Daytime in the context of "Crepuscular animal"

Winter is the coldest and darkest season of the year in temperate and polar climates. It occurs after autumn and before spring. Since the tilt of Earth's axis causes seasons; winter occurs when a hemisphere is oriented away from the Sun. Different cultures define different dates as the start of winter, and some use a definition based on weather.

When it is winter in the Northern Hemisphere, it is summer in the Southern Hemisphere, and vice versa. Winter typically brings precipitation that, depending on a region's climate, is mainly rain or snow. The moment of winter solstice is when the Sun's elevation with respect to the North or South Pole is at its most negative value; that is, the Sun is at its farthest below the horizon as measured from the pole. The day on which this occurs has the shortest day and the longest night, with day length increasing and night length decreasing as the season progresses after the solstice.

The atmosphere of Earth consists of a layer of mixed gas (commonly referred to as air) that is retained by gravity, surrounding the Earth's surface. It contains variable quantities of suspended aerosols and particulates that create weather features such as clouds and hazes. The atmosphere serves as a protective buffer between the Earth's surface and outer space. It shields the surface from most meteoroids and ultraviolet solar radiation, reduces diurnal temperature variation – the temperature extremes between day and night, and keeps it warm through heat retention via the greenhouse effect. The atmosphere redistributes heat and moisture among different regions via air currents, and provides the chemical and climate conditions that allow life to exist and evolve on Earth.

By mole fraction (i.e., by quantity of molecules), dry air contains 78.08% nitrogen, 20.95% oxygen, 0.93% argon, 0.04% carbon dioxide, and small amounts of other trace gases (see Composition below for more detail). Air also contains a variable amount of water vapor, on average around 1% at sea level, and 0.4% over the entire atmosphere.

Autumn, also known as fall in North American English, is one of the four temperate seasons on Earth. Outside the tropics, autumn marks the transition from summer to winter, beginning in September (Northern Hemisphere) or March (Southern Hemisphere). Autumn is the season when the duration of daytime becomes noticeably shorter and the temperature cools considerably. Day length decreases and night length increases as the season progresses until the winter solstice in December (Northern Hemisphere) and June (Southern Hemisphere). One of its main features in temperate climates is the striking change in colour of the leaves of deciduous trees as they prepare to shed.

The winter solstice, or hibernal solstice, occurs when either of Earth's poles reaches its maximum tilt away from the Sun. This happens twice yearly, once in each hemisphere (Northern and Southern). For that hemisphere, the winter solstice is the day with the shortest period of daylight and longest night of the year, and when the Sun is at its lowest daily maximum elevation in the sky. Each polar region experiences continuous darkness or twilight around its winter solstice. The opposite event is the summer solstice.

The winter solstice occurs during the hemisphere's winter. In the Northern Hemisphere, this is the December solstice (December 21 or 22) and in the Southern Hemisphere, this is the June solstice (June 20 or 21). Although the winter solstice itself lasts only a moment, the term also refers to the day on which it occurs. Traditionally, in many temperate regions, the winter solstice is seen as the middle of winter; "midwinter" is another name for the winter solstice, although it carries other meanings as well. Other names are the "extreme of winter", or the "shortest day".

Night, or nighttime, is the period of darkness when the Sun is below the horizon. Daylight illuminates one side of the Earth, leaving the other in darkness. The opposite of nighttime is daytime. Earth's rotation causes the appearance of sunrise and sunset. Moonlight, airglow, starlight, and light pollution dimly illuminate night. The duration of day, night, and twilight varies depending on the time of year and the latitude. Night on other celestial bodies is affected by their rotation and orbital periods. The planets Mercury and Venus have much longer nights than Earth. On Venus, night lasts about 58 Earth days. The Moon's rotation is tidally locked, rotating so that one of the sides of the Moon always faces Earth. Nightfall across portions of the near side of the Moon results in lunar phases visible from Earth.

Organisms respond to the changes brought by nightfall: darkness, increased humidity, and lower temperatures. Their responses include direct reactions and adjustments to circadian rhythms governed by an internal biological clock. These circadian rhythms, regulated by exposure to light and darkness, affect an organism's behavior and physiology. Animals more active at night are called nocturnal and have adaptations for low light, including different forms of night vision and the heightening of other senses. Diurnal animals are active during the day and sleep at night; mammals, birds, and some others dream while asleep. Fungi respond directly to nightfall and increase their biomass. With some exceptions, fungi do not rely on a biological clock. Plants store energy produced through photosynthesis as starch granules to consume at night. Algae engage in a similar process, and cyanobacteria transition from photosynthesis to nitrogen fixation after sunset. In arid environments like deserts, plants evolved to be more active at night, with many gathering carbon dioxide overnight for daytime photosynthesis. Night-blooming cacti rely on nocturnal pollinators such as bats and moths for reproduction. Light pollution disrupts the patterns in ecosystems and is especially harmful to night-flying insects.

The summer solstice or estival solstice occurs when one of Earth's poles has its maximum tilt toward the Sun. It happens twice yearly, once in each hemisphere (Northern and Southern). The summer solstice is the day with the longest period of daylight and shortest night of the year in that hemisphere, when the sun is at its highest position in the sky. At either pole there is continuous daylight at the time of its summer solstice. The opposite event is the winter solstice.

The summer solstice occurs during the hemisphere's summer. In the Northern Hemisphere, this is the June solstice (20 or 21 June) and in the Southern Hemisphere, this is the December solstice (21 or 22 December). Since prehistory, the summer solstice has been a significant time of year in many cultures, and has been marked by festivals and rituals. Traditionally, in temperate regions (especially Europe), the summer solstice is seen as the middle of summer and referred to as "midsummer"; although today in some countries and calendars it is seen as summer's beginning.

The sky is an unobstructed view upward from the surface of the Earth. It includes the atmosphere and outer space. It may also be considered a place between the ground and outer space, thus distinct from outer space.

In the field of astronomy, the sky is also called the celestial sphere. This is an abstract sphere, concentric to the Earth, on which the Sun, Moon, planets, and stars appear to be drifting. The celestial sphere is conventionally divided into designated areas called constellations.

Daylight is the combination of all direct and indirect sunlight during the daytime. This includes direct sunlight, diffuse sky radiation, and (often) both of these reflected by Earth and terrestrial objects, like landforms and buildings. Sunlight scattered or reflected by astronomical objects is generally not considered daylight. Therefore, daylight excludes moonlight, despite it being reflected indirect sunlight.