Reference Terms
from Wikipedia, the free encyclopedia
Altitude
Altitude is the elevation of an object from a known level or datum. Common datums are mean sea level and the surface of the WGS-84 geoid, used by GPS. In the United States and the UK aviation altitude is usually measured in feet. Everywhere else in the world the altitude is measured in metres.
Atmospheric pressure decreases as altitude increases. This principle is the basis of operation of the pressure altimeter, which is an aneroid barometer calibrated to indicate altitude instead of pressure. It is the fall in pressure that leads to a shortage of oxygen (hypoxia) in humans on ascent to high altitude.
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Earth & Climate News
July 22, 2026
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July 21, 2026 China’s Chang’e-6 samples have uncovered a surprising difference between the Moon’s two hemispheres. Solar wind particles penetrated deeper into the far-side soil because Earth’s ...
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July 18, 2026 Scientists have found evidence that a major Cascadia earthquake could trigger a second quake on the San Andreas Fault. The discovery came from unusual sediment layers formed by underwater landslides ...
July 18, 2026 A catastrophic asteroid breakup may have triggered a huge wave of impacts across the inner solar system about 800 million years ago. The debris was launched from near a gravitational gateway controlled by Jupiter, sending fragments toward Earth, the ...
July 18, 2026 Seismic waves have revealed that the oceanic plate beneath the Ontong Java Plateau was dramatically transformed by the colossal volcanic activity that created it more than 100 million years ago. Researchers found a complex structure of horizontal ...
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July 17, 2026 A major DNA study has rewritten the koala's evolutionary story, revealing that the species suffered a dramatic population collapse about 100,000 years ago, long before humans arrived in Australia. By calculating the koala's mutation rate for the ...
July 16, 2026 Researchers have created self-destructing living plastic that uses engineered bacteria to completely break itself down when activated. The material degrades in just six days without creating ...
July 16, 2026 Scientists have identified a hidden feedback loop that may explain how Earth has regulated its climate for tens of millions of years. As sea levels rose and fell, they changed how much phosphate reached the open ocean, affecting marine life and the ...
Latest Headlines
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July 15, 2026 NASA's PACE satellite captured the Black Sea glowing turquoise during its annual phytoplankton bloom. The vivid color comes from massive numbers of coccolithophores, microscopic organisms whose ...
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July 12, 2026 Scientists discovered that extreme deep-sea pressure squeezes valuable nutrients out of sinking organic particles, providing an unexpected food source for ocean microbes. The finding could rewrite ...
July 12, 2026 Why do beaches today have seashells from clams and snails instead of brachiopods? A new study suggests the answer lies in Earth's greatest mass extinction, when warming oceans and falling oxygen ...
July 11, 2026 Two striking Asian praying mantis species that have rapidly spread across Europe have now been officially classified as invasive, raising new concerns about their impact on native wildlife. Boosted ...
July 10, 2026 A newly discovered underwater volcanic eruption north of Papua New Guinea is unfolding in one of the world's most poorly mapped ocean basins. Satellites have spotted steam plumes, ash, thermal ...
July 10, 2026 A next-generation pesticide designed to kill crop pests may also be interfering with the reproductive health of bumblebees. Researchers discovered that low-dose exposure to sulfoxaflor changed gene ...
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