The clock is ticking inexorably toward doomsday even if we kill ourselves by poisoning the environment or overheating the planet. As you’ll see, there is one problem with the sun. The Sun is slowly heating up, as it burns hydrogen in its core. In about five billion years our Sun begins to evolve into a red giant. Its cover foreign gas will expand, engulfing the Earth in the time it reaches its maximum brightness within seven billion years. But long before that terrible moment, in about a billion years the Sun will grow 11%, increasing to an average ground temperature of 50 degrees Celsius. This will cause the oceans disappear by evaporation. Plants and animals could not survive in this heat. Although some single-celled organisms called Archaea might survive, but only for a while. Once the steam reaches the atmosphere, ultraviolet light from the sun split the water molecules and the hydrogen needed to build living cells gradually escape into space. If our descendants, or some other intelligent life forms happens to us-they want to survive, have to move elsewhere. But where? And how? One option might be to use rockets to emigrate from the planet. In the 1930s, the science fiction writer Olaf Stapledon described a future where our descendants fled to Venus, Neptune and later, when Earth became uninhabitable. Eminent scientists of the caliber of Stephen Hawking have endorsed the idea of establishing colonies on the Moon or other planets, so that humanity can survive any catastrophe that annihilate life on Earth. However, the evacuation of the entire world population, some 6,700 million people, equivalent to roughly a billion space shuttle launches. Even if we could launch a thousand ferries per day, it would take 2700 years to evacuate the entire population. Then there is the issue of caring for people once they reach their new home. Traveling to another planet require “terraforming” to provide food, water and oxygen to the many settlers. So why not move the earth, with all the resources it provides? A tiny change Basic physics tells us that we really can move planets. The launch of a rocket into space pushes the Earth in the opposite direction, although an infinitesimal amount. Physicist and science fiction author Stanley Schmidt exploited this fact in his novel The Sins of the Fathers (The sins of the parents), in which some aliens built giant rocket engines at the South Pole to move the earth. In real life, however, the Earth has so massive that a rocket would have little effect on its motion. Launching rockets billion just ten tons in the same direction could only alter the speed of the Earth in 20 nanometers per second, compared with crumbs planet’s current speed: 30 miles per second. Only a few astronomers have tackled the problem of moving planets, but not to deal with disasters on human time scales, but to understand the dynamics of planetary systems in processes that occur on geological timescales. Moving planets Planetary dynamics seemed simple and orderly when all you knew was our own solar system, but this changed with the discovery of “hot Jupiters” orbiting distant stars. These insurance planets were not formed in hot regions where orbit today, for the simple fact that there are no gas and dust in the amount necessary to generate such giant worlds. Therefore, these planets must have migrated from more distant cradles. To understand how planetary systems can reorganize themselves, Greg Laughlin, University of California, Santa Cruz, his colleague Don Korycansky, and the astronomer Fred Adams of the University of Michigan, raised the issue of how move the earth to keep the sun from cooking the planet. For the purposes of their calculation, the three scientists selected the final fate of the Earth in an orbit 1.5 times its current distance from the Sun, in what is now the orbit of Mars. At 6,300 million years, when the sun is in its red giant phase and 2.2 times brighter than today, a planet at that distance will receive about the same amount of sunlight the Earth receives today. Moving the Earth to an orbit at that distance requires increasing its orbital energy by about 30%. That might be possible, say, changing the orbits of icy bodies in the depths of the solar system so that pass near Earth, transferring some of its orbital energy. These bodies are in a ring beyond Neptune called the Kuiper Belt, and an even larger distance, in a region called the Oort Cloud comets. Because they are far from the sun, these objects have lower orbital energies, so that could be diverted using methods that are being designed to deflect asteroids threatening Earth. These range from light-gravity pushing spacecraft flying in the vicinity of the object to the energetic impulses that could give machines to drill the surface of icy bodies, removed large blocks of ice and drive them out into space, pushing the larger object in the opposite direction. Then the orbits of bodies could be calibrated precisely in the inner solar system using jets of ice vaporized, removed from the surface of the object by the special team sent from Earth. But nobody is thinking about hiring a future Bruce Willis to do the job. “It requires a very fine adjustment path, something that a nuclear weapon, indeed, can not achieve,” says Laughlin. Biosphere sterilized About one million of such close encounters can achieve the goal. If a series of steps of the objects is uniformly distributed, the equivalent of one step every 1,000 to 6,000 years, depending on whether we want to achieve Mars orbit in the time they start to evaporate the oceans or when the sun reaches its phase red giant. Fortunately, objects can be reused if kept in an orbit that covers Jupiter and Earth, taking the giant planet’s energy and transferring it to Earth. It would be a big job, and should have enough patience to move the earth steadily as the sun becomes hotter. This also carries a significant risk because the objects would pass just 10,000 miles from the planet’s surface. The bodies would be much more massive than the asteroid that wiped out the dinosaurs, so that the slightest carelessness could be devastating. Laughlin and colleagues take this very seriously, concluding his article with the following warning: “The collision of an object 100 miles across the Earth at cosmic velocity would be able to sterilize the biosphere to the level of bacteria.” Get push the Sun The greatest danger could be avoided by using a giant solar sail, says Colin McInnes, a mechanical engineer at the University of Strathclyde. Solar sails are thin films and mirrors that are driven by the weak pressure of sunlight that falls on them. McInnes’s idea is to place a solar sail somewhere near Earth, where solar radiation pressure balances the gravitational pull of the Earth. Their analysis shows that the reflection of sunlight from the sail “pull” of the Earth outwards, away beside her in physical terms, increasing the Earth’s orbital energy and accelerating the mass center of the system. McInnes calculates that the Earth move quickly enough to avoid the effects of warming would require a disc-shaped sail 19.2 times the diameter of Earth. I should be inclined at an angle of 35 degrees to the Earth-Sun line and should park at a distance five times greater than that between Earth and Moon. Also imagine that the wing could be constructed in space, using materials provided by a metal-rich asteroid six miles wide. The nickel and iron from the asteroid would be used to create a movie of eight microns thick. Driven to chaos The construction and maintenance of solar sail would be extremely complex. The sail would need active control to maintain their proper shape, particularly because of the disruption brought by the lunar gravity. Although McInnes said that it would require moving 10,000 times less massive than in the case of having to move objects from the Kuiper Belt. Geoffrey Landis, NASA scientist and science fiction writer, says that this concept is just that: a notion. “The physics involved seems correct, but, of course, there is at present, nor in developing a technology capable of fabricating a solar sail with a diameter of twenty times that of Earth. For now, this is only science fiction. ” And McInnes himself admits that the idea is not taken too seriously: “For now, it’s a problem for free time. But even if it takes into account the practical difficulties of these scenarios, computer simulations made by Laughlin also point to the real danger of playing with the planetary orbits. The orbits of the planets are shaped by the gravitational pull of their neighbors, so as to move the earth affect the orbits of other planets in the inner solar system in unpredictable and potentially dangerous ways. If the motion of the earth Mercury destabilizes the whole inner solar system could be driven into a chaotic mode that is very difficult, even impossible, to control, “says Laughlin. Source: NewScientist
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