Uranus spins on its side — unlike any other planets and moons in the solar system — is this a stable spin or will it eventually selfright as a spinning top, and how long would that take ?
In: Physics
The top rights itself because of the interaction between the top and whatever it’s spinning on, and that interaction only occurs because there is a universal “downward” force of gravity. The solar system has no such objective preference for which direction is “down,” thus there’s not much reason to suggest Uranus will ever match the other planets. Granted, there *might* be some interaction between Uranus and everything else in the solar system (via gravity) that kinda-sorta rights Uranus, but it would be an extremely slow process that would take *much* longer than the presumed lifespan of our solar system.
A spinning top rights itself because of friction between the point and the surface, and it usually only works if the top has a round bottom. If you tip over a spinning top that has a sharp point, it will actually stay tipped over, and the top of the top will move in a circle, maintaining the angle away from its upright position. An extreme example of this phenomenon is how a spinning wheel or gyroscope hanging on a string will spin sideways, which you can see here. [https://www.youtube.com/watch?v=8H98BgRzpOM](https://www.youtube.com/watch?v=8H98BgRzpOM) This is referred to as gyroscopic precession, and many planets, including the Earth, have an axis of rotation that is off from their planes of orbit. The tilt of the Earth’s axis is about 23.5 degrees, and it takes the Earth approximately 26,000 years for its axis to move in a full circle (although due to the precession of the Earth’s orbit, the combined effect makes the cycle 23,000 years instead). It’s not something that we can see, but the Ancient Egyptians lived long enough ago that they recognized a Thuban as the North Star instead of Polaris. The Earth developed its tilt when a large body hit into it which also created the moon. There isn’t really any friction in space, nor any real sense of up and down, so there aren’t really any forces to cause Urnus to right itself.
Edit: And Venus has a tilt of 177 degrees which means it’s upside down.
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