The risk of a collision course with asteroids has fueled the imagination of countless writers and movie producers. One lump of rock (ice or something) more than 1 kilometer in size strays away from the asteroid belt or outer solar system and goes on a collision course with Earth. The asteroid upon entry will heat up the Earth's atmosphere and end all life, sharing the same fate as the dinosaurs. Fortunately, we now have enough knowhow to meddle with cosmic affairs, such as landing probes and rovers on extraterrestrial territories. But is it enough to stop a 1-kilometer-big bullet from hitting its 6400-kilometer-big target? I don't know. Watch National Geographic, they have a program specifically tailored to this. But that doesn't mean you shouldn't read on.

     Below are some solutions given by external sources with the details explained from my perspective:

A.) Shooting Lasers from the Moon

Effectiveness: 1/10

Simplicity: 2/10

Feasibility: 0/10

     Let us first assume that shooting lasers from the moon is simple and feasible. We now have our very high gain laser mounted on the moon. Here comes the asteroid and we fire the laser. Did the asteroid stop? Yeah, the asteroid stopped your heart from beating because it looked like it had no effect. Lasers DO NOT cause explosions contrary to Hollywood belief. Laser (light amplification by stimulated emission of radiation) is simply concentrating light power by stimulating particle radiation at the right frequency (Remember E2-E1=hf). You'd only manage to pierce a tiny hole in the asteroid, given that you had enough energy to begin with.

     As for simplicity, since it would be a laser with very high gain, a lot of amplification stages are required. Plus, the operation would require that the laser could lock on the fast moving asteroid.

     As for feasibility, it is first useful to know that it is extremely hard to transport heavy equipment to outer space. In fact, the heavier and bigger the payload, the harder. The International Space Station wasn't launched to orbit as a whole. It was assembled there. The proposed laser should be bigger than the ISS so it should be also be assembled in outer space or the moon.

B.) Hitting the Asteroid with a Nuclear Bomb

Effectiveness: 3/10

Simplicity: 8/10

Feasibility: 9/10

     The fact that nuclear bombs have been a technology over 40 years old makes this solution very feasible. It is also quite simple since we only have to hit the asteroid. The question is, will it stop the asteroid? It seems logical that it should, considering the havoc nuclear reactions have caused over human history. A problem with effectiveness springs up from the possibility that the chunks/rubble from the explosion would come together again through the same phenomenon that forms planets (i.e. the gravitational forces of the rubble on the locale of the explosion is greater in magnitude than contradicting forces). The asteroid would continue on its collision course.

C.) Pushing/Pulling the Asteroid Off its Course

Effectiveness: 9/10

Simplicity: 3/10

Feasibility: 7/10

     A probe can be constructed with nets/arms to catch the asteroid and give it a little push/pull away from the collision course, never to collide with Earth again. A very effective solution because not only was the problem solved but the chance of recurrence has been erased. Moderately feasible because the mechanisms required are a little complicated. Robot arms have to extend at the right time and at the right amount to accomodate the asteroid's size. Not so simple because the task of catching the asteroid is very complex. The catcher initially has to travel at the same speed to avoid destructive collision. The push/pull has to be at the right direction. Etc. Etc.

D.) Pushing the Asteroid Off its Course by Nuclear Shockwaves

Effectiveness: 8/10

Simplicity: 8/10

Feasibility: 8/10

     To be honest, I just came up with this one. I thought if using probes made the solution complex, then why not use the shockwaves produced from nuclear explosions to push the asteroid instead. We target the asteroid with a nuclear bomb but we don't detonate it at impact but a few hundred meters from impact. The ratings above are just combinations of the ratings from B and C. I'm not a physicist, but this solution seems reasonable to me.

     There are many near-earth-objects that haven't been accounted for. As long as the asteroid belt and external debris (in the Kepler belt?) remain within the heliosphere of the sun, the safety of life on Earth will always be at risk.