why does the sun go down earlier in the winter and much later in the summer?
In: Physics
Axial tilt of the earth — it rotates on an angle compared to the direction of the sun, so from the earth’s perspective the sun migrates throughout the year to circle closer to the pole in the summer and further from the pole in the winter.
The Earth tilts. The part of the Earth tilting away from the sun receives less light than the part of the Earth tilting toward the sun. This results in a pattern of light on the Earth like below:
[https://i.stack.imgur.com/pYf7o.png](https://i.stack.imgur.com/pYf7o.png)
The right/Eastern edge represents where it is Sunrise is happening and the left/Western edge represents where Sunset is happening. As you can see, as you go further north (in this example) the distance between Sunset and Sunrise increases, representing a longer time between the two, till you get above the artic circle where it is always daylight.
By contrast, as you go further south, the distance gets closer and closer till you get to the antarctic circle where it is always night.
In this specific example, it is Summer in the northern hemisphere and Winter in the Southern hemisphere.
The earth’s North and South poles aren’t exactly perpendicular to the sun. It has a tilt.
If you were to draw a line where the sun is “directly over” on the earth, over the course of a year, it wouldn’t be a straight line across the planet. It varies from 30 degrees north of the equator (called The Tropic of Cancer) to 30 degrees south of the equator (the Tropic of Capricorn).
On the Spring and Autumn equinoxes, it’s more or less directly over the equator. On the solstice in December, it’s 30 degrees south of the equator (which means the farther north you are, the less daylight you get, and the farther south you are the more daylight you get). It’s the opposite on the Solstice in June. You’ll hear them called Summer Solstice and Winter Solstice, but that’s for people who live in the Northern Hemisphere (December is summer time in the Southern Hemisphere).
tl;dr – in the winter, you’re not in the direct sunlight compared to someone on the other side of the planet.
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The earth doesn’t circle around the sun straight up and down. During the year, the top half slowly leans closer to the sun than the bottom half. Then it happens again, but does it in reverse. If you could see the earth moving at high speed, it would look like it’s wobbling back and forth. Now think about this, there’s a sun side and a dark side to the earth (day and night). Because the top and bottom move, one gets more sunlight. More sun also shines on that one, so longer days. And because that half is closer to the sun, it gets hotter. That’s why we have long, hot summer days and long, cold winter nights. Another interesting fact is that the wobbling (also called tilt) is not very much. Just that little bit makes a huge difference. A bit more and you’d be able to go to a place where there was no night for most of the year, and one that was night most of the year. A little bit more and you’d have places that only had daytime and ones that only had nighttime. Fun stuff.
Take a look at these seasons and ecliptic simulators:
https://www.climate.gov/teaching/resources/seasons-and-ecliptic-simulator
They were really helpful when I was answering some family members about the very same question you have.
The earth tilts a little and where the earth is around the sun makes the tilt seem different. Plus, in the USA at least, we have Daylight savings so we change the clocks by an hour and that also affects it.
Imagine you’re holding a light bulb in your left hand (it’s lit up and it’s our make-believe Sun).
In your right hand is an orange and we’ve stuck a thumbtack in the top of it (that’s our north pole… also that orange is Earth.) The orange has a thin, black line drawn around the center dividing it into two halves nicely.
Tilt the orange in your hand so that the thumbtack points *slightly* towards the light bulb. There is more light on the top of the orange (with thumbtack) than on the bottom of the orange (opposite the thumbtack).
Even as the orange rotates (always rotating it on it’s centerline, so that the thin, black line doesn’t appear to move) the side with the thumbtack stays more well lit than the opposite side.
The side with the thumbtack is experiencing summer while the other side is experiencing winter.
Now, don’t adjust the tilt of the orange but swap the orange and the lightbulb from one hand to the other. That represents the position of the Earth six months later. Now when you rotate the orange, the side with the thumbtack has less light than the side without it. The seasons have reversed.
That’s actually the cause of the seasons.
And the cause of less sun in winter and more sun in summer, is the tilt of Earth’s axis relative to the orbit.
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