Top

A top is a toy designed to be spun rapidly on the ground, the motion of which causes it to remain precisely balanced on its tip because of inertia. Such toys have existed since antiquity. Traditionally tops were constructed of wood, sometimes with an iron tip, and would be set in motion by aid of a string or rope coiled around its axis which, when pulled quickly, caused a rapid unwinding that would set the top in motion. Today they are often built of plastic, and modern materials and manufacturing processes allow tops to be constructed with such precise balance that they can be set in motion by a simple twist of the fingers and twirl of the wrist without need for string or rope.

Characteristics

The motion of a top is produced in the most simple forms by twirling the stem using the fingers. More sophisticated tops are spun by holding the axis firmly while pulling a string or twisting a stick or pushing an auger. In the kinds with an auger, an internal weight rotates, producing an overall circular motion. Some tops can be thrown, while firmly grasping a string that had been tightly wound around the stem, and the centrifugal force generated by the unwinding motion of the string will set them spinning upon touching ground.

Top (clothing)

A top is clothing that covers at least the chest, but which usually covers most of the upper human body between the neck and the waistline. The bottom of tops can be as short as mid-torso, or as long as mid-thigh. Men's tops are generally paired with pants, and women's with pants or skirts. Common types of tops are t-shirts, blouses and shirts.

Design

The neckline is the highest line of the top, and may be as high as a head-covering hood, or as low as the waistline or bottom hem of the top. A top may be worn loose or tight around the bust or waist, and may have sleeves or shoulder straps, spaghetti straps (noodle straps), or may be strapless. The back may be covered or bare. Tops may have straps around the waist or neck, or over the shoulders.

Types

Neck styles

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Category of topological spaces

In mathematics, the category of topological spaces, often denoted Top, is the category whose objects are topological spaces and whose morphisms are continuous maps or some other variant; for example, objects are often assumed to be compactly generated. This is a category because the composition of two continuous maps is again continuous. The study of Top and of properties of topological spaces using the techniques of category theory is known as categorical topology.

N.B. Some authors use the name Top for the category with topological manifolds as objects and continuous maps as morphisms.

As a concrete category

Like many categories, the category Top is a concrete category (also known as a construct), meaning its objects are sets with additional structure (i.e. topologies) and its morphisms are functions preserving this structure. There is a natural forgetful functor

to the category of sets which assigns to each topological space the underlying set and to each continuous map the underlying function.

Gamma Microscopii

Gamma Microscopii (γ Microscopii, γ Mic) is the brightest star in the faint southern constellation of Microscopium. It has an apparent visual magnitude of 4.68, which is too dim to be viewed from city skies. The distance to this star has been determined using parallax measurements made during the Hipparcos mission, which place it around 229 light-years (70 parsecs) away with a 2% margin of error.

Based upon a stellar classification of G6 III, this is a G-type giant star. It is a core helium fusing star that is classified as a member of the red clump evolutionary branch, although the metallicity of this star—meaning the abundance of elements other than hydrogen and helium—is anomalously low for a member of this group. The effective temperature of the star's outer envelope is 5,050 K, giving it the yellow-hued glow typical of G-type stars.

In the galactic coordinate system, this star has space velocity components of [U, V, W] = [+13.75, +3.47, –10.50] km s⁻¹. The peculiar velocity of this star, relative to its neighbors, is 1.2 km s⁻¹. It has been listed as likely member of the Ursa Major Moving Group of stars that share a similar location and a common trajectory through space. Backwards extrapolation of the motion of γ Microscopii has shown that approximately 3.8 million years ago, it was only around 6 light-years from the Sun. It would then have had an apparent magnitude of −3 and have been brighter than Sirius is now.

HD 126009

HD 126009 or CI Boötis is a variable star in the northern constellation of Boötes.

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HD 49674

HD 49674 is an 8th magnitude G-type main-sequence star (spectral type G5V) located approximately 144 light years away in the constellation of Auriga. It has a very similar mass to our Sun. It is orbited by a recently discovered planet.

Planetary system

At the time of discovery of the planet HD 49674 b in 2002, it was the least massive planet known, very close to the boundary between sub-Jupiter mass and Neptune-mass at 0.1 M_J. This planet orbits very close to the star.

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Coordinates: 06^h 51^m 30.5164^s, +40° 52′ 03.923″