Have a deep view into what people are curious about.

🔗 United States 🔗 Biography 🔗 Computer science 🔗 Biography/science and academia 🔗 United States/Indiana

John Charles Reynolds (June 1, 1935 – April 28, 2013) was an American computer scientist.

🔗 Mathematics

In number theory, the Green–Tao theorem, proved by Ben Green and Terence Tao in 2004, states that the sequence of prime numbers contains arbitrarily long arithmetic progressions. In other words, for every natural number k, there exist arithmetic progressions of primes with k terms. The proof is an extension of Szemerédi's theorem. The problem can be traced back to investigations of Lagrange and Waring from around 1770.

🔗 Spaceflight

Project Highwater was an experiment carried out as part of two of the test flights of NASA's Saturn I launch vehicle (using battleship upper stages), successfully launched into a sub-orbital trajectory from Cape Canaveral, Florida. The Highwater experiment sought to determine the effect of a large volume of water suddenly released into the ionosphere. The project answered questions about the effect of the diffusion of propellants in the event that a rocket was destroyed at high altitude.

The first flight, SA-2, took place on April 25, 1962. After the flight test of the rocket was complete and first stage shutdown occurred, explosive charges on the dummy upper stages destroyed the rocket and released 23,000 US gallons (87,000 L) of ballast water weighing 95 short tons (86,000 kg) into the upper atmosphere at an altitude of 65 miles (105 km), eventually reaching an apex of 90 miles (145 km).

The second flight, SA-3, launched on November 16, 1962, and involved the same payload. The ballast water was explosively released at the flight's peak altitude of 104 miles (167 km). For both of these experiments, the resulting ice clouds expanded to several miles in diameter and lightning-like radio disturbances were recorded.

🔗 Religion 🔗 Iran 🔗 Central Asia 🔗 Syria 🔗 Iraq 🔗 Turkey 🔗 Ukraine 🔗 Holidays 🔗 Pakistan 🔗 Afghanistan 🔗 Caucasia 🔗 Kurdistan 🔗 Tajikistan 🔗 Georgia (country) 🔗 Azerbaijan 🔗 North Macedonia 🔗 Bahá'í Faith 🔗 Albania

Nowruz (Persian: نوروز‎, pronounced [nowˈɾuːz]; lit.  "new day") is the Iranian New Year, also known as the Persian New Year, which is celebrated worldwide by various ethno-linguistic groups.

Nowruz has Iranian and Zoroastrian origins, however, it has been celebrated by diverse communities for over 7,000 years in Western Asia, Central Asia, the Caucasus, the Black Sea Basin, the Balkans, and South Asia. It is a secular holiday for most celebrants that is enjoyed by people of several different faiths, but remains a holy day for Zoroastrians, Bahais, and some Muslim communities.

Nowruz is the day of the vernal equinox, and marks the beginning of spring in the Northern Hemisphere. It marks the first day of the first month (Farvardin) of the Iranian calendars. It usually occurs on March 21 or the previous or following day, depending on where it is observed. The moment the Sun crosses the celestial equator and equalizes night and day is calculated exactly every year, and families gather together to observe the rituals.

While Nowruz has been celebrated since the reform of the Iranian Calendar in the 11th century CE to mark the new year, the United Nations officially recognized the "International Day of Nowruz" with the adoption of UN resolution 64/253 in 2010.

🔗 Physics 🔗 Antarctica

The lowest natural temperature ever directly recorded at ground level on Earth is −89.2 °C (−128.6 °F; 184.0 K) at the Soviet Vostok Station in Antarctica on 21 July 1983 by ground measurements.

On 10 August 2010, satellite observations showed a surface temperature of −93.2 °C (−135.8 °F; 180.0 K) at 81.8°S 59.3°E / -81.8; 59.3, along a ridge between Dome Argus and Dome Fuji, at 3,900 m (12,800 ft) elevation. The result was reported at the 46th annual meeting of the American Geophysical Union in San Francisco in December 2013; it is a provisional figure, and may be subject to revision. The value is not listed as the record lowest temperature as it was measured by remote sensing from satellite and not by ground-based thermometers, unlike the 1983 record. The temperature announced reflects that of the ice surface, while the Vostok readings measured the air above the ice, and so the two are not directly comparable. More recent work shows many locations in the high Antarctic where surface temperatures drop to approximately −98 °C (−144 °F; 175 K). Due to the very strong temperature gradient near the surface, these imply near-surface air temperature minima of approximately −94 °C (−137 °F; 179 K).

🔗 Technology

A blast valve is used to protect a shelter, such as a fallout shelter or bunker, from the effects of sudden outside air pressure changes. A nuclear weapon creates a shock wave, which may produce sudden pressure changes of more than an atmosphere (about 1 bar) even several kilometres from the detonation point. After the shock wave passes, a sudden negative pressure follows.

If such pressure waves enter a shelter, they will likely do substantial harm to occupants and equipment. A blast valve is placed in air intake/exhaust pipes, that remains open normally, but automatically closes when strong pressure is applied in either direction. Blast dampers operate in the same fashion and are related or identical to blast valves, the former name however is generally used to describe blast mitigation devices, for more conventional explosive events.

A typical blast valve has entries of 15–30 cm diameter, and a larger centre section. Within the centre section is a disk mounted on an axle, with weak springs that keep it centred, away from both entries. Pressure displaces the disk along the axle, until it plugs one entry or the other. After the blast, the springs return the disk to the centre, re-opening the valve.

Another type of blast valve employs rounded metal tubes held in place by springs. As pressure rises it pushes the tubes against the frame of the valve closing the opening. These valves are typically unidirectional in airflow and are employed in large wall structures where large amounts of airflow is required.

One form of blast valve, popularized by the book Nuclear War Survival Skills and tested by ORNL is worn flat rubber tire treads nailed or bolted to frames strong enough to resist the maximum overpressure, with tested closing times cited as being identical to commercial grade blast valves, however the use of this form of blast valve design must also take the risk of the flammable rubber catching fire into consideration.

🔗 Technology 🔗 Sweden 🔗 Metalworking

Gauge blocks (also known as gage blocks, Johansson gauges, slip gauges, or Jo blocks) are a system for producing precision lengths. The individual gauge block is a metal or ceramic block that has been precision ground and lapped to a specific thickness. Gauge blocks come in sets of blocks with a range of standard lengths. In use, the blocks are stacked to make up a desired length.

An important feature of gauge blocks is that they can be joined together with very little dimensional uncertainty. The blocks are joined by a sliding process called wringing, which causes their ultra-flat surfaces to cling together. A small number of gauge blocks can be used to create accurate lengths within a wide range. By using 3 blocks at a time taken from a set of 30 blocks, one may create any of the 1000 lengths from 3.000 to 3.999 mm in 0.001 mm steps (or .3000 to .3999 inches in 0.0001 inch steps). Gauge blocks were invented in 1896 by Swedish machinist Carl Edvard Johansson. They are used as a reference for the calibration of measuring equipment used in machine shops, such as micrometers, sine bars, calipers, and dial indicators (when used in an inspection role). Gauge blocks are the main means of length standardization used by industry.

🔗 Physics 🔗 Weather 🔗 Weather/Weather

A light pillar is an atmospheric optical phenomenon in which a vertical beam of light appears to extend above and/or below a light source. The effect is created by the reflection of light from tiny ice crystals that are suspended in the atmosphere or that comprise high-altitude clouds (e.g. cirrostratus or cirrus clouds). If the light comes from the Sun (usually when it is near or even below the horizon), the phenomenon is called a sun pillar or solar pillar. Light pillars can also be caused by the Moon or terrestrial sources, such as streetlights and erupting volcanoes.

🔗 United States

This is a list of U.S. states and the District of Columbia by annual net migration. The first table lists U.S. states and the District of Columbia by annual net domestic migration, while the second table lists U.S. states and the District of Columbia by annual net international migration. There is a separate table for the U.S. territories. The term net domestic migration describes the total number of people moving to a state from another state minus people moving to another state from that state. The term net international migration describes the total number of people moving to a state from another country minus people moving to another country from that state.