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.
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.
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.
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.
An 18th Century
Persianastrolabe 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.
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).
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.
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.
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.
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.
Sonoluminescence is the emission of short bursts of
light from
implodingbubbles 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
ultrasoundtransducer in a tank of
photographicdeveloper 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.
A Tesla coil is a category of
disruptive dischargetransformer 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.
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.
A railgun is a form of
gun that converts electrical
energy—rather than the more conventional
chemical energy from an
explosivepropellant—into
projectilekinetic 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.
Deep Impact is a
NASAspace probe designed to study the composition of the interior of the
cometTempel 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.
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.
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.
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.
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.
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.
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.
An 18th Century
Persianastrolabe 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.
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).
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.
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.
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.
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.
Sonoluminescence is the emission of short bursts of
light from
implodingbubbles 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
ultrasoundtransducer in a tank of
photographicdeveloper 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.
A Tesla coil is a category of
disruptive dischargetransformer 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.
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.
A railgun is a form of
gun that converts electrical
energy—rather than the more conventional
chemical energy from an
explosivepropellant—into
projectilekinetic 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.
Deep Impact is a
NASAspace probe designed to study the composition of the interior of the
cometTempel 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.
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.
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.