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Pictures 1–20
Portal:Science/Featured picture/6
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.
Portal:Science/Featured picture/10
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.
Portal:Science/Featured picture/11
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.
Portal:Science/Featured picture/12
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.
Portal:Science/Featured picture/14
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.
Portal:Science/Featured picture/17
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.
Portal:Science/Featured picture/19
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.
Portal:Science/Featured picture/20
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.
Pictures 21–40
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The science behind a V-2 rocket.