<P> Given that Earth's own axis of rotation is tilted about 23.5 ° to the line perpendicular to its orbital plane, called the ecliptic, the length of daytime varies with the seasons on the planet's surface, depending on the observer's latitude . Areas tilted toward the Sun are experiencing summer . Their tilt toward the Sun leads to more than half of the day seeing daylight and warmer temperatures, due to the higher directness of solar rays, the longer period of daytime itself, and less absorption of sunlight in the atmosphere . While increased daylight can have some effect on the higher temperatures in the summer, most of temperature rise results from the directness of the Sun, not the increased daylight . The high angles (around the zenith) of the Sun causes the tropics to be warm, while low angles (barely above the horizon) causes the polar regions to be cold . The slight effect of daylight hours on average seasonal temperature can be seen with the poles and tropical regions . The poles are still cold during their respective summers, despite seeing 24 hours of daylight for six months, while the Equator remains warm throughout the year, with only 12 hours of daylight per day . </P> <P> Although the daytime length at the Equator remains 12 hours in all seasons, the duration at all other latitudes varies with the seasons . During the winter, daytime lasts shorter than 12 hours; during the summer, it lasts longer than 12 hours . Northern winter and southern summer concur, while northern summer and southern winter concur . </P> <P> At the Equator, the daytime period always lasts almost twelve hours in length, no matter what the season . The Sun always rises nearly perpendicular to the horizon . From the March Equinox to the September Equinox, it rises a bit north of east, and sets a bit north of west . From the September Equinox to the March Equinox, it rises a bit south of east and sets a bit south of west . The path of the Sun lies entirely in the northern half of the sky for the period from the March Equinox to the September Equinox and is entirely in the southern half of the sky from the September Equinox to the March Equinox, with the Sun passing directly overhead at noon on the equinoxes . </P> <P> The fact that the Sun is always so close to the vertical at noon on the Equator (never being more than 23.5 ° north or south) explains why equatorial regions are the hottest regions on the planet overall . Additionally, sunrise and sunset always occur very quickly at the Equator, because the Sun's path across the sky is so nearly vertical with respect to the horizon; at the equinox, the Sun requires only two minutes to traverse the horizon at sunrise and sunsets . </P>

Where does the length of the day remain the same throughout the year