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HandWiki is the world's largest wiki-style encyclopedia dedicated to science, technology and computing. It allows you to create and edit articles as long as you have external citations and login account. In addition, this is a content management environment that can be used for collaborative editing of original scholarly content, such as books, manuals, monographs and tutorials.

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Age of the Earth
The age of the Earth is estimated to be 4.54 ± 0.05 billion years (4.54 × 109 years ± 1%). This age may represent the age of the Earth's accretion, or core formation, or of the material from which the Earth formed. This dating is based on evidence from radiometric age-dating of meteorite material and is consistent with the radiometric ages of the oldest-known terrestrial and lunar samples. Following the development of radiometric age-dating in the early 20th century, measurements of lead in uranium-rich minerals showed that some were in excess of a billion years old. The oldest such minerals analyzed to date—small crystals of zircon from the Jack Hills of Western Australia—are at least 4.404 billion years old. Calcium–aluminium-rich inclusions—the oldest known solid constituents within meteorites that are formed within the Solar System—are 4.567 billion years old, giving a lower limit for the age of the Solar System. It is hypothesised that the accretion of Earth began soon after the formation of the calcium-aluminium-rich inclusions and the meteorites. Because the time this accretion process took is not yet known, and predictions from different accretion models range from a few million up to about 100 million years, the difference between the age of Earth and of the oldest rocks is difficult to determine. It is also difficult to determine the exact age of the oldest rocks on Earth, exposed at the surface, as they are aggregates of minerals of possibly different ages.
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  • 21 Nov 2022
Biography
Jehiel R. Elyachar
Jehiel Raphael Elyachar (October 20, 1898 – March 29, 1989) was an engineer, real estate developer and philanthropist who contributed to American and Israeli causes. He distinguished himself during World War II as a colonel in charge of military intelligence for the United States Army, earning the Bronze Star Medal, the Legion of Merit, and the Légion d'honneur. Elyachar was born on Octobe
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  • 15 Nov 2022
Topic Review
Independent Video Game Development
Independent video game development, or indie game development, is the video game development process of creating indie games; these are video games, commonly created by individual or small teams of video game developers and usually without significant financial support of a video game publisher or other outside source. These games may take years to be built from the ground up or can be completed in a matter of days or even hours depending on complexity, participants, and design goal. Driven by digital distribution, the concept of independent video game development has spawned an "indie" movement. The increase in popularity of independent games has allowed increased distribution on popular gaming platforms such as the PlayStation Network, Nintendo eShop, Xbox Live and Steam.
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  • 21 Nov 2022
Topic Review
Employee Stock Ownership Plan
An employee stock ownership plan (ESOP) is an employee-owner program that provides a company's workforce with an ownership interest in the company. In an ESOP, companies provide their employees with stock ownership, often at no upfront cost to the employees. ESOP shares, however, are part of employees' remuneration for work performed. Shares are allocated to employees and may be held in an ESOP trust until the employee retires or leaves the company. The shares are then either bought back by the company for redistribution or voided. Some corporations are majority employee-owned; the term "employee-owned corporation" often refers to such companies. Such organizations are similar to worker cooperatives, but unlike cooperatives, control of the company's capital is not necessarily evenly distributed. In many cases, voting rights are given only to certain shareholders, and more senior employees may be allocated more shares than new hires; typically, they are tied to the compensation an employee receives from the company. Compared with cooperatives, ESOP-centered corporations often allow for company executives to have greater flexibility and control in governing and managing the corporation. Most corporations, however, use stock ownership plans as a form of in-kind benefit, as a way to prevent hostile takeovers, or to maintain a specific corporate culture. The plans generally prevent average employees from holding too much of the company's stock.
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  • 15 Nov 2022
Biography
Nils Muižnieks
Nils Muižnieks (born 31 January 1964 in the United States) is a Latvian-American human rights activist and political scientist. He had served as the Council of Europe's Commissioner for Human Rights between 2012 and 2018, succeeding Thomas Hammarberg (2006–2012) and Álvaro Gil-Robles (1999–2006). Muižnieks' parents, Ansis and Ingrid, were both refugees who left Latvia in 1944. They spe
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  • 15 Nov 2022
Topic Review
Sixth Term Examination Paper
Sixth Term Examination Papers in Mathematics, often referred to as STEP, are university admissions tests for undergraduate Mathematics courses developed by the University of Cambridge. STEP papers are typically taken post-interview, as part of a conditional offer of an undergraduate place. There are also a number of candidates who sit STEP papers as a challenge. The papers are designed to test ability to answer questions similar in style to undergraduate Mathematics. There are two official users of STEP Mathematics: the University of Cambridge and the University of Warwick. Candidates applying to study Mathematics or Computer Science with Mathematics at the University of Cambridge are required to take STEP papers as part of the terms of their conditional offer. In addition, other courses at Cambridge University with a large mathematics component, such as engineering occasionally require STEP. Candidates applying to study Mathematics or closely-related subjects at the University of Warwick can take step as part of their offer. A typical STEP offer for a candidate applying to read Mathematics at the University of Cambridge would be at least a grade 1 in both STEP2 and STEP 3. From 2019 some colleges may (depending on the individual applicant's circumstances) require a grade 1 in either STEP 1 or 2 , (or in both). Candidates applying to the University of Warwick to read Mathematics, or closely related subjects, can use a grade 1 from any STEP paper as part of their offer.
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  • 15 Nov 2022
Topic Review
Timoshenko Beam Theory
The Timoshenko beam theory was developed by Stephen Timoshenko early in the 20th century. The model takes into account shear deformation and rotational bending effects, making it suitable for describing the behaviour of thick beams, sandwich composite beams, or beams subject to high-frequency excitation when the wavelength approaches the thickness of the beam. The resulting equation is of 4th order but, unlike Euler–Bernoulli beam theory, there is also a second-order partial derivative present. Physically, taking into account the added mechanisms of deformation effectively lowers the stiffness of the beam, while the result is a larger deflection under a static load and lower predicted eigenfrequencies for a given set of boundary conditions. The latter effect is more noticeable for higher frequencies as the wavelength becomes shorter (in principle comparable to the height of the beam or shorter), and thus the distance between opposing shear forces decreases. If the shear modulus of the beam material approaches infinity—and thus the beam becomes rigid in shear—and if rotational inertia effects are neglected, Timoshenko beam theory converges towards ordinary beam theory.
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  • 15 Nov 2022
Biography
Avi Loeb
Abraham "Avi" Loeb (Hebrew: אברהם (אבי) לייב‎; born February 26, 1962) is an Israeli-United States theoretical physicist who works on astrophysics and cosmology. Loeb is the Frank B. Baird Jr. Professor of Science at Harvard University. He had been the longest serving Chair of Harvard's Department of Astronomy (2011–2020), Founding Director of Harvard's Black Hole Initiative (sin
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  • 17 Nov 2022
Topic Review
Yao's Millionaires' Problem
Yao's Millionaires' problem is a secure multi-party computation problem which was introduced in 1982 by computer scientist and computational theorist Andrew Yao. The problem discusses two millionaires, Alice and Bob, who are interested in knowing which of them is richer without revealing their actual wealth. This problem is analogous to a more general problem where there are two numbers [math]\displaystyle{ a }[/math] and [math]\displaystyle{ b }[/math] and the goal is to determine whether the inequality [math]\displaystyle{ a \geq b }[/math] is true or false without revealing the actual values of [math]\displaystyle{ a }[/math] and [math]\displaystyle{ b }[/math]. The Millionaires' Problem is an important problem in cryptography, the solution of which is used in e-commerce and data mining. Commercial applications sometimes have to compare numbers which are confidential and whose security is important. Many solutions have been introduced for the problem, among which the first solution, presented by Yao himself, was exponential in time and space.
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  • 15 Nov 2022
Biography
Frank Cepollina
Frank J. "Cepi" Cepollina (born December 6, 1936 in Castro Valley, California is an American engineer and inventor. He was officially inducted to the National Inventors Hall of Fame for his pioneering concept of in-orbit satellite servicing in May 2003. His organizational leadership style has been compared to that of Al Davis of the National Football League's Oakland Raiders. Out of work, he
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