Re: Question on gravitational energy

Phil wrote:
On Jun 20, 1:47 am, Phil <toob-head...@xxxxxxxxxxxxx> wrote:

Phil wrote:

On Jun 18, 12:11 am, Phil <toob-head...@xxxxxxxxxxxxx> wrote:

Eric Gisse wrote:

On Jun 17, 12:11 pm, Phil <toob-head...@xxxxxxxxxxxxx> wrote:

Assume a 10 metric ton asteroid has the same orbit around the sun as the
Earth, and in fact is trailing a few million km behind the Earth, just
at the outer reaches of the Earth's gravitational field. At this point,
the velocity of the asteroid relative to the Earth is virtually zero,
maybe a millimeter per year toward the Earth. Ignoring effects from the
Moon and the Earth's atmosphere, this asteroid will eventually be
accelerated by the Earth's gravity and crash into the Earth, acquiring
about 7 mg of kinetic energy (6.9645 to be exact) just before impact.

mg is a force, not an energy.

[snip remaining]

mg is short for "milligrams," as in, the kinetic energy of the 10 ton
asteroid has a kinetic energy which is equivalent, after dividing by
c^2, to 7 mg of mass. My guess is that you didn't really read the
question, or you would have understood the terminology from the context.
That is, of course, your right, but please don't "grade" my question as
if it was an answer on a test; if you can help, that would be greatly
appreciated, otherwise, you're just wasting both your time and mine.

I should have added something: I have been examining this question for
over 3 years, have a 26 page paper written on it which I HOPE to someday
publish, I am NOT trying to jerk anyone around here!!! This is a serious
question. If you WANT to screw around with me, fine, but please don't
think that I am not serious, or have spent no time on this issue.

Thanks,
Phil-

Hey Phil,

Its the other Phil (not the same one). You have a theory of gravity.
Let me ask you. How is freefall principled? Acceleration by virtue
of inertia?

What do you mean by "principled?" Do you mean, why do objects accelerate
in a gravitational field? I'm not sure if there is a true answer. GR
states how objects behave, but it doesn't as far as I have been able to
tell, explain why.

Phil Y.


By principled, I mean the conceptualization of what freefall is. Is
it a purely inertial state where bodies which fall do not gain
energy? Or is it a state of acceleration which results from its
localized inertial motion?

Enough, no one wants to hear about pet theories here.


Yeah, you're right about that. Unfortunately, no one wants to discuss any new ideas in general, unless it's been approved by the Holy Experts. I'm not really sure what freefall is, but I think that the current claims such as it's "the shortest path in space-time," or "matter following curved space," and the like, along with the claim that because freefall CAN be described in these ways, that it is "therefore" NOT a force, are examples of very sloppy thinking. First, the fact that something CAN be described from one point of view hardly means that other viewpoonts suddenly become invalid; since air resistance does affect an artillery shell's flight path, is gravity's effect on the shell now invalid? Second, GR tells us the path a freely faling object will take, but that hardly tells us how or why. Modern scientists will often claim that such questions are meaningless, but they are not, and most of the great advances in history have come from efforts to model the inherent structure of nature, the thing that CAUSES events to turn out the way they do. Pretending that attempts to obtain better, more complete models are useless is an exercise in debate, not intelligence.

Anyway, freely falling objects in a gravitational field DO acquire kinetic energy, and although physicists believe -- at least sort of -- that this energy comes from a conversion of some of the object's mass into energy, even that is a pretty neat trick, assuming it's true. I'm still not sure what you mean by "purely inertial state" versus "its localized inertial motion." I don't think that freely falling objects, which do acquire velocity, are merely CHANGING their velocity with no other effects, and I think one reason that basically NO textbooks come out and state, categorically, what does happen to objects falling in a gravitational field is because the current beliefs lead to serious contradictions and confusion. It's a largely unsolved problem, even today, and simply stating what path the object takes is not enough.

Maybe I can answer you question -- although this is largely MY guess -- as follows. It's similar to what I THINK your second answer is. When an object falls in a G-field, it genuinely accelerates, acquires additional mass in the form of kinetic energy (and maybe also gravitational energy), and in general acts like something to which a FORCE has been applied. We get the right answers, as far as I can tell, if we assume that a gravitational field "performs work on and adds energy to" a falling object, increasing its mass, lowering its time-rate, and in general moving the object to a region of higher energy density. This is true for both matter and photons. A gravitational field is an area of space in which energy can be transferred between normal objects and the medium of space. A ball thrown upward transfers energy TO the medium of space, and if allowed to fall back down, receives energy FROM the medium of space. In contrast, "potential energy" is just as fictional as centrifugal force, since it cannot be found in any normal object or even location; it's a way to balance the books, nothing more.

Phil Y.
.

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