by STAO ADMIN | Nov 12, 2019
The earth, moon, and sun are spheres with relative diameters 1, 1/4, and 100. The sun emits light; the earth and moon shine by reflected light only. The earth rotates on its axis each day, producing day and night. It also revolves around the sun each year, producing...
by STAO ADMIN | Nov 12, 2019
The sun’s mass makes up 99.8% of that of the solar system. The planets move around the sun in almost-circular orbits, all in the same direction, and almost in the same plane. They are kept in their orbits by the sun’s gravity. Moons orbit most of the...
by STAO ADMIN | Nov 12, 2019
In order to be in space, the spacecraft must get there. But it will immediately fall back to earth unless the effect of gravity is balanced by a high enough orbital velocity to keep it in orbit. In near-earth space, that velocity is about 7 km/sec, and is obtained...
by STAO ADMIN | Nov 12, 2019
In space, there are extremes of temperature, high-energy particles and radiation from the sun, no atmosphere or atmospheric pressure. Living organisms must therefore be protected within a spacecraft or space suit. They must have a source of energy (solar panels or...
by STAO ADMIN | Nov 12, 2019
Space exploration has brought many benefits to society. High-quality radio and television signals are now relayed around the globe by satellite. Biological experiments in space, such as the growing of insulin crystals, are contributing to our ability to fight disease....
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