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Newton's Gravitation
F = GMm / r²
Gravity pulls the satellite toward Earth with a force that decreases with the square of the distance. This centripetal force is what keeps the satellite in orbit instead of flying off into space.
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Conservation of Energy
E = ½mv² − GMm/r
Total orbital energy is the sum of kinetic and potential energy. It stays constant in a closed orbit. This is why speeding up raises your orbit — you're adding energy to the system.
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Kepler's Third Law
T² ∝ a³
The orbital period squared is proportional to the semi-major axis cubed. Higher orbits = longer periods. The ISS completes an orbit every 92 minutes; the Moon takes 27 days.