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Why reading the following two pages:
http://www.nasa.gov/centers/glenn/re.../microgex.html http://en.wikipedia.org/wiki/Weightlessness I realized that I misunderstood the notion of microgravity in space and the fact that it is created in LEO as opposed to naturally existing. In the first link on microgravity it became clear after reading this paragragh: Many people mistakenly think that there is no gravity above the Earth's atmosphere, i.e., in "space," and this is why there appears to be no gravity aboard orbiting spacecraft. Typical orbital altitudes for human spaceflight vary between 120 - 360 miles (192 to 576 km) above the surface of the Earth. The gravitational field is still quite strong in these regions, since this is only about 1.8% the distance to the Moon. The Earth's gravitational field at about 250 miles (400 km) above the surface maintains 88.8% of its strength at the surface. Therefore, orbiting spacecraft, like the Space Shuttle or Space Station, are kept in orbit around the Earth by gravity. The part about being motionless at 250 mi. above the earth's surface and still having 88.8% gravity did it. Also, in the second link, this part: As a thought experiment, imagine a spacecraft that had the ability to rise up to orbital altitude by going straight up like a helicopter and hovered over one spot on the Earth. The astronauts inside would not experience weightlessness. Their ride inside this hovering spacecraft would be similar to riding an elevator up an incredibly tall building and stopping at the top floor. While hovering above Earth's atmosphere, their weight would be very close to what they weigh on the surface of the Earth, even as a space shuttle goes zinging by them. So astronauts in a hovering spacecraft are being pulled by strong gravity just as space shuttle astronauts are pulled by strong gravity. The difference between them is that the orbiting shuttle is freely being pulled toward the center of the Earth. The lack of relative acceleration between the orbiting shuttle and its astronauts inside (who are also being freely pulled toward the center of the Earth) result in them being weightless. But the hovering spacecraft (as with an elevator at the top of an incredibly tall building) is not freely falling. The pull of gravity it is experiencing is being opposed by the hovering force. This force gets transfered to the astronauts within (along with everything else within the spacecraft) resulting in weight. This example illustrates the fact that there is plenty of gravity out in space. If you were to take any object that is orbiting the Earth and stop it dead in its track and then release it, the Earth's gravity would pull it straight down back toward the Earth's surface. Yep, very clear there. Eric |
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