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Earth

Credit: Earth Sciences and Image Analysis Laboratory, NASA

View of the Earth as seen by the Apollo 17 crew traveling toward the Moon. This translunar coast photograph extends from the Mediterranean Sea area to the Antarctica south polar ice cap. This is toward the northeast. Earth, also known as Terra, and (mostly in the 19th century) Tellus, is the third-closest planet to the Sun. It is the largest of the Solar System's terrestrial planets and the only planetary body that modern science confirms as harboring life. Scientific evidence indicates that the planet formed around 4.57 billion years ago, and shortly thereafter (4.533 billion years ago) acquired its single natural satellite, the Moon.

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Hubble Space Telescope

Credit: NASA

The Hubble Space Telescope (HST) is a telescope in orbit around the Earth, named after astronomer Edwin Hubble for his discovery of galaxies outside the Milky Way and his creation of Hubble's law, which calculates the rate at which the universe is expanding. Its position outside the Earth's atmosphere allows it to take sharp optical images of very faint objects, and since its launch in 1990, it has become one of the most important instruments in the history of astronomy. It has been responsible for many ground-breaking observations and has helped astronomers achieve a better understanding of many fundamental problems in astrophysics. Hubble's Ultra-Deep Field is the deepest (most sensitive) astronomical optical image ever taken.

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Falkirk Wheel

Photo credit: SeanMack

The Falkirk Wheel is a rotating boat lift connecting the Forth and Clyde Canal with the Union Canal near Falkirk in central Scotland. It consists of two diametrically opposed caissons which rotate to transfer boats between the two canals through a height of 35 metres. Thanks to Archimedes' principle, the caissons always weigh the same, whether carrying up to 600 tonnes worth of canal barges, or just water. As such, the wheel is always perfectly balanced and despite its enormous mass, rotates through 180° in less than four minutes using just a few kilowatts.

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Moon

Credit: Apollo 11 Crew, NASA

The far side of the Moon as photographed by the crew of Apollo 11. The largest crater pictured is the Daedalus crater.

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Paramecium

Credit: Josh Grosse

Paramecium aurelia, the best known of all ciliates. The bubbles throughout the cell are vacuoles. The entire surface is covered in cilia, which are blurred by their rapid movement. Cilia are short, hair-like projections that help with locomotion.

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Astrolabe

Credit: Andrew Dunn

An 18th Century Persian astrolabe used for determining the time at both day and night. The points of the curved spikes on the front rete plate mark the positions of the brightest stars, the name of each star being labeled at the base of each spike. The back plate, or mater, is engraved with projected coordinate lines. From the Whipple Museum of the History of Science collection.

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Featured picture 7

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Gallium

Credit: Foobar

Gallium (IPA: /ˈgaliəm/) is a chemical element that has the symbol Ga and atomic number 31. A rare, soft silvery metallic poor metal, gallium is a brittle solid at low temperatures but liquefies slightly above room temperature and will melt in the hand. It occurs in trace amounts in bauxite and zinc ores. An important application is in the compound gallium arsenide, used as a semiconductor, most notably in light-emitting diodes (LEDs).

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DC plasma (violet) enhances the growth of carbon nanotubes in this laboratory-scale PECVD apparatus.

Chemical vapor deposition

Credit: Polyparadigm

Direct current-generated plasma (violet) enhances the growth of carbon nanotubes in this laboratory-scale PECVD apparatus. Plasma-enhanced chemical vapor deposition processes utilize plasma to enhance chemical reaction rates. PECVD processing allows deposition at lower temperatures, which is often critical in the manufacture of semiconductors. The red color in the picture is black-body radiation.

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Electrostatic discharge

Credit: Mircea Madau

Lightning is a powerful natural electrostatic discharge of lighted streaks produced during a thunderstorm. This abrupt electric discharge is accompanied by the emission of visible light and other forms of electromagnetic radiation. The electric current passing through the discharge channels rapidly heats and expands the air into plasma, producing acoustic shock waves (thunder) in the atmosphere.

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Plasma globe

Credit: Blaise Frazier

A plasma globe is usually a clear glass orb, filled with a mixture of various inert gases at low pressure, and driven by high frequency alternating current at high voltage (approx. 35 kHz, 2–5 kV,15.7 Krem), generated by a high voltage transformer. A much smaller orb in its center serves as an electrode. Beams or snakes of "light" (actually emergent patterns in ionized gas) extend from the inner electrode to the outer glass container, giving an appearance similar to multiple constant beams of coloured lightning. The beams first follow the electric field lines of the dipole, but move up due to convection.

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Rust

Credit: Roger McLassus

Rust is the chemical substance formed when iron compounds corrode in the presence of oxygen and water. It is a mixture of iron oxides and hydroxides. Rusting is a common term for corrosion, and usually corrosion of Iron. Iron is found naturally in the ore haematite as iron oxide, and metallic iron tends to return to a similar state when exposed to air, (hydrogen, oxygen, nitrogen, etc.) and water. This corrosion is due to the oxidation reaction when iron metal returns to an energetically favourable state. Energy is given off when rust forms. The process of rusting can be summarized as three basic stages: The formation of iron(II) ions from the metal; the formation of hydroxide ions; and their reaction together, with the addition of oxygen, to create rust.

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Sonoluminescence

Credit: Dake

Sonoluminescence is the emission of short bursts of light from imploding bubbles in a liquid when excited by sound. The effect was first discovered at the University of Cologne in 1934 as a result of work on sonar. H. Frenzel and H. Schultes put an ultrasound transducer in a tank of photographic developer fluid. They hoped to speed up the development process. Instead, they noticed tiny dots on the film after developing, and realized that the bubbles in the fluid were emitting light with the ultrasound turned on. It was too difficult to analyze the effect in early experiments because of the complex environment of a large number of short-lived bubbles. (This experiment is also ascribed to N. Marinesco and J.J. Trillat in 1933). Sonoluminescence may or may not occur whenever a sound wave of sufficient intensity induces a gaseous cavity within a liquid to quickly collapse. This cavity may take the form of a pre-existing bubble, or may be generated through a process known as cavitation. Sonoluminescence in the laboratory can be made to be stable, so that a single bubble will expand and collapse over and over again in a periodic fashion, emitting a burst of light each time it collapses.

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Saturn V

Credit: 4 Saturn V, s67-50531.jpg NASA

Saturn V was a multistage liquid-fuel expendable rocket used by NASA's Apollo and Skylab programs.

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Tesla coil

Credit: Fir0002

A Tesla coil is a category of disruptive discharge transformer coils, named after their inventor, Nikola Tesla. Tesla coils are composed of coupled resonant electric circuits. Nikola Tesla actually experimented with a large variety of coils and configurations, so it is difficult to describe a specific mode of construction that will meet the wants of those who ask about "Tesla" coils. "Early coils" and "later coils" vary in configuration and setup. Tesla coils in general are very popular devices among high-voltage enthusiasts.

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Featured picture 15

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Skull and craniometric measurement apparatus, from 1902.

Craniometry

Credit: Fawcett & Lee

Craniometry is the technique of measuring the bones of the skull. Craniometry was once intensively practiced in anthropology and ethnology. Human skulls can be classified into three main categories based on cephalic index: dolichocephalic: long and thin; brachycephalic: short and broad; mesocephalic: intermediate length and breadth.

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Featured picture 16

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Railgun

Credit: DrBob

A railgun is a form of gun that converts electrical energy—rather than the more conventional chemical energy from an explosive propellant—into projectile kinetic energy. It is not to be confused with a coilgun (Gauss gun). The term railgun is also used for conventional firearms used in the Unlimited class of benchrest shooting. A Railgun is a type of Magnetic Accelerator Gun (MAG) that utilizes an electromagnetic force to propel an electrically conductive projectile that is initially part of the current path. Sometimes they also use a movable armature connecting the rails. The current flowing through the rails sets up a magnetic field between them and through the projectile perpendicularly to the current in it. This results in the rails and the projectile pushing each other and in the acceleration of the projectile along the rails.

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Featured picture 17

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Deep Impact (space mission)

Credit: NASA

Deep Impact is a NASA space probe designed to study the composition of the interior of the comet Tempel 1. At 5:52 UTC on July 4, 2005, one section of the Deep Impact probe successfully impacted the comet's nucleus, excavating debris from the interior of the nucleus. Photographs of the impact showed the comet to be more dusty and less icy than expected. The impact generated a large, bright dust cloud that obscured the hoped-for view of the impact crater.

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Featured picture 18

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Milky Way

Credit: NASA

The Milky Way is a barred spiral galaxy of the Local Group. Although the Milky Way is but one of billions of galaxies in the universe, the Galaxy has special significance to humanity as it is the home of the Solar System. The term "milky" originates from the hazy band of white light appearing across the celestial sphere visible from Earth, which is composed of stars and other material lying within the galactic plane. The fact that the Milky Way divides the night sky into two roughly equal hemispheres indicates that the solar system lies close to the galactic plane.

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Featured picture 19

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Cloud pattern on Jupiter

Credit: NASA/JPL/University of Arizona

The cloud pattern on Jupiter is the visible system of colored cloud tops in the atmosphere of the planet Jupiter, remarkable for its stability. Astronomers have given names to parts of this pattern, using the word zone for the light stripes and belt for the dark stripes along various latitudes. The pattern and intensity of its belts and zones are famously variable, often changing markedly from one opposition to the next. The normal pattern of bands and zones is sometimes disrupted for a period of time, in events that astronomers call "disturbances". The longest-lived disturbance in recorded history was a "Southern Tropical Disturbance" (STropD) from 1901 until 1939, discovered by Percy B. Molesworth on February 28, 1901. It created a darkened feature over a range of longitudes in the normally bright Southern Tropical zone.

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Featured picture 20

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Wake turbulence

Credit: NASA Langley Research Center (NASA-LaRC)

Wake turbulence, also known as "jetwash", is turbulence that forms behind an aircraft as it passes through the air. This turbulence can be especially hazardous during the landing and take off phases of flight, where an aircraft's proximity to the ground makes a timely recovery from turbulence-induced problems unlikely. Wingtip vortices make up the primary and most dangerous component of wake turbulence, but normal wake effects are also an important part. A method of reducing wingtip vortices employs the use of winglets.

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Pictures 21–40

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Featured picture 21

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Laser

Credit: 彭家杰

A laser is a device that emits light through a process of optical amplification based on the stimulated emission of electromagnetic radiation. The term "laser" originated as an acronym for "light amplification by stimulated emission of radiation". The first laser was built in 1960 by Theodore H. Maiman at Hughes Laboratories, based on theoretical work by Charles Hard Townes and Arthur Leonard Schawlow.