Question & Answer Time
Being always eager to receive feedback about my ideas, when I recently came upon the website, "Ask the Physicist," (http://www.askthephysicist.com/ask_phys_q&a.html) I didn't hesitate to ask my standard question. So far, I've not yet received what I think is the correct answer (you be the judge). But when I get any answer at all, it's usually revealing, as is presently the case. More comments will follow this Q&A:
Before commenting on the lack of curiosity revealed by this answer, I should first point out that even the technical side of it is irrelevant, if we are charitable, and erroneous, if we are not. "The Physicist" appears to have confused an Eötvös balance with a Cavendish balance. An Eötvös balance measures forces only at one fixed place on Earth (and at changing places with respect to the Sun and Moon, as Earth rotates and orbits). I don't see the connection to the question that was asked. The question concerns motion through the center of a massive body. The large masses of the balance would therefore obviously have to have holes through their centers. The Physicist writes of very large masses generating very long oscillation periods. But for the question at hand, Newton's prediction for the oscillation period does not depend on mass, per se, it depends on density. Specifically, Newton says
where G is Newton's constant and ρ is the density. The Physicist must have had something entirely else in mind, because for a sphere of Earth's density, whether it's as big and massive as the Earth or as small and light as a pebble, the Newtonian oscillation period is not months or years; it is about 84 minutes. If the sphere has the density of lead, the period is about 60 minutes.
The Physicist appears to answer lots of questions every week, so misunderstandings are bound to occur. But before getting to the misunderstood part of my question, he showed his true colors.
Is the experiment I've proposed just a casually dismissible "cute little example" of gravity in action? I suppose it would appear to be to someone who thinks of gravity as being among "the best understood of nature's phenomena."
Isn't it striking how much contrast there is between the physicists who ask and those who "know"? How can you know if you haven't looked? Nobody has ever seen a test object oscillate due to gravity through the center of a massive body. They just "know" it would happen. Naturally, there are reasons that they "just" know it. Some of these reasons are regarded as being very persuasive because if anything other than the predicted oscillation were to occur, deeply rooted assumptions would become uprooted. I acknowledge these reasons and see their force. But in the cosmic scheme of things, no matter how good the reasons seem to be they can't hold a candle to a brute physical fact. To see this should be a scientist's first instinct, in my opinion. Clearly physicists sometimes just pretend to know. They are good pretenders because they sometimes even fool themselves.
Perhaps it is expecting too much that the first instinct should be to opt for the empirical fact over the theoretical consequence. Certain doctrines have proven to be so reliable that deferring to them seems just as good as the empirical fact. It's a kind of "economy of thought" approach such as we often unconsciously adopt in our daily lives. If we didn't take some things for granted, we'd hardly be able to take a single step. In the short term this approach saves a lot of trouble. But in the long term it can cause a lot more trouble because it leaves unturned stones...or boulders, as the case may be. It's not unreasonable that we should carry on making assumptions. But when somebody politely points out that "here's a rock that we've not yet looked under" the scientific response should be...?
Then there's the "aesthetic" aspect, if I may call it that. I mean, wouldn't it be cool to watch a test object oscillate through the center of a large mass knowing that gravity was the only thing making it happen? Wouldn't that be beautiful? Then again, it might not oscillate. Wouldn't that also be beautiful? Isn't it always true that the best answers come from Nature herself and not from the puny abstract maps we try to make of her infinite territory?
I don't know whether the test object would oscillate or not. That's why I keep harping on the importance of doing the experiment. If accelerometers and clocks tell the truth about their state of motion, then the best guess (contrary to Newton and contrary to much else that "we know") would be that the test object would not oscillate -- as explained on the Home Page and elsewhere on this site. Among others, "the point of this experiment would be," therefore, to find out whether we have to continue accepting accelerometer and clock readings as confused and ambiguous, or whether they are plainly informing us as to the state of their absolute motion.
Even if my prediction turns out to be wrong, however, the prevalence of this kind of response makes me wonder about the health of physics as a science. Openmindedness appears to be a real rarity. In the worst case it sometimes seems that standard operating procedure is to try to squelch the spirit of Michael Faraday rather than encourage it. Sometimes we find the squelching coming from the same source right alongside the encouraging...see Lee Smolin's comments in both the left and right columns of the Home Page. Fortunately, as long as there are children, Faraday's spirit will live on. I can imagine that a healthy child (or physicist) would give the correct answer to my question. Q: If the experiment is doable and it has never been done, then why not? A: Yeah, why not?
Postscript:
For those wondering whether I might have pursued my question with The Physicist, the answer is no, as per one of his "Groundrules." Askthephysicist is not a discussion forum. Anyhow, his answer to my question struck me much less as the basis for a friendly dialog than as a rude dismissal from an authority to an underling. The pertinent Groundrule is as follows:
"If you don't like my answer, don't try to pursue a debate with me—I do not wish to nor do I have the time to critique your personal theory of the universe!"