Every planet rotates counter clockwise in our solar system as seen from above the North Pole, except for Venus and Uranus. These planets rotate in the clockwise or retrograde direction. One of the most popular explanations for these anomalies is that at some point in history, Venus and Uranus both spun counter-clockwise, just like the other planets.
The evidence of huge craters on the surfaces of these planets has hinted at the possibility that a huge mass collided with the planets in their formative days. But, this isn’t enough to make a truthful argument. But, according to Tennis racket theorem also dubbed as Dzhanibekov effect.
The theorem describes the following effect:
Rotation of an object around its first and third principal axes is stable, while rotation around its second principal axis (or intermediate axis) is not.
This can be demonstrated with the following experiment:
Hold a tennis racket at its handle, with its face being horizontal, and try to throw it in the air so that it will perform a full rotation around the horizontal axis perpendicular to the handle, and try to catch the handle.
In almost all cases, during that rotation the face will also have completed a half rotation, so that the other face is now up. It’s very much possible that Venus could have flipped by on its own. The Earth’s core is moving with anomalous speeds, but it still isn’t strong enough to flip our planet upside down. Turning upside down requires an external force.
Such a force exists, as proven by an astonishing discovery made at an orbital space station. An accidental observation on orbital space station Salyut 7 that made the scientists seriously ponder the possibility that Earth can turn upside down.
Explanation from Russian Scientist
On June 25th 1985, at the Russian orbital space station Salyut 7, Vladimir Dzhanibekov was unpacking supplies delivered from Earth. He had to unscrew the wingnut, to get it moving, it continues to move with constant speed after it came off.
While rotating, the wingnut flies around 1/2 meter and then it flips upside down, as if it disappeared and then emerged again, retaining its volume, except now its notches are facing in the direction of its flight It rolls over abruptly, 180°, and continues spinning, except now the upside down.
This phenomenon was so intriguing that the astronaut performed an experiment, for which he made a small sphere out of plasticine. The plasticine sphere is basically a model of the Earth in space. An unknown external force that makes the sphere roll over also has effect on our planet. The Earth indeed does some sort of rollover.
When Dzhanibekov returned to Earth and told his colleagues about his observations, they all came to a conclusion that the Earth, from time to time, is subject to the very same Dzhanibekov effect, a rollover. It happens suddenly, it can happen tomorrow, or it can happen in 10 to 15 years. Obviously, there’s an area in space, perhaps several, that the Earth passes through, from time to time.
The wingnut in zero G makes a complete turn every 40cm. The Earth’s axis flips every 12000 years. The last time the planet rolled over was back in the time of the mammoths. Waiting for the next rollover won’t take long. If this happens in the future, the event would be catastrophic.
Whether Earth flips or not is a speculation at this point.