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Freckle

Freckles are clusters of concentrated melanin that are most often visible with a fair skin complexion. Freckles are predominantly found on the face, although they may appear on any skin exposed to the sun, such as the lips, neck, arms, shoulders, ...

                                               

Fresh water

Fresh water is water that does not have a lot of salt in it. When people say fresh water, they usually mean water from the lakes, rivers, snow, and ice, which is not salty. It also can mean water that people can drink. The oceans and seas are mad ...

                                               

Fritz Haber Institute of the MPG

The Fritz Haber Institute of the Max Planck Society is a science research group in Dahlem, Berlin, Germany. The original was called Kaiser Wilhelm Institute for Physical Chemistry and Electrochemistry, and it was founded in 1911. That became part ...

                                               

Fulgurite

Fulgurites are a rare type of natural glass made when lightning hits silica-rich minerals that are commonly in sand, soil, and some rocks. Tubular fulgurites are found in places with a lot of silica, like beaches or deserts. Lightning makes a tub ...

                                               

Fuse

A fuse is a device that shuts off the power to an electrical circuit when too much electric current flows through it. This usually happens when too many appliances are plugged in or when there is a short circuit. A fuse is made as an intentional ...

                                               

Fusion power

Nuclear fusion is when two atoms merge to form a new one. This reaction generates energy. The idea behind a fusion reactor is to build a nuclear power plant that uses this process to produce electricity. Nowadays, nuclear power plants use nuclear ...

                                               

Galactic plane

The galactic plane is the plane in which most of a disk-shaped galaxys mass lies. The directions perpendicular to the galactic plane point to the galactic poles. In actual use, the terms "galactic plane" and "galactic poles" usually refer specifi ...

                                               

Gamophobia

Gamophobia is the fear of getting married, being in a relationship, or commitment. The opposite of gamophobia is anuptaphobia-it is the fear of not being in a relationship. A person who has gamophobia may like or love a person, but when he or she ...

                                               

Garnet

A garnet is one kind of silicate mineral. There are many different kinds of garnets, containing different metals. Crystals of garnet are often large and pretty. Their most common color is red or purple, but they can be found in almost all colors ...

                                               

Gas giant

A gas giant is a large planet that has a solid core, but a very thick atmosphere. This means that most of the planet is made up of gas. These planets are very large. In our outer Solar System, there are four gas giants: Jupiter, Saturn, Uranus, a ...

                                               

Gauss (unit)

The gauss is the CGS unit used to measure magnetic fields. One gauss is defined as one maxwell per square centimeter. The tesla is the SI derived unit used to measure the strength of magnetic fields. There are 10.000 gauss in one tesla. The unit ...

                                               

Gelatin

Gelatin is a protein substance that comes from collagen. Collagen is a natural protein found in the tendons, ligaments, and tissues of mammals as well as fish. Gelatin has no smell, no taste, and is either colorless or light yellow. It can be fou ...

                                               

Gemini (constellation)

Gemini is one of the constellations of the zodiac. It was one of the 48 constellations described by the 2nd century AD astronomer Ptolemy. It is one of the 88 modern constellations today. Its name is Latin for "twins." It is from the twins Castor ...

                                               

Geosynchronous orbit

A geosynchronous orbit is an orbit at a height of 35.786 km above sea level on the Earth. At this height, the orbit takes 24 hours, so it is in sync with the land on Earth. The geostationary orbit is the most common type of geosynchronous orbit. ...

                                               

Gestalt therapy

Gestalt therapy is a form of psychotherapy. It is a way of treating people who feel ill at ease. It is based on the idea that it is best to experience what we feel "here and now" and not keep thinking about the past or worry about the future. The ...

                                               

GR 8 (galaxy)

GR 8, or UGC 8091, is a gas-rich dwarf galaxy. The NED database gives the distance between this galaxy and the Earth as about 7.9 million light years. Although near the Milky Way, it is not decided whether it is a member of the Local Group.

                                               

Grafting

Grafting or graftage is a technique used in horticulture that consists of taking tissues from one plant and putting them onto another plant. The two plants will then grow together. The technique is a type of vegetative reproduction. Grafting is c ...

                                               

Gram-positive

Gram-positive bacteria are those that are stained dark blue or violet by Gram staining. This is in contrast to gram-negative bacteria, which cannot hold the crystal violet stain. Instead they take up the counterstain and appear red or pink. The d ...

                                               

Grave (mass)

Grave was the word that was used to describe mass before the word kilogram was introduced. Grave comes from the word gravity and was first used in 1793 in France. The name kilogram was introduced in 1795 but was not the official word for mass unt ...

                                               

Green Climate Fund

The Green Climate Fund is an international fund for fighting climate change. It is part of the United Nations Framework Convention on Climate Change. It was proposed at the Cancun Conference in Mexico in 2010. It was accepted at the Durban Confer ...

                                               

Greenwich Mean Time

Greenwich Mean Time is an internationally standardized time format. It is the main time zone in several countries, including the United Kingdom and Portugal. GMT has the same time as UTC, but there are differences between the two. Technically, GM ...

                                               

Gregorian telescope

A Gregorian telescope was the first telescope to be designed that uses mirrors instead of lenses. It was invented by the English astronomer John Gregory. Even though it was designed in 1663, it wasnt the first reflecting telescope to be built. Ne ...

                                               

Greip (moon)

Greip or Saturn LI is a moon of Saturn. Its discovery was announced by Scott S. Sheppard, David C. Jewitt, Jan Kleyna, and Brian G. Marsden on June 26, 2006, from observations taken between January 5 and May 1, 2006. Greip is about 6 kilometres i ...

                                               

Gypsum

Gypsum is a common sulfate mineral made of calcium sulfate. Gypsum has been used as a building material for a long time, possibly since the neolithic. Today, it is an ingredient of plaster of paris. It can also be used as a fertilizer. It is soft ...

                                               

H I region

An HI region or H I region is a cloud in the interstellar medium composed of neutral atomic hydrogen. These regions do not emit detectable visible light except in spectral lines from metal elements. H I regions are clouds of neutral hydrogen whic ...

                                               

Haber process

The Haber process or the Haber-Bosch process is a chemical reaction that uses nitrogen gas and hydrogen gas to create the chemical compound ammonia. The Haber process uses temperatures ranging from 400°C to 450°C under a pressure of 200 atm. The ...

                                               

Habitat destruction

Habitat destruction is when a habitat is no longer able to support the plants, animals, or other organisms that live in it. When this happens, the organisms could die. Some might move to other places. Habitat loss can happen naturally. Wildfires ...

                                               

Habitat fragmentation

Habitat fragmentation happens when large habitats are divided into smaller ones, separating all the species that lived there and depended on each other.

                                               

Hard water

Hard water is water that has a high mineral content. The main components of these minerals usually are calcium Ca 2+ and magnesium Mg 2+ ions. But there are also dissolved metals, bicarbonates, and sulfates. Calcium usually enters the water as ei ...

                                               

Harpalyke (moon)

Harpalyke or Jupiter XXII, is a non-spherical moon of Jupiter. It was found by a team of astronomers from the University of Hawaii led by Scott S. Sheppard in 2000, and given the designation S/2000 J 5. In August 2003,the moon was named after Har ...

                                               

Hearing test

A hearing test is a check for a persons sense of hearing to measure what kind of sounds they can hear and if they have any hearing loss. There are many types of hearing tests used to understand different things about a persons hearing. Hearing te ...

                                               

Heat capacity

Heat capacity is a measure of how much materials can store up heat as they change temperature. Materials with high heat capacities require a lot of heat to be stored up before a small change. Materials with low heat capacities require very little ...

                                               

Hegemone (moon)

Hegemone or Jupiter XXXIX, is a moon of Jupiter. It was found by a team of astronomers from the University of Hawaii led by Scott S. Sheppard in 2003, and given the designation S/2003 J 8. Hegemone is about 3 kilometres in diameter, and orbits Ju ...

                                               

Helike (moon)

Helike or Jupiter XLV, is a moon of Jupiter. It was found by a team of astronomers from the University of Hawaii led by Scott S. Sheppard in 2003, and given the designation S/2003 J 6. Helike is about 4 kilometres in diameter, and orbits Jupiter ...

                                               

Henna

Henna, also known as mehandi or mendhi is a flowering plant. It has been used since ancient times to dye skin, hair, fingernails, leather, cotton, wool and other fabrics. The name is also used for the dye or color preparation derived from the pla ...

                                               

Herse (moon)

Herse is a moon of Jupiter. It was found by a team of astronomers led by Brett J. Gladman, et al. in 2003 and called S/2003 J 17 until 2009. Herse is about 2 kilometres in diameter, and orbits Jupiter at an average distance of 22.134.000 km in 67 ...

                                               

Highly sensitive person

A highly sensitive person is very easily affected by things. They are said to have a high sensitivity. According to some researchers, highly sensitive people are about one fifth of the population. They process sensory data much more deeply and th ...

                                               

HOMO/LUMO

HOMO stands for highest occupied molecular orbital. LUMO stands for lowest unoccupied molecular orbital. The energy difference between the HOMO and LUMO is termed the HOMO-LUMO gap. HOMO and LUMO are sometimes referred to as frontier orbitals. Ea ...

                                               

Horsepower

Horsepower is a unit of power that is approximately how much work one horse can do. It is equal to 746 watts. The idea of horsepower was originated by James Watt, who invented the steam engine. Because people used horses to pull carts, it was an ...

                                               

Hunger

Hunger is the feeling of wanting to eat. Ghrelin is a hormone that makes people feel hungry. The opposite of hunger is called satiety or fullness. Leptin causes this feeling. People can survive weeks without eating, but they will start to feel hu ...

                                               

Hydra (constellation)

Hydra is a constellation that has parts in the northern sky and parts in the southern sky. It is the biggest constellation. It represents a water snake. The astronomer named Ptolemy listed Hydra when he made a list of 48 constellations. It is als ...

                                               

Hydrosphere

The hydrosphere is the total mass of water on, under, and over the surface of a planet. It is part of physical geography. The oceans, rivers, and lakes are all part of the hydrosphere. Some electricity is made by the hydrosphere. The total mass o ...

                                               

Hyperossification

Hyperossification is when there is much more bone material on a bone than usual. Hyperossification is found in frogs. Many frogs have smooth skulls, but some frogs have skulls that only look smooth from the outside. Under their skins, their skull ...

                                               

Hypnagogia

Hypnagogia is the state of mind that exists between being awake and sleep, or just after waking up. People in this state may have experiences that resemble hallucinations, but are not. The person usually knows that it is not real, but very often ...

                                               

Hypodermic needle model

The hypodermic needle model is an early theory of mass communications. The theory stated that the mass media had direct influence over audiences by injecting their minds with information. According to this theory media messages are powerful force ...

                                               

Hypostatic model of personality

The hypostatic model of personality is a way of viewing the many sides of a persons character. The model says that a person can behave and appear to others in many ways, depending on how that person is, but also on how someone looks at that perso ...

                                               

Hyrrokkin (moon)

Hyrrokkin or Saturn XLIV is a moon of Saturn. Its discovery was announced by Scott S. Sheppard, David C. Jewitt, Jan Kleyna, and Brian G. Marsden on June 26, 2006, from observations taken between December 12, 2004, and April 30, 2006. Hyrrokkin i ...

                                               

Hysteria

Hysteria is when someone has a very strong emotion that is unmanageable. Often, this means a very strong sense of fear. When someone has hysteria, it is called "hysterics". Hysteria could be caused by traumatic events in a persons life. Today, ma ...

                                               

Iapetus (moon)

Iapetus is a large moon of Saturn. It was discovered by Giovanni Domenico Cassini in 1671. Iapetus is unusual: one side is very bright and the other side is very dark. This is because one half of the moon is covered in ice and the other side is c ...

                                               

Ice planet

An ice planet is a theoretical type of exoplanet where everything is frozen. None has been found so far, but astronomers think they do exist. They might have an icy surface of substances which are volatile on Earth, such as water, ammonia, and me ...

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