10 most difficult science riddles

The Britannica is the oldest English-language encyclopaedia still being produced (currently only in the online version). It was first published between 1768 and 1771 in Edinburgh, Scotland. In 1901, after it was taken over by an American firm, the Britannica shortened and simplified articles to broaden its appeal in the North American market. Although publication has been based in the United States since 1901, the Britannica has largely maintained British spelling.

In analytic geometry, an asymptote of a curve is a line such that the distance between the curve and the line approaches zero as one or both of the x or y coordinates tends to infinity. In projective geometry and related contexts, an asymptote of a curve is a line which is tangent to the curve at a point at infinity.The word asymptote is derived from the Greek which means "not falling together".

Throughout his conquests of Asia, Alexander the Great collected many plant and animal specimens for Aristotle’s research. This allowed Aristotle to develop in Athens the first zoo and botanical garden in existence.

In geometry, Cavalieri's principle, a modern implementation of the method of indivisibles, named after Bonaventura Cavalieri, is in 3-dimensional case: Suppose two regions in three-space (solids) are included between two parallel planes. If every plane parallel to these two planes intersects both regions in cross-sections of equal area, then the two regions have equal volumes.

The green tint found in most tempered glass is a result of iron used in the production of glass sheets, where it is added as an ingredient to act as a lubricant. In fact, except in manufacturing processes designed to minimize iron use to avoid the green tint, you’ll find that green cast in all sheets of glass–not just tempered glass

The Armstrong limit or Armstrong's line is a measure of altitude above which atmospheric pressure is sufficiently low that water boils at the normal temperature of the human body. Humans absolutely cannot survive above this limit in an unpressurized environment. Above Earth, this begins at 18–19 km (11–12 mi; 59,000–62,000 ft) above sea level. The term is named after United States Air Force General Harry George Armstrong, who was the first to recognize this phenomenon

The bibcode (also known as the refcode) is a compact identifier used by several astronomical data systems to uniquely specify literature references.

Beta Cancri, also named Tarf is the brightest star in the zodiacal constellation of Cancer. It has an apparent visual magnitude of +3.5 and an absolute magnitude of −1.2. Based on parallax measurements obtained during the Hipparcos mission, it is approximately 290 light-years distant from the Sun.

The cerebellum (Latin for "little brain") is a major feature of the hindbrain of all vertebrates. In humans, the cerebellum plays an important role in motor control. It may also be involved in some cognitive functions such as attention and language as well as in regulating fear and pleasure responses. Based on the surface appearance, three lobes can be distinguished within the cerebellum: the anterior lobe (above the primary fissure), the posterior lobe (below the primary fissure), and the flocculonodular lobe (below the posterior fissure).

Auxetics are structures or materials that have a negative Poisson's ratio. When stretched, they become thicker perpendicular to the applied force. This occurs due to their particular internal structure and the way this deforms when the sample is uniaxially loaded. Auxetics can be single molecules, crystals, or a particular structure of macroscopic matter.