New answers tagged orbit
4
Technically stars and planets orbit a common barycenter. In case of single star systems the barycenter is usually within the star. However, the barycenter between the Sun and Jupiter is outside the Sun (though very close to it). Otherwise, colloquially, when we say something orbits another body, the body that's "being orbited" is usually the most ...
6
The thing is, there is more than one Geocentric system, there's the Ptolemaic system, with the sun and planets revolving around the Earth and then there's the Tychonian system (named after the famous astronomer Tycho Brahe, who invented it in the mid 16th century), with the Sun and stars going around the Earth and the planets going around the Sun, it looked ...
-5
To add to Jerry Coffin's very good answer, there've been experiments that disproved geokinetism and proved geocentricity. They're called the Michelson Morley experiment and Airy's failure and made clear whether absolute gocentrism is correct or not. Since then, it was made effort to disprove the results of these experiments because absolute geocentrism would ...
12
None other than Galileo himself pointed out that there is no real right or wrong with this.
In fact, you can choose any arbitrary point you want, and calculate the movements of the sun, planets, the moon, and so on, all relative to that point.
Now, it is true that the movements of most objects are pretty simple relative to the center of mass of the solar ...
27
Ptolemy's epicyclic, geocentric model, in use until the Renaissance, was very accurate in terms of predicting the positions of planets and the times of eclipses. What it couldn't account for were things like the correlations between apparent size and phase of Venus, or to properly account for the variation in brightness of the planets.
Thus the reason for ...
9
There is more than one heliocentric model.
Copernicus modelled orbits with circles and this article suggests that Tycho found that the predictions of Copernicus agreed better with observations of the superior planets and solar eclipses, while Ptolemy's (geocentric) predictions were more accurate for lunar eclipses and the positions of the inferior planets.
...
2
Fortunately all diagrams in the question are consistent in these respects:
the true anomaly $\nu$ or $f$ is measured around the focus at the central body
the eccentric anomaly $E$ is measured around the center of the ellipse
both are zero at the periapsis
The mean anomaly $M$ is a pseudo-angular quantity useful in computing $E$ and $\nu$, with the same ...
4
But where is this orbit centered?
The true anomaly is the angle as measured from the central body between periapsis passage and the object's current location. The orbit is an ellipse with one of the two foci at the central body. This concept is central to Kepler's laws and Newtonian mechanics.
The eccentric anomaly is the angle as measured from the center ...
0
Assuming that wikipedia formulas are right (didn't check), here it is how to pass from "compound angle" (sum of angles on different planes) to "pure angle" (both angles on ecliptic plane):
$$ ϖ = \omega + \Omega \text { (compound angle)} $$
$$
\tan ϖ = \frac { \sin α \cos ε + \tan δ \sin ε} {\cos α}
$$
$$ ϖ = \arctan \left (\frac { \...
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