic, and mainly geologic layers. .

Although a link to such Indo-European languages has not been proved, several Semitic languages have similar-sounding words for Earth: aard in Arabic, irtsitu in Akkadian, araa in Aramaic, erets in Phoenician (which appears in the Mesha Stele), and ארץ (arets, or erets when followed by a noun modifier) in Hebrew. tierra in Spanish). Taking into account metathesis, we can find cognates of the word Earth in the Latin terra and in the modern Romance languages (i.e. It is derived from Old English eorðe.

The root also has cognates in extinct languages such as ertha in Old Saxon and ert (meaning 'ground') in Middle Irish. Examples in modern tongues include aarde in Dutch, Erde in German and arde in Arabic. The English word Earth has cognates in many modern as well as defunct - including ancient - languages. Besides words derived from Terra, such as terrestrial, terms that refer to the Earth include tellur- (telluric, tellurion, from the goddess Terra's alternate name, Tellūs) and geo- (geography, geocentric, geothermal; from the Greek goddess Gaia).

Its astronomical symbol consists of a circled cross, representing a meridian and the equator; a variant puts the cross atop the circle (Unicode: ⊕ or ♁). Earth is sometimes known as Terra in some languages, after the Roman goddess Terra. Scientific evidence indicates that the planet formed around 4.57 billion (4.57×10⁹) years ago, and shortly thereafter (4.533 billion years ago) acquired its single natural satellite, the Moon. It is the largest of the solar system's terrestrial planets, and the only planetary body that modern science confirms as harboring life.

Earth is the third planet from the Sun. Other: 30% (1993 est.). Urban areas: 1.5%. Forests and woodland: 32%.

Permanent pastures: 26%. Permanent crops: 1%. Arable land: 10%. The land-based ecosystem depends upon topsoil and fresh water, and the oceanic ecosystem depends upon dissolved nutrients washed down from the land.

Earth's biosphere produces many useful biological products, including (but far from limited to) food, wood, pharmaceuticals, oxygen, and the recycling of many organic wastes. These ore bodies form concentrated sources for many metals and other useful elements. Mineral ore bodies have been formed in Earth's crust by the action of erosion and plate tectonics. These deposits are used by humans both for energy production and as feedstock for chemical production.

Earth's crust contains large deposits of fossil fuels: (coal, petroleum, natural gas, methane clathrate). Highest point: Mount Everest 8,844 m (2005 est.). Lowest point overall: Mariana Trench in the Pacific Ocean −10,924 m [1]. Lowest point on land: Dead Sea −417 m.

42 nations and other areas are completely landlocked (see list of landlocked countries). Note: boundary situations with neighboring states prevent many countries from extending their fishing or economic zones to a full 200 nautical miles (370.4 km). Territorial sea: 12 nautical miles (22.2 km) claimed by most, but can vary. Exclusive economic zone: 200 nautical miles (370.4 km) claimed by most, but can vary.

Exclusive fishing zone: 200 nautical miles (370.4 km) claimed by most, but can vary. Continental shelf: 200 m depth claimed by most or to depth of exploitation; others claim 200 nautical miles (370.4 km) or to the edge of the continental margin. Contiguous zone: 24 nautical miles (44.4 km) claimed by most, but can vary. Note: 70.8 % of the world's surface is covered by water, 29.2 % is exposed land.

Water: 361.132 million km². land: 148.94 million km². Total: 510.073 million km². 5100 to 6378 km - Inner Core.

2890 to 5100 km - Outer Core. 100 to 700 km - Asthenosphere. 35 to 2890 km - Mantle