# Uranus, the Physical model to change its rotation axle

Uranus rotates pretty wierd, it's 90-degrees tilted; Why is Uranus's axis of rotation tilted?

The best answer for this is;

that at a distant point in its past, Uranus was struck by a very large object, which knocked it to its side, and current tilt.

Imagine if you took a top, and smacked it with a rock. The top might be turning perfectly alright at first, but after it had been hit, the top would most likely be wobbling significantly. Similarly, after an impact, a planet tends to wobble, and it would even more if the impact occurred from a certain axis.

Ok, so my Question is; Is such a collision even physically possible without simultaneously causing the Planet to fly away from its orbit?

The Axial-Rotation Energy of Uranus is 1.11 x 10^32 J

R= 25 000 km, m= 8.683 x 10^25, Rotation time 62064 Seconds. ,, just to scale; this is 432 x times the one of Earth.

About the Meteorite impact; Calculated with the info provided by this link, we need a following metheorite size;

• Mass 7.698 x 10^23 kg, More than Mars.

• Volume 2.96 x 20^20 m3

• Radius; 8 270 km; bigger Than Mars.

I don't quite believe this. What about multiple collisions? According to the link for Meteoric impacts a 1000 m diameter Meteorite might collide every 440 000 Years. Such an Meteorite has an energy of 2 x 10^20 J. So we need only 556198778270 pcs of these, and it would take some 244 727 462 438 800 000 Years.

I don't quite believe this either. I rather believe that I have calculated here something wrong. Or there must be some other explanation.

This Question is combined with this one; Earth's Kinetic energy change

A question from Mercury's rotation might still follow.

• The orbital velocity of the planet is about 6.8km/s, the equatorial rotation velocity is 2.59km/s, so the answer is, yes, it is possible to change the rotation with an impact without dislodging it from its orbit completely. Commented Oct 28, 2015 at 7:28
• @CuriousOne Thanks. Did you also thought about the depth of this collision with such a gas planet? The collision might not be perfectly elastic. And as there must have been also the original rotation, should you calculate the change in velocity too. Commented Oct 28, 2015 at 7:31
• To be frank, I don't think that I am buying into the single collision hypothesis, to begin with. I find it more likely that there have been multiple events. The simple fact remains that a trivial back of the envelope shows that one can transfer more than enough angular momentum without kicking the planet out of the solar system. Commented Oct 28, 2015 at 7:41
• @CuriousOne Wow. That was good. This aspect I havent thought at all. ,,, I need to think,,, Then Why isn't all the other planets rotating to complete random directions? And there is even Venus,, which rotates about in the "right" plane, but only in wrong direction. I also see some problem with equatorial bulge. Ref to my thoughts is Jupiter moon IO. Commented Oct 28, 2015 at 9:20
• check my answer on this question physics.stackexchange.com/questions/25153/… Commented Feb 29, 2016 at 0:11