Department of Energy Argonne National Laboratory Office of Science NEWTON's Homepage NEWTON's Homepage
NEWTON, Ask A Scientist!
NEWTON Home Page NEWTON Teachers Visit Our Archives Ask A Question How To Ask A Question Question of the Week Our Expert Scientists Volunteer at NEWTON! Frequently Asked Questions Referencing NEWTON About NEWTON About Ask A Scientist Education At Argonne Weightlessness Altitude
Name:  Ken A.
Status:  other
Age:  30s
Location: N/A
Country: N/A
Date: 2000-2001

In the traditional sense of escaping earth's gravitional pull, how high up from sea level must one go to achieve weightlessless?

Right here on earth. Just jump. While you are in the air, you are weightless. Weight is the support force; take away the support force, you are weightless. The astronauts are well within the pull of the earth (230 miles up), since they are in orbit. They are going at such a speed that they fall from a straight line at the same rate as the earth beneath them curves, hence, they fall "around" the earth. That is why they have no support force, and are weightless. Even out at the moon (265,000 miles) the force of the earth's gravity is enough to hold it in orbit. It is not the escape from gravity that causes weightlessness, it is the lack of support force.

See Paul Hewitt's Conceptual Physics textbook for a more in depth discussion.

---Nathan A. Unterman

Since for every action force, there is an equal and opposite reaction force (Newton's Third Law), what you are witnessing is a rebound of the seat (couch) against the astronaut. The six point restraints are tight, particularly against the pelvis bones. Upon release, the "spring force" of the seat propels the astronaut a tiny bit up.

On many roller coasters (The Giant Drop at Six Flags Great America, for one) have points of weightlessness where you have "air time" out of your seat. For safety reasons (so you do not tumble out) you have restraints. But for those brief moments, you are as weightless as the astronauts.

For a more prolonged effect, a diving airplane in hyperbolic flight can simulate the same thing, and NASA uses that as a training vehicle. It has been dubbed the "vomit comet" for those who tend to become ill on it.

The effect can be had right here on earth.

Nathan A. Unterman

Click here to return to the Physics Archives

NEWTON is an electronic community for Science, Math, and Computer Science K-12 Educators, sponsored and operated by Argonne National Laboratory's Educational Programs, Andrew Skipor, Ph.D., Head of Educational Programs.

For assistance with NEWTON contact a System Operator (, or at Argonne's Educational Programs

Educational Programs
Building 360
9700 S. Cass Ave.
Argonne, Illinois
60439-4845, USA
Update: June 2012
Weclome To Newton

Argonne National Laboratory