# What stabilises the axial tilt of planets?

All known bodies of the space rotate around their axis. For example, Earth completes a full rotation cycle in about 24 hours. However, the axial tilt seems to be constant, even though it changes a little bit over a long (in comparison with rotational period) time.

What causes the tilt to stop getting smaller or bigger after some limit?
Why is the axial tilt variation so slow compared to the rotation?

One article regarding the 177.3° axial tilt of Venus suggests that "it’s possible that Venus was knocked upside down by a massive impact early in its history". Let's assume that the impact happened. What caused Venus to stop after 177.3°?

Why doesn't our South pole appear in the equator after some time, and after some more become the North pole?

• en.wikipedia.org/wiki/Axial_precession – Craig Constantine Dec 15 '14 at 18:14
• I have undeleted this post (deleted by OP after being challenged that it's off-topic). I'd argue that it is on-scope for us considering we have multiple planetary-science and celestial-mechanics questions that weren't closed as off-topic and, after some discussions in our Space Exploration Meta and Space Exploration Chat have included planetary-science into our scope. I have re-tagged the question to reflect this. I'd also argue that they're relevant to interpreting multiple aspects of mission designs. Thanks! – TildalWave Dec 15 '14 at 19:01
• Yea, I agree with you after giving it more thought – Stu Dec 15 '14 at 19:25
• Please note that it's since not too long ago™ now also possible to retract close votes, if any of you wish to do so. The button is accessible via "close" link, bottom right of the dialog. /modmod – TildalWave Dec 15 '14 at 19:32