Have a deep view into what people are curious about.

🔗 Philately

A Royal Mail rubber band is a small red elastic loop used by the postal delivery service in the United Kingdom. In the course of its work, the Royal Mail consumes nearly one billion rubber bands per year to tie together bundles of letters at sorting offices. In the 2000s, complaints about Royal Mail rubber bands littering the streets of Britain gave rise to ongoing press interest in this minor cultural phenomenon. The Royal Mail no longer uses red rubber bands.

🔗 Philosophy 🔗 Greece 🔗 Cognitive science 🔗 Philosophy/Ancient philosophy 🔗 Alternative Views 🔗 Philosophy/Epistemology

The Allegory of the Cave, or Plato's Cave, is an allegory presented by the Greek philosopher Plato in his work Republic (514a–520a) to compare "the effect of education (παιδεία) and the lack of it on our nature". It is written as a dialogue between Plato's brother Glaucon and his mentor Socrates, narrated by the latter. The allegory is presented after the analogy of the sun (508b–509c) and the analogy of the divided line (509d–511e).

In the allegory "The Cave", Plato describes a group of people who have lived chained to the wall of a cave all their lives, facing a blank wall. The people watch shadows projected on the wall from objects passing in front of a fire behind them and give names to these shadows. The shadows are the prisoners' reality, but are not accurate representations of the real world. The shadows represent the fragment of reality that we can normally perceive through our senses, while the objects under the sun represent the true forms of objects that we can only perceive through reason. Three higher levels exist: the natural sciences; mathematics, geometry, and deductive logic; and the theory of forms.

Socrates explains how the philosopher is like a prisoner who is freed from the cave and comes to understand that the shadows on the wall are actually not the direct source of the images seen. A philosopher aims to understand and perceive the higher levels of reality. However, the other inmates of the cave do not even desire to leave their prison, for they know no better life.

Socrates remarks that this allegory can be paired with previous writings, namely the analogy of the sun and the analogy of the divided line.

🔗 Robotics

Micromouse is an event where small robot mice solve a 16×16 maze. It began in the late 1970s. Events are held worldwide, and are most popular in the UK, U.S., Japan, Singapore, India, South Korea and becoming popular in subcontinent countries such as Sri Lanka.

The maze is made up of a 16×16 grid of cells, each 180 mm square with walls 50 mm high. The mice are completely autonomous robots that must find their way from a predetermined starting position to the central area of the maze unaided. The mouse needs to keep track of where it is, discover walls as it explores, map out the maze and detect when it has reached the goal. Having reached the goal, the mouse will typically perform additional searches of the maze until it has found an optimal route from the start to the finish. Once the optimal route has been found, the mouse will run that route in the shortest possible time.

Competitions and conferences are still run regularly.

🔗 Germany 🔗 Archaeology 🔗 Visual arts 🔗 Fashion

The Berlin Gold Hat or Berlin Golden Hat (German: Berliner Goldhut) is a Late Bronze Age artefact made of thin gold leaf. It served as the external covering on a long conical brimmed headdress, probably of an organic material. It is now in the Neues Museum on Museum Island in Berlin, in a room by itself with an elaborate explanatory display.

The Berlin Gold Hat is the best preserved specimen among the four known conical golden hats known from Bronze Age Europe so far. Of the three others, two were found in southern Germany, and one in the west of France. All were found in the 19th and 20th centuries. It is generally assumed that the hats served as the insignia of deities or priests in the context of a sun cult that appears to have been widespread in Central Europe at the time. The hats are also suggested to have served astronomical/calendrical functions.

The Berlin Gold Hat was acquired in 1996 by the Berlin Museum für Vor- und Frühgeschichte as a single find without provenance. A comparative study of the ornaments and techniques in conjunction with dateable finds suggests that it was made in the Late Bronze Age, circa 1,000 to 800 BC.

🔗 Electronics

The two capacitor paradox or capacitor paradox is a paradox, or counterintuitive thought experiment, in electric circuit theory. The thought experiment is usually described as follows: Two identical capacitors are connected in parallel with an open switch between them. One of the capacitors is charged with a voltage of ${\displaystyle V_{i}}$, the other is uncharged. When the switch is closed, some of the charge ${\displaystyle Q=CV_{i}}$ on the first capacitor flows into the second, reducing the voltage on the first and increasing the voltage on the second. When a steady state is reached and the current goes to zero, the voltage on the two capacitors must be equal since they are connected together. Since they both have the same capacitance ${\displaystyle C}$ the charge will be divided equally between the capacitors so each capacitor will have a charge of ${\displaystyle {Q \over 2}}$ and a voltage of ${\displaystyle V_{f}={Q \over 2C}={V_{i} \over 2}}$. At the beginning of the experiment the total initial energy ${\displaystyle W_{i}}$ in the circuit is the energy stored in the charged capacitor:

${\displaystyle W_{i}={1 \over 2}CV_{i}^{2}}$.

At the end of the experiment the final energy ${\displaystyle W_{f}}$ is equal to the sum of the energy in the two capacitors

${\displaystyle W_{f}={1 \over 2}CV_{f}^{2}+{1 \over 2}CV_{f}^{2}=CV_{f}^{2}=C({V_{i} \over 2})^{2}={1 \over 4}CV_{i}^{2}={1 \over 2}W_{i}}$

Thus the final energy ${\displaystyle W_{f}}$ is equal to half of the initial energy ${\displaystyle W_{i}}$. Where did the other half of the initial energy go?

🔗 Time 🔗 Christianity

The computus (Latin for 'computation') is a calculation that determines the calendar date of Easter. Easter is traditionally celebrated on the first Sunday after the Paschal full moon, which is the first full moon on or after 21 March (an approximation of the March equinox). Determining this date in advance requires a correlation between the lunar months and the solar year, while also accounting for the month, date, and weekday of the calendar. The calculations produce different results depending on whether the Julian calendar or the Gregorian calendar is used.

In late antiquity, it was feasible for the entire Christian church to receive the date of Easter each year through an annual announcement from the Pope. By the early third century, however, communications had deteriorated to the point that the church put great value in a system that would allow the clergy to independently and consistently determine the date for themselves. Additionally, the church wished to eliminate dependencies on the Hebrew calendar, by deriving Easter directly from the vernal equinox.

In The Reckoning of Time (725), Bede uses computus as a general term for any sort of calculation, although he refers to the Easter cycles of Theophilus as a "Paschal computus." By the end of the 8th century, computus came to refer specifically to the calculation of time.

🔗 Philosophy 🔗 Philosophy/Philosophy of religion

The self-referencing doomsday argument rebuttal is an attempt to refute the doomsday argument (that there is a credible link between the brevity of the human race's existence and its expected extinction) by applying the same reasoning to the lifetime of the doomsday argument itself.

The first researchers to write about this were P. T. Landsberg and J. N. Dewynne in 1997; they applied belief in the doomsday argument to itself, and claimed that a paradox results.

🔗 California 🔗 California/San Francisco Bay Area 🔗 Photography

Group f/64 or f.64 was a group founded by seven 20th-century San Francisco Bay Area photographers who shared a common photographic style characterized by sharply focused and carefully framed images seen through a particularly Western (U.S.) viewpoint. In part, they formed in opposition to the pictorialist photographic style that had dominated much of the early 20th century, but moreover, they wanted to promote a new modernist aesthetic that was based on precisely exposed images of natural forms and found objects.

Déformation professionnelle (French: [defɔʁmasjɔ̃ pʁɔfɛsjɔnɛl], professional deformation or job conditioning) is a tendency to look at things from the point of view of one's own profession or special expertise, rather than from a broader or humane perspective. It is often translated as "professional deformation", though French déformation can also be translated as "distortion". The implication is that professional training, and its related socialization, often result in a distortion of the way one views the world. Nobel laureate Alexis Carrel observed, "Every specialist, owing to a well-known professional bias, believes that he understands the entire human being, while in reality he only grasps a tiny part of him."

As a term in psychology, it was likely coined by the Belgian sociologist Daniel Warnotte or Russian-American sociologist Pitirim Sorokin.

🔗 Military history 🔗 Military history/Military science, technology, and theory 🔗 Military history/Weaponry 🔗 Engineering 🔗 Photography 🔗 Photography/History of photography

The rapatronic camera (a portmanteau of rapid action electronic) is a high-speed camera capable of recording a still image with an exposure time as brief as 10 nanoseconds.

The camera was developed by Harold Edgerton in the 1940s and was first used to photograph the rapidly changing matter in nuclear explosions within milliseconds of detonation, using exposures of several microseconds. To overcome the speed limitation of a conventional camera's mechanical shutter, the rapatronic camera uses two polarizing filters and a Faraday cell (or in some variants a Kerr cell). The two filters are mounted with their polarization angles at 90° to each other, to block all incoming light. The Faraday cell sits between the filters and changes the polarization plane of light passing through it depending on the level of magnetic field applied, acting as a shutter when it is energized at the right time for a very short amount of time, allowing the film to be properly exposed.

In magneto-optical shutters, the active material of the Faraday cell (e.g. dense flint glass, which reacts well to a strong magnetic field) is located inside an electromagnet coil, formed by a few loops of thick wire. The coil is powered from a pulse forming network by discharging a high-voltage capacitor (e.g. 2 microfarads at 1000 volts), into the coil via a trigatron or a thyratron switch. In electro-optical shutters, the active material is a liquid, typically nitrobenzene, located in a cell between two electrodes. A brief impulse of high voltage is applied to rotate the polarization of the passing light.

For a film-like sequence of high-speed photographs, as used in the photography of nuclear and thermonuclear tests, arrays of up to 12 cameras were deployed, with each camera carefully timed to record sequentially. Each camera was capable of recording only one exposure on a single sheet of film. Therefore, in order to create time-lapse sequences, banks of four to ten cameras were set up to take photos in rapid succession. The average exposure time used was three microseconds.