The first egg presented in the video is hard boiled. The yoke inside sits firmly in the white. Both parts get the same rotational momentum.
The second one is not boiled. The yoke inside has a momentum different than the white. The egg wobbles a bit but doesn't rotate like the first one does.
***
That phenomenon helps us to understand the theory of the Earth's magnetic field. We think that the field is generated as the result of a layer of liquid metal, surrounding the solid iron core. The layer of liquid metal rotates with a different momentum than the planet's surface. From the surface, the inner flow of liquid metal can be seen as an electric current inside the planet. That current generates the Earth's magnetic field. Isn't that cool? In addition, the theory is useful to explain the magnetic pole reversal.
