Editing 2561: Moonfall
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For the moon to fall from the sky, it would have to stop orbiting. Most forces applied it to will simply change the way in which it is orbiting, making the orbit more elliptical, larger or smaller. To stop it from orbiting entirely, a 'braking' force would need to be applied in the opposite direction of its travel, to halt it. | For the moon to fall from the sky, it would have to stop orbiting. Most forces applied it to will simply change the way in which it is orbiting, making the orbit more elliptical, larger or smaller. To stop it from orbiting entirely, a 'braking' force would need to be applied in the opposite direction of its travel, to halt it. | ||
| − | The moon's mass is about | + | The moon's mass is about 0.07346×10²⁴ kg and its speed about 1.022 km/s, so the energy needed to stop it is ½''mv''² or about 3.8364×10²⁸ joules. That's about the energy of 1 trillion large nuclear explosions, centered on the leading-most point of the moon's surface. A precisely-oriented stellar body could strike the moon to do this, like a billiard ball colliding with tons of interstellar moon shrapnel instead of dust. |
Less counteractive energy could make the Moon change orbit to one with a {{w|perigee}} below the surface of the Earth, close enough to (partially) enter the atmosphere or merely bring it down beneath the applicable {{w|Roche limit}}. These scenarios would be only technically less catastrophic, and whether the Moon fragments from the initially applied force, the stresses of its nearest (non-contact) distance to Earth or actually survives largely intact until there is a more direct physical interaction, the precise degree of the effect might be practically academic. | Less counteractive energy could make the Moon change orbit to one with a {{w|perigee}} below the surface of the Earth, close enough to (partially) enter the atmosphere or merely bring it down beneath the applicable {{w|Roche limit}}. These scenarios would be only technically less catastrophic, and whether the Moon fragments from the initially applied force, the stresses of its nearest (non-contact) distance to Earth or actually survives largely intact until there is a more direct physical interaction, the precise degree of the effect might be practically academic. | ||
