In the United States, we have daylight saving. We move an hour forward or backward according to the different daylight hours in summer and winter. But why number of daylight hours changes as season changes? Here’s the answer.

     Due to the fact that the Earth tilts on its vertical axis by 23.5°, and the north end of the axis always point towards the North Star as the Earth revolves around the Sun, we get season changes.In summer, the Northern Hemisphere leans toward the Sun in its revolution, there are more daylight hours, and the Sun’s angle is more perpendicular to us than at other times of year and we get shorter shadows. Longer daylight exposure to the ground also makes the temperature go much higher.

     In winter, the Northern Hemisphere leans away from the Sun, and there are less daylight hours, and the Sun hits us at an angle and hits the southern hemisphere more perpendicularly so the southern hemisphere is having summer as northern hemisphere having winter. We got longer shadows at the northern hemisphere at this point and we got less daylight hours,and the sunlight is not as sharp as before because they are spreaded out at an angle instead of being at the top of our head. Less daylight hours also makes the temperature go lower.

     During the spring and fall, the Earth leans neither toward nor away from the Sun; daylight and nighttime hours tends to be equal and temperatures are moderate. It is quite interesting that some places at high latitude like Norway will have an extremely long days (daylight hours) in summer and super short days (daylight hours) in winter, and in places close to equator (lower latitudes), like Singapore, Malaysia, the daylight hours doesn’t change too much all through the year, because the sun is almost always hitting these places perpendicularly!