While gazing out his window most professorially, a chaos theorist once asked me, "Natalie: when you shake a bowl of mixed nuts, why do the Brazil nuts always rise to the top?"We hadn't been talking about nuts so I was slightly caught off guard. But that's the thing with chaos theory. "Um... hmm." (Silence.)
I seldom knew the answers to questions this physicist asked me, but it turned out that in matters of rising nuts my ignorance was somewhat forgivable. The so-called "Brazil nut effect" is a major unanswered question in many-body physics.
Among an assortment of objects (such as nuts), the larger ones tend to work their way upwards through the mix in spite of their greater gravitas. Most of us have probably noticed this phenomenon in our bowls of nuts or breakfast cereal, and yet, believe it or not, it totally confounds physicists.
Why should bigger nuts rise? The answer is probably - but not definitely - some combination of the following:
1) Small nuts can trickle down through the nooks and crannies of a pile while big ones cannot.
2) Because small nuts pack together more tightly than big ones, they can achieve higher densities. Gravity requires these to sit lower in a pile.
3) Convection currents exist in containers which push particles up through the center and pull them down the sides. Though Brazil nuts get pushed up by convection, there isn't enough wiggling room for them to be dragged back down around the edges.
No one can figure out to what extent each explanation plays a part, and so no very successful simulations can be made. It's a difficult problem but a surprisingly important one. Manufacturers of all kinds of inhomogeneous materials (mixed nuts included), as well as pharmacologists, geologists, astronomers, and many others would benefit from a solid understanding of the effect.
Aside from the applications it also just seems like something we ought to know about, and I think that's the main scientific appeal. Physicists aren't always contemplating the cosmos when they gaze thoughtfully out of windows. They're asking questions about everything... even their endearingly old-fashioned snacks.
Yay! That is awesome. Although I sometimes resent this effect because it makes it too easy for me to disproportionately consume my trail mixes.
ReplyDeleteAlso Tang and instant iced tea powder; and regular ground sugar and turbinado cane sugar mixes; both have color differences which make it easy to spot the different components. Shake and watch! I discovered the proof of the effect and wrote it in a margin of a book, but now I can't find the book; sorry!
ReplyDeletereminds me of the lost proof of fermat's last theorem:
ReplyDeleteI have discovered a truly marvelous proof that it is impossible to separate a cube into two cubes, or a fourth power into two fourth powers, or in general, any power higher than the second into two like powers. This margin is too narrow to contain it. - Fermat, in a margin
(Oh, to be a genius mathematician with ample under-sized margins and a wicked sense of humor...)
ReplyDeleteGreetings Facto,
ReplyDeleteYou are very objective and scientific in your exposition and delivery, and although I have not read all of your articles, I have read my fair share, and you bring great clarity with your writing. I am wondering that if in the near future you will venture to demystifying the intrigue of astrology as it's manifested itself in ancient civilization throughout the world, as well as perhaps in our contemporary society, and provide us with the facts of this seemingly pseudo-scientific '-ology' that many ascribe to as truth. Thank you for your informative and illuminating journal, and thank you in advance for your consideration - keep up the good work.
Respectfully Submitted,
S. Meadows
I think nobody likes the Brazil nuts, and keep putting them back in the can, on top. The next person comes along, digs around for the almonds, and puts the Brazil nuts back, again on top. That's my scientific theory. It's called the 'Theory of Refusal' and it also accounts for Brussel Sprouts on top of the marinated salad at the salad bar in Whole Foods.
ReplyDeleteAs a hater of Brazil nuts, I resent them for this. And there seems to be a never-ending supply worming their way to the top of my current box of muesli.
ReplyDeleteAwesome.
ReplyDeleteyou do say "um... hmm" and then silently ponder. Just like you wrote it. I had a strikingly clear image in my head of you doing it. I bet I could draw it better than that Savant Stephen.
ReplyDelete