Kids (en)
Our Universe
Life in Space
Liftoff
Useful Space
Earth
 
 
lab
fun
news
 
Orbits

Space velocity

back to article
Newton's cannon
More than 300 years ago Isaac Newton pointed out that a powerful cannon on a hilltop could shoot a ball right around the world and back to its starting point - if only there were no air to resist it. At every moment, the ball falls towards the ground but it gets no closer because the Earth is round. The speed of the ball to accomplish this feat is 7.9 kilometres per second (more than 28,000 km/h) and 84.4 minutes elapse before an unwary gunner is hit on the back of his head.
printer friendly page
More about orbits...
Eye openers
Quiz
 
Copyright 2000 - 2011 © European Space Agency. All rights reserved.