| Myths disproved (3) | Tuesday, Jan 10, 2006 9:58 pm |
LiveScience taught me that several popular myths are completely made-up. I'm most amazed by these false myths:
1. The Great Wall of China is the only man-made structure visible from space. (False. There are others.)
2. Draining water forms a backwards funnel in the Southern Hemisphere due to the Earth's rotation. (False. Funnels traveling in both directions can be formed in either hemisphere. It's based on the shape of the sink/toilet and how the water is poured.)
3. Lightning never strikes the same place twice. (False. It definitely does. Think lightning rods.)
4. There is no gravity in space. (False. Astronauts are traveling tangent to the earth at a speed that's fast enough to keep them from being pulled in by the Earth's gravitational pull.)
5. Hair and fingernails continue to grow after death. (False. Dead bodies dehydrate so much that it causes the skin to retract, which in turn exposes more hair and nail.)
About #2. If you assume a perfect hemisphere with a circular hole at the bottom, and no initial perturbation (don't stir it ), the coriolis effect will manifest itself, and the water will form a whirlpool in the opposite direction depending on whether you are in the northern or southern hemisphere. How about on the equator, you may ask? In theory it might flow straight out, but in practice, there would be some imperfection in the bowl or hole, or some slight perturbation as the water begins to drain, and that would give it a rotation. You are correct, though, since we aren't dealing with a perfect hemisphere at all, and the water is definately given an initial rotation.
I guess that would be a matter of perspective. How far in space are you from the Earth? According to your post; what other man made structures can been seen from space?
Rich: Thanks for the physics lesson. It sounds like you know what you're talking about.
Guest: Space.com says astronauts can see many things from space, including highways, airports, dams, cities, and the Egyptian Pyramids. Astronauts in low Earth orbit are about 135 miles from the surface of the earth, and they're traveling at about 17,000 mph.