Saturday, August 18, 2007
One of my more geeky readers passed this along:How To Catch a Lion in the Sahara Desert
Theoretical Physics Methods
The Dirac method: We assert that wild lions can ipso facto not be observed in the Sahara desert. Therefore, if there are any lions at all in the desert, they are tame. We leave catching a tame lion as an exercise to the reader.
The Schrödinger method: At every instant there is a non-zero probability of the lion being in the cage. Sit and wait.
The Quantum Measurement Method: We assume that the sex of the lion is ab initio indeterminate. The wave function for the lion is hence a superposition of the gender eigenstate for a lion and that for a lioness. We lay these eigenstates out flat on the ground and orthogonal to each other. Since the (male) lion has a distinctive mane, the measurement of sex can safely be made from a distance, using binoculars. The lion then collapses into one of the eigenstates, which is rolled up and placed inside the cage.
The nuclear physics method: Insert a tame lion into the cage and apply a Majorana exchange operator on it and a wild lion. As a variant let us assume that we would like to catch (for argument's sake) a male lion. We insert a tame female lion into the cage and apply the Heisenberg exchange operator, exchanging spins.
The Newton method: Cage and lion attract each other with the gravitation force. We neglect the friction. This way the lion will arrive sooner or later in the cage.
The Special relativistic method: One moves over the desert with light velocity. The relativistic length contraction makes the lion flat as paper. One takes it, rolls it up and puts a rubber band around the lion.
The general relativistic method: All over the desert we distribute lion bait containing large amounts of the companion star of Sirius. After enough of the bait has been eaten we send a beam of light through the desert. This will curl around the lion so it gets all confused and can be approached without danger.
The Heisenberg method: Position and velocity from a moving lion can not be measure at the same time. As moving lions have no physical meaningfull position in the desert, one can not catch them. The lion hunt can therefore be limited to resting lions. The catching of a resting, not moving lion is left as an exercise for the reader.
Experimental Physics Methods
The thermodynamics method: We construct a semi-permeable membrane which lets everything but lions pass through. This we drag across the desert. The atomic fission method We irradiate the desert with slow neutrons. The lion becomes radioactive and starts to disintegrate. Once the disintegration process is progressed far enough the lion will be unable to resist.
The magneto-optical method: We plant a large, lens-shaped field with cat mint (nepeta cataria) such that its axis is parallel to the direction of the horizontal component of the earth's magnetic field. We put the cage in one of the field's foci . Throughout the desert we distribute large amounts of magnetized spinach (spinacia oleracea) which has, as everybody knows, a high iron content. The spinach is eaten by vegetarian desert inhabitants which in turn are eaten by the lions. Afterwards the lions are oriented parallel to the earth's magnetic field and the resulting lion beam is focussed on the cage by the cat mint lens.
We're going to do something a little different this week – this time our puzzler is about history, not science or technology. Post your answer at right…
Three (out of five) people who answered got this right: what you see is the skydiver accelerating both downward and backwards.
I've met quite a few people who believe that a skydiver is in danger of hitting the elevator (the small, horizontal rear wing on a conventional airplane). They think the wind blast will blow the jumper back – nearly straight back. In fact, many skydivers have tried to touch the elevator and have failed – even when carrying a broomstick or other implement to extend their reach.
The physics here are actually pretty straightforward…
The downward acceleration is from gravity, of course – the jumper accelerates until the drag from his speed reaches equilibrium with the force of gravity. For most people, falling in the natural “frog” position, this occurs between 115 and 135 miles per hour. If the jumper falls head-down (a surprisingly difficult feat), this “terminal velocity” can be as high as 400 miles per hour!
The backwards acceleration (from the perspective of the observer in the airplane) is actually a deceleration – the jumper initially is traveling horizontally at the same speed as the airplane, but the drag of the wind decelerates him to zero horizontal speed, while the airplane is still moving forward at the same speed. Thus, from the observer's perch it appears that the jumper is moving ever faster, backwards.
