Henry Fountain
Simulation of an asteroid impact. A polite shift, not a wild shift
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Sooner or later it will happen. Sooner or later, say scientists who study asteroids, astronomers will find an asteroid that has a good chance of hitting Earth.
Recently, it is becoming clear that the long-standing assumption of many scientists (and of Hollywood filmmakers), according to which the use of nuclear weapons is the best way to save the Earth from a threatening asteroid, may turn out to be wrong. And some scientists studying the dangers of asteroids now argue that a gentler, quieter, slower approach may be needed.
A nuclear explosion, some scientists say, could break the asteroid into several large pieces—which would increase the threat, rather than eliminate it. An explosion that would be made at some distance from an asteroid, with the aim of pushing it into a slightly different coffee orbit around the sun, may also not achieve the goal; The asteroid may simply absorb the released energy. "I think we should forget about these methods," said Dr. Keith Holsapple, a professor at the University of Washington who studies the effects of nuclear explosions on asteroids through simulations.
Most of the alternative approaches talk about a cumulative force, which will push the asteroid gently and not forcefully push it. Some of these ideas have been starring in science fiction for years. For example, an electromagnetic convective band that will mount on the asteroid and slowly throw pieces of rock into space; Or a concave mirror that will attack the asteroid, focus sun rays on it, heat its surface and cause it to evaporate.
But the most fascinating idea – which may be less far-fetched than it sounds – was proposed by Dr. Joseph Spittal of the University of Arizona. To move an asteroid, says Dr. Spittal, you only need to change its color. Painting the asteroid black will change the amount of sunlight it will absorb, and the degree to which it will heat up. Heat emitted from an asteroid (in the form of thermal photons) will produce a small force in the opposite direction - a phenomenon known as the Yarkovsky effect, named after the Russian engineer who first described it a century ago. And the change in applied forces will affect the lap route.
The application of this technology and the other technologies will of course cause logistical problems. Moving paint buckets to an asteroid, for example, is not an easy (or cheap) thing to do. Many scientists recognize that under certain circumstances, nuclear weapons may be the only option.
The chances of an asteroid colliding with the Earth in the near future are slim, and the scientists who claim that humanity must develop a system to divert asteroids from their orbit are a minority among researchers in the field. "A significant technological effort at this time is probably not recommended, because our children will be much more successful in this than we are," said Dr. Alan Harris of the Space Science Institute in Boulder, Colorado. Instead, most scientists say that money should be invested in finding and investigating asteroids, and this is to understand Better the potential threat.
But the information that scientists have recently gained about asteroids actually anchors the alternatives that are now being proposed for the use of nuclear weapons. According to scientists, many asteroids are rather loose clumps of rock fragments that have stuck together over the years in the cosmic jumble of rocks called the Solar System. These are not solid giant rocks; "Maybe popcorn is a good image to describe it," Holsapple said.
He said it would be difficult to move or destroy such porous objects in a nuclear explosion, even if carried out at some distance from the asteroid's surface. "But light pushes for a long time will be just as effective, whether the asteroid is porous or not," he added.
New York Times
The knowledge of cosmic collisions
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