Someone needs to show how such a change of reference frame actually works out in a way geocentrists would agree with.
Here you speak of a "change of reference frame". Apparently you assume some pre-chosen reference frame and want to change to an earth-fixed one. Your pre-chosen reference frame obviously is the classical absolute space, where fixed stars and the sun classically are at rest, and the earth moves.
No I'm not assuming that. Not at all.
There is no use in denying! Every reader can see that you implicitly assume a certain reference frame. Talking about a "change of reference frame", there obviously has to be a chosen reference frame. One cannot change what is not there. Also, right from the beginning you talk about a "velocity of the observer". It is not appropriate to talk about a "velocity of the observer", if there is no given reference frame with respect to which the observer is moved or at rest.
Likewise obviously, you implicitly assume a reference frame where the sun is at rest. If that was not the case, you would not ask for the "geocentrist explanation" alone.
The quoted explanation uses the orbital velocity. There is no orbital velocity of the earth in geocentrism.
The quoted explanation says that Bradley uses the orbital velocity v
to, while in the relativistic case one has to use v
tr.
Bradley assumes the classical model with a fixed sun. Now, if the sun is assumed unmoved, then surely earth would have to move. Nobody denies that. Geocentrists, on the one hand, reject the premise, that the sun is unmoved. Bradley, on the other hand, does not prove Heliocentrism using aberration, he rather already assumes it as a premise.
In the relativistic case the sun does not play any role at all, neither any orbital velocity v
to. Aberration is an effect noticed by the observer on earth, observing a star. The velocity v
tr is the transverse velocity of the relative motion between the observer and the star. Transverse means perpendicular to the line through observer and star. This velocity is independent of any reference frame. No matter whether the observer alone is moved with respect to any chosen reference frame, or the star alone, or both.
That's just one aspect of the problem - what actually causes aberration in a geocentric system? The cause I've considered would have several problems, so I would really like to hear how geocentrists themselves explain it.
More broadly, your approach appears to be taking results that are explained by standard orbital mechanics, and nodding at relativity to claim it would work in an earth-centered coordinate system. That still doesn't actually explain how aberration comes about in that system.
It's also odd to invoke relativity to say any frame is OK, then also claiming the earth-centered frame is special, but that's a different issue.
Imagine a big raining cloud above your head. Reference frame for movement is the ground beneath your feet:
Case 1: You don't move. The cloud does not move.
=> drops hit the ground coming from vertically above
=> drops hit your head coming from vertically above
Case 2: You move. The cloud does not move.
=> drops hit the ground coming from vertically above
=> drops hit your head coming from a diagonal direction with respect to your moved head
Case 3: You don't move. The cloud moves.
=> drops hit the ground coming from a diagonal direction with respect to the ground
=> drops hit your head coming from a diagonal direction with respect to your head
Your head is the observer. The observation is the same in cases 2 and 3. Drops coming in diagonally.
Conclusion: One does not have to invoke relativity to recognize that aberration does only depend on relative motion of observer (your head) and source (cloud).
Topic: What is the geocentrist explanation for stellar aberration? (Read 4340 times)