Timeline for What is physically different about a moving vs still object in space?
Current License: CC BY-SA 4.0
9 events
| when toggle format | what | by | license | comment | |
|---|---|---|---|---|---|
| Dec 31, 2018 at 14:59 | comment | added | Draco18s no longer trusts SE | Electromagnetism is weird, innit? Entirely the result of relativity, despite the incredibly slow movement of the electrons...but still enough to cause length contraction and thereby a charge. | |
| Dec 31, 2018 at 14:34 | comment | added | S. McGrew | My understanding is that the Thirring-Lense effect refers to rotating objects, but that it derives from frame dragging that will occur near any non-rotating gravitating mass moving relative to an observer. By analogy, a moving electron is surrounded by a circular magnetic field. When lot of electrons move around in a circle, all those circular magnetic fields add together to produce a dipole field - so a rotating assembly of charges produces a magnetic field because of the instantaneous linear motions of the charges, not because of the rotation per se. | |
| Dec 31, 2018 at 13:30 | comment | added | Deschele Schilder | @S.McGrew- Is the additional field you named in your answer caused by frame dragging (Thiring-Lense effect; gravitomagnetism)? If so, doesn't this effect appear only around rotating massive objects, like rotating asteroids (to which the OP refers but without writing that they are rotating) and not around non-rotating objects moving in a straight line with constant velocity? Or does the effect (again, if you mean that the additional field is caused by gravitomagnetism) occur because the two asteroids have an angular momentum w.r.t. each other? | |
| Dec 31, 2018 at 4:55 | comment | added | S. McGrew | In such a snapshot, it is reasonable to imagine that the fields are frozen and a probe particle is moved here and there to measure the fields. Remove the probe and "unfreeze" the fields, and the fields evolve just as if they had never been frozen. But we, who have the imaginary power to freeze and probe, can then use Maxwell's equations to predict accurately the fields' evolution. | |
| Dec 31, 2018 at 4:49 | comment | added | S. McGrew | In classical physics, we represent systems in terms of their degrees of freedom, as functions of time. It is very common to talk about the* state* of a system at a moment in time. That state is as close to a snapshot" as we can get. That kind of "snapshot" not only describes the configuration of a system, but also describes its momenta. In the case of the electromagnetic fields, the field itself has momentum. If you know the field (E and B) everywhere, you know the rate of change of the field.That is, the "momentum" of the field is part of the snapshot. | |
| Dec 31, 2018 at 1:46 | comment | added | M. Winter | I wonder how meaningful it is to talk about fields in a "snapshot of reality", as the value of a field can only be observed by its effect on particles, in particular, their acceleration. On the other hand, the concept of snapshot is not well-defined here, and everything is a field in the end anyway. | |
| Dec 30, 2018 at 23:40 | comment | added | InertialObserver | It's important to note though that there does exist a frame (CM frame) in which both planets will have the identical snapshot of their E&B fields, and that even though you will be able to say that the planet is moving from the combination of $E$ fields under LTs that they both will have the same equations of motion that govern a nearby particles behavior. | |
| Dec 30, 2018 at 23:34 | vote | accept | Jack | ||
| Dec 30, 2018 at 23:29 | history | answered | S. McGrew | CC BY-SA 4.0 |