Hello This probably sounds like a pretty retarded question but..... My A-Level maths (Applied - circular motion) teacher told us today that the earths orbit is dependant on it "spinning" on its axis, and that somehow if the earth stopped spinning on its axis it would fly out of its orbit with the sun(although he couldnt explain why). The whole class seemed to agree with his view but I havent actually heard or read of anything like this ever, and it sounds ridiculous to say that objects only orbit one another if they are spinning... I disagreed with him and it ended up in a class discussion where they concluded that planets only orbit the sun if they are spinning... I disagree with this, although I may be wrong - which wouldnt be the first time ;-) and if I am theres like a whole area of physics that I seem to have missed....and need to learn :-D Could someone who knows what they are talking about please tell me if I am correct or incorrect in saying that something will still orbit a sun/planet/object even if it is not "spinning" on its axis ? Thankyou Very Much Gerg - n00b
No, you're right. Rotation of the object in orbit has nothing to do with it staying in orbit. Simple newtonian mechanics. -AntonK
i can think of no reason why the rotation of a body would affect its revolution around another body. i m pretty sure your teacher is wrong.
THANKYOU !!!!! I was sure I was correct, and that it was the rest of the world going mad not me ¬_¬ Going to have to print this out & pin it to his head ;-) (unless someone else can think of a reason - in which case I'm in for some embarrasement) Gerg
Just point to huge variety of rotational periods among the planets, and yet they have similar orbits. If rotation was a factor, only planets within a given parameter of spin would have stable orbits.
There is a consideration with regard to spin. The spinning mass has a gravitomagnetic effect ( frame dragging is postulated and attempts to measure it will be made by Gravity Probe B ). The earth would however still orbit the sun without its spin. When considering such orbital motions, the orbit of the earth would be regarded as unstable if it were orbiting the position of the sun where it was (retarded position) at approx. 8 minutes ago - the time for light to reach us. If however, we take the contribution of the sun's spin into account, the gravitomagnetic effect of the sun causes the earth to orbit the sun's real time position. In this regard, the spin contribution is important, but it is the spin of the sun that is a primary consideration.
Hmmm...... beta has a point. Remember that electromagnetism is common in our solar system, and heavily affected by movements. So, why not?
electromagnetism is not common in our solar system. It is not common in the system earth-moon. All planets and other macroscopic objects in our solar system are (nearly perfectly) electrically neutral and hence (almost) do not interact electromagnetically. Gravitomagnetics ? :bugeye: Bye! Crisp
>>electromagnetism is not common in our solar system. It is not common in the system earth-moon. All planets and other macroscopic objects in our solar system are (nearly perfectly) electrically neutral and hence (almost) do not interact electromagnetically. Gravitomagnetics ? << Please note. Gravitomagnetism is a very well know and recognized analogy to describe the gravitational equivalent of a charge in motion, which has a magnetic moment. Gravitomagnetism has nothing to do with electromagnetism, or magnetism. It is the effect seen by an observer due to mass in relative motion ( one type of gravitomagnetism is called frame dragging). We will soon be launching Gravity Probe B, in an effort to quantify the expected frame dragging of the earth. This will hopefully detect frame dragging by noting the effect on a number of high precision gyroscopes. Frame dragging is predicted by GR. I repeat- Gravitomagnetism has nothing to do with either electromagnetism or magnetism or electric charge. It is common in our solar system, or wherever there is mass in relative motion. There are two common descriptors for gravitation. Gravitoelectric- The usual stationary curved spacetime that results from mass or energy density and gravitomagnetism, as explained above.
Gerg: Are you sure that the problem with your teacher is not an issue of semantics? I find it hard to believe that a person allowed to teach even an elementary science course could be so ignorant of simple orbital mechanics. I was often aware of science teachers who were terrible at explaining what they knew.
Your teacher could have intended "Fly out of its orbit" to indicate that the orbit would change, though the term "fly out" is a bit melodramatic, IMO.
wobble of a rotating non-unform/dynamic mass can't effect it's orbit of a body if it changes quickly?
Quote: Gravitomagnetism has nothing to do with electromagnetism, or magnetism.It is the effect seen by an observer due to mass in relative motion ( one type of gravitomagnetism is called frame dragging). We will soon be launching Gravity Probe B, in an effort to quantify the expected frame dragging of the earth. This will hopefully detect frame dragging by noting the effect on a number of high precision gyroscopes. >>Like the coriolis force and centrifugal acceleration? No, not at all. Frame dragging is predicted to effect the usual curved spacetime around the earth. Coriolis can be detected as a result of a change in angular momentum, but this is not related to the curved spacetime around a spinning mass. As for 'centrifugal acceleration'-- Nothing to do with gravitomagnetic effect.
