Magnetic Bubble

a portion of computer memory which consists of a small region in a material such as garnet (a silicate mineral), which is magnetized in one direction. Slices of this material placed on a SUBSTRATE (base material) produce a magnetic chip that under a magnetic field produces magnetic bubbles. Information can be stored on the chip, which may contain up to one million bubbles in 20 square millimetres, in BINARY form, through the presence or absence of a bubble in a specific location.

Taken from Dictionary of Science

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The magnetic bubble apparatus consists of a thin (8-12μm) single crystal film of Ferromagnetic Garnet (FMG) sandwiched between a pair of crossed Polaroids. The FMG crystals are magnetically anisotropic, that is, they have a strong tendency to orient themselves in fixed directions under the influence of an external magnetic field. The preferred or "easy" axis of orientation is perpendicular to (in or out of) the crystal surface. With no external magnetic field, the domains in the crystal orient up or down in roughly equal amounts. Polarized light passing through the crystal will have its plane of polarization rotated by due to interaction with the magnetic field of the domains (an effect called Faraday rotation). For the 'up' domains, the light will be crossed with respect to the exiting Polaroid therefore appearing dark, and for 'down' domains uncrossed (or vice versa) so appearing bright. The domains appear as serpentine patterns of alternating bright and dark (figure 1a.). Application of an external magnetic field (provided by a built-in electromagnet) flips the domains to one preferred orientation. As the field is increased, the serpentine patterns gradually disappear until you are left with one or two strings and isolated "bubbles".

Taken from fas.harvard.edu

Umbra

a region of complete shadow, which is usually applied to eclipses. The area of half or partial shadow is termed the penumbra.

Taken from Dictionary of Science

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The umbra, penumbra and antumbra are the names given to three distinct parts of a shadow, created by any light source. For a point source only the umbra is cast.

These names are usually used when referring to the shadows cast by celestial bodies.

The umbra (Latin for "shadow") is the darkest part of the shadow. From within the umbra, the light source is completely occluded. In astronomy, an observer in the umbra is said to be in the shadows experiencing total eclipse.

Taken from Wikipedia

Jet Stream

a high-speed westerly wind in the region of the tropopause. The principal jets are the polar front and subtropical jets, which occur at heights between 10 and 15 km. The winter jet stream occurs between 50 and 80 km in the upper STRATOSPHERE. The wind speeds can reach 300 km/h. The air streams move north and south of their general trend, in surges, which are probably the cause of depressions and anticyclones. There are a number of separate jet streams, but the most constant is that of the subtropics. Jet stream speed and location are of importance to high-flying aircraft.

Taken from Dictionary of Science