Daytime

Daytime is when the sun is in the sky.

The sun shines on half of our world. This light helps us see everything.

As Earth spins, the daytime part moves.

The sun rises in the east. It sets in the west.

Days change with the seasons. In summer, the days are long. In winter, the days are short.

Near the middle of the Earth, the days stay about the same. At the top and bottom, days can be very different.

Some places even have sun all day long in summer! It is fun to watch the sun move.

Daytime is when the Sun is above the horizon.

At any time, the Sun lights up about half of the Earth. This light comes from direct sunlight and light from the sky.

As the Earth spins on its axis, the daytime part moves. This spin causes the Sun to rise in the east and set in the west. The length of the day changes as the Earth moves around the Sun. This happens because the Earth's axis is tilted. This tilt creates the seasons.

At the Equator, the day is always about 12 hours long. In the tropics, the Sun can pass almost directly overhead.

Near the poles, the days change a lot. In summer, some places see the midnight sun. This means the Sun stays up for 24 hours! In winter, the Sun may not rise at all. At middle latitudes, the change in day length is moderate. In summer, the sky stays light late into the night. In winter, it gets dark much sooner.

Daytime is the period when the Sun is above the local horizon.

During this time, an area is lit by daylight. This is a mix of direct sunlight and indirect light from the sky.

At any moment, about half of the Earth faces the Sun. This means about half the planet experiences daytime. Because the atmosphere bends light, slightly more than half the surface is actually lit. This light makes the world visible and bright.

Daytime works because the Earth rotates on its own axis. This spin causes the Sun to appear to rise in the east. It then disappears below the horizon in the west at sunset. The Sun is a large disc rather than a tiny point. This means sunrise and sunset are not instant events. The Earth's atmosphere also helps by bending and spreading the light. This process makes the period of sunrise and sunset longer. There is even a time called twilight when the sky stays light.

The length of the day changes as the Earth orbits the Sun. This happens because the Earth's axis is tilted at 23.44 degrees. This tilt is not straight up and down. As the planet moves, the tilt stays mostly fixed toward the stars. This creates the different seasons we see each year. At the Equator, the daytime is always about 12 hours long. The Sun there rises and sets almost vertically. This makes the sunrise and sunset periods very short.

Different parts of the world have very different day lengths. The tropics sit between 23.44 degrees north and south. In this zone, the Sun can pass almost directly overhead. This happens at the Tropic of Cancer and the Tropic of Capricorn. Near the poles, the changes are much more extreme. Within 23.44 degrees of the poles, the Sun may never set. This is called the midnight sun during the summer. In the winter, there may be days when the Sun never rises.

You can see these changes in your own life. In middle latitudes, the seasons change how much light you see. In places like Paris, the sky might stay light until 10 pm in summer. In the winter, it might get dark by 5 pm. The amount of daylight changes by about 4 hours between seasons in some areas. Even the time of solar noon changes throughout the year. This change is called the equation of time. It can vary by about 30 minutes over a full year.

Daytime is the period when the Sun is above the local horizon for a specific location.

During this time, a region is illuminated by daylight. This light is a combination of direct sunlight and indirect light coming from the sky. At any single moment, about half of the Earth faces the Sun. This means roughly half of the planet is experiencing daytime. However, because the atmosphere bends light, the actual area covered by illumination is slightly more than half the surface.

The mechanism of daytime is driven by the Earth's rotation on its axis. As the planet spins, the part of the surface facing the Sun changes continuously. A surface observer defines daytime as the period between sunrise and sunset. Sunrise occurs when the Earth's rotation toward the east causes the Sun's disc to appear above the horizon. Sunset happens when the continuing rotation causes the Sun to disappear below the horizon to the west. Because the Sun is a luminous disc rather than a single point of light, these events are not instantaneous. Furthermore, the atmosphere bends and diffuses light, which lengthens the periods of sunrise and sunset. This creates a period called twilight, where indirect light keeps the sky bright before sunrise or after sunset.

The length of daytime varies based on latitude and the time of year. This variation occurs because the Earth's axis is tilted 23.44° relative to the ecliptic. The ecliptic is the plane of Earth's orbit around the Sun. As the Earth orbits the Sun, this axis remains relatively fixed in relation to the stars. This tilt causes seasonal variations in how much daylight different parts of the planet receive.

At the Equator, the daytime period is consistently about 12 hours long regardless of the season. In contrast, middle latitudes experience moderate changes. In higher middle latitudes, like Paris or Montreal, the sky might stay light until 10 pm in summer but turn dark by 5 pm in winter. In lower middle latitudes, the difference between summer and winter daylight is about 4 hours.

Different zones on Earth experience unique solar patterns. The tropics are located between 23.44° north and 23.44° south of the Equator. In this zone, the Sun will pass almost directly overhead, or culminate, at least once a year. The boundary at 23.44° north is the Tropic of Cancer. The boundary at 23.44° south is the Tropic of Capricorn. On the Tropics of Cancer and Capricorn, the Sun is directly overhead only once per year, during the solstice. Closer to the Equator, the Sun can be overhead twice per year. This phenomenon is sometimes called Lahaina Noon or a zero shadow day.

Near the poles, the seasonal variations in daylight are extreme. The Arctic Circle marks the boundary at 66.56° north, while the Antarctic Circle marks 66.56° south. Within 23.44° of the poles, there are days when the Sun never sets. This 24-hour summer daylight is known as the midnight sun. Conversely, there are also days when the Sun never rises. Even during the summer solstice, the Sun only reaches a maximum height of 23.44° above the horizon at the poles. This low angle, combined with the reflection of solar radiation from snow and ice, helps keep polar regions cold.

The Sun's position also changes throughout the year in a way called the equation of time. This term describes how the exact instant of solar noon varies. Solar noon is the moment when the Sun reaches its highest point in the sky. Over the course of a full year, this variation is approximately 30 minutes.

While the length of day changes, the Equator remains warm because the Sun stays close to the zenith, which is the point directly overhead. At the Equator, the Sun's path is nearly perpendicular to the horizon. This results in the shortest sunrise and sunset durations, sometimes taking only two minutes to cross the horizon on the equinoxes.

Understanding daytime is essential for studying how energy is distributed across our planet. The amount of directness in solar rays affects temperature more than the length of daylight itself. For example, the poles remain cold even with 24 hours of daylight because the Sun's rays hit at such low angles. The Equator stays warm with only 12 hours of daylight because the Sun is so much more direct. These patterns of light and heat drive the complex systems of our global climate and seasons.