Answer to Question #4200 in Astronomy | Astrophysics for Sam

Question

How would the seasons change if the Earth had no axial tilt?

Answer 1

How would
the seasons change if the Earth had no axial tilt?


The Earth
currently has an axial tilt of about 23.4°.The axis remains tilted in the same
direction towards the stars throughout a year and this means that when a
hemisphere (a northern or southern half of the earth) is pointing away from the
Sun at one point in the orbit then half an orbit later (half a year later) this
hemisphere will be pointing towards the Sun. This effect is the main cause of
the seasons (see effect of sun angle on climate). Whichever hemisphere is
currently tilted toward the Sun experiences more hours of sunlight each day,
and the sunlight at midday also strikes the ground at an angle nearer the
vertical and thus delivers more energy per unit surface area.


Lower
obliquity causes polar regions to receive less seasonally contrasting solar
radiation, producing conditions more favorable to glaciation. Like changes in
precession and eccentricity, changes in tilt influence the relative strength of
the seasons, but the effects of the tilt cycle are particularly pronounced in
the high latitudes where the great ice ages began. Obliquity is a major factor
in glacial/interglacial fluctuations .


So if the
Earth had no axial tilt there would simply be no change of seasons.