This simulation is based on Isaac Newton’s famous thought
experiment and illustration of firing a projectile from a high
mountaintop at various speeds, as he described in
Treatise of the System of the World.
The calculation behind it uses Newton's Second Law and the Law of Gravitation to predict step by step the progress of the projectile. Each time step lasts only 5 seconds. The projectile starts from a mountain that is 0.165 times Earth's radius above the mean surface to match Newton's original drawing scale.