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1.媒體來源:
Inside Science

2.完整新聞標題:

Sound Waves May Fall Up in Gravity Instead of Down

New findings suggest that ordinary sound has negative gravitational mass.

聲波在重力下可能會上升而不是落下  新發現表明:普通聲波具有負引力質量

3.完整新聞內文:

The sound of a sonic boom may produce about the same magnitude of
gravitational pull as a 10-milligram weight, a new study finds. Oddly, the
findings also suggest the pull is in the opposite direction of the
gravitational pull generated by normal matter, meaning sound waves might fall
up instead of down in Earth's gravitational field.
一項新的研究發現:音爆的聲音可能會產生與10毫克重量相同的拉力。研究結果還表明:
拉力與正常物質產生的引力相反，這意味著聲波可能會在地球引力場中上升而不是下降。


One might assume these findings are related to Einstein's famous equation
E=mc2, which revealed that anything with energy could be converted to an
equivalent amount of mass and vice versa. One consequence of this
relationship according to Einstein's theory of relativity is that matter
traveling near the speed of light will get heavier.


However, these new findings suggest that even in regular conditions that
ignore relativity, sound possesses gravitational mass.
然而這些新發現表明，即使在忽略相對論的常規條件下，聲音也具有引力質量。

Any sound waves on Earth would have extraordinarily weak gravitational
effects on their surroundings compared to the effect of the Earth itself,
which has a mass of about 6 trillion trillion kilograms. "It is a tiny, tiny
effect," said study lead author Angelo Esposito, a high-energy physicist at
the Swiss Federal Polytechnic School of Lausanne.


Still, the finding challenges long-held assumptions about how sound works.
儘管如此，這一發現仍然挑戰了關於聲音如何運作的長期假設。

"It's surprising in this day and age that it is still possible to find new
results in classical Newtonian physics," said particle physicist Ira
Rothstein at Carnegie Mellon University in Pittsburgh, who did not take part
in this study.
匹茲堡卡內基梅隆大學的粒子物理學家Ira Rothstein說：“令人驚訝的是在這個時代，
人們仍然可以在經典的牛頓物理學中找到新的結果。”

Sound waves are fluctuations of density within materials. In classical
physics, their energy can make matter move back and forth, but they were not
thought to possess mass.
聲波是材料內密度的波動。在經典物理學中，它們的能量可以使物質來回移動，但它們
並不被認為具有質量。

However, this view began to change when scientists investigated a very
slippery kind of fluid known as a superfluid, which flows with virtually zero
friction or viscosity. Liquid helium can act like a superfluid when cooled to
temperatures just a few degrees above absolute zero. In 2018, researchers
reported sound waves in superfluid helium might interact with gravity in ways
that require they possess mass.


Now, Esposito and his colleagues have found that sound waves traveling in
more familiar materials such as solids and fluids also may possess
gravitational mass, which means they respond to gravitational fields like
matter does. According to the researchers' equations, sound that carries one
watt of power for one second in air -- comparable to that from heavy thunder
-- will generate an equivalent of 10 milligrams of gravitational mass.

such mass is negative. All known matter has positive gravitational mass, and
such masses attract each other. However, positive gravitational mass repels
negative gravitational mass instead of attracting it.
這些發現不僅表明聲音具有引力質量，而且這種質量是負的。所有已知的物質都具有正
的 引力質量，並且這種質量相互吸引。

"It follows that if I generate a sound wave traveling, say, horizontally in a
standard material, this will tend to bend its path upward -- float -- under
the influence of the Earth's gravitational field," said Esposito. However,
since this work suggests that all sound waves have negative gravitational
mass, they should gravitationally attract each other, the researchers added.



The researchers suggest that experiments may soon be able to detect whether
this effect is real. For instance, the effect may be measureable in an exotic
form of supercooled matter called a Bose-Einstein condensate. They calculate
that a sound wave in a condensate of cesium atoms roughly 100 microns wide --
about the average diameter of a human hair -- might have a gravitational mass
of up to one-thousandth that of the condensate, potentially within the limits
of detection.


In addition, earthquakes generate sound waves in rock, and the scientists
estimated that a quake of magnitude 9 on the Richter scale would generate 100
million metric tons of gravitational mass. This would exert a force about 100
trillion times weaker than Earth's gravitational pull, which atomic clocks
and quantum gravimeters might be sensitive enough to detect in the near
future, they said.
此外，地震在岩石中產生聲波，芮氏9級的地震估計將產生1億公噸的引力質量。這將產
生 比地球引力弱100萬億倍的力，原子鐘和量子重力儀的敏感度在不久將來可能足夠量測
。

"It would be really interesting to see if these effects are measurable,"
Esposito said.
Esposito說：“看這些效應是否可以測量，真的很有意思。”

The scientists detailed their findings online March 1 in the journal Physical
Review Letters.
科學家在3月1日的“物理評論快報”上詳細介紹了他們的發現。
https://journals.aps.org/prl/abstract/10.1103/PhysRevLett.122.084501

4.完整新聞連結 (或短網址):
https://www.insidescience.org/news/sound-waves-may-fall-gravity-instead-down

5.備註:

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