Author Marianne Dyson's
May 2018 Science Snacks Newsletter
Slowing Down from Space
Many people mistakenly think that there is no gravity in space, and thus all that’s needed to reach space is to attain a certain altitude. But this is NOT true! Earth’s gravity at the surface is defined as 1g. A simple calculation* shows that the gravity at 200 miles (320 km) altitude is 90 percent of what it is on the surface, or 0.9g.
The reason spacecraft stay in orbit is not because there isn’t any gravity, but because they have attained the speed necessary to balance gravity’s pull. They must go up high enough to avoid running into mountains and the upper atmosphere which would slow them down.
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