In the history of the Earth was at least five mass extinctions of flora and fauna. The biggest accident happened about 250 million years ago. Then, for some reason, lost 95% of all beings on the planet. Among the versions on the causes of extinctions there are several associated with real threats from space. And this is not some fantasy about aliens or evil gods. So what can come out of the depths of interstellar space and cause a global catastrophe? And how can we predict such a threat? The main problem of mankind is that people do not take seriously the threat of space. And for good reason. Strike from Space - a matter of time. Watch the video of our friends from the Sci-One, and read the text version under the cut.
According to statistics, in the visible part of our universe every second there is at least one explosion of a star. If the star several times greater than our Sun, it usually turns into a supernova with the exhaustion of the hydrogen in its core. And the bigger the star, the faster exhausted "tank" - just a few million years. There is a gravitational collapse. The radius of the "defeat" of supernova - a few tens of light years.
Rigid radiation resulting from flash, ionizes the oxygen and nitrogen in the atmosphere, due to form nitrogen dioxide. In large quantities, it can have a catastrophic effect on the protective ozone layer of our planet. But that's not all: the interaction of nitrogen dioxide and water vapor formed nitric acid, precipitates in the form of malicious rains. However hard ultraviolet radiation and heavy acid rain can destroy the vegetation on Earth (in the film "Interstellar" shows such a total disaster when humanity left no chance to grow something). And in addition to all the nitrogen dioxide will reduce the transparency of the atmosphere, which could cause global cooling.
Destroy Earth can and gamma-ray burst - the most powerful release of energy in the universe. In just a few seconds, the energy is released as much as our Sun emits over 10 billion years. Scientists have not yet come to a consensus, which is a source of gamma-ray bursts, the most severe form of electromagnetic radiation. It could be collapsing massive stars.
Since gamma-ray bursts, some researchers have linked Ordovician-Silurian mass extinction on Earth, which occurred about 450 million years ago. Then the creatures lived mostly in the seas and oceans. And he died, at last count, 85% of marine species. From such a catastrophe, we saved, it is not likely to succeed unless mankind does not migrate in advance of the planet. But the good news is that in the next millennium, it seems, does not threaten us to be in range of a gamma-ray burst. In our galaxy, this happens very rarely, and nearby stars were found, which could arrange such an unpleasant surprise.
Comets and asteroids
Not all threats can be noticed in time. In our solar system, according to rough estimates, there are about three thousand "invisible" comets. They almost do not reflect the light, because it is partially evaporated - have lost water and gases. In 1983, one such comet yet noticed, but it happened almost by accident, and after she flew close to the Earth. It passed unnoticed by 5 million kilometers from Earth - closer than any comet in the past 200 years. Of the estimated 3,000 "invisible" comets humanity today managed to trace only 25.
Asteroid threat is very real, too. Most asteroids are concentrated within the asteroid belt between the orbits of Mars and Jupiter. But sometimes they collide with each other or under the influence of gravity larger objects leave the usual orbit.
The UN even established an international network of warning: if astronomers notice a potentially dangerous asteroid, the UN Office for Outer Space Affairs should organize a rescue mission
Scientists and engineers are considering a lot of planet saving scenarios. The most famous and most obvious - is the destruction of a potentially dangerous object. Just like in the movie "Armageddon." But that can happen to an asteroid when its attempt to destroy? Scientists at the Los Alamos National Laboratory simulated explosion of a nuclear bomb capacity of 1 megaton surface of an asteroid the size of 500 by 150 meters. According to calculations, this should be enough to avoid the threat of a large impact. But there is no guarantee that the fragments of the asteroid hit the Earth not buckshot. So they completely burned in the atmosphere and do not reach the surface of the planet, each of them need to be at least 30 meters in diameter.
Other simulation of protection from asteroids with nuclear explosions: one, two
It is true that humanity has no more or less effective ways to save the Earth from a really big lumps. According to NASA in January 2016, in the solar system discovered more than 700 thousand asteroids. The agency even set up on its website a separate page where you can see when and what objects are flying towards the Earth and how dangerous they are. But some single tracking system yet. Although the size of celestial bodies from 100 meters in the world are able to arrange a regional catastrophe, and those that are more than a kilometer, humanity will leave little chance. Such attacks will generate huge explosion, the shock wave from the collision will bypass the globe. Part of the kinetic energy will be transferred crust and cause earthquakes and tsunamis. To assess the potential danger of rapprochement two scales used - Turin and Palermo. They are similar, but the second is more complicated. Both take into account the scale of the kinetic energy of an object and the probability of collision with the Earth.
One of the largest proven impact craters located in South Africa - its diameter is three hundred kilometers. In 2005, it listed as a UNESCO World Heritage Site. According to current estimates, the Vredefort crater appeared after the impact of an asteroid with a diameter of 5 to 10 kilometers - this is enough to destroy all civilization. Fall vredefortskogo asteroid caused numerous earthquakes, tsunamis, and the heat generated by this shock wave could cause fires worldwide. As a consequence, the release into the atmosphere large amounts of carbon black and carbon dioxide has led to climate change, for several years, depriving the planet sunlight. Perhaps it is this accident put an end to the dominance of the dinosaurs, but until it is accepted theory.
One of the most familiar at first glance threats - flash on our sun. More precisely, coronal mass ejections. They look very nice. Often you can hear that these emissions cause geomagnetic storms that can affect the physical well-being and mood of people. Federal Reserve Bank of Atlanta even conducted a study on this subject. It is proved that the Sun's coronal emissions so affect the speculators that they fall into despair and acquire a tendency to urgently get rid of the shares. Imagine going to happen any megavspyshka and crazed traders will start massively sell shares? This can cause panic because of which the world economy will collapse in a couple of days. And then - war, famine and disease. While some scientists still doubt that CMEs can affect the way humanity. So far not confirmed a direct link between our physical condition, behavior and geomagnetic storms that provoked particularly violent blows of solar plasma streams.
Nevertheless, the sun can still kill modern civilization alone his wind, if you try. And the more, the higher the risk of such. CMEs can occur several times a day. On average, one emission of our star gets rid of the 10 billion tons of plasma. It looks like this: from the Sun off the closed loop of twisted magnetic field lines. It carries with it a bunch of plasma of electrons and protons with a small amount of helium, oxygen and other elements. This loop is pulled into interplanetary space, and can be formed "tourniquet" that encircles the plasma clot - then it turns magnetic cloud. "Impact" of the Earth's magnetosphere, it causes very strong perturbations in the near-Earth space.
The strongest of recorded geomagnetic storm occurred in 1859 and known as the "Carrington Event". During storms were observed large-scale failures and disabling telegraphy in Europe and North America, and in magnetic observatories arrow magnetometers rested on the edge of the scale. Northern Lights could be seen all over the world, even in the Caribbean. Releases like this are taking place on the Sun about once every 500 years. The modern world is so much dependent on electricity and electronics, today a similar storm would cause enormous damage to civilization. Because of the magnetic field fluctuations in the many kilometers of power transmission lines will be induced currents. There would overload due to them will be shut down the entire system. The lights go down, stop the elevator and electric transport, begin water shortages in hospitals will cease to operate medical equipment, an accident will happen in the industry. In short, it affected virtually every sphere of human life. Electricity may trip on entire continents, and recovery would take months and years.
Finally, in many respects unexpected consequence of solar flares - swelling of the atmosphere. In 1979, it has already led to an uncontrolled descent from orbit and fall to the ground first and only American space station Skylab. Abnormal radiation can not only damage the many satellites in near-Earth space, but also affect the operation of onboard equipment of passenger aircraft - and there in the sky every day flying over 8000. By the way, something like this could happen in 2012, but the Earth and the main stream plasma missed.