Do you understand the difference between the words "temporally" and "temporarily?"
Yes. Sorry, I mis-read "temporally."
The use of the word "temporally" is extremely significant here because it points out changes in position that are in spacetime, not just space. When you realize that your argument is still based on the notion of movement relative to the now "missing" sun, you have--very ironically--continued to base the definition of the term "motion" on "change in relative distance."
I consider "spacetime" a "fabrication" in service to the metric or matrix overlaid or imposed on the real cosmos by relativity... a very useful fabrication at that, but not *ontologically* an existing entity, medium, etc. (As per the whole long tedius "spacetime" thread.)
No! My comet exercise was not "still based on the notion of movement relative to the now "missing" sun. It was intended to remove everything but the comet from the universe to illustrate that with nothing to stop it, the comet would continue to move through empty space, relative to nothing... intrinsic motion... as I have called it in disagreement with the common notion, as quoted from Wiki (twice now) as follows:
...Motion is always observed and measured relative to a frame of reference. As there is no absolute reference frame, absolute motion cannot be determined;
First, my exercise has no observer and no "frame of reference." If you accept the terms of the exercise, there is no force acting upon the comet anymore, so it would continue to move at the same speed, with the same inertia/momentum as it had with the universe intact. The straight line trajectory was just an aside, as, obviously it would no longer be in orbit around the non-existing sun. Simple as that!
In none of your posts so far have you really defined motion without reference to another point in any critical way...
I agreed with Wiki that:
Motion involves change in position...
In physics, motion means a change in the location of a body. Change in motion is the result of applied force. Motion is typically described in terms of velocity, acceleration, displacement, and time. An object's velocity cannot change unless it is acted upon by a force, as described by Newton's first law also known as Inertia. An object's momentum is directly related to the object's mass and velocity, and the total momentum of all objects in a closed system (one not affected by external forces) does not change with time, as described by the law of conservation of momentum.
One can assign a virtual point *in now empty space* marking the locus of the comet at the time everything else disappeared (leaving only empty space... not an "entity" btw) and then "measure" its continued velocity from that virtual point as it continues to move through empty space... But,
its continued motion is not dependent on this measurement!... which is why I call it intrinsic motion, not "relative" (necessarily) to anything else.
The above references to inertia and momentum apply to my argument that the comet's motion continues as it was ( but without an orbit.)
Unless you understand the above, we are going nowhere... fast!
...which as I pointed out in my previous post--but which you chose to ignore--is making motion an axiom of your system. That is, it is definitional, and does not constitute an observable ontological property.
I have defined motion as above as independent of measurement, tho measurement is still possible, as from its virtual locus before the disappearing act.
Btw, ontology is not only about categories and relationships of things that exist.
Quoting Wiki, it is also the
philosophical study of the nature of being, existence or reality in general, as well as of the basic categories of being and their relations.
Ontologically, the comet, now the only thing in the universe, still exists and is still moving... through empty space, relative to nothing... tho the virtual point of departure, as above is optional for relativity theorists who simply must measure things and have "two points" to even allow "movement."
More importantly though, by saying that there are no entities that have the state "not in motion," you make the entire notion of "motion" ontologically uninteresting, because ontology is only interested in the properties of things that distinguish one set of entities from another.
Ontologically, the comet, as the only thing left still exists and is still moving. (Am I repeating myself... very well... I'll skip most of the rest rather than continue such repetition.) Philosophically, I think the existence of only one thing is still existence, and it is still moving... if you accept the exercise on the terms it was presented.
But I may be reading too much into your statement, so please try to clarify if you can.
I hope the above does so.
Note however that if you are not simply saying "everything is in motion, therefore the comet is moving" you do indeed need to have a definition for "motion" in order to make any discussion of it as an ontological property because it must be possible to perceive it in some way, shape or form.
There it is, in the mind's eye only... still a lonely little ball of ice and dirt still moving through empty space... now without a tail, poor thing!
This is where your understanding of the notion of "observe" gets contradictory: I have in my previous posts even granted several ways for there to be a way to measure motion that is not dependent on a in-Universe observer with a reference frame. Oddly enough, the one that is most supportable is to use ether as an effective Cartesian Coordinate system for the Universe, however you have insisted that you do not accept the existence of ether--something that most of the rest of us would agree with.
If you get what I said above, you will see that the only contradiction is in your misunderstanding of my basic philosophy, stated here many times. The cosmos and all its moving parts exist and move around totally independently of measurement.
The latter is the job of science, but measurement does not create that which is measured, including motion. And each "part" is moving regardless of the consideration "relative to what?"
The other key mechanism is to literally be "outside the system": that is, to be able to see all points simultaneously as if the Universe were a big disk drive that would let you be anywhere you wanted to be at anytime.
Yes! This is the perspective I have presented many times as transcending the locality arena of relativity... which is *cosmos as a whole* for which "it is always now, everywhere" transcending measurement of selected events being clocked for specific durations.
Also this perspective doesn't give a hoot about the constant speed of light and what local perspectives can see what and when relative to each other.
But the weakness of this is that it still requires either a coordinate system or other objects to compare the motion to to determine "if it's really moving."
Cosmos exists all by itself whether a coordinate system and measurements are applied or not.
And, yes, the lonely comet is still moving through empty space... velocity to be measured from virtual point of "departure" (from orbit) or not.
You need to explain motion without anything else being there to compare it to.
That was the whole point of the exercise, all references to inertia and momentum, etc... *through empty space* with nothing else left!
The comet exercise is simply using the *formerly existing point* represented by the Sun as the comparison point. It does not matter whether it was "there a minute ago and we were moving relative to it then, so we're moving relative to it now." You're still using it as a point of reference.
No. The sun disappeared. It's locus could
still be used as a *reference point* for its continued motion, as could its point of departure from orbit
non of this is required for the comet to continue to exist and move all by its lonely self.
Gotta go. back soon to see what I've not yet addressed.