Shop Windows to the Universe

Dig into Montana Before History: 11K Years of Hunter-Gatherers in the Rockies and Plains by D. H. MacDonald, Ph.D. See our online store book collection.
The flight of this basketball pass is like the orbit of a satellite. If there was no gravity, the pass would fly straight. With gravity, the ball curves downward. A slow pass curves more than a fast pass. Satellite orbits are like very, very fast passes.
Windows to the Universe original artwork.

What does falling have to do with keeping a satellite in orbit?

The key to understanding satellite motions is in recognizing that gravity acts only in the downward direction - forward motion and falling are totally independent of each other.

If there were no gravity or frictional forces acting on the basketball in the figure, it would follow the straight line path forever. Gravity makes it drop down from this straight line path. The forward speed of the ball determines whether the path is only slightly curved or sharply curved. The distance it falls from the straight line depends on the time it takes to travel to a given spot. If the ball is thrown at high speed along the path it will get to the net rapidly and have very little time to fall along the way. If the basketball is thrown more softly, it will have time to fall quite far before arriving at the basketball net.

The relationship between forward speed and the curvature of the path is at the heart of satellite orbits.

Last modified February 2, 2010 by Randy Russell.

Shop Windows to the Universe Science Store!

Our online store includes books on science education, ranging from evolution, classroom research, and the need for science and math literacy!

Windows to the Universe Community

News

Opportunities

You might also be interested in:

Satellites and Robotic Spacecraft

Satellites and robotic spacecraft are crucial to space exploration. They let us explore space without having to support life, and can travel longer, in more dangerous areas, and at lower risk than manned...more

Gravity Definition Page

Gravity is one of the universal forces of nature. It is an attractive force between all matter, and is very weak as compared to the other forces of nature. The gravitational force between two objects is...more

The Heart of Satellite Orbits

Starting at the same altitude above the surface of a small moon, balls are thrown at different speeds. Regardless of the horizontal speed of the balls, they all fall at the same rate and hit the surface...more

What does falling have to do with keeping a satellite in orbit?

The key to understanding satellite motions is in recognizing that gravity acts only in the downward direction - forward motion and falling are totally independent of each other. If there were no gravity...more

PAH

PAH is the short name for a "polycyclic aromatic hydrocarbon". A PAH is a stable structure made up of multiple rings that are fused together. The rings are made of carbon and hydrogen (though other elements...more

Acid

Acids are well known as substances capable of dissolving things. If you've ever gotten some battery acid on your clothes and had a hole develop in a couple weeks you'll know what we mean. In this regard,...more

Base

Like an acid, a base is a substance capable of dissolving things. Unlike an acid in which the active agent is a substance which has a positive electric charge (H+), in a base the active agent has a negative...more

Generating a Magnetic Field

Scientists believe, although it is not certain, there are two essential ingredients for generating a magnetic field. Those two ingredients are magnetic material currents A bar of iron can be made into...more

Windows to the Universe, a project of the National Earth Science Teachers Association, is sponsored in part by the National Science Foundation and NASA, our Founding Partners (the American Geophysical Union and American Geosciences Institute) as well as through Institutional, Contributing, and Affiliate Partners, individual memberships and generous donors. Thank you for your support! NASA AGU AGI NSF