The Northern Hemisphere is the half of Earth that is north of the Equator. For other planets in the Solar System, north is defined as being in the same celestial hemisphere relative to the invariable plane of the Solar System as Earth's North Pole.
A solstice is the time when the Sun reaches its most northerly or southerly excursion relative to the celestial equator on the celestial sphere. Two solstices occur annually, around 20-22 June and 20-22 December. In many countries, the seasons of the year are defined by reference to the solstices and the equinoxes.
In geography, the temperate climates of Earth occur in the middle latitudes, which span between the tropics and the polar regions of Earth. These zones generally have wider temperature ranges throughout the year and more distinct seasonal changes compared to tropical climates, where such variations are often small; they usually differ only in the amount of precipitation.
The tropics are the regions of Earth surrounding the Equator, where the sun may shine directly overhead. This contrasts with the temperate or polar regions of Earth, where the Sun can never be directly overhead. This is because of Earth's axial tilt; the width of the tropics is twice the tilt. The tropics are also referred to as the tropical zone and the torrid zone.
The Tropic of Cancer, also known as the Northern Tropic, is the Earth's northernmost circle of latitude where the Sun can be seen directly overhead. This occurs on the June solstice, when the Northern Hemisphere is tilted toward the Sun to its maximum extent. It also reaches 90 degrees below the horizon at solar midnight on the December Solstice. Using a continuously updated formula, the circle is currently 23°26′09.9″ (or 23.43607°) north of the Equator.
A circumpolar star is a star that, as viewed from a given latitude on Earth, never sets below the horizon due to its apparent proximity to one of the celestial poles. Circumpolar stars are therefore visible from said location toward the nearest pole for the entire night on every night of the year. Others are called seasonal stars.
A circle of latitude or line of latitude on Earth is an abstract east–west small circle connecting all locations around Earth at a given latitude coordinate line.
In observational astronomy, culmination is the passage of a celestial object across the observer's local meridian. These events are also known as meridian transits, used in timekeeping and navigation, and measured precisely using a transit telescope.
The Southern Hemisphere is the half (hemisphere) of Earth that is south of the Equator. It contains all or parts of five continents and four oceans, as well as New Zealand and most of the Pacific Islands in Oceania. Its surface is 80.9% water, compared with 60.7% water in the Northern Hemisphere, and it contains 32.7% of Earth's land.
The thermal equator is a belt encircling Earth, defined by the set of locations having the highest mean annual temperature at each longitude around the globe. Because local temperatures are sensitive to the geography of a region, mountain ranges and ocean currents ensure that smooth temperature gradients are impossible, the location of the thermal equator is not identical to that of the geographic Equator.
The middle latitudes are a spatial region on Earth located between the Tropic of Cancer to the Arctic Circle (66°33′50.1″), and Tropic of Capricorn (-23°26′09.9″) to the Antarctic Circle (-66°33′50.1″). They include Earth's subtropical and temperate zones, which lie between the two tropics and the polar circles. Weather fronts and extratropical cyclones are usually found in this area, as well as occasional tropical cyclones or subtropical cyclones, which have traveled from their areas of formation closer to the Equator.
Rainfall and the tropical climate dominate the tropical rain belt, which oscillates from the northern to the southern tropics over the course of the year, roughly following the solar equator. The tropical rain belt is an area of active rain that is positioned mostly around the tropics.
The subsolar point on a planet is the point at which its Sun is perceived to be directly overhead ; that is, where the Sun's rays strike the planet exactly perpendicular to its surface. It can also mean the point closest to the Sun on an astronomical object, even though the Sun might not be visible.
The five main latitude regions of Earth's surface comprise geographical zones, divided by the major circles of latitude. The differences between them relate to climate. They are as follows:
- The North Frigid Zone, between the North Pole at 90° N and the Arctic Circle at 66°33′50.1″ N, covers 4.12% of Earth's surface.
- The North Temperate Zone, between the Arctic Circle at 66°33′50.1″ N and the Tropic of Cancer at 23°26′09.9″ N, covers 25.99% of Earth's surface.
- The Torrid Zone, between the Tropic of Cancer at 23°26′09.9″ N and the Tropic of Capricorn at 23°26′09.9″ S, covers 39.78% of Earth's surface.
- The South Temperate Zone, between the Tropic of Capricorn at 23°26′09.9″ S and the Antarctic Circle at 66°33′50.1″ S, covers 25.99% of Earth's surface.
- The South Frigid Zone, from the Antarctic Circle at 66°33′50.1″ S and the South Pole at 90° S, covers 4.12% of Earth's surface.
Daytime or day as observed on Earth is the period of the day during which a given location experiences natural illumination from direct sunlight. Daytime occurs when the Sun appears above the local horizon, that is, anywhere on the globe's hemisphere facing the Sun. In direct sunlight the movement of the sun can be recorded and observed using a sundial that casts a shadow that slowly moves during the day. Other planets and natural satellites that rotate relative to a luminous primary body, such as a local star, also experience daytime, but this article primarily discusses daytime on Earth.
Sun path, sometimes also called day arc, refers to the daily and seasonal arc-like path that the Sun appears to follow across the sky as the Earth rotates and orbits the Sun. The Sun's path affects the length of daytime experienced and amount of daylight received along a certain latitude during a given season.
The equator is a circle of latitude that divides a spheroid, such as Earth, into the Northern and Southern hemispheres. On Earth, the Equator is an imaginary line located at 0 degrees latitude, about 40,075 km (24,901 mi) in circumference, halfway between the North and South poles. The term can also be used for any other celestial body that is roughly spherical.
The solar equator is the latitude on Earth at which the Sun is observed directly overhead at midday. Due to the obliquity of Earth's axis, the solar equator varies during the year, from the Tropic of Capricorn on the December solstice to the Tropic of Cancer on the June solstice. On the day of either equinox, the Sun's position is at the zenith when viewed from the geographic equator. The Sun can never be observed directly overhead from outside of the tropics.
The Antarctic Circle is the most southerly of the five major circles of latitude that mark maps of Earth. The region south of this circle is known as the Antarctic, and the zone immediately to the north is called the Southern Temperate Zone. South of the Antarctic Circle, the Sun is above the horizon for 24 continuous hours at least once per year and the centre of the Sun is below the horizon for 24 continuous hours at least once per year ; this is also true within the equivalent polar circle in the Northern Hemisphere, the Arctic Circle.
The Arctic Circle is one of the two polar circles, and the most northerly of the five major circles of latitude as shown on maps of Earth at about 66° 34' N. Its southern equivalent is the Antarctic Circle.
A sign marking the Tropic of Capricorn as it passes through Namibia
A monument marking the Tropic of Capricorn as it passes through Botswana
A monument in Kruger National Park, South Africa
A sign marking the Tropic of Capricorn in Atsimo-Andrefana Region, Madagascar
A sign at the Mozambican line
