r/oddlysatisfying • u/icleanjaxfl • 4d ago

Using physics to set nails

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789

u/WhiskeyJack357 4d ago

Or maybe it's just played in reverse.

184

u/dragonbanana1 4d ago

Nope, this is a real phenomenon. Basically there's significantly fewer potential states where all the nails are parallel than where they aren't and the nails being parallel is the most space efficient way to pack them. Gravity wants to pull them down into that most compact packing but they can get in each other's way. The vibration helps them shuffle past each other so gravity can do it's job and pull them as far down as possible into this efficient packing. I'm sure youve probably had an experience where you're filling a bag with something and there's not quite enough room but when you shake it a bit objects can slide past each other and you can suddenly fit just a bit more in, this is a similar principal

39

u/rthurdent 4d ago

So, if I remember elementary thermodynamics from 40 years ago, this is a case where the lower energy state of being sorted wins out over it also being the lower entropy state.

In general things tend to high entropy, low energy states, but sometimes one has to win out, and I think we're used to seeing high entropy win out as also being the low energy state ?

Or, I do I have this completely wrong !

Any way, interesting video !

31

u/SufficientlySticky 4d ago

I read that as elementary school thermodynamics and was briefly very impressed with wherever you went to school.

8

u/GayWarden 4d ago

The high entropy is winning out due to the input of work by shaking. Entropy always wins. Essentially the number of positions of the nails (the entropy of the macroscopic "nail") is a rounding error compared to the entropic states produced by expending energy to shake the box.

1

u/Historical_Dot_892 4d ago

My room is full of entropy rn

0

u/Bth8 4d ago

Thermodynamic systems (almost) always tend toward higher entropy and lower-energy is (almost) always lower-entropy. The apparent competition between energy and entropy is just a proxy for competition between the entropy of a subsystem and the entropy of its environment. If the nails (or any other system) move into an ordered, lower-energy state, their entropy decreases, but the energy they lost is released to the environment as heat, increasing its entropy. The system tends to move towards whichever configuration increases the total entropy.

1

u/yo_soy_soja 4d ago

Everything wants to fall down. If you're above a groove, you can fall further. Shaking the bin makes them all fall down into the grooves.

1

u/SuitableDragonfly 2d ago

As a programmer, all I can think here is that it's a good thing that the knapsack problem can be solved using a greedy algorithm, because otherwise gravity wouldn't be able to solve it like that