The way 'shaking' a packet of nuts brings the big ones up

You’d think the heavy Brazil nuts would sink to the bottom, but the big lads always end up at the top, lording it over the crumbs.

When you shake the packet, you create tiny gaps. The small bits—the peanuts and salt—are like nimble fans at a gig; they slip into those spaces the second they appear.

Since the little ones fill every hole underneath, the big nuts get nudged higher. They’re essentially being crowd-surfed to the top by a sea of smaller snacks.

Wait, why don't the big lads ever slip down into the gaps first?

It’s simple geometry, mate. The gaps you open by shaking are tiny—just big enough for a grain of salt or a peanut fragment to tumble into.

Think of a packed tube station. A toddler can weave through the crowd to find a gap, but a bloke carrying a double bass isn't going anywhere.

The big nut is too chunky for the holes. It stays stuck while the small stuff steals its floor space, leaving it stranded at the top with nowhere to go but up.

Shouldn't gravity win though, since the big ones are way heavier?

You’d think so, right? Gravity is pulling on everyone, but it’s a bit of a rigged game. When you shake the tin, you’re giving everything a bit of 'lift'—basically a momentary holiday from gravity.

In that split second of airtime, the little bits move faster. They’re like cheeky kids darting for a seat on the bus while the old man is still finding his balance.

By the time gravity pulls everything back down, the floor is already gone. The big nut hasn't 'floated'; it’s just been evicted from the bottom by a thousand tiny squatters.

Does the direction of the shake actually matter then?

Spot on. Vertical movement is the secret sauce. You need that upward 'pop' to create the gaps for the small bits to dive into.

If you just wiggle the tin side-to-side like you’re indecisive at the bar, the nuts just shuffle around on the same level. They’re basically just rubbing shoulders without anyone actually moving house.

Without that little bit of 'jump' from an up-and-down shake, the small bits can't get under the big lads' feet. No lift, no eviction, no Brazil nut at the top.

So if the bag is stuffed tight, does the magic stop?

Bang on. If you've got zero headroom, the whole party is cancelled. It’s like being stuck in a rush-hour tube carriage where you’re so packed in you can’t even reach for your phone.

Without that bit of empty space at the top, the nuts can't do their gravity-defying hop. If they can’t jump, those gaps never open, and the small bits stay trapped exactly where they started.

That's why cereal boxes look half-empty. They need 'shakedown' space so the contents can settle during the bumpy lorry ride without turning the whole lot into a solid brick.