Space Craft and Gravity ```Name: oswald Status: educator Age: 50s Location: N/A Country: N/A Date: 1999 ``` Question: how can gravity be overcome? Replies: By definition you must exceed the escape velocity in order to leave earth orbit (if this is what you are interested in). The escape velocity is a function of the distance from the earth so if you choose you can keep applying lift (always just barely greater than the gravitational force) and you would eventually escape from the earth without ever achieving a large velocity. However, you have now applied a somewhat smaller force for a much longer period of time. This would not be energy efficient. Bradburn To experience gravitational pull is equivalent to the facts of having mass and being near another mass. Hence what you need to do is remove one or the other fact. If you destroy the Earth, your spacecraft will no longer be pulled toward it. But of course it will be pulled toward other bodies, so, to be on the safe side, you should destroy your spacecraft. It will then be free of any gravitational attraction. Your question is not unlike the question of: how can I travel in time so that I can become my own grandfather? in the sense that the question itself, with all terms given their proper physical meaning, is logically inconsistent. The existence of mass is proven by its response to gravity. That is, when a region of space does not respond to gravity, it contains no mass, by definition. Grayce Actually, it isn't really necessary to achieve the escape velocity from the surface of the earth. Escape velocity means that you have enough kinetic energy to escape the earth's gravitational field; in a rocket flight, the engine burns over a period of time, constantly applying kinetic energy to the craft until it has enough to get where it needs to go. Once you are in orbit, escape velocity is much less than from the surface. So, escape from the earth CAN be done at any speed, but it takes a whole lot of energy no matter how fast or slow you go. As far as cheating gravity is concerned, we don't know of anyting that can do this. The problem is that gravity is purely an attractive force; everything with mass has a gravitational field that interacts with everything else that has mass. We haven't found anything that screens or neutralizes a gravitational field. Richard Barrans Jr., Ph.D. You cannot shield gravity. Under typical conditions in the universe the force is always there between two or more objects. Jules Verne suggests other ideas but that is pure fiction. Check out any Conceptual Phyics textbook (Gravitational Force) by Paul Hewett Lou Harnsich Click here to return to the Physics Archives

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