In the past this tilt, or obliquity of the Earth's axis, has varied from 24.50 to 21.50 on a cycle of 40,000 years.
(this tilt, or obliquity of the Earth's axis; has varied; from 24.50 to 21.50; T:In the past)
this tilt, or obliquity of the Earth's axis
has varied
from 24.50 to 21.50 T:In the past