THE MATH behind NUMB3RS
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Episode 301: Spree--Explore the Math
Original Math Notes
Episode 301: Spree
Interactive Computations
Use the free Wolfram Mathematica Player to interact with the math behind NUMB3RS.
Scene 7:
POV -- CHARLIE, sandwiched between TWO BEDS OF NAILS -- a
SLAB OF CONCRETE on top of the upper bed.

LARRY, protective glasses on, has a sledgehammer over his
head, about to smash the concrete slab.

                 DON (CONT'D)
          Okay....
          
                 CHARLIE       
          This isn't what it looks like.
          
                 EDGERTON
          That's a relief... since it looks
          like your friend there is about to
          perforate you.
          
                 LARRY
          Actually, Professor Eppes is
          protected by the most impenetrable
          armor of all -- physics.
          
                 CHARLIE       
          My weight is distributed among the
          spikes at a very comfortable 1.7
          pounds each, with the kinetic
          energy of the hammer --
          
                 LARRY
          -- I believe, Charles, that the
          drama of demonstration will be more
          instructive.
          
                 CHARLIE       
          Right...
          
Larry brings down the sledgehammer...

                 DON
          Whoa! Larry --
          
... SHATTERING the concrete. Charlie is still for a beat.

                 DON (CONT'D)
          Charlie -- ?
          
Charlie grins -- enjoying the rush.

                 CHARLIE       
          Fine... I'm fine.
          
They remove the concrete, and help Charlie off the spikes.

Bed of Nails

Bed of Nails
A bed of nails can actually be comfortable, if there are enough nails. A person's weight is divided by the number of nails under them. Here, Mr. Slab weighs 200 pounds, so the default bed is actually extremely painful.
Scene 9:
ENTER CHARLIE VISION --
The map becoming a scattered, fragmented pastiche of images
that will explain themselves later on:
-- a BIPLANE flying through the air
-- a MOUSE scampering across a field
-- a CURVING GRAPH LINE

                 CHARLIE       
          Didn't you forget to mark one --
             (points to a spot in Wyoming)
          -- here?
          
Edgerton looks at the map, double checks the reports --

                 EDGERTON
          No... we don't have sightings
          anywhere in Wyoming.
          
Charlie is a little surprised --

                 CHARLIE       
          Oh... okay...
          
                 DON
          Why'd you think there was?
          
                 CHARLIE       
          Actually --
             (beat)
          -- I looked at the map and... just
          thought there should be a point
          there.
          
Larry looks at the map.

                 LARRY
          Did you see some sort of pattern,
          perhaps a Markovian path --

Finite State Discrete Time Markov Chains

Finite State Discrete Time Markov Chains
Consider a system that is always in one of n states, numbered 1 through n. Every time a clock ticks, the system updates itself according to an n×n matrix of transition probabilities, the (i,j)th entry of which gives the probability that the system moves from state i to state j at any clock tick. A Markov chain is a system like this, in which the next state depends only on the current state and not on previous states.
Scene 17:
ALAN and LARRY playing chess.

                 LARRY
          Relocation is considered a highstress
          event, but in my experience
          it's been nothing less than
          exhilarating.
             (beat)
          When I sold my house... it was a
          Promethean shrug, the chains of
          earthly concerns falling from my
          shoulders.

Explaining Real Estate Price Bubbles

Explaining Real Estate Price Bubbles
Bubbles form in investment real estate, leading to the questions: Where is the top? When will prices no longer rise? An answer to both of these questions is: when the money runs out. In real estate investment there are two sources of funds: the buyer's investment (down payment) and the lender's capital (the loan amount). The lender operates as a sort of governor, investing less as prices rise, thereby refusing to finance the speculative part of the bubble (that part unsupported by commensurate increases in net rent).
Scene 27:
     
                 CHARLIE       
          This is the Green River robbery.
          The missing point on a curve I
          didn't realize I was looking at.
             (beat)
          It's a complex variation of
          something called a pursuit curve...
          created when one point chases
          another across a graph. You see...
          
BACK TO AUDIENCE VISION --
of our WWI dogfight --

                 CHARLIE (CONT'D)
          -- if a fighter pilot flies
          straight at the point where he sees
          an enemy plane --
          
-- the biplane turns, but the the Red Baron flies straight --
seeing nothing but empty air --

                 CHARLIE (CONT'D)
          -- by the time he gets there, the
          plane will be gone.
          
-- turning and finding the biplane again -- this time
matching its maneuvers, banking when the biplane banks,
dipping when the biplane dips --

                 CHARLIE (CONT'D)
          Just to maintain his following
          distance, the chasing pilot has to
          constantly adjust his direction --
          matching the movements of his
          quarry.

-- then, when the biplane turns -- the Red Baron turns deeper
-- cutting into its path --

                 CHARLIE (CONT'D)
          If he wants to catch the plane, he
          has to anticipate its movement --
          aim his nose ahead of the lead
          plane --
          
-- and firing its machine gun, which hits the biplane
broadside; it goes down in a plume of smoke...

BACK TO SCENE
                 CHARLIE (CONT'D)
          (to Edgerton)
          You've been locked in a pursuit
          curve with the killers; constantly
          adjusting and readjusting your
          search pattern to anticipate their
          movement.

Pursuit Curves

Pursuit Curves
Given a moving prey (black path) with unit speed and a time-dependent position (x(t), y(t)), a predator (colored path), moving with speed v, runs at all times in the direction of the current position of the prey. The resulting path is known as a pusuit curve.
 
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