Falling around the Earth
Gravity does not disappear above the atmosphere. A satellite moves sideways fast enough that it continuously falls around Earth instead of striking its surface. In a circular orbit, gravity provides the inward acceleration.
Higher orbit, longer period
At higher circular altitudes, the orbital path becomes longer while orbital speed decreases. The period increases. Our Q Lab model uses Earth’s radius and gravitational parameter to calculate speed and period, ignoring atmospheric drag and irregularities in the gravity field.
Explore the idea
Open the orbital laboratory and move the altitude from 400 to 2,000 kilometres. Compare the speed and period. The diagram illustrates the relationship; the numbers come from a simplified circular-orbit model.