Centuries: 3rd century - 4th century - 5th century
Decades: 340s - 350s - 360s - 370s - 380s - 390s - 400s - 410s - 420s - 430s - 440s
Years: 390 391 392 393 394 395 396 397 398 399 400
... for the device's operation, the groove must not be lubricated. The acceleration of the gyroscope is best when the precession of the gyroscope is supported an ...