Mass is both a property of a physical body and a measure of its resistance to acceleration when a net force is applied. The object's mass determines the strength of its gravitational attraction to other bodies; the basic SI unit of mass is the kilogram. In physics, mass is not the same as weight though mass is determined by measuring the object's weight using a spring scale, rather than balance scale comparing it directly with known masses. An object on the Moon would weigh less than it does on Earth because of the lower gravity, but it would still have the same mass; this is because weight is a force, while mass is the property that determines the strength of this force. There are several distinct phenomena. Although some theorists have speculated that some of these phenomena could be independent of each other, current experiments have found no difference in results regardless of how it is measured: Inertial mass measures an object's resistance to being accelerated by a force. Active gravitational mass measures the gravitational force exerted by an object.
Passive gravitational mass measures the gravitational force exerted on an object in a known gravitational field. The mass of an object determines its acceleration in the presence of an applied force; the inertia and the inertial mass describe the same properties of physical bodies at the qualitative and quantitative level by other words, the mass quantitatively describes the inertia. According to Newton's second law of motion, if a body of fixed mass m is subjected to a single force F, its acceleration a is given by F/m. A body's mass determines the degree to which it generates or is affected by a gravitational field. If a first body of mass mA is placed at a distance r from a second body of mass mB, each body is subject to an attractive force Fg = GmAmB/r2, where G = 6.67×10−11 N kg−2 m2 is the "universal gravitational constant". This is sometimes referred to as gravitational mass. Repeated experiments since the 17th century have demonstrated that inertial and gravitational mass are identical.
The standard International System of Units unit of mass is the kilogram. The kilogram is 1000 grams, first defined in 1795 as one cubic decimeter of water at the melting point of ice. However, because precise measurement of a decimeter of water at the proper temperature and pressure was difficult, in 1889 the kilogram was redefined as the mass of the international prototype kilogram of cast iron, thus became independent of the meter and the properties of water. However, the mass of the international prototype and its identical national copies have been found to be drifting over time, it is expected that the re-definition of the kilogram and several other units will occur on May 20, 2019, following a final vote by the CGPM in November 2018. The new definition will use only invariant quantities of nature: the speed of light, the caesium hyperfine frequency, the Planck constant. Other units are accepted for use in SI: the tonne is equal to 1000 kg. the electronvolt is a unit of energy, but because of the mass–energy equivalence it can be converted to a unit of mass, is used like one.
In this context, the mass has units of eV/c2. The electronvolt and its multiples, such as the MeV, are used in particle physics; the atomic mass unit is 1/12 of the mass of a carbon-12 atom 1.66×10−27 kg. The atomic mass unit is convenient for expressing the masses of molecules. Outside the SI system, other units of mass include: the slug is an Imperial unit of mass; the pound is a unit of both mass and force, used in the United States. In scientific contexts where pound and pound need to be distinguished, SI units are used instead; the Planck mass is the maximum mass of point particles. It is used in particle physics; the solar mass is defined as the mass of the Sun. It is used in astronomy to compare large masses such as stars or galaxies; the mass of a small particle may be identified by its inverse Compton wavelength. The mass of a large star or black hole may be identified with its Schwarzschild radius. In physical science, one may distinguish conceptually between at least seven different aspects of mass, or seven physical notions that involve the concept of mass.
Every experiment to date has shown these seven values to be proportional, in some cases equal, this proportionality gives rise to the abstract concept of mass. There are a number of ways mass can be measured or operationally defined: Inertial mass is a measure of an object's resistance to acceleration when a force is applied, it is determined by applying a force to an object and measuring the acceleration that results from that force. An object with small inertial mass will accelerate more than an object with large inertial mass when acted upon by the same force. One says. Active gravitational mass is a measure of the strength of an object's gravitational flux. Gravitational field can be measured by allowing a small "test object" to fall and measuring its free-fall acceleration. For example, an object in free fall near the Moon is subject to a smaller gravitational field, hence
Yvan Dutil is a Canadian astrophysicist who, together with his colleague Stéphane Dumas, has created a noise-resistant coding system for messages aimed at communicating with extraterrestrial civilization. This system was used in the creation of messages beamed towards close stars from the Yevpatoria RT-70 radio telescope in Ukraine in 1999 and 2003, he is a member of the Bioastronomy Commission of the International Astronomical Union and of the International Academy of Astronautics's Permanent Committee on the Search for Extra-Terrestrial Intelligence. He was a candidate for the Green Party of Quebec in the Quebec election of September 2008, for the Green Party of Canada in the Canadian federal election of 2011, he is very active in fighting light pollution in Québec, specially about the creation of a Dark Sky preserve around Mont Mégantic Observatory. The history of astronomy attracts him, as well as the voting system reform and all matters of durable development, he always asks a lot of questions during the meetings of the Mont Mégantic Research Centre.
SETI Lincos with Dr. Yvan Dutil Lexique du Cosmic Call Error Correction Scheme in Active Seti Social Choice and Equity Theories: Seeking to Common Good as a Common GroundLight Pollution Qui a volé les étoiles? Éclairage Nocturne et Pollution Lumineuse, Mémoire Ville de Québec Plan de protection du ciel noir, Document d’information produit pour la conférence régionale des élus de Chaudière-AppalachesVoting System Reform Pour une meilleure démocracie: Notion d'ingénierie électoraleOthers Une crise énergétique annoncée, Les Choix et le Défi du Québec à l'horizon 2025 L’astronomie Québécoise d'hier à aujourd’hui Personal web site Autobiographie Site SETI Actif Velomobile World Market 2006
The Solar System is the gravitationally bound planetary system of the Sun and the objects that orbit it, either directly or indirectly. Of the objects that orbit the Sun directly, the largest are the eight planets, with the remainder being smaller objects, such as the five dwarf planets and small Solar System bodies. Of the objects that orbit the Sun indirectly—the moons—two are larger than the smallest planet, Mercury; the Solar System formed 4.6 billion years ago from the gravitational collapse of a giant interstellar molecular cloud. The vast majority of the system's mass is in the Sun, with the majority of the remaining mass contained in Jupiter; the four smaller inner planets, Venus and Mars, are terrestrial planets, being composed of rock and metal. The four outer planets are giant planets, being more massive than the terrestrials; the two largest and Saturn, are gas giants, being composed of hydrogen and helium. All eight planets have circular orbits that lie within a nearly flat disc called the ecliptic.
The Solar System contains smaller objects. The asteroid belt, which lies between the orbits of Mars and Jupiter contains objects composed, like the terrestrial planets, of rock and metal. Beyond Neptune's orbit lie the Kuiper belt and scattered disc, which are populations of trans-Neptunian objects composed of ices, beyond them a newly discovered population of sednoids. Within these populations are several dozen to tens of thousands of objects large enough that they have been rounded by their own gravity; such objects are categorized as dwarf planets. Identified dwarf planets include the trans-Neptunian objects Pluto and Eris. In addition to these two regions, various other small-body populations, including comets and interplanetary dust clouds travel between regions. Six of the planets, at least four of the dwarf planets, many of the smaller bodies are orbited by natural satellites termed "moons" after the Moon; each of the outer planets is encircled by planetary rings of dust and other small objects.
The solar wind, a stream of charged particles flowing outwards from the Sun, creates a bubble-like region in the interstellar medium known as the heliosphere. The heliopause is the point at which pressure from the solar wind is equal to the opposing pressure of the interstellar medium; the Oort cloud, thought to be the source for long-period comets, may exist at a distance a thousand times further than the heliosphere. The Solar System is located in the Orion Arm, 26,000 light-years from the center of the Milky Way galaxy. For most of history, humanity did not understand the concept of the Solar System. Most people up to the Late Middle Ages–Renaissance believed Earth to be stationary at the centre of the universe and categorically different from the divine or ethereal objects that moved through the sky. Although the Greek philosopher Aristarchus of Samos had speculated on a heliocentric reordering of the cosmos, Nicolaus Copernicus was the first to develop a mathematically predictive heliocentric system.
In the 17th century, Galileo discovered that the Sun was marked with sunspots, that Jupiter had four satellites in orbit around it. Christiaan Huygens followed on from Galileo's discoveries by discovering Saturn's moon Titan and the shape of the rings of Saturn. Edmond Halley realised in 1705 that repeated sightings of a comet were recording the same object, returning once every 75–76 years; this was the first evidence that anything other than the planets orbited the Sun. Around this time, the term "Solar System" first appeared in English. In 1838, Friedrich Bessel measured a stellar parallax, an apparent shift in the position of a star created by Earth's motion around the Sun, providing the first direct, experimental proof of heliocentrism. Improvements in observational astronomy and the use of unmanned spacecraft have since enabled the detailed investigation of other bodies orbiting the Sun; the principal component of the Solar System is the Sun, a G2 main-sequence star that contains 99.86% of the system's known mass and dominates it gravitationally.
The Sun's four largest orbiting bodies, the giant planets, account for 99% of the remaining mass, with Jupiter and Saturn together comprising more than 90%. The remaining objects of the Solar System together comprise less than 0.002% of the Solar System's total mass. Most large objects in orbit around the Sun lie near the plane of Earth's orbit, known as the ecliptic; the planets are close to the ecliptic, whereas comets and Kuiper belt objects are at greater angles to it. All the planets, most other objects, orbit the Sun in the same direction that the Sun is rotating. There are exceptions, such as Halley's Comet; the overall structure of the charted regions of the Solar System consists of the Sun, four small inner planets surrounded by a belt of rocky asteroids, four giant planets surrounded by the Kuiper belt of icy objects. Astronomers sometimes informally divide this structure into separate regions; the inner Solar System includes the asteroid belt. The outer Solar System is including the four giant planets.
Since the discovery of the Kuiper belt, the outermost parts of the Solar Sys
Cetaceans are aquatic mammals constituting the infraorder Cetacea. There are around 89 living species; the first is the Odontoceti, the toothed whales, which consist of around 70 species, including the dolphin, beluga whale, sperm whale, beaked whale. The second is the Mysticeti, the baleen whales, which have a filter-feeder system, consist of 15 species divided into 3 families, include the right whale, bowhead whale, pygmy right whale, gray whale; the ancient and extinct ancestors of modern whales lived 53 to 45 million years ago. They diverged from even-toed ungulates, they were amphibious, evolved in the shallow waters that separated India from Asia. Around 30 species adapted to a oceanic life. Baleen whales split from toothed whales around 34 million years ago; the smallest cetacean is Maui's dolphin, at 50 kg. Baleen whales have a tactile system in the short hairs around their mouth. Cetaceans have well-developed senses—their eyesight and hearing are adapted for both air and water, they have a layer of blubber, under the skin to maintain body heat in cold water.
Several species exhibit sexual dimorphism. Two external forelimbs are modified into flippers. Cetaceans have streamlined bodies: they can swim quickly, with the killer whale able to travel at 56 kilometres per hour in short bursts, the fin whale able to cruise at 48 kilometres per hour, dolphins able to make tight turns at high speeds, some species diving to great depths. Although cetaceans are widespread, most species prefer the colder waters of the Northern and Southern Hemispheres, they spend their lives in the water of rivers. This has drastically affected their anatomy to be able to do so, they feed on fish and marine invertebrates. Some baleen whales are specialised for feeding on benthic creatures. Male cetaceans mate with more than one female, although the degree of polygyny varies with the species. Cetaceans are not known to have pair bonds. Male cetacean strategies for reproductive success vary between herding females, defending potential mates from other males, or whale song which attracts mates.
Calves are born in the fall and winter months, females bear all the responsibility for raising them. Mothers of some species fast and nurse their young for a short period of time, more typical of baleen whales as their main food source aren't found in their breeding and calving grounds. Cetaceans produce a number of vocalizations, notably the clicks and whistles of dolphins and the moaning songs of the humpback whale; the meat and oil of cetaceans have traditionally been used by indigenous peoples of the Arctic. Cetaceans have been depicted in various cultures worldwide. Dolphins are kept in captivity and are sometimes trained to perform tricks and tasks, other cetaceans aren't as kept in captivity. Cetaceans have been relentlessly hunted by commercial industries for their products, although this is now forbidden by international law; the baiji has become "Possibly Extinct" in the past century, while the vaquita and Yangtze finless porpoise are ranked Critically Endangered by the International Union for Conservation of Nature.
Besides hunting, cetaceans face threats from accidental trapping, marine pollution, ongoing climate change. The two parvorders, baleen whales and toothed whales, are thought to have diverged around thirty-four million years ago. Baleen whales have bristles made of keratin instead of teeth; the bristles filter other small invertebrates from seawater. Grey whales feed on bottom-dwelling mollusks. Rorqual family use throat pleats to expand their mouths to sieve out the water. Balaenids have massive heads. Most mysticetes prefer the food-rich colder waters of the Northern and Southern Hemispheres, migrating to the Equator to give birth. During this process, they are capable of relying on their fat reserves; the parvorder of Odontocetes – the toothed whales – include sperm whales, beaked whales, killer whales and porpoises. The teeth are designed for catching fish, squid or other marine invertebrates, not for chewing them, so prey is swallowed whole. Teeth are shaped like cones, pegs, tusks or variable.
Female beaked whales' teeth are hidden in the gums and are not visible, most male beaked whales have only two short tusks. Narwhals have vestigial teeth other than their tusk, present on males and 15% of females and has millions of nerves to sense water temperature and salinity. A few toothed whales, such as some killer whales, feed on mammals, such as pinnipeds and other whales. Toothed whales have well-developed senses – their eyesight and hearing are adapted for both air and water, they have advan
Astrophysics is the branch of astronomy that employs the principles of physics and chemistry "to ascertain the nature of the astronomical objects, rather than their positions or motions in space". Among the objects studied are the Sun, other stars, extrasolar planets, the interstellar medium and the cosmic microwave background. Emissions from these objects are examined across all parts of the electromagnetic spectrum, the properties examined include luminosity, density and chemical composition; because astrophysics is a broad subject, astrophysicists apply concepts and methods from many disciplines of physics, including mechanics, statistical mechanics, quantum mechanics, relativity and particle physics, atomic and molecular physics. In practice, modern astronomical research involves a substantial amount of work in the realms of theoretical and observational physics; some areas of study for astrophysicists include their attempts to determine the properties of dark matter, dark energy, black holes.
Topics studied by theoretical astrophysicists include Solar System formation and evolution. Astronomy is an ancient science, long separated from the study of terrestrial physics. In the Aristotelian worldview, bodies in the sky appeared to be unchanging spheres whose only motion was uniform motion in a circle, while the earthly world was the realm which underwent growth and decay and in which natural motion was in a straight line and ended when the moving object reached its goal, it was held that the celestial region was made of a fundamentally different kind of matter from that found in the terrestrial sphere. During the 17th century, natural philosophers such as Galileo and Newton began to maintain that the celestial and terrestrial regions were made of similar kinds of material and were subject to the same natural laws, their challenge was. For much of the nineteenth century, astronomical research was focused on the routine work of measuring the positions and computing the motions of astronomical objects.
A new astronomy, soon to be called astrophysics, began to emerge when William Hyde Wollaston and Joseph von Fraunhofer independently discovered that, when decomposing the light from the Sun, a multitude of dark lines were observed in the spectrum. By 1860 the physicist, Gustav Kirchhoff, the chemist, Robert Bunsen, had demonstrated that the dark lines in the solar spectrum corresponded to bright lines in the spectra of known gases, specific lines corresponding to unique chemical elements. Kirchhoff deduced that the dark lines in the solar spectrum are caused by absorption by chemical elements in the Solar atmosphere. In this way it was proved that the chemical elements found in the Sun and stars were found on Earth. Among those who extended the study of solar and stellar spectra was Norman Lockyer, who in 1868 detected bright, as well as dark, lines in solar spectra. Working with the chemist, Edward Frankland, to investigate the spectra of elements at various temperatures and pressures, he could not associate a yellow line in the solar spectrum with any known elements.
He thus claimed the line represented a new element, called helium, after the Greek Helios, the Sun personified. In 1885, Edward C. Pickering undertook an ambitious program of stellar spectral classification at Harvard College Observatory, in which a team of woman computers, notably Williamina Fleming, Antonia Maury, Annie Jump Cannon, classified the spectra recorded on photographic plates. By 1890, a catalog of over 10,000 stars had been prepared that grouped them into thirteen spectral types. Following Pickering's vision, by 1924 Cannon expanded the catalog to nine volumes and over a quarter of a million stars, developing the Harvard Classification Scheme, accepted for worldwide use in 1922. In 1895, George Ellery Hale and James E. Keeler, along with a group of ten associate editors from Europe and the United States, established The Astrophysical Journal: An International Review of Spectroscopy and Astronomical Physics, it was intended that the journal would fill the gap between journals in astronomy and physics, providing a venue for publication of articles on astronomical applications of the spectroscope.
Around 1920, following the discovery of the Hertsprung-Russell diagram still used as the basis for classifying stars and their evolution, Arthur Eddington anticipated the discovery and mechanism of nuclear fusion processes in stars, in his paper The Internal Constitution of the Stars. At that time, the source of stellar energy was a complete mystery; this was a remarkable development since at that time fusion and thermonuclear energy, that stars are composed of hydrogen, had not yet been discovered. In 1
Space is the boundless three-dimensional extent in which objects and events have relative position and direction. Physical space is conceived in three linear dimensions, although modern physicists consider it, with time, to be part of a boundless four-dimensional continuum known as spacetime; the concept of space is considered to be of fundamental importance to an understanding of the physical universe. However, disagreement continues between philosophers over whether it is itself an entity, a relationship between entities, or part of a conceptual framework. Debates concerning the nature and the mode of existence of space date back to antiquity. Many of these classical philosophical questions were discussed in the Renaissance and reformulated in the 17th century during the early development of classical mechanics. In Isaac Newton's view, space was absolute—in the sense that it existed permanently and independently of whether there was any matter in the space. Other natural philosophers, notably Gottfried Leibniz, thought instead that space was in fact a collection of relations between objects, given by their distance and direction from one another.
In the 18th century, the philosopher and theologian George Berkeley attempted to refute the "visibility of spatial depth" in his Essay Towards a New Theory of Vision. The metaphysician Immanuel Kant said that the concepts of space and time are not empirical ones derived from experiences of the outside world—they are elements of an given systematic framework that humans possess and use to structure all experiences. Kant referred to the experience of "space" in his Critique of Pure Reason as being a subjective "pure a priori form of intuition". In the 19th and 20th centuries mathematicians began to examine geometries that are non-Euclidean, in which space is conceived as curved, rather than flat. According to Albert Einstein's theory of general relativity, space around gravitational fields deviates from Euclidean space. Experimental tests of general relativity have confirmed that non-Euclidean geometries provide a better model for the shape of space. Galilean and Cartesian theories about space and motion are at the foundation of the Scientific Revolution, understood to have culminated with the publication of Newton's Principia in 1687.
Newton's theories about space and time helped. While his theory of space is considered the most influential in Physics, it emerged from his predecessors' ideas about the same; as one of the pioneers of modern science, Galilei revised the established Aristotelian and Ptolemaic ideas about a geocentric cosmos. He backed the Copernican theory that the universe was heliocentric, with a stationary sun at the center and the planets—including the Earth—revolving around the sun. If the Earth moved, the Aristotelian belief that its natural tendency was to remain at rest was in question. Galilei wanted to prove instead that the sun moved around its axis, that motion was as natural to an object as the state of rest. In other words, for Galilei, celestial bodies, including the Earth, were inclined to move in circles; this view displaced another Aristotelian idea—that all objects gravitated towards their designated natural place-of-belonging. Descartes set out to replace the Aristotelian worldview with a theory about space and motion as determined by natural laws.
In other words, he sought a metaphysical foundation or a mechanical explanation for his theories about matter and motion. Cartesian space was Euclidean in structure—infinite and flat, it was defined as that. The Cartesian notion of space is linked to his theories about the nature of the body and matter, he is famously known for his "cogito ergo sum", or the idea that we can only be certain of the fact that we can doubt, therefore think and therefore exist. His theories belong to the rationalist tradition, which attributes knowledge about the world to our ability to think rather than to our experiences, as the empiricists believe, he posited a clear distinction between the body and mind, referred to as the Cartesian dualism. Following Galilei and Descartes, during the seventeenth century the philosophy of space and time revolved around the ideas of Gottfried Leibniz, a German philosopher–mathematician, Isaac Newton, who set out two opposing theories of what space is. Rather than being an entity that independently exists over and above other matter, Leibniz held that space is no more than the collection of spatial relations between objects in the world: "space is that which results from places taken together".
Unoccupied regions are those that could have objects in them, thus spatial relations with other places. For Leibniz space was an idealised abstraction from the relations between individual entities or their possible locations and therefore could not be continuous but must be discrete. Space could be thought of in a similar way to the relations between family members. Although people in the family are related to one another, the relations do not exist independently of the people. Leibniz argued that space could not exist independently of objects in the world because that implies a difference between two universes alike except for the location of the material world in
Canadians are people identified with the country of Canada. This connection may be residential, historical or cultural. For most Canadians, several of these connections exist and are collectively the source of their being Canadian. Canada is a multilingual and multicultural society home to people of many different ethnic and national origins, with the majority of the population made up of Old World immigrants and their descendants. Following the initial period of French and the much larger British colonization, different waves of immigration and settlement of non-indigenous peoples took place over the course of nearly two centuries and continue today. Elements of Indigenous, French and more recent immigrant customs and religions have combined to form the culture of Canada, thus a Canadian identity. Canada has been influenced by its linguistic and economic neighbour—the United States. Canadian independence from the United Kingdom grew over the course of many years since the formation of the Canadian Confederation in 1867.
World War I and World War II in particular, gave rise to a desire among Canadians to have their country recognized as a fully-fledged sovereign state with a distinct citizenship. Legislative independence was established with the passage of the Statute of Westminster 1931, the Canadian Citizenship Act of 1946 took effect on January 1, 1947, full sovereignty was achieved with the patriation of the constitution in 1982. Canada's nationality law mirrored that of the United Kingdom. Legislation since the mid-20th century represents Canadians' commitment to multilateralism and socioeconomic development; as of 2010, Canadians make up only 0.5% of the world's total population, having relied upon immigration for population growth and social development. 41% of current Canadians are first- or second-generation immigrants, 20% of Canadian residents in the 2000s were not born in the country. Statistics Canada projects that, by 2031, nearly one-half of Canadians above the age of 15 will be foreign-born or have one foreign-born parent.
Indigenous peoples, according to the 2011 Canadian Census, numbered at 1,400,685 or 4.3% of the country's 33,476,688 population. While the first contact with Europeans and indigenous peoples in Canada had occurred a century or more before, the first group of permanent settlers were the French, who founded the New France settlements, in present-day Quebec and Ontario. 100 Irish-born families would settle the Saint Lawrence Valley by 1700, assimilating into the Canadien population and culture. During the 18th and 19th century; this arrival of newcomers led to the creation of the Métis, an ethnic group of mixed European and First Nations parentage. The British conquest of New France was preceded by a small number of Germans and Swedes who settled alongside the Scottish in Port Royal, Nova Scotia, while some Irish immigrated to the Colony of Newfoundland. In the wake of the British Conquest of 1760 and the Expulsion of the Acadians, many families from the British colonies in New England moved over into Nova Scotia and other colonies in Canada, where the British made farmland available to British settlers on easy terms.
More settlers arrived during and after the American Revolutionary War, when 60,000 United Empire Loyalists fled to British North America, a large portion of whom settled in New Brunswick. After the War of 1812, British and Irish immigration was encouraged throughout Rupert's Land, Upper Canada and Lower Canada. Between 1815 and 1850, some 800,000 immigrants came to the colonies of British North America from the British Isles as part of the Great Migration of Canada; these new arrivals included some Gaelic-speaking Highland Scots displaced by the Highland Clearances to Nova Scotia. The Irish Potato Famine of the 1840s increased the pace of Irish immigration to Prince Edward Island and the Province of Canada, with over 35,000 distressed individuals landing in Toronto in 1847 and 1848. Descendants of Francophone and Anglophone northern Europeans who arrived in the 17th, 18th, 19th centuries are referred to as Old Stock Canadians. Beginning in the late 1850s, the immigration of Chinese into the Colony of Vancouver Island and Colony of British Columbia peaked with the onset of the Fraser Canyon Gold Rush.
The Chinese Immigration Act placed a head tax on all Chinese immigrants, in hopes of discouraging Chinese immigration after completion of the Canadian Pacific Railway. The population of Canada has risen, doubling every 40 years, since the establishment of the Canadian Confederation in 1867. In the mid-to-late 19th century, Canada had a policy of assisting immigrants from Europe, including an estimated 100,000 unwanted "Home Children" from Britain. Block settlement communities were established throughout western Canada between the late 19th and early 20th centuries; some were planned and others were spontaneously created by the settlers themselves. Canada was now receiving a large number of European immigrants, predominantly Italians, Scandinavians, Dutch and Ukrainians. Legislative restrictions on immigration that had favoured British and other European immigrants were a