Have You Ever Wondered…
- Why does the Sun rise and set at different times each day?
- What is the shortest day of the year?
- Is Earth’s axis perpendicular to the plane of its orbit?
hat time did the Sun rise this morning? What time will it set this evening? The answers to those questions depend upon where you live and what time of year it is.
Have you ever given much thought to sunrises and sunsets? Wouldn’t it be great if the Sun rose every morning at the same time? Wouldn’t you enjoy the convenience of knowing exactly when the Sun would set at the same time each night?
Unfortunately, the world doesn’t work that way. If you live in North America, you probably look forward to those long summer days when you can play outside for hours on end because the Sun doesn’t set until late in the evening.
Likewise, you might dread short winter days. You get up for school before the Sun rises and then you barely have any time to play after school and do homework before it gets dark.
Things would be different if: (1) Earth orbited the Sun in a perfect circle; and (2) Earth’s axis was perpendicular to the plane of its orbit (straight up and down). If that were the case, the Sun would rise and set at the same times every day. It would also take the same path across the sky every day of the year.
However, neither of those conditions is true for Earth. Instead of a perfectly-circular orbit, Earth’s orbit around the Sun is slightly elliptical. This means that the Sun travels across the sky at slightly different speeds from day to day depending upon where Earth is in its orbit.
