The "true" or instantaneous obliquity includes the nutation. The "true" or instantaneous obliquity includes this nutation. Eratosthenes most probably used a solstitial armilla for measuring the obliquity of the ecliptic. This will be associated with wild swings in the obliquity of the ecliptic as well. In addition, the rotational tilt of the Earth (its obliquity) changes slightly. Astrophysicists have applied tidal theories to predict the obliquity of extrasolar planets. The second is a shift in the tilt of the Earth's axis, or obliquity. Regular changes in climate may be due to variations of a planet's tilt (called obliquity). During times when the tilt is less (low obliquity), the seasons are less extreme. When the tilt is greater (high obliquity), the seasons are more extreme. So far, it has not been possible to constrain the obliquity of an extrasolar planet. The Moon has a stabilizing effect on Earth's obliquity. The stellar obliquity was found to be degrees. This obliquity causes Earth's seasons. The doxographer and theologian Aetius attributes to Pythagoras the exact measurement of the obliquity.