3 ms·
I helped my daughter with a science fair project in which we mapped the relative position of the sun and mars as viewed from a "stationary" earth, when all thre
by mvcalder 7y ago
I helped my daughter with a science fair project in which we mapped the relative position of the sun and mars as viewed from a "stationary" earth, when all three correctly followed Newton's laws. I was very surprised how it turned out. I expected odd cycles or other misbehavior, but actually things were smooth and round. It was eye opening.
- Seenso 7y ago> I expected odd cycles or other misbehavior, but actually things were smooth and round. It was eye opening. How long did you map them? My understanding is that to see the "odd cycles and misbehavior" you need to make observations over the course of months at the right time of year. https://en.wikipedia.org/wiki/Apparent_retrograde_motion https://en.wikipedia.org/wiki/Apparent_retrograde_motion
- mannykannot 7y agoThis should be more widely known, as it gives some insight into the nature of scientific truth. I understand that the explanation of this surprising result is related to harmonic analysis, such as Fourier series - the evolution of any periodic process in time can be just as correctly represented by a collection of harmonics of the correct amplitude and phase. This does not, however, seem to lead one to gravity, while Kepler's laws do. One thing that Newton showed is that epicycles are unnecessary as part of an explanation of planetary motion. If you were to apply the epicyclic model with sufficient precision to show the gravitational effects between the planets, I would guess you would have to include, for any one planet, epicycles with frequencies that are harmonics of the other planets' orbits. Without a theory of gravity, there is no obvious reason why that should be so.