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Readers weigh in on Brazil’s nut effect, clock entropy and more


How do you boot them?

X-ray tomography reveals that pushing a box of mixed nuts pushes the oblong Brazil nuts to aim more vertically, allowing the bulky nuts to rest on top while the small ones sink down. Maria Temming reported in “How Physics Helps Brazil Nuts Get Out of the Head” (SN: 05/05/21, p. 4).

Reader Charvak Kant I was asked if this phenomenon, called the Brazil nut effect, applies to objects of all shapes, including spheres whose orientations would not change.

The shape affects the nut effect of Brazil, but exactly as it is still unclear, says the scientist in the picture Parmesh Gajjar of the University of Manchester in England. It is very difficult to experimentally examine mixtures of objects, Gajjar says, but size strongly influences the way particles are segregated. Even spheres of different sizes in a mixture will separate. In fact, the first study that used the phrase “Brazil Nut Effect,” published in Physical Review Letters in 1987, was done on spherical objects, according to him.

Chaotic clocks

As a watch becomes more accurate, it creates more clutter, Emily Conover reported in “Rigorous Hour Creates Entropy” (SN: 05/05/21, p. 13).

Reader Steve Comins I was wondering why an accurate watch would emit more clutter than an inaccurate watch that dials too fast.

In short, consistency is key, Conover of. In the context of the story, an inaccurate clock refers to one whose ticks are unevenly spaced, she says. Some ticks can arrive faster and others slower than they should, so the time cannot be predicted. But a watch that dials constantly faster or slower than normal might still be accurate, as long as you find out how fast you’re ticking.

For example, a clock that constantly dials twice in a second could still accurately indicate the time; you would only have to count each tick as half a second. Such a fast clock would produce more entropy than a normal clock, but it would also be more accurate, according to the researchers ’results. Conover of.

Fluid definitions

A wave in one of Saturn's rings shows that the planet's core is extended and swollen with hydrogen and helium, Ken Croswell reported in “Saturn’s heart is fuzzy and diffuse” (SN: 5/5/21, p. 9).

Saturn's immense gravity squeezes most of the planet's hydrogen and helium, which exist as gases on Earth, into a fluid, Croswell reported. Reader Ken Koutz questioned the use of the term “fluid,” since gases are already considered fluids.

While a fluid can be a gas or a liquid, physicists often use the term to refer to supercritical states, in which different gaseous and liquid phases fade, story editor Chris Crockett of. “That’s exactly what is believed to happen at the bottom of giant planets like Saturn,” he says. "The fluid there is neither gas nor liquid, strictly speaking, but it still has fluid properties."

Putting the grip on the dead stars

The most massive neutron star known has a surprisingly large diameter, suggesting that matter inside it is less squeezable than expected, Emily Conover reported in “Neutron stars may not be as cool” (SN: 05/05/21, p. 8).

Reader Jim Barr wanted to know what “squeezable” means in the context of neutron stars.

This term refers to what a material compresses under pressure, Conover of. For example, if you squeeze a steel ball in your hand, it will not be significantly smaller. But if you do the same with a foam ball, it will. And the tighter the foam ball, the smaller it will get.

For neutron stars, the question is whether the nucleus becomes smaller when it is tightened by gravity. The more massive a star, the greater the gravitational pressure. So whether a more massive star is larger, smaller, or the same size as a less massive star depends on whether the core of the star is compressed or not.



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