Tidal Friction
The gravitational interaction where ocean tidal bulges drag ahead of the Earth-Moon axis, causing frictional dissipation of Earth's rotational energy.
Governing formula
dΩ/dt < 0 (Earth rotation slowing by ~2.3 ms/century)
SI unit
ms/century (Length of Day Increase)
In depth
Earth's rapid rotation drags ocean tidal bulges ahead of the Moon. Frictional drag slows Earth's rotation (lengthening the day by ~2.3 ms/century) while transferring angular momentum to the Moon, causing it to recede from Earth at ~3.8 cm/year.
Examples in the real world
Laser ranging measurements confirming the Moon's orbit is expanding by 3.8 cm every year due to tidal friction.