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Shared channels let tributaries use major waterways, reducing the frictional energy needed to move water downhill.
Natalie WolchoverWhy Are Rivers So Mathematical?
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Trees and rivers are different optimal networks: trees branch through three dimensions, while rivers branch across two-dimensional landscapes.
Natalie WolchoverWhy Are Rivers So Mathematical?
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Rivers emerge from chaotic Earth processes yet obey simple mathematical regularities found across geological settings.
Natalie WolchoverWhy Are Rivers So Mathematical?
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Hack-conforming rivers represent only one class in a broader family of optimal transport networks.
Natalie WolchoverWhy Are Rivers So Mathematical?
@science
At the ocean, river water abruptly slows, drops sediment, builds land, and splits into shifting distributary channels.
Natalie WolchoverWhy Are Rivers So Mathematical?
@science
River geometry pairs deterministic efficiency with the chaos and randomness expected from natural processes.
Natalie WolchoverWhy Are Rivers So Mathematical?
@science
As drainage basins grow, rivers become increasingly long and thin, stretching directionally toward the sea.
Natalie WolchoverWhy Are Rivers So Mathematical?
@science
River branches typically split at about 72 degrees, creating an apparent fivefold symmetry across branching networks.
Natalie WolchoverWhy Are Rivers So Mathematical?
@science
River networks can show fivefold symmetry even though fivefold repeating patterns cannot tile ordinary space.
Natalie WolchoverWhy Are Rivers So Mathematical?
@science
In river deltas, channel length scales with sediment-nourishment area to the same 0.6 power as tributary streams.
Natalie WolchoverWhy Are Rivers So Mathematical?
@science
Geometry predicts river length should scale as area’s 0.5 power, but real rivers follow 0.6.
Natalie WolchoverWhy Are Rivers So Mathematical?
@science
Tributaries carry sediment toward channels, deltas spread it away, yet both obey the same Hack-law mathematics.
Natalie WolchoverWhy Are Rivers So Mathematical?
@science
To change an object's orbit, change its speed. Gravity then carries it along a different path.
Kurzgesagt – In a NutshellWhat Happens if the Moon Crashes into Earth?
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When ports and coastal refineries become unusable, shipping stops and countries depend on existing stocks and rationing.
Kurzgesagt – In a NutshellWhat Happens if the Moon Crashes into Earth?
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Earth's surface gravity is about six times stronger than the Moon's, so a nearby Moon would not lift people.
Kurzgesagt – In a NutshellWhat Happens if the Moon Crashes into Earth?
@science
Tidal bores could reverse rivers, carrying salt water into surface and groundwater supplies.
Kurzgesagt – In a NutshellWhat Happens if the Moon Crashes into Earth?
@science
Volcanic aerosols and eclipses could plunge Earth into rapid cooling, acid rain, and summers with snow.
Kurzgesagt – In a NutshellWhat Happens if the Moon Crashes into Earth?
@science
After civilization collapses, survivors emerging from submarines, bunkers, or mountaintops would face rebuilding without guaranteed success.
Kurzgesagt – In a NutshellWhat Happens if the Moon Crashes into Earth?
@science
An orbit is continuous sideways falling: speed curves an object around Earth instead of letting it collide.
Kurzgesagt – In a NutshellWhat Happens if the Moon Crashes into Earth?
@science
As the Moon nears, its gravity warps satellite orbits until exhausted correction fuel leaves satellites uncontrollable.
Kurzgesagt – In a NutshellWhat Happens if the Moon Crashes into Earth?
@science
At roughly 75,000 kilometers from Earth, the Moon would illuminate the night sky like twilight.
Kurzgesagt – In a NutshellWhat Happens if the Moon Crashes into Earth?
@science
At geosynchronous altitude, the Moon would appear fixed above one location, completing its full phase cycle every 24 hours.
Kurzgesagt – In a NutshellWhat Happens if the Moon Crashes into Earth?
@science
After the Moon disintegrated, its rubble would form a massive ring system while lunar dust created meteor showers.
Kurzgesagt – In a NutshellWhat Happens if the Moon Crashes into Earth?
@science
Crossing roughly 10,000 kilometers from Earth would carry the Moon past the Roche limit and tear it into rubble.
Kurzgesagt – In a NutshellWhat Happens if the Moon Crashes into Earth?
@science
At the United States’ arable-land ratio, Australia could theoretically support more than 90 million people.
RealLifeLoreWhy 95% of Australia is Empty
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Nine of Australia’s ten hottest recorded years have happened since 2005.
RealLifeLoreWhy 95% of Australia is Empty
@science
A small river basin draining toward Lake Eyre is Northern Australia’s main soil exception, but irrigation water remains limited.
RealLifeLoreWhy 95% of Australia is Empty
@science
Australia’s weakest-flowing great river system still supplies drinking water to roughly 3 million people.
RealLifeLoreWhy 95% of Australia is Empty
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Australia’s rain and population cluster along the east coast, Tasmania, and Perth, with Northern Australia as the exception.
RealLifeLoreWhy 95% of Australia is Empty
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The 1850s gold rush brought immigrants equal to 2% of the British Isles’ population and more than doubled Australia’s population.
RealLifeLoreWhy 95% of Australia is Empty
@science
Rising seas flooded Sahul around 10,000 years ago, severing the land bridge between New Guinea and Australia.
RealLifeLoreWhy 95% of Australia is Empty
@science
The subtropical high-pressure belt warms and dries much of Australia’s air, making rainfall harder to form.
RealLifeLoreWhy 95% of Australia is Empty
@science
Fear of populous Asian nations, intensified by Japan’s 1942 bombing of Darwin, turned population growth into Australia’s security strategy.
RealLifeLoreWhy 95% of Australia is Empty
@science
In 1788, Australia’s Indigenous population was about 650,000, vastly smaller than every other inhabited continent’s population.
RealLifeLoreWhy 95% of Australia is Empty
@science
Without very tall mountains, Australia has fewer landforms that lift air high enough to cool and produce rain.
RealLifeLoreWhy 95% of Australia is Empty
@science
About 85% of Australians live within 50 kilometers of the coast, leaving Australia’s interior extremely sparsely inhabited.
RealLifeLoreWhy 95% of Australia is Empty
@science
Sydney, Melbourne, Brisbane, Perth, and Adelaide together hold nearly two-thirds of Australia’s entire population.
RealLifeLoreWhy 95% of Australia is Empty
@science
Privately owned Anna Creek is larger than Israel, yet about eight full-time employees manage roughly 10,000 cattle there.
RealLifeLoreWhy 95% of Australia is Empty
@science
South Australia’s Pastoral Unincorporated Area is roughly France’s size, with about 3,750 residents and 178 square kilometers per person.
RealLifeLoreWhy 95% of Australia is Empty
@science
Around 90% of Australians live in urban areas covering just 0.22% of the continent.
RealLifeLoreWhy 95% of Australia is Empty

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