<p>The apparent motion of planets is complex but predictable.</p>

<p>The apparent motion is due to the combination of three different motions:      </p>

<ul>
<li>The rotation of the Earth,</li>
<li>the motion of the Earth around the Sun,</li>
<li>and the motion of the planet around the Sun. </li>
</ul>

<p>The Planets move in ellipses, slightly perturbed by other planets. </p>

<p>These motions are predictable, and their combination is straightforward trigonometry. The resultant motion is complex, the planets appear to loop relative to the stars, but entirely predictable. We know exactly where the planets will be in the sky for any time for many thousands of years in the future or the past. </p>

CC BY-SA 3.0
2016-06-04T17:10:56.480Z
Small point to add cause it's often overlooked but inclination too.  It was only after Kepler worked out that orbital inclinations were constant, always with the sun in the center, that he was able to do away with orbital oscillations and work out his famous laws.  His estimated Mars was 1 degree 50 minutes (1.833 degrees), which was impressively accurate.  Currently listed at 1.851 degrees inclination to Earth.   Source below.
userLTK
CC BY-SA 3.0
2016-06-04T17:11:04.403Z
https://books.google.com/books?id=OgRAAQAAIAAJ&pg=PA383&lpg=PA383&dq=when%20was%20angle%20of%20inclination%20of%20the%20planets%20first%20observed&source=bl&ots=PWoP0sTkHb&sig=xFsoFQtZB1yIlWGNaXjSLKV3kUk&hl=en&sa=X&ved=0CD0Q6AEwBWoVChMIyIC27qziyAIVgTs-Ch0jqwC7#v=onepage&q=when%20was%20angle%20of%20inclination%20of%20the%20planets%20first%20observed&f=false
userLTK
CC BY-SA 3.0
2016-06-04T07:43:10.263Z
2016-06-04T09:09:14.360Z
2016-06-04T09:09:14.360Z
James K
<p>As you probably know, <strong>the planets have pretty predictable orbits</strong> around the sun but <strong>what exactly causes the complex movement of celestial bodies in the sky from Earth's surface?</strong> Mars is an excellent example of this.</p>

<p><a href="https://youtu.be/kbynKfNfHk4" rel="nofollow">Mars example</a></p>

CC BY-SA 3.0
2016-06-04T02:46:16.233Z
It is unclear what you are asking
Conrad Turner
CC BY-SA 3.0
2016-06-04T03:51:56.077Z
The planets orbits are actually quite predictable.   It just took many centuries and improvements in equipment and telescopes before they were figured out.   Is this what you're referring to?   https://www.youtube.com/watch?v=kbynKfNfHk4   Youtube links aren't recommended for questions but in your case, your question needs more clarity.
userLTK
<planet><orbit><earth>
What causes celestial bodies to move like they do from Earth's surface?
HotSaucey
# What causes celestial bodies to move like they do from Earth's surface?

(Asked by: username_0 on 2016-06-03)

As you probably know, **the planets have pretty predictable orbits** around the sun but **what exactly causes the complex movement of celestial bodies in the sky from Earth's surface?** Mars is an excellent example of this.

[Mars example](https://youtu.be/kbynKfNfHk4)

**Tags:** planet, orbit, earth
> **Comments:**
> **username_1**: It is unclear what you are asking  
> **username_2**: The planets orbits are actually quite predictable.   It just took many centuries and improvements in equipment and telescopes before they were figured out.   Is this what you're referring to?   https://www.youtube.com/watch?v=kbynKfNfHk4   Youtube links aren't recommended for questions but in your case, your question needs more clarity.  

---

## 1 answers

### Answer by username_3 on 2016-06-04. Score: 2 | Accepted answer

The apparent motion of planets is complex but predictable.

The apparent motion is due to the combination of three different motions:

* The rotation of the Earth,
* the motion of the Earth around the Sun,
* and the motion of the planet around the Sun.

The Planets move in ellipses, slightly perturbed by other planets.

These motions are predictable, and their combination is straightforward trigonometry. The resultant motion is complex, the planets appear to loop relative to the stars, but entirely predictable. We know exactly where the planets will be in the sky for any time for many thousands of years in the future or the past.

> **Comments:**
> **username_2**: Small point to add cause it's often overlooked but inclination too.  It was only after Kepler worked out that orbital inclinations were constant, always with the sun in the center, that he was able to do away with orbital oscillations and work out his famous laws.  His estimated Mars was 1 degree 50 minutes (1.833 degrees), which was impressively accurate.  Currently listed at 1.851 degrees inclination to Earth.   Source below.  
> **username_2**: https://books.google.com/books?id=OgRAAQAAIAAJ&pg=PA383&lpg=PA383&dq=when%20was%20angle%20of%20inclination%20of%20the%20planets%20first%20observed&source=bl&ots=PWoP0sTkHb&sig=xFsoFQtZB1yIlWGNaXjSLKV3kUk&hl=en&sa=X&ved=0CD0Q6AEwBWoVChMIyIC27qziyAIVgTs-Ch0jqwC7#v=onepage&q=when%20was%20angle%20of%20inclination%20of%20the%20planets%20first%20observed&f=false  

---

