Can you solve the honeybee riddle? - Dan Finkel
You’re a biologist on a mission
to keep the rare honeybee
Apis Trifecta from going extinct.
The last 60 bees of the species
are in your terrarium.
You’ve already constructed wire frames
of the appropriate size and shape.
Now you need to turn
them into working beehives
by helping the bees fill
every hex with wax.
There are two ways to fill a given hex.
The first is to place a bee into it.
Once placed, a bee cannot
be removed without killing it.
The second:
if at any point an unfilled hex has three
or more neighboring wax-filled hexes,
the bees already in the hive
will move in and transform it.
Once the bees have transformed
every hex in a hive,
you can place an additional bee inside
and it’ll specialize into a queen.
The hive, if well cared for,
will eventually produce new bees
and continue the species.
If there are no hexes with three or more
transformed neighbors,
the bees will just sit and wait.
And once a bee transforms a hex,
it can never become a queen.
You could put 59 bees in one wire hive,
wait till they transform all the hexes,
and then create a queen.
But then just one collapse
would end the species.
The more viable hives
you can make now, the better.
So how many can you make with 60 bees?
Pause the video to figure
it out yourself
Answer in 3
Answer in 2
Answer in 1
Answer in 0
What you're looking for here is some
kind of self-sustaining chain reaction,
where a small number of bees
will transform an entire hive.
The lower the number of bees needed,
the better.
So how low can we go,
and how can we engineer a chain reaction?
Let’s start with the first question.
There's a really clever approach to this,
which involves counting the sides
of the filled-in hexes,
and examining their total perimeter.
Let’s suppose we put bees
in these three hexes.
The total transformed
perimeter has 18 sides.
But the middle hex
has three transformed neighbors,
so the bees will transform it too.
What happens to the perimeter?
It’s still 18!
And even after the bees transform the next
sets of hexes with three neighbors,
it still won’t change.
What’s going on here?
Each hex that has at least three sides
touching the bee-friendly space
will remove those sides from the perimeter
when it transforms.
Then it adds at most three new sides
to the perimeter.
So the perimeter of the transformed hexes
will either stay the same or shrink.
The final perimeter
of the entire hive is 54,
so the total perimeter of the hexes
we place bees in at the start
must be at least 54 as well.
Dividing that 54 by the six sides
on each non-adjacent hex
tells us it’ll take at least 9 bees
to transform the entire hive.
That’s a great start,
but we still have the tough question
of where the nine bees should go,
and if we’ll need more.
Let’s think smaller.
We already know that three bees could
completely transform a hive this big.
What about a slightly bigger one?
The perimeter of this hive is 30,
which means we’ll need
at least 5 bees to fill it in.
With 6 it’d be easy.
Placing them like this would fill out
the whole hive in just three steps.
But we can do better! We don’t actually need to place a bee on this hex, since the other bees will transform that spot on their own.
It looks like we have the beginning of a pattern. Can we extend it to our full hive? That would mean placing our 9 bees like so. Once they get to work, they’ll create a chain reaction that fills in the center of the hive and extend it to its edges.
Add a 10th bee to the completed hive and it becomes a queen. Repeat that process five more times and you’ve helped the last 60 members of Apis trifecta create 6 producing hives. All in all, it’s a pretty good bee-ginning.
But we can do better! We don’t actually need to place a bee on this hex, since the other bees will transform that spot on their own.
It looks like we have the beginning of a pattern. Can we extend it to our full hive? That would mean placing our 9 bees like so. Once they get to work, they’ll create a chain reaction that fills in the center of the hive and extend it to its edges.
Add a 10th bee to the completed hive and it becomes a queen. Repeat that process five more times and you’ve helped the last 60 members of Apis trifecta create 6 producing hives. All in all, it’s a pretty good bee-ginning.
