Yes, I agree with this defense of the concept of universal gravitation. It may seem strange to say that objects can instantaneously exert a force on a distant object but it enables us to explain and accurately predict motions.
I have in mind a different type of criticism of Newton's laws of motion, that apparently wasn't made but could have been. The criticism would go as follows: "The laws depend on the notion of force. Since forces are inferred by observing motions, why don't we do away with this extraneous idea and simply talk about motion. Moreover forces are not only pure fictions, they are wonderful fudge factors that explain away the many examples of how the laws of motion fail to describe the actual motion we see in the real world. For example, one of the laws says an object in motion tends to keep moving at the same speed and in the same direction. But this isn't true –a ball rolling on the ground tends to slow down and eventually stop". A disciple of Newton might reply, "The ball only slows down because a force is acting on it, in fact the ground exerts a frictional force that accounts for the slowing down". To which the critic might say, "Yeah and I suppose the frictional force is calculated as the precise amount needed to account for the discrepancy with the law about staying in motion. Similarly, an iron object which is at rest will suddenly start to move when a magnet is placed nearby, thus violating another 'law' of motion. I suppose you will have to postulate a 'magnetic force' to account for this discrepancy. Mark my words, if we are ever to have a good theory of motion, we will have to do away with fictional concepts such as force." But of course the concept of force, along with a few provisions about calculating gravitational, frictional and magnetic forces, makes it possible to state an amazingly predictive theory about a wide range of motions. We are willing to accept the fictional notion of force because it leads to a theory that can be verified empirically. I remember a conversation, decades ago, with a psychologist who was attacking Freud for using "mystical" notions such as the ego, the id, libido etc. The psychologist felt his subject needed to eliminate mystical concepts and express everything in terms of "concrete" concepts such as foot-pounds, voltages and decibels. After the conversation ended, it occurred to me that the problem with Freud was not that he invented fictional notions but that the resulting theory did not have anything close to the predictive ability of Newton's theory. I wished I had said, "You seem willing to accept the fictions of physics, but not to accept any fictions for psychology." ________________________________________ From: [email protected] [[email protected]] On Behalf Of Bruce Sherwood [[email protected]] Sent: Friday, May 18, 2012 6:13 PM To: [email protected]; The Friday Morning Applied Complexity Coffee Group Subject: Re: [FRIAM] Unsolved Problems in Psychology Newton famously said about action at a distance, "I frame no hypotheses". I take this to mean something like the following: "I completely agree with you that I haven't explained gravity. Rather I've shown that observations are consistent with the radical notion that all matter attracts all other matter, here and in the heavens, made quantitative by a one-over-r-squared force 'law'. On this basis I have shown that the orbits of the planets and the behavior of the tides and the fall of an apple, previously seen as completely different phenomena, are 'explainable' within one single framework. I propose that we provisionally abandon the search for an 'explanation' of gravity, which looks fruitless for now, and instead concentrate on working out the consequences of the new framework. Let's leave it as a task for future scientists to try to understand at a deeper level than 'action-at-a-distance' what the real character of gravity is. There has been altogether too much speculation, such as maybe angels push the planets around. Let's get on with studying what we can." I think Newton doesn't get nearly enough credit for this radical standpoint, which made it possible to go forward. And of course we know that eventually Einstein found a deep 'explanation' for gravity in terms of the effects that matter has on space itself. There are hints in the current string theory community of even deeper insights into the nature of gravity. Bruce On Fri, May 18, 2012 at 1:38 PM, Russ Abbott <[email protected]> wrote: > John, I like your gravity question. If this were Google+, I'd click its +1 > button. My wife, who studies these things, says that one of the > fiercest contemporary criticisms of Newton's theories was that they depended > on a mysterious (magical?) action at a distance. > > -- Russ Abbott ============================================================ FRIAM Applied Complexity Group listserv Meets Fridays 9a-11:30 at cafe at St. John's College lectures, archives, unsubscribe, maps at http://www.friam.org ============================================================ FRIAM Applied Complexity Group listserv Meets Fridays 9a-11:30 at cafe at St. John's College lectures, archives, unsubscribe, maps at http://www.friam.org
