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  • One foggy morning in 1884,

  • the British steamer "Rumney" crashed into the French ship "Frigorifique."

  • Seeing their ship filling with water,

  • the French crew climbed aboard the "Rumney."

  • But as they sailed towards the nearest port,

  • a silent form suddenly emerged from the fog:

  • the abandoned "Frigorifique."

  • It was too late to turn,

  • and the impact was enough to sink the "Rumney."

  • As the sailors scrambled into the lifeboats,

  • the empty "Frigorifique" sailed back into the fog,

  • having seemingly taken its revenge.

  • In reality, the French sailors had left the engines running,

  • and the "Frigorifique" sailed in a circle

  • before striking the "Rumney" and finally sinking.

  • But its story became one of the many tales of ghost ships,

  • unmanned vessels that apparently sail themselves.

  • And although they've influenced works like "Dracula"

  • and "Pirates of the Caribbean,"

  • crewless ships aren't the product of ghostly spirits,

  • just physics at work.

  • One of the most famous ghost ships was the "Mary Celeste",

  • found sailing the Atlantic in 1872 with no one aboard,

  • water in its hold,

  • and lifeboats missing.

  • The discovery of its intact cargo and a captain's log that ended abruptly

  • led to wild rumors and speculation.

  • But the real culprits were two scientific phenomena:

  • buoyancy

  • and fluid dynamics.

  • Here's how buoyancy works.

  • An object placed in a liquid displaces a certain volume of fluid.

  • The liquid in turn exerts an upward buoyant force

  • equal to the weight of the fluid that's been displaced.

  • This phenomenon is called Archimedes's Principle.

  • Objects that are less dense than water,

  • such as balsa wood,

  • icebergs,

  • and inflatable rafts always float.

  • That's because the upward buoyant force

  • is always stronger than the downward force of gravity.

  • But for objects or ships to float when they're made of materials, like steel,

  • that are denser than water,

  • they must displace a volume of water larger than their weight.

  • Normally, the water filling a ship's hull would increase its weight and cause it to sink -

  • just what the "Mary Celeste's" crew feared when they abandoned ship.

  • But the sailors didn't account for fluid dynamics.

  • The water stopped flowing at the point of equilibrium,

  • when it reached the same level as the hole.

  • As it turned out, the weight of the water wasn't enough to sink the ship

  • and the "Mary Celeste" was found a few days later

  • while the unfortunate crew never made it to shore.

  • Far stranger is the tale of "A. Ernest Mills,"

  • a schooner transporting salt,

  • whose crew watched it sink to the sea floor following a collision.

  • Yet four days later, it was spotted floating on the surface.

  • The key to the mystery lay in the ship's heavy cargo of salt.

  • The added weight of the water in the hull made the vessel sink,

  • but as the salt dissolved in the water,

  • the weight decreased enough

  • that the force of gravity became less than the buoyant force

  • and the ship floated back to the surface.

  • But how do we explain the most enduring aspect of ghost ship legends:

  • multiple sightings of the same ships hundreds of miles and several years apart?

  • The answer lies in ocean currents,

  • which are like invisible rivers flowing through the ocean.

  • Factors, like temperature,

  • salinity,

  • wind,

  • gravity,

  • and the Coriolis effect from the Earth's rotation

  • create a complex system of water movement.

  • That applies both at the ocean's surface and deep below.

  • Sailors have always known about currents,

  • but their patterns weren't well known until recently.

  • In fact, tracking abandoned ships was how scientists determined the shape

  • and speed of the Atlantic Gyre,

  • the Gulf Stream,

  • and related currents in the first place.

  • Beginning in 1883, the U.S. Hydrographic Office

  • began collecting monthly data that included navigation hazards,

  • like derelict ships, whose locations were reported by passing vessels.

  • So abandoned ships may not be moved by ghost crews or supernatural curses,

  • but they are a real and fascinating phenomenon

  • born through the ocean

  • and kept afloat by powerful, invisible, scientifically studied forces.

One foggy morning in 1884,

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B1 TED-Ed water sink ghost buoyant force celeste

【TED-Ed】Are ghost ships real? - Peter B. Campbell

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    Jenny posted on 2017/03/05
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