Why Figure Skaters Make All Their Moves

Figure Skater
Next time you watch figure skating, observe closely this and similar patterns

Tonight I was watching part of the 20.16 US Figure Skating Championship on NBC (an American television network, for foreign readers of this blog).  Ever wonder why a figure skater can do what s/he does, particularly concerning when the skater crosses his/her arms and thereupon spins at a much faster speed?  Sometimes more elaborate moves can cause similar effects.

Some basic physics principles will do here.  First, I shall discuss friction.  Friction keeps things still when they are juxtaposed against one another.  There is a little bit of friction involved with contact of the skates on icy surfaces, which helps allow for quick motion (as inertia keeps things moving unless a force opposes it, in this case, friction applied to stop the skater).  Ice provides just enough friction for starting and stopping the skater, but otherwise it is smooth.

At the very core of figure skating, however, is angular momentum, or the momentum of rotation.  Momentum, when in a straight line, is simply mass times velocity.  In situations of rotation, however, it is the angular velocity (speed of rotation) times the “moment of inertia.”  Without going into details, the latter quantity takes into account shapes of different objects.  Since momentum, by its very nature, must be conserved, a change in the distribution of mass (and hence the moment of inertia) into a more condensed form will cause an acceleration of the skater when s/he spins!

Finally, Newton’s ever-famous third law (i.e., that of equal and opposite reaction) allows the skater to glide forward (or even leap up!), as the force directs down and back.  The exact backward force determines the exact forward force, depending on the details of each.

Like classical music, classical mechanics can sure be beautiful!

Source:  http://www.livescience.com/6120-physics-figure-skating.html

Why Owls Can Turn their Heads Toward their Backs

Owls, aside from their folklore-based wisdom, bear one capacity that we humans can only dream of:  viewing what’s behind them without turning around.  Their heads can turn 270° from the frontal position, which is really just 90° in the opposite direction.

However, what really warrants this need is 1) their very large, almost motionless eyes, and 2) the arterial organization toward the brain.

In owls, the vertebrae give ample space in certain arteries, which in humans are confined to small spaces.  Also, the carotid artery, a “confined” artery, happens to be at the central axis of rotation.  And like humans, predatory birds, and animal able to hunt, their vision is binocular and thus with good depth perception.

These details and more, can be seen in the attached YouTube video below, courtesy of the principal source (at the bottom of the page, which you can also visit.  By the way, this observation was not primarily studied by ornithologists, but by medical doctors who specialize in vascular issues.  Their insight is highly appreciated.

 

With the eyeful they receive on a daily basis, no wonder they’re considered so “wise.”

Source:  people.eku.edu/ritchisong/birdbrain2.htm