Where Did the Earth's Water Come From?

The earth has few fresh water resources, but much salt water. It is currently the only living planet in the solar system. However, the world's water is unevenly distributed, most of the fresh water is in Antarctica, and the water resources increase with the population, and the pollution is getting more and more serious, so we must save fresh water resources.

Earth water

Little water on earth

Earth is one of the eight planets in the solar system, and it has been 4.6 billion years since its birth. It is the third from nearest to farthest from the sun, behind Mercury and Venus; it ranks fifth among the eight major planets. Earth is the only name not derived from Greek and Roman mythology. The word Earth comes from Old English and Germanic. There are of course many other language names here. In Roman mythology, the earth goddess is called Tellus-fertile land (Greek: Gaia, Mother Earth). Earth is currently the only planet with known life.

Age: 4.4 to 4.6 billion years.

Revolution cycle: about 365.2422 days

Return year length: 366.2422 days.

Orbit: Pear-shaped. The apogee is at the beginning of July, and the perihelion is at the beginning of January.

Rotation cycle: The stellar day is 23 hours, 56 minutes, and 04 seconds. The solar day is 24 hours.

Rotation direction: from west to east.

Satellite (natural)-1 (Moon)

Main components of the atmosphere

About two thirds of the rain and snow falling on the ground are consumed by plant transpiration and ground evaporation, and the fresh water resources available for people's living and production are about 10,000 cubic meters per person per year. However, due to the disproportion of the population distribution on the earth and the distribution of fresh water resources, coupled with the pollution of water resources and the waste in the process of use, there are tensions in fresh water resources in many countries and regions in the world. Desalination plants or take other measures to alleviate conflicts in freshwater supply. With the continuous development of the economy, people's demand for fresh water continues to increase. In 2025, the shortage of fresh water resources will become a serious problem commonly faced by countries around the world. Although 70.8% of the earth is covered by water, freshwater resources are extremely limited. Of the total water resources, 97.5% is salt water and is not drinkable. Of the remaining 2.5% of fresh water, 87% are bipolar ice caps, alpine glaciers and snow and ice that are difficult for humans to use. What humans can really use is rivers, lakes, and a part of groundwater, which only accounts for 0.26% of the total water of the earth, and is unevenly distributed. About 65% of the water resources are concentrated in less than 10 countries, while 80 countries and regions, which account for about 40% of the world's population, are severely short of water. According to statistics released by the United Nations, 1.1 billion people worldwide currently lack water and 2.6 billion people lack basic sanitation facilities.

Countries and regions of the world have very different amounts of water resources due to their different geographical environments. According to the amount of water resources, the first few are: Brazil, Russia, Canada, the United States, Indonesia, China, and India. If you average by population, this is another result. China's per capita water resources are equivalent to 1/4 of the world's per capita.

China is a country with a shortage of water resources and frequent floods and droughts. If we consider the total water resources, the total water resources rank sixth in the world, but our country has a large population. If calculated based on per capita water resources, the per capita share is only 2500. Cubic meters, about 1/4 of the world's per capita water volume, ranks 110th in the world (according to the statistics of 149 countries, the unified use of the United Nations 1990 population statistics), has been listed by the United Nations as one of the 13 poor countries.

Cavendish thinks the mass of the earth is about 6 × 10 ^ 24 kg

The equatorial radius of the earth is ra = 6378137m6.378 × 10 ^ 6m, the polar radius is rb = 6356752m6.357 × 10 ^ 6m, the oblateness is e = 1 / 298.257, and the non-spherical symmetry of the earth is ignored. The average radius is r = 6.371 × 10 ^ 6m. The value of gravity acceleration at a certain sea level at the equator is ga = 9.780m / s ^ 2, the value of gravity acceleration at a certain sea level in the Arctic is gb = 9.832m / s ^ 2, and the global standard value of gravity acceleration g = 9.807m / s ^ 2, the Earth's rotation period is 23 hours, 56 minutes, and 4 seconds (the stellar day), that is, T = 8.616 × 10 ^ 4s.

If the earth is regarded as having a uniform mass and the influence of other celestial bodies is ignored, the mass of the earth can be calculated by the following methods.

Method 1: On the equator, the gravity of the earth to an object of mass m is equal to the sum of the gravity of the object and the centripetal force that rotates with the earth, which is 5.984 * 10 ^ 24 kg

Method 2: In the North Pole, irrespective of the rotation of the earth, it is calculated as 5.954 * 10 ^ 24kg

Method 3: Treat the earth as a sphere with uniform mass, ignore the effects of rotation, take the average radius, and take the standard value of gravity acceleration. Then 5.965 * 10 ^ 24kg

The distance between the moon and the earth is r = 3.884 × 10 ^ 8m, and the moon revolution period is 27 days, 7 hours, 43 minutes, and 11 seconds (the stellar day), that is, T moon 2.361 × 10 ^ 6s. The quality is m months.

Method 4: 6.220 * 10 ^ 24kg

It wasn't until the sixteenth century that humans realized that the earth was nothing more than a planet in the solar system.

The earth can be known without a space exploration ship, but it wasn't until the twentieth century that we really sketched the whole picture of the earth. Of course, being able to obtain its image from space is one of the most important factors. The space image of the earth is very helpful for weather forecasting, especially the typhoon (hurricane) forecast, and the earth seen from space is really beautiful ,lovely.

From the perspective of chemical composition and seismic characteristics, the Earth's body can be divided into several layers, and their names and ranges (depth, in kilometers) are indicated below:

0 40 crust 40 2890 mantle 2890 5150 outer core 5150-6378 inner core

The thickness of the solid crust varies considerably. The crust in the marine area is thinner, about 7 km thick. The continental crust is much thicker, about 40 km thick on average. The ground function is also solid, but there is a small layer of melting in the upper part The area above is called the asthenosphere, and the top of the ground function and the entire crust are called the lithosphere; as for the outer core is liquid and the inner core is solid. These different layers are bounded by discontinuities. The most famous is the Mohorovicic discontinuity between the crust and the ground function.

The mantle occupies the main mass of the earth, but the core of the earth is second. As for the space in which we live, it is only a very small part of the entire earth (mass, unit of 24 to the kilogram of 10: atmosphere = 0.0000051, ocean = 0.0014, crust = 0.026, mantle = 4.043, outer core = 1.835, inner core = 0.09675,)

The main component of the earth's core is iron (or iron-nickel), but there may also be some lighter substances. The temperature of the earth's core is about 7,500K, which is higher than the surface temperature of the sun. , Magnesium, oxygen, plus some iron, calcium, and aluminum; the main components of the upper mantle are olivine and pyroxene (iron-magnesium silicate rocks), as well as calcium and aluminum. All the above-mentioned understandings are derived from seismic data. Although the upper mantle material is sometimes brought to the surface by volcanic lavas, we still cannot reach the main part of the solid earth. The current seabed drilling operations and the crust None have been dug through. The composition of the earth's crust is mainly quartz (silica) and silicates such as feldspar. As a whole, the weight percentage of geochemical composition is: iron 34.6%, oxygen 29.5%, silicon 15.2%, magnesium 12.7%, nickel 2.4%, sulfur 1.9%, and 0.05% titanium.

Earth is the main star with the highest average density.

Other terrestrial planets also have structures and compositions similar to Earth, but there are some differences: the smallest proportion of the moon's core; the largest proportion of the core of Mercury; the functions of Mars and the moon are relatively thick; the moon and Mercury have no chemical composition Significantly different letters and shells; the Earth may be the only one that can be subdivided into inner and outer cores. Please note, however, that our understanding of the planet's interior is largely derived from theoretical derivations, even for Earth.

Unlike other terrestrial planets, the outermost layer of the earth (including the top of the crust and the upper mantle) is cut into several pieces and "floats" above the hot mantle beneath it. This is the well-known theory of plate tectonic movement. This doctrine mainly describes two types of movement: tension and occlusion, the former occurs when the two plates are far away from each other, and the magma underneath erupts to generate a new crust; the latter occurs when the two plates collide with each other, and one of them dives into the other Under one party, it was eventually eliminated in the ground letter. In addition, there are some plate boundaries that are laterally staggered relative movements or two continental plates slamming together.

Most of the Earth's surface is very young, only about 500 million years old, and it is really short from an astronomical perspective. However, there are very few places that show the basement of the earth's crust at that timegranite. For example, Suizhong County, Huludao City, Liaoning Province, China. The granite is very developed because of the long cooling time when granite is formed. , The side length is 1-2 cm, so it is named Suizhong granite. Due to erosion and tectonic geological movements that constantly destroy and reconstruct most of the surface, early geological records on the surface are not easy to find, such as impact pits, so most of the early earth history is nowhere to be seen. The earth is about 4.5 to 4.6 billion years old, but the oldest known rock is only about 4 billion years ago (the earth has a long period of time as a fireball formed by molten magma), and it is more than 3 billion years old Rock is very rare. The oldest living fossils are no earlier than 3.9 billion years ago, and there are no records of the critical period concerning the origin of life.

71% of the Earth s surface area is covered by water. The Earth is the only planet in the solar system that can have liquid water on the surface (Titan has liquid ethane or methane on its surface, and Europa may have liquid water hidden beneath its surface. However, the presence of liquid water on the Earth's surface is still unique). Liquid water is an indispensable element of the known form of life; and because of the large specific heat of water, the thermal volume of the ocean has become a major contributor to keeping the earth's temperature constant; liquid water is also an erosion and weathering effect on land. This is the only place in the solar system that has this effect (maybe Mars also had these effects in the early days, but no longer).

Of the composition of the Earth's atmosphere, 77% is nitrogen and 21% is oxygen, followed by trace amounts of argon, carbon dioxide and water vapor. Most of the atmosphere when the earth was first formed was mostly carbon dioxide, but most of them have been combined by carbonate rocks, and the rest are dissolved into the ocean and depleted by green plants; now plate tectonics and biological functions are in the atmosphere. Sustained controller of the rise and fall of carbon dioxide. The greenhouse effect caused by the presence of water vapor and trace carbon dioxide in the atmosphere is a very important role in maintaining the surface temperature. The greenhouse effect raises the surface temperature by about 35 ° C, otherwise the average surface temperature will be -21 ° C. Without water and carbon dioxide, seawater would freeze and the known life forms would not be able to develop. In addition, water vapor is an indispensable cornerstone of the earth's water cycle and weather changes.

The existence of free oxygen is also a major feature of geochemical composition, because oxygen is a highly reactive gas, and it should reasonably be easy to combine with other elements in the atmosphere. The oxygen on the earth is completely generated and maintained by biological action. Without life there would be no free oxygen.

The tidal force between the Earth and the Moon will increase the Earth's rotation period by about 2 milliseconds per century. New research shows that there were only 18 hours a day 900 million years ago and 481 days a year. The earth has a modest magnetic field, and it is speculated that the magnetic field is caused by the current in the liquid outer core. Due to the interaction of the solar wind with the Earth's magnetic field and the outer atmosphere, aurora is generated by radon; the imbalance of the above factors causes the magnetic poles to move on the surface. At present, the magnetic north pole is located in the northern part of Canada. Due to the interaction of the solar wind with the Earth's magnetic field and the outer atmosphere, aurora is generated by radon;

The Earth's magnetic field and its interaction with the solar wind have also created Van Allen radiation belts, which are pairs of annular belts that surround the earth. They look like donuts and are made of gas ions (plasma). The outer ring extends from 19,000 kilometers to 41,000 kilometers above sea level; the inner ring ranges from 13,000 to 7,600 kilometers above sea level.

The temperature of the earth's core is about 4700 ° C, which is slightly lower than the surface temperature of the solar sphere (6000 ° C). The highest temperature on Earth occurs in lightning. A lightning bolt can release 10 billion joules of energy to 30,000 ° C, which is five times the temperature of the sun's surface, but much lower than the temperature of the sun's core (14 million degrees Celsius). Where is the coldest place on earth? The "cold pole" in the northern hemisphere is in Oymyakon, eastern Siberia, with the lowest temperature in January 1961 being 71 ° C. The "cold pole" in the southern hemisphere is on the Antarctic continent, with a temperature of 88.3 ° C on August 24, 1960.

The rotation of the earth around its axis is called the rotation of the earth. The spatial position of the ground axis is basically stable. Its northern end always points near the North Star, and the direction of the Earth's rotation is from west to east; viewed from above the North Pole, it rotates counterclockwise. The Earth's rotation time is about 23 hours and 56 minutes. This time is called the stellar day; however, on Earth, the day we feel is 24 hours, because the reference object we choose is the sun. Since the earth's rotation is also revolving at the same time, the 4 minute gap is the result of the superposition of the earth's rotation and revolution. In astronomy, the 24 hours of the day we feel is called the solar day. The rotation of the earth produces a circadian change. The change of day and night makes the surface temperature of the earth not too high or too low, suitable for human survival. The average angular velocity of the earth's rotation is 15 degrees per hour. On the equator, the linear speed of rotation is 465 meters per second. The phenomenon of various celestial bodies rising and falling in the sky is a reflection of the rotation of the earth. People first used the rotation of the earth to measure time. Studies have shown that the Earth's rotation speed slows down by nearly 2 milliseconds every 100 years. It is mainly caused by tidal friction, which also makes the moon away from the earth at a speed of 3 to 4 cm per year. In addition to the long-term slowdown of the earth's rotation speed, there are also irregular changes that are fast and slow, and the real reason for this change is not yet clear.

The movement of the earth around the sun is called the revolution. Viewed from above the North Pole, it revolves counterclockwise around Japan. The orbit of the earth is called the orbit. It is a nearly perfect elliptical orbit. The sun is in one of the two focal points of the ellipse. On January 3 each year, the earth moves to the position closest to the sun, this position is called the perihelion; on July 4, the earth moves to the position farthest from the sun, this position is called the apical point. The direction of the earth's revolution is also from west to east. The orbital length of the movement is 940 million kilometers. The time required for one revolution is one year, about 365.25 days. The average angular velocity of the Earth's revolution is about 1 degree per day, and the average linear velocity is about 30 kilometers per second. The revolution speed is faster at the perihelion and slower at the distant. The plane of the earth's rotation is called the equator plane, and the plane of the earth's orbit is called the ecliptic plane. The intersection angle of the two planes is called the yellow-red intersection angle. The ground axis is perpendicular to the equatorial plane and the angle of intersection with the ecliptic plane is 66 ° 34 & apos ;, or the yellow-red intersection angle between the equatorial plane and the ecliptic plane is 23 ° 26 & apos ;. Slanted around the sun.

The ultimate question: where does water on earth come from

The water of the Yellow River is up in the sky? For many years, scientists have insisted that the water on the earth was obtained by icy comets and other things that bombarded the earth 3.9 billion years ago.

Recently, a new study found that the water on Earth may come from spontaneous origin. From the rocks that form the earth. This discovery may help explain the source of life on Earth. Similarly, in other rocky planets, life may be slowly forming just like Earth.

Geological expert Linda Elkins-Tanton from MIT led the study. Her model shows that 4.4 billion years ago, water was stored in some molten rock / lava rock, then slowly formed water vapor, and finally formed the ocean. ^[1]