Afternoon is the time after
solar noon. It is the time when the
sun is descending from its peak in the
sky to somewhat before its terminus at the
horizon
The horizon is the apparent line that separates the surface of a celestial body from its sky when viewed from the perspective of an observer on or near the surface of the relevant body. This line divides all viewing directions based on whether i ...
in the west. In human life, it occupies roughly the latter half of the standard
work and school day. In literal terms, it refers to a time specifically after noon. The equivalent of Earth's afternoon on another planet would refer to the time the principal star of that
planetary system
A planetary system is a set of gravitationally
In physics, gravity () is a fundamental interaction which causes mutual attraction between all things with mass or energy. Gravity is, by far, the weakest of the four fundamental interacti ...
would be in descent from its
prime meridian, as seen from the planet's surface.
Terminology
Afternoon is often defined as the period between
noon and
evening.
If this definition is adopted, the specific range of time varies in one direction: noon is defined as the time when the sun reaching its highest point in the sky, but the boundary between afternoon and evening has no standard definition. However, before a period of transition from the 12th to 14th centuries, ''noon'' instead referred to 3:00 pm. Possible explanations include shifting times for prayers and midday meals, along which one concept of ''noon'' was defined—and so ''afternoon'' would have referred to a narrower timeframe.
The word ''afternoon'', which derives from ''after'' and ''noon'', has been attested from about the year 1300;
Middle English contained both ''afternoon'' and the synonym ''aftermete''. The standard phrasing was ''at afternoon'' in the 15th and 16th centuries, but has shifted to ''in the afternoon'' since then. In
Southern American
Southern American English or Southern U.S. English is a regional dialect or collection of dialects of American English spoken throughout the Southern United States, though concentrated increasingly in more rural areas, and spoken primarily by ...
and
Midland American English, the word ''evening'' is sometimes used to encompass all times between noon and
night.
The
Irish language contains four different words to mark time intervals from late afternoon to nightfall; this period is considered mystical. Metaphorically, the word ''afternoon'' refers to a relatively late period in the expanse of time or in one's life.
Events
Afternoon is a time when the
sun is descending from its daytime peak. During the afternoon, the sun moves from roughly the center of the sky to deep in the west. In late afternoon,
sunlight
Sunlight is a portion of the electromagnetic radiation given off by the Sun, in particular infrared, visible, and ultraviolet light. On Earth, sunlight is scattered and filtered through Earth's atmosphere, and is obvious as daylight when t ...
is particularly bright and glaring, because the sun is at a low angle in the
sky.
The standard
working time in most
industrialized countries
A developed country (or industrialized country, high-income country, more economically developed country (MEDC), advanced country) is a sovereign state that has a high quality of life, developed economy and advanced technological infrastruct ...
goes from the morning to the late afternoon or evening — archetypally, 9:00 am to 5:00 pm — so the latter part of this time takes place in the afternoon.
Schools usually let their students out around 3:00 pm during the mid afternoon.
Effects on life
Hormones
In
diurnal animals, it is typical for blood levels of the hormone
cortisol
Cortisol is a steroid hormone, in the glucocorticoid class of hormones. When used as a medication, it is known as hydrocortisone.
It is produced in many animals, mainly by the ''zona fasciculata'' of the adrenal cortex in the adrenal gland ...
—which is used to increase
blood sugar, aid
metabolism and is also produced in response to
stress—to be most stable in the afternoon after decreasing throughout the morning. However, cortisol levels are also the most reactive to environmental changes unrelated to sleep and daylight during the afternoon. As a result, this time of day is considered optimal for researchers studying stress and hormone levels. Plants generally have their highest
photosynthetic
Photosynthesis is a process used by plants and other organisms to convert light energy into chemical energy that, through cellular respiration, can later be released to fuel the organism's activities. Some of this chemical energy is stored in c ...
levels of the day at noon and in the early afternoon, owing to the sun's high angle in the sky. The large proliferation of
maize crops across Earth has caused tiny, harmless fluctuations in the normal pattern of atmospheric
carbon dioxide levels, since these crops photosynthesize large amounts of carbon dioxide during these times and this process sharply drops down during the late afternoon and evening.
Body temperature
In
humans,
body temperature is typically highest during the mid to late afternoon.
However, human athletes being tested for physical vigor on exercise machines showed no statistically significant difference after lunch.
Owners of
factory farms are advised to use buildings with an east–west (as opposed to north–south) orientation to house their
livestock, because an east–west orientation generally means thicker walls on the east and west to accommodate the sun's acute angle and intense glare during late afternoon. When these animals are too hot, they are more likely to become belligerent and unproductive.
Alertness
The afternoon, especially the early afternoon, is associated with a dip in a variety of areas of human cognitive and productive functioning. Notably,
motor vehicle accidents occur more frequently in the early afternoon, when drivers presumably have recently finished lunch. A study of motor accidents in
Sweden
Sweden, formally the Kingdom of Sweden,The United Nations Group of Experts on Geographical Names states that the country's formal name is the Kingdom of SwedenUNGEGN World Geographical Names, Sweden./ref> is a Nordic country located on ...
between 1987 and 1991 found that the time around 5:00 pm had by far the most accidents: around 1,600 at 5:00 pm, compared to around 1,000 each at 4:00 pm and 6:00 pm. This trend may have been influenced by the afternoon
rush hour
A rush hour (American English, British English) or peak hour (Australian English) is a part of the day during which traffic congestion on roads and crowding on public transport is at its highest. Normally, this happens twice every weekday: on ...
, but the morning rush hour showed a much smaller increase. In
Finland, accidents in the
agriculture industry are most common in the afternoon, specifically Monday afternoons in September.
One psychology professor studying
circadian rhythm
A circadian rhythm (), or circadian cycle, is a natural, internal process that regulates the sleep–wake cycle and repeats roughly every 24 hours. It can refer to any process that originates within an organism (i.e., Endogeny (biology), endogeno ...
s found that his students performed somewhat worse on exams in the afternoon than in the morning, but even worse in the evening. Neither of these differences, however, was statistically significant.
Four studies carried out in 1997 found that subjects who were given tests on differentiating
traffic signs had longer
reaction times when tested at 3:00 pm and 6:00 pm than at 9:00 am and 12:00 pm. These trends are held across all four studies and for both complex and abstract questions. However, one UK-based researcher failed to find any difference in exam performance on over 300,000 A-level exam papers sat in either the morning or afternoon.
Human productivity routinely decreases in the afternoon.
Power plants have shown significant reductions in productivity in the afternoon compared to the morning, the largest differences occurring on Saturdays and the smallest on Mondays. One 1950s study covering two female factory workers for six months found that their productivity was 13 percent lower in the afternoon, the least productive time being their last hour at work. It was summarized that the differences came from personal breaks and unproductive activities at the workplace. Another, larger study found that afternoon declines in productivity were greater during longer work shifts.
It is important to note, however, that not all humans share identical circadian rhythms. One study across
Italy and
Spain had students fill out a questionnaire, then ranked them on a "
morningness–eveningness" scale. The results were a fairly standard
bell curve. Levels of alertness over the course of the day had a significant correlation with scores on the questionnaire. All categories of participants—evening types, morning types, and intermediate types—had high levels of alertness from roughly 2:00 pm to 8:00 pm, but outside this window their alertness levels corresponded to their scores.
See also
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Morning
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Sunset
Sunset, also known as sundown, is the daily disappearance of the Sun below the horizon due to Earth's rotation. As viewed from everywhere on Earth (except the North and South poles), the equinox Sun sets due west at the moment of both the spring ...
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Twilight
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12-hour clock
The 12-hour clock is a time convention in which the 24 hours of the day are divided into two periods: a.m. (from Latin , translating to "before midday") and p.m. (from Latin , translating to "after midday"). For different opinions on represent ...
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Night owl (person)
A night owl, evening person or simply owl, is a person who tends to stay up until late at night, or to the very early hours of the morning. Night owls who are involuntarily unable to fall asleep for several hours after a normal time may have de ...
References
Further reading
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External links
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{{Authority control
Parts of a day