My mom and I always say that my gyroscope was born broken as if it was some kind of internal geographical positioning device. Call it a GPS or my navigation habilities if you will. Truth is I don't seem to have this talent - though sometimes I surprise myself knowing directions quite well -, and worse, this is not the true use or definition of a gyroscope!
      Like I said yesterday, the name "Gyroscope" is credited to Foucault, although he wasn't the one who invented it.
   The gyroscope itself is a device used for measuring and/or mantaining orientation, based on the principles of angular momentum. Its mechanics are like so: it is a spinning wheel or disc with a free axle that can assume any orientation. That orientation may not stay fixed, but it changes less and in a different direction in response to an external torque than it would do without the large angular momentum associated with the disc's high rate of spin and moment of inertia. So, the orientation of the device remais nearly fixed, regardless of the motion of the mounting platform.
     It can be used inn inertial navigation systems where magnetic compasses would not work (such as the Hubble telescope) or would not be precise enough, or for the stabilization of flying vehicles like radio-controlled helicopters or unmanned aerial vehicles. Due to their precision, gyroscopes are also used in gyrotheodolites to maintain direction in tunnel mining.
     Based on those descriptions, then, I guess my "inner gyroscope" is practically absent.

~Ally

     Blame Google's Doodle for today's post!
     I'm not a huge fan of physics, but Foucault's name is vaguely familiar to me. So, when I saw his pendulum doodle, I felt the sudden urge to know more about him (perhaps again!).
     He was a French physicist made famous for his demonstration of the "Foucault pendulum", a device that can demonstrate the effect of Earth's rotation. He is also credited for making an early measurement of the speed of light, discovering eddy currents, and naming the gyroscope (although he did not invent it). Before turning to physics, though, he studied medicine, but dropped out because of blood phobia. After that, he worked on improving Daguerre's photographic processes.
     His pendulum is considered a simple device that allows a demonstration of Earth's rotation. Back in those days, people already knew about this phenomena, but they had not proved it with an easy-to-see experiment.
     The first exhibition of a "Foucault pendulum" took place in 1851 in the Meridian of the Paris Observatory. A few weeks later Foucault made his most famous pendulum when he suspended a 28 kg brass-coated lead bob with a 67 metre long wire from the dome of the Panthéon, also in Paris. The plane of the pendulum's swing rotated clockwise 11° per hour, making a full circle in 32.7 hours.
     The basic experimental apparatus consists of a tall pendulum free to swing in any vertical plane. The actual plane of swing appears to rotate relative to the Earth. The wire needs to be as long as possible (lengths of 12-30m are common). At either the North Pole or South Pole, the plane of oscillation of a pendulum remains fixed relative to the distant masses of the Universe while Earth rotates underneath it, taking one sidereal day to complete a rotation. So, relative to Earth, the plane of oscillation of a pendulum at the North Pole undergoes a full clockwise rotation during one day; a pendulum at the South Pole rotates counterclockwise.
      A "Foucault pendulum" requires care to set up because imprecise construction can cause additional veering which masks the desired terrestrial effect. The initial launch of the pendulum is critical and, traditionally, it is used a flame to burn through a thread which temporarily holds the bob in its starting position, thus avoiding unwanted sideways motion. Air resistance damps the oscillation, so some pendulums in museums incorporate an electromagnetic to keep the bob swinging; others are restarted regularly, sometimes with a launching ceremony as an added attraction.
    A "pendulum day" is the time needed for the plane of a freely suspended "Foucault pendulum" to complete an apparent rotation about the local vertical. This is one sidereal day divided by the sine of the latitude.

~Ally

      Next time you get dizzy and fall on your butt, blame it on your ears!
     Our sense of balance seems to depend on them and on a substance called endolymph, which lies inside our ears' cannals. When we spin, the endolymph accompanies the movement but, when we stop, it doesn't stop immediately. This causes a stimuli that generates the impression that we are still spinning, so we get dizzy for a while and, after a few moments, the endolymph gets back to normal and the dizziness goes away.

~Ally

     I thought the expression "Animal Magnetism" referred to a special kind of sexual attraction of one animal towards another. Blame Shrek's Donkey for that.
     Turns out that this is another name for Mesmerism or Biomagnetism, originally studied by Antoine Mesmer (1734 - 1815), which can be defined as the reciprocal action of two living beings through an intermediate, a special agent, called the magnetic fluid. This was a science well known in ancient Egypt, where it was practiced as part of religious mysteries.
     This science states that the human body is capable of producing magnetic fields of the order of nanoteslas (10^9 T), which can be measured and used for treatments and diagnosis.

~Ally

     I remember reading that the Moon influenced the tides in my old science books back when I was in elementary school. But I believe I forgot exactly how does it works.
     Turns out that the influence in the tides is the only Lunar effect that is scientifically proved. It's gravitational force on the Earth is what makes the tides stronger in the Full and New Moons.
     A curious information is that the fate of World War 2 was kind of determined by the Moon. That is because General Dwight Eisenhower only decided the date of landing in Normandy (June 6 1944) after consulting the Moon cale. Given that it would be a clear night, with low tides, it was ideal. The date was initially decided for June 5, but a strong storm made him change his mind... And to change the course of war.

~Ally

     I'm not sure how it didn't occur to me before! It took a lot of years - and a couple of movies like The Wolfman (2010) - for me to notice it.
     I live in the Southern Hemisphere, so I'm used to the Crescent Moon in a "C" shape and the Waning Moon as a "D". Turns out that, in the North, the phases are the exact opposite - Crescent as a "D" and Waning as a "C". In the equatorial sky, though, the Moon walks lying, like a boat or a bow (the boat upside down). Personally, I think the Southern phases are easier to learn and recognize.
    I also learned that, to know in which phase the Moon is, there are two ways:
  1) If the Moon is visible in the afternoon, it is Crescent. If it appears in the morning, it's Waning. In other hours, you've got to have some notion about the Cardinal Points. If, before midnight, the Moon is in the West (where the Sun sets), it's Crescent. But, if after midnight it is seen in the East side (where the Sun rises), it is Waning.
  2) Another form of discovering the Moon Phase is to notice which side the illuminated edge is turned to: for West, it's Crescent; to West, it is Waning. These two methods work for any point of the Earth you're at, except the Poles, where there is no East and West.

~Ally