tag:blogger.com,1999:blog-3634628224045926034.post6736947455477794894..comments2023-08-29T01:27:13.772-07:00Comments on Magpie's Asymmetric Warfare: Grasping at Epicycles with … Something.Magpiehttp://www.blogger.com/profile/07528637318288802178noreply@blogger.comBlogger6125tag:blogger.com,1999:blog-3634628224045926034.post-41009164717826880172015-12-10T20:19:42.287-08:002015-12-10T20:19:42.287-08:00No reason at all to apologize. My main point was t...No reason at all to apologize. My main point was to disagree with DeLong's: "But just because your theory is good does not mean that the entities in your theory are 'really there', whatever that might mean."<br /><br />You criticize it later in "NASA vs Econosophers: Inference in Science". But I was earlier under the wrong impression here that you agreed (somewhat) with DeLong. <br /><br />It still seems to me that you are both talking in terms of Absolute Space = denying the relativity of motion. "But that's not the real positions, in 3D space, of astronomical bodies" etc. DeLong muddies the water further by bringing in General Relativity. <br /><br />But this is not at all uncommon, even among forgetful working physicists! As Walter Noll says: "To this day, physicists seem to be brainwashed by Newton’s idea of absolute space." <a href="http://www.math.cmu.edu/~wn0g/FC.pdf" rel="nofollow">Five Contributions to Natural Philosophy</a> page 5. The point is there is no "real position" in 3d space. There is just apparent / relative motion. For purposes of living on a planet like Earth, a fixed Earth frame of reference is a very good idea. But it makes the motion of other planets complicated, with retrograde motion that makes it look like Ptolemy's complicated epicycles are there. So for dealing with planets in a solar system, a fixed sun or whatever frame of reference is better.Calgacushttps://www.blogger.com/profile/06031818010224747000noreply@blogger.comtag:blogger.com,1999:blog-3634628224045926034.post-49258638966710813032015-11-22T18:15:43.681-08:002015-11-22T18:15:43.681-08:00I confess: I'm confused. And in case of confus...I confess: I'm confused. And in case of confusion, in my experience, is usually a good idea to apologise, for I might be mistaken. So, apologies.<br /><br />Let's press the reset button. What was your point below?<br /><br />"Epicycles, apparent movement etc are quite real. Drive into a tree with only apparent motion relative to you and there is no apparent difference from the tree moving into your parked car. As you note, (amateur) astronomers see retrograde motion and epicycles all the time. They're real."<br />Magpiehttps://www.blogger.com/profile/07528637318288802178noreply@blogger.comtag:blogger.com,1999:blog-3634628224045926034.post-70289058627680265172015-11-22T15:03:47.059-08:002015-11-22T15:03:47.059-08:00However, by steering your parked car's wheel y...<i>However, by steering your parked car's wheel you can make the approaching tree avoid your car.</i><br /><br />By parked, I mean parked. The engine is not running. It is motionless relative to the surface of the earth. How does steering the wheel avoid an approaching tree? Two parked cars don't usually crash of course, and trees don't usually approach them, but picking up bits of lumber around your car after a hurricane is instructive. Calgacushttps://www.blogger.com/profile/06031818010224747000noreply@blogger.comtag:blogger.com,1999:blog-3634628224045926034.post-25243967021246515502015-11-21T19:13:47.584-08:002015-11-21T19:13:47.584-08:00Incidentally, how did our parked cars manage to cr...Incidentally, how did our <i><b>parked</b></i> cars manage to crash?<br /><br />After all, your car was parked when you saw mine approaching; just like I did see yours moving menacingly towards mine. :-)Magpiehttps://www.blogger.com/profile/07528637318288802178noreply@blogger.comtag:blogger.com,1999:blog-3634628224045926034.post-59873355874990723652015-11-21T15:49:54.244-08:002015-11-21T15:49:54.244-08:00Calgacus: Quibble: Kepler should not be forgotten ...Calgacus: Quibble: Kepler should not be forgotten - the real jump in explanatory accuracy, of getting rid of/understanding epicycles, came with him, not Copernicus or Newton. <br /><br />Me: Absolutely.<br /><br /><br />Calgacus: Epicycles, <i><b>apparent</b></i> movement etc are quite <i><b>real</b></i>. Drive into a tree with only apparent motion relative to you and there is no apparent difference from the tree moving into your parked car. As you note, (amateur) astronomers see retrograde motion and epicycles all the time. They're real.<br /><br />Me: However, by steering your parked car's wheel you can make the approaching tree avoid your car. Apparently, what you do inside your car affects what the tree does. Shouldn't a mechanism accounting for that be advanced?Magpiehttps://www.blogger.com/profile/07528637318288802178noreply@blogger.comtag:blogger.com,1999:blog-3634628224045926034.post-31832176228325245822015-11-21T13:18:51.580-08:002015-11-21T13:18:51.580-08:00DeLong: "Ptolemy's epicycles are a very g...DeLong: <i>"Ptolemy's epicycles are a very good model of planetary motion--albeit not as good as General Relativity. Nobody believes that epicycles are real."</i><br /><br />Magpie: <i>"The driver sees trees, buildings, mountains, moving in parallel to the car, but in the opposite direction. Their movements, however, are apparent only."</i><br /><br />DeLong & you seem to be speaking in terms of Newtonian Absolute Space. A jolly good space it is, but it is not the only way of speaking, not the most modern. NASA needs our pal Albert, not just Isaac occasionally.<br /><br />Quibble: Kepler should not be forgotten - the real jump in explanatory accuracy, of getting rid of/understanding epicycles, came with him, not Copernicus or Newton. <br /><br />Epicycles, apparent movement etc are quite real. Drive into a tree with only apparent motion relative to you and there is no apparent difference from the tree moving into your parked car. As you note, (amateur) astronomers see retrograde motion and epicycles all the time. They're real.<br /><br />DeLong: <i>"There is something there. But just because your theory is good does not mean that the entities in your theory are 'really there', whatever that might mean."</i><br /><br />Of course it means the entities are really there. There is no other intelligible meaning of "really there". What is rational is real, and all that.Calgacushttps://www.blogger.com/profile/06031818010224747000noreply@blogger.com