Earth farthest from Sun (only 1/30th farther than at nearest back in January).
Earth
closest
to Sun on Sunday.
Earth farthest from Sun (only 1/30th farther than at nearest
back in January).
Our vantage point is the Sun (again, let's hope we survive this heat).
We look at the Earth and get a frame every 14 days over the course of a
full year. Since the animation starts over again when it's
done it looks like continuous years - which is just fine.
The animation views Earth from the Sun: During a year, the apparent
size of Earth is constant - an indication for the distance to be constant.
Also, you can see how the axis seems to tilt towards and away from the
sun.
Seasons have absolutely nothing to do with the Earth-Sun distance, which varies by less than 2% (you can see that Earth's size hardly changes - because the distance hardly changes). This means that the Earth theoretically receives 4% more sunlight in winter - that's when we are closest to the Sun.
In winter?
Yes, right! OUR (northern hemisphere) winter, which is Australia's
& New Zealand's, Southern South America's, Southern Africa's SUMMER.
While we have summer, they have winter. Our fall is their spring. Etc.
So that can't be it.
One could argue that one hemisphere is a little closer, since it's
tilted towards the Sun. But by how much closer? About 2 thousand miles
- compare that to the total distance of 91 MILLION miles - that's a difference
of only 0.002 % - no way that could account for seasons either.
Instead, the Earth's tilt (of its axis) produces two other effects: It accounts for the Sun's height above the horizon - the Sun appears higher in the sky in summer and lower in winter, right? Therefore the Sun's light hits Earth at a more favorable angle (higher - summer) and more light and heat are absorbed - or less favorable angle (lower - winter) and more heat and light are reflected back into space.
Summer
Winter
(Both animations show pictures in intervals of 1 hour.)
The axis' tilt also accounts for the length of a day. Shorter days in winter mean less sunlight received.
In summary (watch the animations), length of day and height of Sun are
important (note also that our Sun rises and sets more North during the
summer).
One viewpoint: The Earth's axis is "fixed" in space (it always
points toward Polaris) as we revolve around the Sun.
Now, the other viewpoint is to look at Earth as it orbits the Sun.
The axis points in the same direction ("fixed") in space, but as we orbit
the axis (e.g. the North Pole) points - with respect to the Sun - towards
the Sun - summer. Or it points away - winter. Or it points neither toward
nor away - spring and fall.
You may want to try that with a little ball through which you
poke a knitting needle, and let this ball with needle "orbit" around a
light bulb (the Sun), thereby pointing the needle towards the same point
in the room. As you notice, in doing so, the needle points away, past,
towards, past the bulb.