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Originally Posted by yassin  is it realy the high rise building can make a bad effect on the rotation of the earth?!! |
I can't answer most of your questions but can certainly address this one: the answer is NO! At least, not in any practical way. The concept here is that when you lift the weight of building materials into the sky you increase the moment of inertia of the earth as a whole, which has the effect of slowing the rotation of the earth (in order to conserve rotational inertia). But the mass of building materials for all high rises when added together, and the heights they are being lifted to in constructing buildings, is insignificant compared to the mass of the earth or its radius. Here are the numbers and a back-of-the-envelope computation:
The moment of inertia of the earth is about 8 * 10^37 Kg-m^2. The weight of a high rise can vary a lot, of course. But consider the Empire State Building - it's mass is reported to about 392,000 tons, or about 3.6 * 10^8 Kg. Assume for arguments sake that all the mass is concentrated at the top of the building (1453 ft), or 443 m. To keep the math simple, assume also that the building material was all mined from deep underground, so that the total change in height for all that material due to construction is 2 Km. Under these assumptions the change in the earth's total moment of inertia caused by lifting all that material is 9.1 * 10^18 Kg-m^2. That's a big number, but it is infinitesimal compared to the inertia of the earth. To put it in perspective - this would effect the length of the day by about 0.000000000000001 seconds. Even if you built a billion Empire State Buildings - their total effect on the length of the day would be about 0.00001 seconds. Obviously it's a silly thing to worry about.
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