What relationship between earth and the sun causes the seasons?
The Earth is tilted on its axis. 'Summer' (the warmest season)
occurs when a hemisphere, either the northern hemisphere or the
southern hemisphere, is tilted towards the Sun and thus receives
more direct sunlight (the Sun is closer to the zenith and is above
the horizon longer).
A common misconception is that the seasons have to do with the
Earth being closer to the Sun due to the elliptical nature of its
orbit. The orbit is elliptical and the Earth is closest to
the Sun [aphelion] in early January, farthest away [perihelion] in
early July. This has a minor effect on the seasons, but more
important is the number of days and weeks the Sun is higher in the
sky; near perihelion for the northern hemisphere (although the Sun
is further away) the atmosphere has the opportunity to heat up
Twice during the year (spring and fall Equinox - around the 20th
of March and September respectively), the Sun appears to circle
more directly over the equator [the axis of the Earth is in a plane
perpendicular to the orbit], and most areas of the globe receive
similar amounts of daylight. The poles are exceptions, with
extremely long periods of the Sun either above or below the
From late December to late March, the Southern Hemisphere
experiences 'summer' while the Northern Hemisphere experiences
'winter'. From late June to late September, the position is the
other extreme, and it is summer in the Northern Hemisphere, winter
in the Southern.
These yearly changes in insolation (incoming energy from the
Sun) cause the seasons, in conjunction with the prevailing
directional wind patterns, ocean areas, currents, and pressure
systems which all affect the local climate.
The tilt of the Earth in combination to its position during its
orbit around the Sun.
The reason for the northern hemisphere summer/ southern
hemisphere winter is that at the time of the June solstice the sun
is directly over the Tropic of Cancer. The reason for the northern
hemisphere winter/ southern hemisphere summer is that at the time
of the December solstice the sun is directly over the Tropic of
Capricorn. The reason for spring and fall is that at the times of
the March and September equinoxes the sun is directly over the
Seasons are caused by the tilt of Earth's axis, which is 23.5
degrees (with respect to the perpendicular to the plane of Earth's
orbit). This results in parts of the Earth getting more sunlight at
some times of the year, and less sunlight at others.