In Which Direction The Hard Drive Rotates And Why

Why does the left wheel of a car in air rotate in reverse direction when the right wheel is rotated in one direction?

Research the operation of something called differential gearing. The driven wheels of a vehicle must be able to rotate at slightly different speeds when the vehicle goes round corners, otherwise the tyres would scrub off their tread abnormally fast. Differential gearing allows this.One of the side effects of this gearing is when the vehicle is jacked up and the engine is off and out of gear turning one driven wheel causes the opposite wheel to rotate in the reverse direction.

Which direction does the Milky way rotate?

Clockwise and counterclockwise are concepts that are dependent on our orientation with respect to a rotating object, and are meaningless in space.That being said, it turns out that the question is actually not meaningless.In 1925, Bertil Lindblad realized that galaxy arms could not represent stars arranged permanently in a spiral shape. The angular speed of rotation of the galactic disk varies with distance from the center of the galaxy. Therefore, a set of fixed spiral arms would, after a few galactic rotations, become increasingly curved, winding tighter and tighter around around the galaxy. This is called the winding problem.Spiral arms must therefore be transient phenomena.There are two leading hypotheses for the spiral structures of galaxies:Spiral arms represent density waves. Bertil Lindblad proposed that the arms represent regions of enhanced density—like sound waves—that do not rotate at the same speed as the galaxy’s orbital motions. These regions of compressed gas result in the formation of new stars, many of them bright and short-lived.A spin-off of Lindblad’s density wave model is different enough from its parent to be considered a separate theory in itself. The SSPSF model proposes that spiral arms represent waves of star formation caused by shock waves, produced by stellar winds and supernovae in the interstellar medium.Since the spiral arms are not fixed structures, there is no a priori reason why the spiral arms necessarily trail behind as the galaxy rotates.It turns out, in fact, that for most spiral galaxies, the spiral arms do trail with the tips of the spiral arms winding away from the direction of the disks orbital rotation. This, of course, is the direction that matches intuition.At least one exception is known: NGC 4622, which has been called the “backward galaxy.” In NGC 4622, the tips of the outer spiral arms point forwards in the direction of disk rotation.File:NGC 4622HSTFull.jpg - WikipediaAlthough the outer spiral arms of NGC 4622 point forwards in the direction of rotation, one inner arm trails.The Milky Way, the subject of the question, rotates in a normal direction.Further reading:Spiral galaxy spins the wrong waySpiral Galaxy Winds BackwardsNGC 4622 - Wikipedia

Can loud noises damage rotating hard drives due to induced vibrations?

Without qualifying how loud the noise is, the answer is definitely yes.Sound is basically pressure waves passing through air. You can create pressure waves that can damage just about anything if you have a large enough power source (e.g. atomic bomb) behind it.It seems like the spirit of your question though is a sound that would not be destructive to anything else in the environment around the drive but would still damage the drive.I believe if you could determine a harmonic frequency targeted at causing the hard drive actuator arm to vibrate in a vertical direction and you can deliver enough power to overcome the stabilizing aerodynamics of the drive head, you should be able to crash the head into the platter.So I would say it is plausible but not necessarily true. It needs a good Mythbust'n.

Why does the hard disk rotate counterclockwise?

Thanks for A2A.Why does the hard disk rotate counterclockwise?When I think about it, most early R&D on hard drives would have taken place in the Northern Hemisphere and, if the technology were as “pico” as it is today, then HDDs intended to operate in a flat-plane only would have been designed clock-wise to make use of the Coriolis effect—of course, the sheer intensity of voice-coil magnets counteracts any influence that the Coriolis effect could now have, and HDDs are often mounted vertically or upside-down (effectively clock-wise).When the Hard Disk was first being developed, direction of rotation would have been based on what type of spindle-motor was supplied. Engineering a mirror-opposite of a Hard Drive would not be difficult, except for what could not be re-used from a previous model when developing the new one.The first prototype Floppy Drive would also have relied on the direction of the supplied Spindle-motor, but when it came to producing multiple units with interchangeable media, the original direction of the prototype would have been copied as a matter of necessity.