What Causes the Length of Daylight Through the Year?

Orbit

• Orbits are the path celestial bodies take around other, for example, the planets orbit the Sun and moons orbit the planets. These are often thought of as circular paths, but are in fact elliptical, or egg shaped. When the Earth is at its closest point to the Sun it is summer in the Northern Hemisphere and when it is furthest away it is winter. When the Earth is closest to the Sun it is exposed to its solar radiation for longer and at greater intensity. This is why the days are longer and hotter during the summer months.

Axis

• The axis of the Earth has a major effect on the length of the days and the position of the Sun on the horizon. During the winter the Earths axis tilts the Northern Hemisphere away from the Sun. This results in shorter days and the lower position of the Sun. This is why in Canada, Alaska and Scandinavia there are some months when the Sun is not seen at all. As the Southern Hemisphere is always more tilted towards the Sun, its annual temperatures are much higher on average than above the equator.

Solstices

• The Vernal and Autumnal Equinox are days during the year when day and night are exactly 12 hours in length. These not only mark the months between Autumn and Winter and Spring and Summer, but also occur at the halfway point of the Earth's orbit around the Sun.

Daylight Savings

• If the clocks stayed the same the variation in daylight hours would still occur, but the introduction of daylight savings time exaggerates these changes. The idea originally was so it would be lighter in the early mornings allowing farmers to tend crops. This is why the clocks go forward in the spring and return to normal in the autumn after the harvest has been collected.