Escapement in 2015 as the most accurate open-air mechanical clock, deviating of a second during 100 days. It continues to run and oscillate ±0.5 seconds around 0.00 seconds of error after 2 years after a barometric correction was applied. A gravity escapement uses a small weight or a weak spring to give an impulse directly to the pendulum. The earliest form consisted of two arms which were pivoted very close to the suspension spring of the pendulum with one arm on each side of the pendulum. Each arm carried a small dead beat pallet with an angled plane leading to it.
Anchor escapement to a fork pushed by the pendulum, so the anchor swings back and forth, with the pallets alternately catching and releasing an escape wheel tooth on each side. Each time one pallet moves away from the escape wheel, releasing a tooth, the wheel turns and a tooth on the other side catches on the other pallet, which is moving toward the wheel. The momentum of the pendulum continues to move the second pallet toward the wheel, pushing the escape wheel backwards for a distance, until the pendulum reverses direction and the pallet begins to move away from the wheel, with