Trade routeA trade route is a logistical network identified as a series of pathways and stoppages used for the commercial transport of cargo. The term can also be used to refer to trade over bodies of water. Allowing goods to reach distant markets, a single trade route contains long-distance arteries, which may further be connected to smaller networks of commercial and noncommercial transportation routes. Among notable trade routes was the Amber Road, which served as a dependable network for long-distance trade.
GyroscopeA gyroscope (from Ancient Greek γῦρος gŷros, "round" and σκοπέω skopéō, "to look") is a device used for measuring or maintaining orientation and angular velocity. It is a spinning wheel or disc in which the axis of rotation (spin axis) is free to assume any orientation by itself. When rotating, the orientation of this axis is unaffected by tilting or rotation of the mounting, according to the conservation of angular momentum.
Revolutions per minuteRevolutions per minute (abbreviated rpm, RPM, rev/min, r/min, or r⋅min−1) is a unit of rotational speed (or rotational frequency) for rotating machines. ISO 80000-3:2019 defines a physical quantity called rotation (or number of revolutions), dimensionless, whose instantaneous rate of change is called rotational frequency (or rate of rotation), with units of reciprocal seconds (s−1). A related but distinct quantity for describing rotation is angular frequency (or angular speed, the magnitude of angular velocity), for which the SI unit is the radian per second (rad/s).
Frequency analysisIn cryptanalysis, frequency analysis (also known as counting letters) is the study of the frequency of letters or groups of letters in a ciphertext. The method is used as an aid to breaking classical ciphers. Frequency analysis is based on the fact that, in any given stretch of written language, certain letters and combinations of letters occur with varying frequencies. Moreover, there is a characteristic distribution of letters that is roughly the same for almost all samples of that language.
Enigma machineThe Enigma machine is a cipher device developed and used in the early- to mid-20th century to protect commercial, diplomatic, and military communication. It was employed extensively by Nazi Germany during World War II, in all branches of the German military. The Enigma machine was considered so secure that it was used to encipher the most top-secret messages. The Enigma has an electromechanical rotor mechanism that scrambles the 26 letters of the alphabet.
Spice tradeThe spice trade involved historical civilizations in Asia, Northeast Africa and Europe. Spices such as cinnamon, cassia, cardamom, ginger, pepper, nutmeg, star anise, clove, and turmeric were known and used in antiquity and traded in the Eastern World. These spices found their way into the Near East before the beginning of the Christian era, with fantastic tales hiding their true sources. The maritime aspect of the trade was dominated by the Austronesian peoples in Southeast Asia, namely the ancient Indonesian sailors who established routes from Southeast Asia to Sri Lanka and India (and later China) by 1500 BC.
One-way speed of lightWhen using the term 'the speed of light' it is sometimes necessary to make the distinction between its one-way speed and its two-way speed. The "one-way" speed of light, from a source to a detector, cannot be measured independently of a convention as to how to synchronize the clocks at the source and the detector. What can however be experimentally measured is the round-trip speed (or "two-way" speed of light) from the source to a mirror (or other method of reflection) and back again to detector.
Fluting (architecture)Fluting in architecture consists of shallow grooves running along a surface. The term typically refers to the grooves (flutes) running vertically on a column shaft or a pilaster, but need not necessarily be restricted to those two applications. If the hollowing out of material meets in a point, the point (sharp ridge) is called an arris. If the raised ridge between two flutes is blunt, the ridge is a . Fluting promotes a play of light on a column which helps the column appear more perfectly round than a smooth column.
Speed of gravityIn classical theories of gravitation, the changes in a gravitational field propagate. A change in the distribution of energy and momentum of matter results in subsequent alteration, at a distance, of the gravitational field which it produces. In the relativistic sense, the "speed of gravity" refers to the speed of a gravitational wave, which, as predicted by general relativity and confirmed by observation of the GW170817 neutron star merger, is the same speed as the speed of light (c).
