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Readers ask about buoyancy, Stonehenge sounds, and more


Shake the boat

Scientists caused a toy boat to float upside down at the bottom of a layer of levitating liquid, Maria Temming reported in “Toy Boats Challenge Gravity Floating Upside Down” (SN: 26/09/20, p. 32).

“I was pretty intrigued by the boat upside down. The explanation of buoyancy versus gravity suggests a balance for the boat upside down, but it seems to be unstable in theory, "reader David Edmonston he wrote. "If the boat upside down were pushed up slightly, then its buoyancy should increase, causing the boat to climb to the top of the liquid layer." Edmonston he wrote. "If it were pushed down, then its buoyancy should decrease, allowing it to fall below the bottom of the levitated liquid. That would be an unstable equilibrium, like being a pencil at its point. Is there anything else in the explanation? Is there surface tension involved? Ascending force since levitation? ”He asked.

The ship exists in an unstable balance, Temming of. “Shaking the container holding the boat and the liquid helps the boat upside down to maintain a stable position at the bottom of the liquid layer,” he says. "Because the ship is also constantly shaking up and down, its own vertical vibrations nullify any external firing that would knock the boat down from its float. Massive boats require stronger agitation to withstand the collapse to the bottom of the vessel. or to the top of the liquid layer ".

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Spooky sound effects

A scale model of Stonehenge revealed that the entire structure would have amplified the speech and improved the musical sounds for the people inside. Bruce Bower reported in “Stonehenge improved the sounds inside” (SN: 26/09/20, p. 14).

“I always found Stonehenge very interesting. It is in the middle of the fields, but a busy road passes it for about a mile or so … It has a strange thrill to see it come out of the fog while driving, "reader Michelle Reeve he wrote. "Another strange acoustic effect is that even though the road is visible from the monument … strangely you can't hear the traffic. The sound usually goes well on open ground." Reeve he wrote. “It gives the impression of a ghostly path of another dimension. A spooky effect! ”

Energy matters

Space-time waves revealed that two black holes merged to form the first definitive example of a medium-sized black hole. Emily Conover reported in “Medium Black Holes Really Exist” (SN: 26/09/20, p. 7).

The energy value of eight solar masses was carried by gravitational waves during fusion. Reader Jonathan Lis I wondered if matter became that energy.

Matter particles are not being converted into energy in this case, Conover of. Instead, other forms of energy are transformed into gravitational wave energy. “Orbiting black holes have kinetic energy and potential. It’s that energy that becomes gravitational waves, ”she says. Because energy and mass are equivalent in general relativity, that means the total mass of the system decreases when black holes melt.

Life story

Bacteria groups exposed to the harsh conditions of outer space could withstand a journey between Earth and Mars, Jonathan Lambert reported in “Bacteria can survive for years in space” (SN: 26/09/20, p. 10).

Reader Daniel Jameson I wondered if such floating groups of microbes could sow life on early Earth.

That idea is one of many theories about how life on Earth began, Lambert of. Although there is no direct evidence that life descended from microbes from another world, amino acids and sugars have been found in outer space and inside Earth's meteorites. This suggests that space rocks could deliver these and other ingredients necessary for life to the planet. Another theory is that the early Earth formed the ingredients and eventually life, on its own (SN: 26/09/20, p. 22).


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