Chapter III External Threat

Section II Threat on Solar System

In the vast universe, the solar system only a very small corner of living, but it is home to our common human being, the planet we live on the sun is a star system in this one small planet.

Stand in the sun over the Arctic, we can see all of the solar system eight planets are in the same direction along the same anti-clockwise rotation around the sun, their orbits almost in the same plane, the plane known as the ecliptic plane, which is elliptical orbit In fact, almost circular.

8 composition of planets vary considerably, but it can be divided into two categories known as terrestrial planets, they are Mercury, Venus, Earth and Mars, by rock, metal composition of the solid planet, their density high, slow rotation, the satellite less the same as the Earth; the other known as the Jovian planets, and Jupiter, Saturn, Uranus, Neptune, their size, quality, weight, but the density is very low, like Jupiter, the main by liquid substances such as hydrogen and helium composition, as "water polo" wandering in space, they spin faster, multi-satellite, as well as Central.

Earth as the solar system's third planet from the sun 150 million kilometers, the outermost of Neptune from the sun is 4.5 billion kilometers, but this is far from the boundaries of the solar system, in addition to dwarf planet Neptune (such as Pluto) and many small celestial bodies, as well as interstellar matter.

The planets in the solar system is also very important satellite of celestial bodies, is already confirmed a total of 139 satellites, and there are many satellites need to be further identified. Although our planet in the solar system is a smaller planet, but Earth's moon is a satellite of the larger satellites, each satellite in the solar system was ranked No. 5.

In the solar system there are a large number of small objects such as dwarf planets, asteroids, comets and meteoroids, as they are too many specific statistics as well as impossible. In addition, interplanetary dust and interstellar rays, they are part of the composition of the solar system.

I. Threat of the sun

(1) Sun into a red giant

The quality of the sun for 2 × 1030 kg, a diameter of 1.39 million kilometers, which is composed of 71% hydrogen, 27% for helium, and 2% for carbon, oxygen, silicon, iron and other elements. First and foremost the protection of human existence are the sun, its brilliant shine and warm us, to leave the sun's shining on Earth would be a dead, cold planet, major changes in the sun, the earth and mankind will be drowned.

Issued by the sun light and heat is to rely on nuclear energy, which the energy generated per second is equivalent to 12 billion tons of coal combustion, the Earth its only less than 22 billionths of a brilliant, but sufficient to maintain the earth's ecology, so that the earth has become a beautiful and pleasant planet.

On the sun's energy has always been a concern of scientists, it is a time of combustion in the human experience, has never been divorced from the concept of chemical combustion, regardless of the burning of coal, oil, or trees, are based on atomic displacement can be caused by chemical , according to people that the highest value of burning fuel, the sun kept burning this continues, the burning period of several thousand years, however, is not the most optimistic estimate several hundred thousand years. On this basis, a lot of people come to wrong conclusions, such as: that the Earth's history, as well as human and biological history significantly less than the actual length of time. Further concluded that for the future of human being  is extremely pessimistic, because the fate of the sun determines the fate of the planet and human being , if the sun out in the thousands of years, mankind will not be able to survive no doubt, this is also said that after thousands of years human beings will be extinct.

However, research on the Earth's crust, as well as paleontological studies suggest that the Earth's age and history of life on Earth is far longer than people imagine, and then also understand that, through astronomical observations, the actual history of the stars of the past than the understand the difference between the thousands of miles, therefore, the energy of the sun have had doubts.

As early as age 60 in the 19th century, scientists have been based on optical analysis of the major components of the sun that for hydrogen, the late 19th century the discovery of radioactive elements, scientists recognized that the existence of a natural world that we do not know the past has the energy, which is nuclear energy. Understanding of nuclear energy after the constant breakthroughs, especially Einstein's famous mass-energy formula proposed theoretically established the existence of nuclear energy, as well as the relationship between energy and quality. Further observation and studies have shown that the sun there are more than 10 million degrees Celsius, which show that the core of the sun, high temperature, the nucleus of intense exercise can be to break through the electromagnetic force between the nuclei of the exclusion. Thus, the scientists finally come to the conclusion; I believe that the ongoing thermonuclear reaction inside the sun, the sun's light and heat is provided by nuclear energy. Moreover, the other stars of the energy come from nuclear energy.

Today, our understanding of the sun has reached a very high degree of elaboration that the following have sufficient grasp:

Our sun as a star was born in about 50 million years ago, the predecessor of the sun's heat is a huge corporation, basically can be identified, the hot group is the second generation of the universe or the third generation of great stars of the ruins after the explosion. Through the hundreds of millions of years of evolution, the final heat, through their own quality of its own gravity to form the center of intensive regional, and then formed a primitive planet, the planet through their powerful gravitational absorption material around, and finally set fire to the core parts of the hydrogen atom, and this is the sun as a star was born.

Elements of the solar hydrogen burning roughly 100 million years time, at present, it has been burning for 50 million years, and then also is able to burn 50 million years, and this is a period of moderate stability in the sun. However, after 50 million years, the helium atoms inside the sun will be lit, the sun will be turned into a huge red giant. He will continue to burn 10 million years, when all the helium burning, the sun will become a white dwarf quietly, although it is heat, but has no internal nuclear burning, and then slowly over time will be the natural cooling.

The sun turned into a red giant, as the new diameter of the sun than the sun's diameter will be more than 100 times larger, it will quickly Mercury, Venus swallowed, and eventually swallow the Earth, we gave birth to the life of this planet -- Earth will cease to exist, the homeland of mankind in the universe disappear.

Hundreds of millions of years of standing on a long-term point of view of the external forces for the threats to the survival of mankind, then, after 50 million years, the sun turned into a red giant is a definite threat. In fact, before the time of the last million years the sun has not so stable, and in this transition period, the Earth will continue to suffer harassment sun.

And when the sun turned into a red giant, when its flame will remain around the proliferation of not only the earth will be swallowed up, it will not be able to live on Mars, the world needs to continue to consider the relocation field. At that time, Jupiter or Saturn, satellites of a satellite or a few may be transformed into a place for human habitation, but the external environment has become very poor.

Then, when the sun is into a white dwarf, the last human in the solar system will not continue to survive. Although the hot white dwarf in the cooling process can also be light and heat radiation from outside, but its radiation energy is extremely limited, and perhaps the location of this Mercury can enjoy just such a brilliant, but the Mercury into a red giant in the sun has been swallowed up when therefore, it is human must be time to move out of the solar system, unless human being can be moved around a white dwarf planet or living in the man-made objects. Moreover, the white dwarf can not rely on a planet a long time; it will cool slowly, until the total loss of light and heat.

In fact, the human from the beginning of the transition period may be simply that they can no longer survive in the solar system, because that's when the sun is already very unstable, radical changes in the total, the human race can not be fully and accurately grasp its laws, which as long as there is a strong changes, will be able to complete the destruction of mankind.

(2) Impact of solar activity

Then, in the sun into a red giant before the billions of years in the future, we can absolutely rely on it? One day it wills suddenly some problems, greatly against human being again? We really understand the sun and have no problem with that base?

The Sun is a gas planet; it is divided into the core from the inside out, the radiation layer, the troposphere and the solar atmosphere. Solar atmosphere can be divided into photosphere, chromospheres and corona, which is not separate from the three-tier, but their penetration. Sun part of the troposphere and below the adoption of an astronomical telescope can not directly see only by the nature of their data and to determine the theoretical calculation.

Sun on the Earth have a direct impact on the factors that are mainly the activities of the sun's surface, the surface activities, including sunspots, flares, prominence, and the solar wind.

People do not use instruments can also be observed on the sun often black ball point, these spots is that sunspots. Sunspots are often inseparable pairs, and from west to east with the sun's rotation direction and rotation around the sun, to disappear from the formation of at least a few days, as many as dozens of years. Sunspot center temperature is about 4500K, the surface than the light ball about 1200K, so show contrast black. Sunspots generally oval-shaped, black son of a few kilometers in diameter, large sunspots up to tens of thousands of kilometers in diameter, and sometimes appear in groups of sunspots, and even as a few up to 100,000 kilometers. Is generally believed that the emergence of sunspots is the result of the solar magnetic field? Sunspot activity has obvious cyclical, sometimes frequent, sometimes a rare occurrence, with an average period of 11 years.

Flare in the chromospheres appears bright local region; it is in a very short amount of time focused on the explosion of solar energy. Flares broke out, in a very short period of time out a large number of charged particles and solar wind can be accelerated at times.

Prominence is the explosion of chromospheres layer of a strong stream of hydrogen, this hydrogen flow into the combustion flame red, the number of 100,000 kilometers straight. Is generally believed that the solar magnetic field prominence is the result of a sudden change, or because changing the hydrogen flow generated.

Flares and prominence of the activities are related to sunspot activity is closely linked to sunspot activity has been that solar activity is the main indicator of the strength.

The earth's ecology and the sun's activity is closely related to, when the flare erupted, the strong solar wind on the Earth's magnetic field have a strong interference, known as magnetic storms. Earth's short-wave communications, through fifty or sixty kilometers above the surface of the ionosphere reflection of the dissemination of information, the occurrence of geomagnetic storms, the ionosphere sharp increase in degree of dissociation, resulting in the ionosphere reflection of electromagnetic waves can not be normal, and will absorb electromagnetic waves, resulting in The attenuation of the signal, making short-wave communications.

Geomagnetic storms affect the Earth's upper atmosphere but also the chemical structure and dynamics, and long-term harassment of the storm will affect a large extent, the Earth's climate, causing floods or drought. Based on the analysis of global climate, climate change cycle is about 22 years, which the sun's magnetic cycle is the same.

Solar activity and Earth's earthquake was also associated, through the cycle of seismic activity around the world for many years to analyze the earthquake cycle for 11 years, with the sunspot activity cycle, exactly the same. With regard to the impact of solar activity on the causes of earthquakes, some scientists believe that when the peak year of solar activity, solar wind energy on Earth than the impact of higher than normal, making the earth's rock layers have a discharge pressure, and under the alternating electromagnetic field stretching vibration generated, making the already pent-up stress of the rock layer in the case of resonance when the fracture and dislocation, which triggered the earthquake.

In the study of old trees that ring the solar activity years wide, that fast-growing trees, on the contrary, low solar activity years narrow rings on the slow growth of trees, which confirmed the solar activity effects of life on earth. Based on historical statistics, the growth of crops is also in line with the law.

The sun's activities and human health is closely related to, for example, solar activity increased UV-strong, and strongly disturbed the Earth's magnetic field, so easy to influence cardiovascular function. Solar maximum bacterial growth was faster, so influenza, diphtheria epidemics of diseases such as high incidence. According to Russian scientists study the history of cholera pandemics have occurred in basically peak in solar activity.

However, while the sun's activity can be completely sure about the earth's ecosystem can be, the sun can not only nurtured life on Earth, can also harm life on Earth, but above all the factors that can endanger the survival of mankind.

This conclusion is not the sun decade, observed for centuries, nor is it for thousands of years, years' experience, but 50 million years of history has proved. In the past 50 million years in the sun with its warmth and good to the Earth's environment from a transformation of the planet has become a beautiful and pleasant planet, it makes the Earth from the doldrums of reviving them, finally the 38 million years ago has nurtured the first life, it is the most simple organisms. This started life in the glorious sun evolving, never stopped until 5.3 billion years ago large and complex life in the ocean there, and then the lives of 4 million years ago to the land, 600 million years ago apes into the human threshold, and nearly 5 million years ago to complete their own human evolution.

50 million years have lived up to the sun from us, from this point we can have every reason to believe that the next 50 million years old remain in the main sequence stars the sun, we also will not live up to. This conclusion, of the universe, astronomers from other similar observational stars the sun, as well as analysis of existing scientific theories can be confirmed.

II. Celestial collision

July 1994, amateur astronomers around the world through telescopes, witnessed the collision of comet astronomical wonders of wood. Shoemaker - Levy 9 comets on Jupiter over the enormous gravity of Jupiter have been torn into 21 pieces, these fragments to the speed of 60 kilometers per second crashed into Jupiter produce an explosion, a huge fireball and flash, and Jupiter the atmosphere to form a series of spots. So every time the impact is equivalent to 100,000 of the power of nuclear bomb, if there is on Earth, the Earth as a whole will suffer a great ecological damage, human survival will be seriously threatened.

However, the impact relative to the Earth has been subjected to the impact is certainly not the largest. Before 6500, have been rampant in the earth's giant dinosaurs, which many people believe that extinction is the result of an asteroid colliding with Earth, and believe that a diameter of about 15 km asteroid impact in Mexico's Yucatan peninsula. At present, scientists are on the Yucatan Peninsula in the sedimentary rocks buried under an estimated diameter of 180 kilometers, 900 meters depth study of the impact crater. So, the survival of mankind in those days also should be subjected to a major catastrophe. In fact, a sufficiently large extraterrestrial objects colliding with Earth can be the extinction of mankind, therefore, to study the survival of human being  as a whole, it is necessary to study the impact of the issue of foreign objects.

The solar systems that may exist within the scope of the impact of celestial bodies are asteroids, comets, meteorites and meteoroids. As a result of meteorites and meteor is too small, not to human being as a whole constitute a threat to survival, therefore, here we only discuss the impact of asteroids and comets problem.

(1) Asteroid impact

Asteroids are the same as our planet around the sun, but its size is very small. A lot of the solar system asteroids, which are mainly concentrated in two regions, one near the orbit of Pluto Kuiper Belt, and the other are between Mars and Jupiter in the asteroid belt. Because we are very far away from the Kuiper, where the asteroid can not threaten our security, the threat of asteroid scientists generally do not consider the Kuiper Belt of asteroids.

Roughly estimated that the total number of asteroids in the solar system more than 500,000 (other than the Kuiper Belt of asteroids and lateral), and they are mostly very small size, although the large number, but the total does not add up to five ten thousandths of the Earth's mass. The vast majority of these planets are in the asteroid belt, a region in the 2.17-3.64 astronomical units (an astronomical unit is the distance between the sun and the earth, the day the text of units of about 150 million kilometers). Therefore, the asteroid belt asteroids are very distant from us; the general could not pose a threat to us. However, the asteroid as a result of small size, light weight, the planet vulnerable to disturbance, resulting in the possibility of changes in the larger orbit, which requires us to distance to the asteroid belt to give a considerable degree of concern.

Why did the solar system's asteroid on mainly in between Mars and Jupiter, and many scientists believe that this is because of Jupiter's gravitational force of the original asteroids in the inner circle to attract the past, because Jupiter is the solar system's largest planet, as opposed to inner circle planet, its gravity is much greater.

A small number of asteroids are very special, and they stay away from the asteroid belt, near the Earth orbit to go inside, then went to the far outside Saturn's orbit, especially close to some of the asteroid away from Earth, known as the Near-Earth small planet. We really care about is that these near-Earth asteroids, they are more than the asteroid belt asteroid threat to our much larger.

Although written in the year, human being has not had a record of asteroid impact, but in the face of so many around us asteroids, as well as reference to our experience of the universe, the observation of celestial bodies, or that the asteroid is a very real threat, it compared Day said before the threat of the universe, as well as the sun into a red giant, it seems, in sight of the threat. But really a large enough asteroid colliding with Earth is entirely possible for the extinction of human being , even if a large asteroid colliding with Earth also has the potential to cause great harm human beings, so, several major countries have considerable used for observation and research into the asteroid. For example, NASA asked the U.S. Congress on the need for all the diameter of the asteroid more than one kilometer recorded and classified.

At present, we have found and a number of near-Earth asteroids close to 3000, of which more than one kilometer in diameter to about 1100, and the largest is the well-known stars of Venus.

Venus stars in their orbits between Earth and Mars, 22 kilometers in diameter. Like this is really an asteroid colliding with Earth, it will greatly affect the global ecosystem, many species would have been extinct, human life will not only suffer great destruction, and the results of human civilization would have been great damage. Fortunately, this asteroid we have full understanding of the special launch from NASA's exploration of Eros stars no probe NEAR-Shoemaker on February 14, 2000 entered orbit around Venus Star in the successful detection of one year after close and in February 12, 2001 Eros landing smoothly stars, their research has been very successful.

However, not the entire near-Earth asteroid Eros as the stars we all know it, especially those the size of small asteroids is their situation; we do not fully grasp it. For example: March 18, 2004, small objects from the Earth 2004FH over 43,000 kilometers (more than the Earth-Moon distance of nearly 10-fold) over, astronomers over the first 3 days and found it, this 30 meters in diameter if the objects just hit a medium-sized cities, the city will be destroyed. Of course, this is still far from adequate for the destruction of human extinction.

Some from very close to the Earth if an asteroid hit the Earth it is possible to bring greater harm. According to observation and analysis, the asteroid (29075) 1950DA will be in 2880 from the Earth's surface over a very low place, if its orbit changes slightly small it may be crashed into the Earth, this 1.4-kilometer diameter asteroid would hit the earth, to bring disaster on Earth can affect the global ecology, and tens of thousands of square kilometers of the scope of a large number of organisms (including humans) will most be destroyed. Fortunately, there are 800 years, we have sufficient time to track this asteroid re-evaluation, but also have enough time to deal with its impact.

(2) Comet impact

Comet from the rocks, frozen water and carbon dioxide, dust and a variety of impurities, is a quality of smaller celestial bodies. Comet material will be fully compressed together, the comet but also dozens of kilometers in diameter.

Referred to as the core of the comet nucleus, the external cladding cloudlike fat known as coma, when the comet close to the sun, the strong solar wind and the sun's radiation pressure will push the growth of hair coma tail length, tail length is shorter Tens of thousands of kilometers, while the 100 million kilometers long. Tail is very thin material, the surface density of only a few of one billionth billon of atmosphere.

Comets is difficult to grasp the running track is not only an oval-shaped track, as well as parabolic and the hyperbolic orbit. Moreover, the comet's orbit is highly susceptible to via the planets and the impact of distant stars, so some of the comet's orbit changes continuously, and some comets gone forever, there are some new nameless came to the solar system comets.

Many of the comets in the solar system, but scientists only observed more than 1600 stars, and only a small portion of the comet's trajectory has been to master. The gap between the operating cycles of the comet is also very large, short, or only a few years more than 100 days, up to several thousand years’ long or even years.

The comet itself is unstable, and each time when passing the sun, the solar wind would disperse the material will be part of it into space, thus, the quality of the comet is getting smaller and smaller, and finally left the nucleus, and some entirely by ice and dust the composition of the comet may be the last completely disappear.

Comets also are likely to be the sun or the planet's gravitational force cracking, the famous comet than the drawing is an example of revolution around the Sun's cycle of 6.6 years, January 13, 1846 Birane comet suddenly split into two, and then return after they At the same time also the return of two comets, but in 1859, they were gone, and then, in their orbits intersect Earth's orbit and where there is a large meteor shower, comet Birane This shows that have been completely neutralized.

Large comet colliding with Earth at the time, the threat to humans is obvious. So far, there are records of a comet colliding with the largest in the June 30, 1908 took place the morning of that day, the Tunguska in Siberia in Russia have taken place over a violent explosion, in addition to 1,000 km have seen a huge explosion fireball, but also heard the explosion sound explosion shock wave will be within the scope of a few hundred square kilometers of forests and tear down all the burning, the forest full of dead animals, including feeding a large group of reindeer in this. Fortunately, this desolate and uninhabited, so there were no casualties. After the visit here of scientists found that in addition to the land, as well as charred animal died, the meteorite and found no crater, so assume that this is a matter entirely composed of water comet, the comet into the Earth, friction with the atmosphere produce very high temperature, its evaporation so fierce comet at about 10 kilometers away from the ground over the intense explosion occurred.

Compared to the larger asteroids, the comet's impact on the devastating impact of human being  smaller, but a large comet impact, but also human enough to suffer huge losses overall, it falls short of human extinction.

Near-Earth comets and asteroids than the much smaller, and they generally have a long tail, but also to facilitate observation. Today, we have observed near-Earth comets have been about 50, the figure is far below the near-Earth asteroids; it seems that the probability of a comet colliding with Earth is much smaller, but this is not the case. The most prominent feature of comets is that it highly vulnerable to the sun with the planets orbit perturbations and transformation, but also in the edge of the solar system's comet may inexplicably went inside the solar system, so the probability of the comet colliding with asteroids even have to large, and very hard to detect. Thus, scientists in recent years have paid more and more attention to the study of comets.

(3) Comprehensive analysis of extraterrestrial objects'impacts

Large extraterrestrial objects the chance of colliding with Earth is very small, but is a sufficiently large asteroid colliding with Earth, was the whole of human being may become extinct. Therefore, we can not because of the small probability of such a thing then to ignore it, because as long as human beings to catch up so once again it is impossible to make up for losses, Furthermore, this kind of impact there is very realistic.

What would be finally the threat of extraterrestrial objects for human being? Many scientists have carried out this study conducted an in-depth, but the difference was larger perspective, different people have different conclusions, in a combination of many different viewpoints, we can narrow it down the following conclusions:

1. The more the impact of large chance of the smaller objects, and each of the solar system with a large celestial bodies (including Earth) billions of years in their own orbit operation repeated several times against this kind of impact will the increasing frequency lower.

2. For objects of different sizes against the impact of frequency and can be estimated as follows:

① 1 for about 80 meters in diameter, the impact of celestial bodies may occur once in 100 years, so the impact can cause a few hundred square kilometer area of a large number of lives have been destroyed, and the range of 10 thousand square kilometers on the ecological impact will be;

② A diameter of about 800 meters in the celestial collision may occur once in 2000, so the impact can cause tens of thousands of square kilometer area of a large number of lives have been destroyed, and one million square kilometers on the scope of the ecological impact will be;

③ A diameter of about 3 kilometers in the impact of celestial bodies may occur once in 1,000 years, so the impact can cause one and two hundred thousands of square kilometer area of a large number of lives have been destroyed, and the global ecosystem will be affected;

④ A more than 10 kilometers in diameter, the impact of celestial bodies may occur once in 7,000 years, so the impact could cause global extinction of many biological species, subjected to enormous global ecological destruction, until the restoration of many years;

⑤ A diameter of more than 100 kilometers to the impact of celestial bodies hundreds of millions of years to occur, so the impact should be able to destroy the global ecosystem, the extinction of mankind and human civilization.

3. The most frightening and more realistic impact of celestial bodies is the impact of Eros stars, it is the largest near-Earth objects in the first, as a diameter of 22 kilometers of the asteroid, if colliding with Earth, will lead to a large number of personnel were killed and the Earth the overall ecological destruction of human civilization suffered great devastation. However, the impact of Eros stars does not lead to human extinction. But it appears from the present it does not impact the earth signs, and this asteroid we have a reliable follow-up observation.

In fact, today we have the impact of extraterrestrial objects has considerable ability to prevent. Observing the development of space technology has been more and more details will allow us to grasp the solar system and operation of the distribution of celestial bodies, in particular, larger for those who may pose a threat to the survival of human whole objects, the degree of master is increasingly high. And the development of space technology, it gives us the ability to travel in space is becoming increasingly strong, and mankind has landed on the moon and continue on to Mars or other planets, in this century will be entirely achievable. As for the explosion of nuclear warheads, not only can destroy large celestial bodies, but also can change their orbit. Moreover, not only the spacecraft can be nuclear warheads accurately into the depths of space, missiles can also put them into the space near Earth. Because of the conditions above, then to the power of human beings the possibility of interception of the celestial bodies colliding with Earth, it is becoming increasingly likely.

Scientists are optimistic that, as long as several years in advance to predict the possibility of objects colliding with Earth, they can change their orbit, away from the earth away. If the forecast for several decades ahead of such objects, using ordinary explosives spacecraft into space will be slightly changed the orbit of celestial bodies would be able to impact the Earth from. Therefore, as long as human observation to further enhance the capacity of its own, completely avoid the impact of small objects is a very real thing.

In fact, scientists for celestial bodies colliding with Earth to deal with a wide range of options being considered, it was suggested that the laser can be used to allow slow down the asteroid to change its orbit; was also made to promote an even smaller possibility of the asteroid impact into the Earth's larger asteroid to change the orbit.

It is worth mentioning that, NASA is implementing an asteroid colliding with Earth to prevent the plan known as the "angry Chinese" project. It is to be known as "Han anger" of the robot equipped with a nuclear power may be launched into the celestial bodies colliding with Earth, and then, like a pile-like robot fixed in the celestial bodies themselves, and the use of electromagnetic thrust has always been the role of technology in objects so that objects to change its orbit gradually.

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