I watched a documentary on the youtube https://www.youtube.com/watch?v=nH3bmG-KjvU and I wrote the following comment: The video did not explain what controls the spin speed of Earth, let alone what would make Earth slow down. We studied at high school the Fleming’s left hand rule for motors and it could very well explain what makes our planet spin and its speed varies on daily basis by milliseconds up and down since measurement began 400 years ago. When electric current flows in a wire, and an external magnetic field is applied across that flow, the wire experiences a force perpendicular both to that field and to the direction of the electric current flow. Inside Earth we have a similar phenomenon. First, let us identify the presence of electric current and anticipate the direction of its flow: As a result of Earth spin we observe bulged crust/ oceans. A bulged Outer Core follows the same principle although the Outer Core radius is half of the crust’s but the outer core density is five to six times that of the crust. Being a radio active isotope, the inner core emits free electrons that flow in the high density viscous outer core. Such electrons elect to flow across the major axis of the bulged Outer Core i.e. the equatorial plane. Second, let us identify the presence of a permanent magnetic field and see if it has a fixed direction: The Inner Core is free to move, swivel and rotate. What if the Inner Core is a permanent magnet; the result of its movement is observed by the wandering of its magnetic poles. Currently, the north magnet is emerging out of Antarctica and the south magnet is pointing into the Arctic circle. The pulling of some of the magnetic field force lines by another magnet/ planet could lead to divergence of some of the field force lines towards space instead of circulating the Earth from Antarctica to Arctic, increasing the wandering of the magnetic poles and of course increasing the rate of Earthquakes. Third, a Lorentz force is generated along the circumference where the Outer Core meets the Inner Mantle. The force is dependent on the product of the electric current, magnetic field force and the angle in between. Such a force that is applied consistently along the perimeter of the Outer Core/ Inner Mantle, makes Earth spin. Assuming no change neither in the magnetic field strength nor the electric current intensity; a maximum force is generated when the electric current and magnetic field are at 90 degrees angle apart. If the angle grows less, the Lorentz force would grow less and Earth spin would slow down. Earth stops spinning when the electric current and magnetic field are flowing in the same direction. The spin could be reversed if the magnetic field force flips. The sun will then rise from the west! This does not mean that I totally disagree with every part of the video. I agree that low spin speed of Earth shall cause sea level to change but I disagree that a sever temperature fluctuation between day and night will occur since not all thermal radiation is arriving from the sun as I explained earlier on the Earth Temperature page of this site. I also disagree that changes of Troposphere altitude would mean less breathable air at the equatorial region.