- #1
nonequilibrium
- 1,439
- 2
Hello,
Imagine two stars orbiting in circles around their center of mass. Is this movement generally called a translation, a rotation, or both? The concept of "revolution" is bothering me; is this always nothing but a rotation? Is a revolution a certain part of a rotation? A specific case?
Let me ask this concrete question:
Imagine we're in the center of mass (for the double star) and we stop the rotations -if present- of the stars, and by rotations I here mean like the rotation of the earth, so we leave the revolution intact (i.e. the sidereal day for a star has become zero). Can't we then call the movement of a star a translation? The star itself has all the characteristics the definition of translation asks.
Or is it perhaps the following: in this case, each star is translating (by definition?), but the whole system (the two stars) is seen as a rotation (because their center of mass is a fixed point?).
Imagine two stars orbiting in circles around their center of mass. Is this movement generally called a translation, a rotation, or both? The concept of "revolution" is bothering me; is this always nothing but a rotation? Is a revolution a certain part of a rotation? A specific case?
Let me ask this concrete question:
Imagine we're in the center of mass (for the double star) and we stop the rotations -if present- of the stars, and by rotations I here mean like the rotation of the earth, so we leave the revolution intact (i.e. the sidereal day for a star has become zero). Can't we then call the movement of a star a translation? The star itself has all the characteristics the definition of translation asks.
Or is it perhaps the following: in this case, each star is translating (by definition?), but the whole system (the two stars) is seen as a rotation (because their center of mass is a fixed point?).