Lawrence M. Krauss - Beyond Star Trek: From Alien Invasions to the End of Time

SCULLY: There's a marsh over there. The lights... may have been swamp gas.... It's a natural phenomenon, in which phosphine and methane rising from decaying organic matter ignite, creating globes of blue flame.

MULDER: That happens to me when I eat Dodger Dogs.

It's just that in most of my work, the laws of physics rarely seem to apply!

Fox Mulder

A dark, ominous shadow descends over your house. The furniture starts to rattle, the walls and ceiling vibrate, and you hear a strange whistling in your ears. You rush to the window to see what's causing all the commotion. Only 5,000 feet off the ground, a huge black disk at least 15 miles across floats motionless in the sky, blotting out the sun, darkening the entire neighborhood. You run to the kitchen sink and splash cold water on your face. Surely this can't be happening! Back to the window once more, and the massive object is still there. You scurry out to the garage to get away, then you remember something. Hurrying back to the house, you pick up the phone to call your daughter's school, but the line is dead. You lose bladder control. The realization terrifies you. Aliens have arrived! As you begin to black out, your last thought is, I am about to become toast!

Hold on! While F-14s or computer viruses or even H. G. Wells's microbes might not be able to protect us from the sheer terror generated by the, attack of a 15-mile-wide floating saucer, Isaac Newton wouldsort of. Newton's laws would ensure that you'd probably be dead before you had time to get terrified. Even 350 years after the fact, Hollywood still has to get past Newton before it can indulge in all the fancy stuff. Alas, the aliens piloting the Mother Ship in the blockbuster Independence Day seem to have skipped that semester back home....

What instead might actually transpire if we were visited by the Mother Ship and her children reads more like a scenario for the Salem witch trials.

DEATH BY DROWNING

A Mother Ship full of aliens bent on ending life on Earth may not need to send out a squadron of huge flying saucers in order to destroy our major cities. Long before the first shadow fell on the Empire State Building or the Hollywood sign, New York might be underwater and Los Angeles could be leveled by earthquakes. Early in Independence Day, the telemetry tracking the approach of the Mother Ship reveals that it is almost 1/4 the mass of the Moon. Before it releases its squad of death saucers, the mammoth ship pulls into a geostationary orbit above the Earththe same sort of orbit the U.S.S. Enterprise uses to visit a new planet. In such an orbit, a spacecraft or a satellite moves at the same rate as the planet rotates, so that it always stays directly above the same spot on the planetary surface. The large communication satellites that transmit our international messages, as well as the network of Global Positioning navigational satellites that guide our airplanes and well-equipped trekkers (the terrestrial wilderness type), sit in such orbits. Newton's law of gravity determines how high such an orbit must be, regardless of the object's mass. It is one of the many miracles of the law of gravity that any object, no matter how heavy, must orbit at exactly the same speed as any other object at the same distance from Earth. (If that weren't the case, NASA would have to design a different trajectory for every space shuttle, depending upon the weight of the astronauts inside.) The distance from Earth for an object in geostationary orbit is about 22,500 miles, or almost 1/10 the distance from Earth to the Moon. At 22,500 miles up, the gravitational attraction on the Earth of an object the mass of the Moon would be 100 times stronger than the Moon's gravitational pull; since the Mother Ship is 1/4the mass of the Moon, its gravitational pull on the Earth would be 25 times that of the Moon!