RichardBenish

HebaruSan: Beginning with your final quip concerning the idea of drilling a tunnel through Earth, it seems to reveal the intent to misunderstand, because I have never suggested doing this. In 1632 Galileo suggested it as a thought experiment. In the late 1960s and early 1970s various physicists proposed doing a small-scale version, to be launched into Earth orbit to measure G. https://ntrs.nasa.gov/search.jsp?R=19750014902 Their reasons to not go ahead and build any of these devices were not about feasibility, but about the poor cost/benefit ratio. Technology available at the time would have resulted in little or any improvement in measurements of G over those that had already been conducted in Earth-based laboratories. More recently, George Herold of Teachspin (Buffalo, NY) has conceived of building an Earth-based laboratory version using a modified Cavendish balance. Apparently he is currently either underfunded, under-motivated or both. So we may have to wait (a few years?) till Feldman et al get their device launched and on the way to deep space before we discover whether their apparatus functions as a clock or not. My website does not “pooh-pooh” the standard oscillation prediction. It simply presents another possibility. From the Newtonian perspective, your description is accurate. But I question what it means to “feel a gravitational pull.” Do we or anything else ever feel a gravitational pull? The answer is yes only in such cases as being suspended from above, as an apple being pulled upward by the branch of a tree. While seemingly “at rest” on Earth, we actually feel gravity pushing us upward. All of these circumstances correspond to clear-cut accelerometer readings. All accelerometers attached to Earth give readings indicating that they are accelerating upward. Accelerometers that fall (as in a tunnel) all give zero readings. They feel no pull. In the Newtonian framework one learns to disbelieve accelerometer readings by, for example, invoking a “normal” upward force that supposedly neutralizes the unfelt downward pull, leaving an accelerometer attached to Earth in a state of “rest.” Without any intent to “dazzle” anybody, it should be pointed out that one of the founding principles of Einstein’s theory of gravity, the Equivalence Principle, recognizes in the above facts that our experience of gravity is exactly “as though” the ground were accelerating upward. One thus finds in the standard literature remarks like the one by Lewis C. Epstein: “Einstein’s view of gravity is that things don’t fall; the floor comes up!” The idea that this fact of our gravitational experience ought to be interpreted more literally than it typically is, has arisen several times in the last 120 years or so. Superficially, the idea seems like preposterous pseudo-science. In its most naïve sense of suggesting the “accelerated expansion of matter,” many objections may be adduced to refute it. Having about reached the end of an acceptably-lengthed blog comment, I cannot here defend against these objections or ones that I expect may be forthcoming. The defense exists in the form of papers cited earlier and one more: Rethinking Einstein’s Rotation Analogy ( http://fqxi.org/data/essay-contest-files/Benish_Rethinking_Rotation.pdf ). The latter paper adopts the perspective of an alien civilization (Rotonians) who evolved in a distant rotating cylindrical world where matter-produced gravity is unknown and everyone learns to believe accelerometer readings as meaning what they say. When they disembark from a long voyage and encounter a gravitating planet for the first time, they too adopt the initial idea that “the floor comes up” (because they instinctively believe their accelerometers). Being conscientious scientists, they then plan to discover empirically whether or not this idea is true by conducting Galileo’s experiment. If accelerometers always tell the truth, then an object falling into the center of a massive body will not pass the center because nothing ever pulled it downward. Whereas accelerometers attached to the tunnel walls all indicate upward acceleration, as though the material body were an inexhaustible source of space, and an inexhaustible source of perpetual propulsion. Rotonians suspect this is what gravity is. But they refrain from concluding before hearing Nature’s testimony on the matter.

Paul23: For the purpose of the present discussion, it suffices (and maintains maximum simplicity) by defining inside the same way general relativity's Schwarzschild solutions distinguish as between inside and outside. Inside is at radii less than the surface radius R. And outside is at R or greater distances. Of course we are inside the solar system. But for the purpose of basic gravitational phenomena the effects of the Moon and outer planets are extremely small. They do not affect the argument at hand. It would make sense to worry about such things only after the simpler questions before us are answered. How are the rates of clocks affected by mass inside matter? What happens to an object that falls into a hole through the center of a larger body? If I were a child with limited resources who saw a house on fire I would THINK that somebody (with greater access to resources) ought to "do something" about it. I would not hesitate, in fact, I would yell and scream with all the power I could muster to "urge" somebody to do something about it. I "observe" that physicists seem to be oblivious of the sorry state (fire) of their enterprise; they sometimes admit to being especially confused about gravity. I observe that, though they routinely pay lip service to empirical ideals, they do not hesitate to invent the most unrealistic, untestably fantastic "theories." In the present case I observe that they kick their ideals to the curb, satisfied that they "know" the result of an experiment they have not yet performed. Every form of communication, every grunt, cry, attempt to sell scriptures or snake oil, every Hollywood movie or PhD dissertation is a "mind game." Marvelous, isn't it? Observing other humans helps us to navigate the quagmires and celebrations of human existence. Observing Nature is the only reliable way to unfurl and understand the magnificence of physical reality. Which is the more "religious" response: to urge others to do an experiment, or to pretend to know the result before doing it? Which is the more scientific response?

HebaruSan: Excellent question. And thank you for spending some time on my website. The shell theorem is fine because it is a consequence of the inverse-square law. Anything that spreads itself out from a point-like origin (electricity, light, spray paint) will obey this law. The gravity that would be caused by any concentric shell of matter interior to the shell is exactly canceled everywhere inside the shell because the amount of matter involved varies as the square of the distance. (Do a search for Gauss' Law and look at the images found there to get the idea.) A beautiful thing, really. The question is, what exactly does the inverse-square law refer to. According to Newton's theory (and also Einstein's, although expressed in different terms) it refers to a force of attraction. According to the model discussed on my website, it refers to the generation of space. For more detailed discussions about how I support this idea, please read the "Maximum Force" paper on the website. You may also want to trace the argument further back to the work of Tangherlini (cited therein) or to the work of Tom Martin, who relates Tangherlini's work to his own hypothesis on "spatial flows": http://www.gravityresearch.org/pdf/GRI-010515.pdf It is pertinent to mention that the same kind of symmetry argument should seemingly also apply to the prediction for the rates of clocks inside such a shell, or inside a more physically realistic ball of dense matter. General relativity predicts that inside the shell, the rates of clocks are uniformly slowed, corresponding to the prediction for the ball of dense matter that the rates of clocks reach a minimum at the center. Curiously, general relativity does not explain how matter produces this effect. One might reasonably surmise that the same "shell theorem"-like symmetry argument should apply, resulting in a maximum (not minimum) rate for the central (or inner shell) clock. These issues are discussed in some detail in my most recent paper, which was motivated by Feldman et al's recent proposal to send a Small Low-Energy Non-Collider to deep space to measure Newton's constant G. They call the device a "gravitational clock" because they expect it to tick; the oscillation period is the observable from which they would calculate G. But according to my model the device will not function as a clock. So I've urged the authors to consider building a simpler Earth-based version prior to investing in a fancy version that would be sent to "deep space." A summary article describing Feldman et al's proposal is found here: https://cqgplus.com/2016/05/25/taking-newton-into-space/ . My response paper may be found on my website or at http://vixra.org/abs/1612.0341 .

What follows addresses p1t1p’s gracious response to my earlier comment. Evidently responding to my request to challenge a particular claim, p1t1o wrote: “I challenge the claim that the results of the ‘Small Low-Energy Non-Collider experiment’ cannot be predicted by current Newtonian/Einsteinian theory.” Current theory does of course make a definite prediction. So I guess what you mean is just that you think the standard prediction is correct and mine is wrong. The basis for your confidence (a “gut feeling”) is pretty much the same as what I’ve encountered from physicists. A few of these correspondents have agreed that it would be worthwhile to do the experiment. Yet no concrete steps have been taken. This, I agree, is “telling in itself.” What is actually told by this? I am reminded of a blog post by Caltech cosmologist Sean Carroll. It concerns Carroll’s chastisement of two social scientists who had recently published an article in which they propose to replace empirical evidence with “thinking deeply.” Carroll asserts: I commented that, until Newton’s “deeply thought” prediction for Galileo’s experiment is tested, Carroll effectively commits the same error. Though Carroll has not replied to me, I should mention that some of my work has elicited responses (some of it quite favorable) from prestigious physicists (e.g., from Berkeley, Harvard, Oxford, Sydney, a Nobel Laureate, et al). Why none of this communication has led to someone doing the experiment is an excellent question. In my essay, Gravity: The Inside Story, I’ve argued that the main reason is probably embarrassment. Of the sociology of physics, physicist Daniel Kennefick has written: This remark was not about outsiders, but about members of the established physics community. Say something to embarrass the group and you pay. The undone experiment, proposed by the veritable Father of Modern Science, has been on the books for 384 years. I don’t think physicists fear the embarrassment of being proved wrong. I think they fear the embarrassment of having left this stone unturned for so long and of having it be pointed out by an amateur. Physicists may sometimes be kind enough to salute me, and to respond momentarily to my valid observations. But when my probing implies negligence on their part, they withdraw; they think they can afford to ignore me. Sociological issues may appear to you as “excuses.” Yet they certainly bear on this curious circumstance, because “people are not especially logical creatures.” Finally, don’t they make colorful little jelly-candy hats?

As the author of the work referred to by Dills0n, I am grateful for the opportunity to provide some clarification to this discussion. First, if the Kerbal software accommodates only one point source-mass, the desired simulation would not work. But if three source masses are allowed (and one test mass) then the principle could be tested. Simply arrange the three sources in an equilateral triangle that rotates in its plane just enough to maintain stability. Then “drop” the test mass from any height over (or under) the triangle’s plane, perpendicular to its center. If gravity is modeled as an inverse-square force of attraction, the test object will oscillate through the center of the triangle. P1t1o, who has offered to eat his hat if my non-standard prediction were to be confirmed, may be interested to know that, in response to my work, Italian physicist Carlo Rovelli offered 100 to 1 odds for the same bet. When I replied, “OK, let’s do it,” he reneged. Though testing my non-standard prediction is an important motivation, I regard this as my “Plan B” argument. Plan A is simply that the idea of doing the experiment has been on the books at least since Galileo proposed it in 1632. It is routinely discussed in hundreds or thousands of modern articles, books, and physics classrooms, as though the result were “well-known.” Yet no empirical back-up is ever given. Human beings have never observed gravity-induced radial motion through the centers of massive bodies. The empirical ideals of science have, in this case, been sacrificed. Observations of trajectories in the Solar System do not suffice as a substitute because the directions of the force vectors are completely different. Inside a solid sphere with a hole through its diameter, Newton says the force toward the center gets stronger as one moves away from the center to the surface. In the case pointed out by Stratoroc, for example, moving outward from the point of force cancelation between the Earth and Moon, the force gets stronger toward the Earth and Moon. The circumstances are therefore not at all analogous. In response to Otis, p1t1o defended his standard stance by asking whether Otis has “looked at the claims,” i.e., things written on or linked to my website. I would ask, do you (p1t1o) have an issue with any particular claim? I am prepared to defend every claim I’ve made. If the hypothesis underlying my Plan B strikes you as too far-fetched, I would recommend “Rethinking Einstein’s Rotation Analogy,” which frames the hypothesis as being the most natural one for an imaginary civilization that evolved on a distant rotating world. Most importantly, I claim that we don’t know the result of the Small Low-Energy Non-Collider experiment proposed by Galileo nearly 400 years ago. I stand to be corrected. I yearn to be corrected—not by vaguely connected allusions to other predictions of Newton and Einstein, but by direct empirical evidence involving gravity-induced radial motion through the centers of massive bodies.