
The kilogram or kilogramme, (symbol: kg) is the SI base unit of mass. A gram is defined as one thousandth of a kilogram. Conversion of units#Mass describes equivalent units of mass in other systems. == Multiples == SI prefixes are used to name multiples and subdivisions of the kilogram. The most commonly used ones are: ; tonne : 1 E3 kg (strictly speaking, this should be named ''megagram'', but the name is less commonly used) (not to be confused with non-metric Ton#Units_of_mass units) ; gram : 1 E-3 kg ; milligram : 1 E-6 kg = 1 E-6 kg ; microgram :1 E-9 kg = 1 E-9 kg == Definition == The kilogram is the only one of the SI units which is still defined in relation to an artifact rather than to fundamental physical properties. It is also the only ''base'' unit that employs one of the prefixes. The kilogram was ''originally'' defined as the mass of one litre of pure water at a temperature of 4 degrees Celsius and standard atmospheric pressure. This definition was hard to realize accurately, partially because the density of water depends ever-so-slightly on the pressure, and pressure units include mass as a factor, introducing a circular definition in the definition of the kilogram. To avoid these problems, the kilogram was redefined as ''precisely'' the mass of a particular standard mass created to approximate the original definition. Since 1889, the SI system defines the unit to be equal to the mass of the international prototype of the kilogram, which is made from an alloy of platinum and Iridium (element) of 1 E-2 m height and diameter, and kept at the Bureau International des Poids et Mesures (International Bureau of Weights and Measures). Official copies of the prototype kilogram are made available as national prototypes, which are compared to the Paris prototype ("''Le Grand Kilo''") roughly every 1 E8 s. The international prototype kilogram was made in the 1880s. By definition, the error in the repeatability of the current definition is exactly zero; however, in the usual sense of the word, it can be regarded as of the order of 2 micrograms. This is found by comparing the official standard with its official copies, which are made of roughly the same materials and kept under the same conditions. There is no reason to believe that the official standard is any more or less stable than its official copies, thus giving a way to estimate its stability. This procedure is performed roughly once every forty years. The international prototype of the kilogram seems to have lost about 50 micrograms in the last 100 years, and the reason for the loss is still unknown (reported in ''Der Spiegel'', 2003 #26). The observed variation in the prototype has intensified the search for a new definition of the kilogram. It is accurate to state that any object in the universe (other than the reference metal in France) that had a mass of 1 kilogram 100 years ago, and has not changed since then, now is considered to have a mass which is 50 micrograms larger than a kilogram. This perspective is counterintuitive and defeats the purpose of a standard unit of mass, since the standard should not change arbitrarily over time. == The gram == The gram or gramme, symbol g, is a unit of mass, and is defined in the SI system of units as one one-thousandth of a kilogram (i.e., 1 × 10−3 kg). One ounce avoirdupois is 28.34952 grams (see Conversion of units#Mass). Although the gram is not an SI base unit, it is a submultiple of the kilogram, which ''is'' a base unit. In SI, ''gram'' is also the root to which SI prefixes are applied. However, the gram is a base unit of the older cgs system of measurement, a system which is no longer widely used. The gram is an essential measurement unit in scientific endeavors worldwide. A gram was originally defined as the weight of one cubic centimeter of water at its densest. This occurs at a temperature near four degrees Celsius. However, its definition was changed to the mass of a metal artifact in the eighteenth century. == Proposed future definitions == There is an ongoing effort to introduce a new definition for the kilogram by way of fundamental or atomic constants. The proposals being worked on are: ===Atom-counting approaches=== * The Avogadro approach attempts at defining the kilogram by a fixed count of silicon atoms. As a practical realization, a sphere will be used where the size is measured by interferometry. * The ion accumulation approach involves accumulation of gold atoms and measuring the electrical current required to neutralise them. ===Fundamental-constant approaches=== * The Watt balance uses the current balance that formerly was used to define the ampere to relate the kilogram to a value for Planck's constant, based on the definitions of the volt and the ohm. * The levitated superconductor approach relates the kilogram to electrical quantities by levitating a superconducting body in a magnetic field generated by a superconducting coil, and measuring the electrical current required in the coil. * Since the values of the Josephson constant (CIPM (1988) Recommendation 1, PV 56; 19) and von Klitzing constant (CIPM (1988), Recommendation 2, PV 56; 20) constants have been given conventional values, it is possible to combine these values (KJ ≡ 4.835 979×1014 Hz/V and RK ≡ 2.581 280 7×104 Ω) with the definition of the ampere to define the kilogram. As follows: :The kilogram is the mass which would be accelerated at precisely 2×10-7 m/s² if subjected to the per metre force between two straight parallel conductors of infinite length, of negligible circular cross section, placed 1 metre apart in vacuum, through which flow a constant current of exactly 6.241 509 629 152 65 × 1018 elementary charges per second. ==Link with weight== When the weight of an object is given in kilograms, the property intended is almost always mass. Occasionally the gravitational force on an object is given in "kilograms", but the unit used is not a true kilogram: it is the deprecated kilogram-force (kgf), also known as the kilopond (kp). An object of mass 1 kg at the surface of the Earth will be subjected to a gravitational force of approximately 9.80665 newtons (the SI unit of force). Note that the factor of 980.665 cm/s² (as the CGPM defined it, when cgs systems were the primary systems used) is only an agreed-upon conventional value (3rd CGPM (1901), CR 70) whose purpose is to define grams force. The local gravitational acceleration ''g'' varies with latitude and altitude and location on the Earth, so before this conventional value was agreed upon, the gram-force was only an ill-defined unit. (See also gee, a standard measure of gravitational acceleration.) ===Orders of magnitude=== *A yottagram (symbol: Yg) is 1024 g *A zettagram (symbol: Zg) is 1021 g. This is equal to one million trillion kilograms. *An exagram (symbol: Eg) is equal to 1018 grams. *A petagram (symbol: Pg) is 1015 g *A teragram (symbol: Tg) is 1012 g *The gigagram, with symbol Gg, is equal to 1,000,000 kg, or 1,000 tonne. It rarely has any practical application. * A centigram (symbol cg) is 1/100 of a gram. *The milligram (symbol mg) is defined as 10−6 kg. It is used for stating the masses of small objects. A grain of sand might be close in mass to a milligram. Laboratory scientists frequently measure masses in milligrams. Substances found in small amounts, such as sodium in food, and doses of pharmaceuticals, such as aspirin, are generally measured in milligrams. **One milligram is the weight of 1 millimetre3 of water (a cube of size 1 mm × 1 mm × 1 mm). **See 1 E-6 kg for comparisons. * The microgram (symbol µg, sometimes mcg) is defined as 1 µg = 10−9 kilogram. See 1 E-9 kg for comparisons. * The nanogram (symbol ng) is defined as 1 × 10−12 kilogram * The picogram (symbol pg) defined as 1 × 10−15 kilogram * The femtogram (symbol fg) defined as 1 × 10−18 kilogram * An attogram (symbol ag) is 10−18 gram. In 2004, a research team at Cornell University made a detector using NEMS cantilevers with sub-attogram sensitivity. *A zeptogram (symbol zg) is 10−24 kilograms *A yoctogram (symbol yg) equals 1 × 10−24 grams. It can be used for masses of nucleons, atoms and molecules. It is a little large for light particles, but yocto- is the last official prefix in the sequence. **The coefficient is close to the reciprocal of Avogadro's number: 1 atomic mass unit = 1.660 54 yg ** Although the amu is often convenient as a unit, one may sometimes want to use yoctograms to relate easily to other SI values. **Mass of an electron: 0.000 91 yg **Mass of a proton : 1.672 6 yg **Mass of a neutron: 1.674 9 yg ==See also== * orders of magnitude (mass) for comparisons with other masses ==External links== *[http://www.npl.co.uk/mass/faqs/kilogram.html National Physical Laboratory FAQ on kilogram definition, the need for a new definition, and some alternatives] * [http://www.ex.ac.uk/trol/scol/index.htm Conversion Calculator for Units of MASS (& Weight)] *[http://nvl.nist.gov/pub/nistpubs/jres/106/4/j64schw.pdf More on the NIST Watt Balance] *[http://www.npl.co.uk/mass/avogadro.html More on the Avogadro project] *[http://www.ex.ac.uk/trol/scol/ccmass.htm Conversion: Units of Weight] *[http://www.bipm.fr Le Bureau International des Poids et Mesures] *[http://www.hgc.cornell.edu/Nems%20Folder/Attogram%20Sensitivity%20Using%20Nanoelectromechanical.html Attogram Detection] *[http://www.newscientist.com/article.ns?id=dn7208&feedId=online-news_rss20 ''World's most sensitive scales weigh a zeptogram'', by New Scientist.com] *[http://news.bbc.co.uk/1/hi/sci/tech/4394947.stm Scales tip with tiniest mass yet, by BBC News Online] SI base units Units of mass lv:Kilograms zh-min-nan:Kong-kin simple:Kilogram th:กิโลกรัม vi:Kilôgam
All terms of science, including units of measure, use ''operational definitions'', that is, definitions based on actually performable experiments and observable results. The kilogram is intended to represent the mass of one litre of water (where litre is defined in terms of metre, and metre is defined in terms of the measurable speed of light), but that's a theoretical thing --it's not possible with today's technology (nor was it in the past) to conduct any specific experiment with water to produce this value. The kilogram has always been officially ''defined'' in terms of the artifact in Paris (the metre once was as well, but now we have new experiments). There is a movement among some scientists now to redefine it in terms of a new experiment in which measurable electrical potentials move a specific mass, but this is still in the works. --User:Lee Daniel Crocker :The kilogram as = 1 L of water was true between 1901 and 1964 (definition of the Litre; see CGPM). :User:Urhixidur 20:29, 2004 Nov 23 (UTC) I was under the impression that the kilogram had recently been redefined in relation to ''x'' moles of a certain isotope, rather than the kilogram at Sèvres. Is that not true? - montréalais :There are a number of competing plans to redefine the kilogram in terms of something repeatable. No plan has yet been decided on. -- User:The Anome 22:10 22 Jun 2003 (UTC) According to the Bureau International des Poids et Mesures, the kilogram is still defined by the international prototype in Paris. Do you think it's fair use to put a picture of it from the BIPM site in the article? User:Basil Fawlty 15:12 22 Jun 2003 (UTC) :Seems like it would be fair if the source and a Wikipedia:Image_copyright_tags were included. As the Wikipedia:Fair_use states, "Unique historical images which we cannot reproduce by other means" can be classified as fair use. The [http://www.bipm.org/en/scientific/mass/pictures_mass/prototype.html big pic] is nice. -- User:Mjwilco 19:12, 11 Sep 2004 (UTC) ---- What does this mean: "grain in now obsolete Portuguese spelling"? Is that supposed to imply that the word "gram" comes from obsolete Portuguese? Webster's 1913 says: "F. gramme, from Gr. ? that which is written, a letter, a small weight, fr. ? to write.". Or is it some weird reference to the imperial unit ''grain'', meaning 1/7000 of a pound? -- User:EvanProdromou 05:37 20 Jul 2003 (UTC) ---- Am I right in assuming that, by E=mc^2, if you heat an object, you will (ever-so-slightly) increase its mass, by adding thermal energy? (according to http://www.google.com/search?q=1%20calorie%20in%20grams&ie=UTF-8&oe=UTF-8 to heat 1 gram of water by 1 degree C, requires ~0.465 femtograms of energy. Therefore any atom-based definition of the kilogram will require a temperature reference. User:Csmiller 11:39, Nov 23, 2004 (UTC) :You are quite right. In Einsteinian terms, we would refer to the zero K mass as the object's rest mass. Note that the SI definition of the second also takes care to specify that the ground state hyperfine transition used occurs at zero K. :User:Urhixidur 20:29, 2004 Nov 23 (UTC) == Kilogram as Base unit? == Has the kilogram always been considered a base unit? If so, why does it have a prefix? Why doesn't the metric system use a basic word for that unit, and instead call the gram milli-whatever? If it wasn't considered a base unit initially, when did it come to be considered the base unit? It has always seemed strange to me that a so-called "base" unit has a prefix User:Nik42 09:00, 26 Jan 2005 (UTC) :It really is quite stupid, but its too late to change that now :P. My theory is that the gram initially was the base unit, but people realised that it was smarter to use kg (less room for error when copying the base-sphere, and also derived definitions like the newton make more sense. That and it would be strange to measure the human body in grams "I weigh 75345 g, what do you wheigh?) So they just changed the base and kept the name to avoid confusion. This is my theory anyway User:Gkhan 04:33, Feb 27, 2005 (UTC) ::Well, the weight thing's not really an issue. That's what prefixes are for anyways :-) I mean, no one would say that two cities were 52,000 meters apart, they'd say they were 52 kilometers apart. Still, kg definitely does make more sense as a basic unit for pretty much any purpose, which is why I find it odd that gram gets the basic name. - User:Nik42 07:50, 1 Mar 2005 (UTC) ---- AFAIK there is no atomic definition for kilogram. In 1967 the kilogram[http://physics.nist.gov/cgi-bin/cuu/Value?kgu] was defined as the mass of 5.0188 X 10 (power 25) atoms of the carbon isotope of atomic mass number 12. The experimental uncertainty in the count was about 1 part in 20,000. -- User:Orionix 03:11, 4 Feb 2005 (UTC) == Clarify changes over the last 100 years == From the article: Although it is accurate to state that all other objects in the universe have gained 50 micrograms per kilogram, this perspective is counterintuitive and defeats the purpose of a standard unit of mass. This makes no sense to me. If you counted the number of micrograms in a kilogram 100 years ago, you'd get a billion (if my metric conversions are correct). And the article is implying that if you count the number of micrograms in a kilogram today, you'd get 1,000,000,050? Wrong. Maybe a more clear way to say it would be "It is accurate to state that any object in the universe (other than the reference metal in France) that had a mass of 1 kilogram 100 years ago, and has not changed since then, now is considered to have a mass which is 50 micrograms larger than a kilogram. This perspective is counterintuitive and defeats the purpose of a standard unit of mass, since the standard should not change arbitrarily over time." --User:24.29.11.65 11:27, 27 Feb 2005 (UTC) :How is it known that the standard has lost weight? How can one compare a standard to itself over time? It seems like a paradox to me. User:Prometheus235 19:03, 16 Jun 2005 (UTC) ::Presumably because you can compare the weight of other objects over time. If you consistently find that items measured 100 years ago appeared to possess slightly greater mass than they do today, the simplest explanation is not that all of those items gained mass, but that the standard lost mass. - User:Nik42 18:25, 17 Jun 2005 (UTC) :::Also the standard has "official copies" that are stored and treated in the same manner as the standard itself. What's actually been found is that the standard is lighter in comparison to the average of these copies than it previously was. User:PakaranUser talk:Pakaran 19:12, 17 Jun 2005 (UTC)
See other meanings of words starting from letter:
Words begining with Kilogram:
Kilogram
Kilogram
Kilogram-force
Kilogramme
Kilograms
Kilogram_per_cubic_meter
Kilogram_per_cubic_metre
Kilogram_per_metre_cubed
Kilogram
The kilogram or kilogramme, (symbol: kg) is the SI base unit of mass. A gram is defined as one thousandth of a kilogram. Conversion of units#Mass describes equivalent units of mass in other systems. == Multiples == SI prefixes are used to name multiples and subdivisions of the kilogram. The most commonly used ones are: ; tonne : 1 E3 kg (strictly speaking, this should be named ''megagram'', but the name is less commonly used) (not to be confused with non-metric Ton#Units_of_mass units) ; gram : 1 E-3 kg ; milligram : 1 E-6 kg = 1 E-6 kg ; microgram :1 E-9 kg = 1 E-9 kg == Definition == The kilogram is the only one of the SI units which is still defined in relation to an artifact rather than to fundamental physical properties. It is also the only ''base'' unit that employs one of the prefixes. The kilogram was ''originally'' defined as the mass of one litre of pure water at a temperature of 4 degrees Celsius and standard atmospheric pressure. This definition was hard to realize accurately, partially because the density of water depends ever-so-slightly on the pressure, and pressure units include mass as a factor, introducing a circular definition in the definition of the kilogram. To avoid these problems, the kilogram was redefined as ''precisely'' the mass of a particular standard mass created to approximate the original definition. Since 1889, the SI system defines the unit to be equal to the mass of the international prototype of the kilogram, which is made from an alloy of platinum and Iridium (element) of 1 E-2 m height and diameter, and kept at the Bureau International des Poids et Mesures (International Bureau of Weights and Measures). Official copies of the prototype kilogram are made available as national prototypes, which are compared to the Paris prototype ("''Le Grand Kilo''") roughly every 1 E8 s. The international prototype kilogram was made in the 1880s. By definition, the error in the repeatability of the current definition is exactly zero; however, in the usual sense of the word, it can be regarded as of the order of 2 micrograms. This is found by comparing the official standard with its official copies, which are made of roughly the same materials and kept under the same conditions. There is no reason to believe that the official standard is any more or less stable than its official copies, thus giving a way to estimate its stability. This procedure is performed roughly once every forty years. The international prototype of the kilogram seems to have lost about 50 micrograms in the last 100 years, and the reason for the loss is still unknown (reported in ''Der Spiegel'', 2003 #26). The observed variation in the prototype has intensified the search for a new definition of the kilogram. It is accurate to state that any object in the universe (other than the reference metal in France) that had a mass of 1 kilogram 100 years ago, and has not changed since then, now is considered to have a mass which is 50 micrograms larger than a kilogram. This perspective is counterintuitive and defeats the purpose of a standard unit of mass, since the standard should not change arbitrarily over time. == The gram == The gram or gramme, symbol g, is a unit of mass, and is defined in the SI system of units as one one-thousandth of a kilogram (i.e., 1 × 10−3 kg). One ounce avoirdupois is 28.34952 grams (see Conversion of units#Mass). Although the gram is not an SI base unit, it is a submultiple of the kilogram, which ''is'' a base unit. In SI, ''gram'' is also the root to which SI prefixes are applied. However, the gram is a base unit of the older cgs system of measurement, a system which is no longer widely used. The gram is an essential measurement unit in scientific endeavors worldwide. A gram was originally defined as the weight of one cubic centimeter of water at its densest. This occurs at a temperature near four degrees Celsius. However, its definition was changed to the mass of a metal artifact in the eighteenth century. == Proposed future definitions == There is an ongoing effort to introduce a new definition for the kilogram by way of fundamental or atomic constants. The proposals being worked on are: ===Atom-counting approaches=== * The Avogadro approach attempts at defining the kilogram by a fixed count of silicon atoms. As a practical realization, a sphere will be used where the size is measured by interferometry. * The ion accumulation approach involves accumulation of gold atoms and measuring the electrical current required to neutralise them. ===Fundamental-constant approaches=== * The Watt balance uses the current balance that formerly was used to define the ampere to relate the kilogram to a value for Planck's constant, based on the definitions of the volt and the ohm. * The levitated superconductor approach relates the kilogram to electrical quantities by levitating a superconducting body in a magnetic field generated by a superconducting coil, and measuring the electrical current required in the coil. * Since the values of the Josephson constant (CIPM (1988) Recommendation 1, PV 56; 19) and von Klitzing constant (CIPM (1988), Recommendation 2, PV 56; 20) constants have been given conventional values, it is possible to combine these values (KJ ≡ 4.835 979×1014 Hz/V and RK ≡ 2.581 280 7×104 Ω) with the definition of the ampere to define the kilogram. As follows: :The kilogram is the mass which would be accelerated at precisely 2×10-7 m/s² if subjected to the per metre force between two straight parallel conductors of infinite length, of negligible circular cross section, placed 1 metre apart in vacuum, through which flow a constant current of exactly 6.241 509 629 152 65 × 1018 elementary charges per second. ==Link with weight== When the weight of an object is given in kilograms, the property intended is almost always mass. Occasionally the gravitational force on an object is given in "kilograms", but the unit used is not a true kilogram: it is the deprecated kilogram-force (kgf), also known as the kilopond (kp). An object of mass 1 kg at the surface of the Earth will be subjected to a gravitational force of approximately 9.80665 newtons (the SI unit of force). Note that the factor of 980.665 cm/s² (as the CGPM defined it, when cgs systems were the primary systems used) is only an agreed-upon conventional value (3rd CGPM (1901), CR 70) whose purpose is to define grams force. The local gravitational acceleration ''g'' varies with latitude and altitude and location on the Earth, so before this conventional value was agreed upon, the gram-force was only an ill-defined unit. (See also gee, a standard measure of gravitational acceleration.) ===Orders of magnitude=== *A yottagram (symbol: Yg) is 1024 g *A zettagram (symbol: Zg) is 1021 g. This is equal to one million trillion kilograms. *An exagram (symbol: Eg) is equal to 1018 grams. *A petagram (symbol: Pg) is 1015 g *A teragram (symbol: Tg) is 1012 g *The gigagram, with symbol Gg, is equal to 1,000,000 kg, or 1,000 tonne. It rarely has any practical application. * A centigram (symbol cg) is 1/100 of a gram. *The milligram (symbol mg) is defined as 10−6 kg. It is used for stating the masses of small objects. A grain of sand might be close in mass to a milligram. Laboratory scientists frequently measure masses in milligrams. Substances found in small amounts, such as sodium in food, and doses of pharmaceuticals, such as aspirin, are generally measured in milligrams. **One milligram is the weight of 1 millimetre3 of water (a cube of size 1 mm × 1 mm × 1 mm). **See 1 E-6 kg for comparisons. * The microgram (symbol µg, sometimes mcg) is defined as 1 µg = 10−9 kilogram. See 1 E-9 kg for comparisons. * The nanogram (symbol ng) is defined as 1 × 10−12 kilogram * The picogram (symbol pg) defined as 1 × 10−15 kilogram * The femtogram (symbol fg) defined as 1 × 10−18 kilogram * An attogram (symbol ag) is 10−18 gram. In 2004, a research team at Cornell University made a detector using NEMS cantilevers with sub-attogram sensitivity. *A zeptogram (symbol zg) is 10−24 kilograms *A yoctogram (symbol yg) equals 1 × 10−24 grams. It can be used for masses of nucleons, atoms and molecules. It is a little large for light particles, but yocto- is the last official prefix in the sequence. **The coefficient is close to the reciprocal of Avogadro's number: 1 atomic mass unit = 1.660 54 yg ** Although the amu is often convenient as a unit, one may sometimes want to use yoctograms to relate easily to other SI values. **Mass of an electron: 0.000 91 yg **Mass of a proton : 1.672 6 yg **Mass of a neutron: 1.674 9 yg ==See also== * orders of magnitude (mass) for comparisons with other masses ==External links== *[http://www.npl.co.uk/mass/faqs/kilogram.html National Physical Laboratory FAQ on kilogram definition, the need for a new definition, and some alternatives] * [http://www.ex.ac.uk/trol/scol/index.htm Conversion Calculator for Units of MASS (& Weight)] *[http://nvl.nist.gov/pub/nistpubs/jres/106/4/j64schw.pdf More on the NIST Watt Balance] *[http://www.npl.co.uk/mass/avogadro.html More on the Avogadro project] *[http://www.ex.ac.uk/trol/scol/ccmass.htm Conversion: Units of Weight] *[http://www.bipm.fr Le Bureau International des Poids et Mesures] *[http://www.hgc.cornell.edu/Nems%20Folder/Attogram%20Sensitivity%20Using%20Nanoelectromechanical.html Attogram Detection] *[http://www.newscientist.com/article.ns?id=dn7208&feedId=online-news_rss20 ''World's most sensitive scales weigh a zeptogram'', by New Scientist.com] *[http://news.bbc.co.uk/1/hi/sci/tech/4394947.stm Scales tip with tiniest mass yet, by BBC News Online] SI base units Units of mass lv:Kilograms zh-min-nan:Kong-kin simple:Kilogram th:กิโลกรัม vi:Kilôgam
Kilogram
All terms of science, including units of measure, use ''operational definitions'', that is, definitions based on actually performable experiments and observable results. The kilogram is intended to represent the mass of one litre of water (where litre is defined in terms of metre, and metre is defined in terms of the measurable speed of light), but that's a theoretical thing --it's not possible with today's technology (nor was it in the past) to conduct any specific experiment with water to produce this value. The kilogram has always been officially ''defined'' in terms of the artifact in Paris (the metre once was as well, but now we have new experiments). There is a movement among some scientists now to redefine it in terms of a new experiment in which measurable electrical potentials move a specific mass, but this is still in the works. --User:Lee Daniel Crocker :The kilogram as = 1 L of water was true between 1901 and 1964 (definition of the Litre; see CGPM). :User:Urhixidur 20:29, 2004 Nov 23 (UTC) I was under the impression that the kilogram had recently been redefined in relation to ''x'' moles of a certain isotope, rather than the kilogram at Sèvres. Is that not true? - montréalais :There are a number of competing plans to redefine the kilogram in terms of something repeatable. No plan has yet been decided on. -- User:The Anome 22:10 22 Jun 2003 (UTC) According to the Bureau International des Poids et Mesures, the kilogram is still defined by the international prototype in Paris. Do you think it's fair use to put a picture of it from the BIPM site in the article? User:Basil Fawlty 15:12 22 Jun 2003 (UTC) :Seems like it would be fair if the source and a Wikipedia:Image_copyright_tags were included. As the Wikipedia:Fair_use states, "Unique historical images which we cannot reproduce by other means" can be classified as fair use. The [http://www.bipm.org/en/scientific/mass/pictures_mass/prototype.html big pic] is nice. -- User:Mjwilco 19:12, 11 Sep 2004 (UTC) ---- What does this mean: "grain in now obsolete Portuguese spelling"? Is that supposed to imply that the word "gram" comes from obsolete Portuguese? Webster's 1913 says: "F. gramme, from Gr. ? that which is written, a letter, a small weight, fr. ? to write.". Or is it some weird reference to the imperial unit ''grain'', meaning 1/7000 of a pound? -- User:EvanProdromou 05:37 20 Jul 2003 (UTC) ---- Am I right in assuming that, by E=mc^2, if you heat an object, you will (ever-so-slightly) increase its mass, by adding thermal energy? (according to http://www.google.com/search?q=1%20calorie%20in%20grams&ie=UTF-8&oe=UTF-8 to heat 1 gram of water by 1 degree C, requires ~0.465 femtograms of energy. Therefore any atom-based definition of the kilogram will require a temperature reference. User:Csmiller 11:39, Nov 23, 2004 (UTC) :You are quite right. In Einsteinian terms, we would refer to the zero K mass as the object's rest mass. Note that the SI definition of the second also takes care to specify that the ground state hyperfine transition used occurs at zero K. :User:Urhixidur 20:29, 2004 Nov 23 (UTC) == Kilogram as Base unit? == Has the kilogram always been considered a base unit? If so, why does it have a prefix? Why doesn't the metric system use a basic word for that unit, and instead call the gram milli-whatever? If it wasn't considered a base unit initially, when did it come to be considered the base unit? It has always seemed strange to me that a so-called "base" unit has a prefix User:Nik42 09:00, 26 Jan 2005 (UTC) :It really is quite stupid, but its too late to change that now :P. My theory is that the gram initially was the base unit, but people realised that it was smarter to use kg (less room for error when copying the base-sphere, and also derived definitions like the newton make more sense. That and it would be strange to measure the human body in grams "I weigh 75345 g, what do you wheigh?) So they just changed the base and kept the name to avoid confusion. This is my theory anyway User:Gkhan 04:33, Feb 27, 2005 (UTC) ::Well, the weight thing's not really an issue. That's what prefixes are for anyways :-) I mean, no one would say that two cities were 52,000 meters apart, they'd say they were 52 kilometers apart. Still, kg definitely does make more sense as a basic unit for pretty much any purpose, which is why I find it odd that gram gets the basic name. - User:Nik42 07:50, 1 Mar 2005 (UTC) ---- AFAIK there is no atomic definition for kilogram. In 1967 the kilogram[http://physics.nist.gov/cgi-bin/cuu/Value?kgu] was defined as the mass of 5.0188 X 10 (power 25) atoms of the carbon isotope of atomic mass number 12. The experimental uncertainty in the count was about 1 part in 20,000. -- User:Orionix 03:11, 4 Feb 2005 (UTC) == Clarify changes over the last 100 years == From the article: Although it is accurate to state that all other objects in the universe have gained 50 micrograms per kilogram, this perspective is counterintuitive and defeats the purpose of a standard unit of mass. This makes no sense to me. If you counted the number of micrograms in a kilogram 100 years ago, you'd get a billion (if my metric conversions are correct). And the article is implying that if you count the number of micrograms in a kilogram today, you'd get 1,000,000,050? Wrong. Maybe a more clear way to say it would be "It is accurate to state that any object in the universe (other than the reference metal in France) that had a mass of 1 kilogram 100 years ago, and has not changed since then, now is considered to have a mass which is 50 micrograms larger than a kilogram. This perspective is counterintuitive and defeats the purpose of a standard unit of mass, since the standard should not change arbitrarily over time." --User:24.29.11.65 11:27, 27 Feb 2005 (UTC) :How is it known that the standard has lost weight? How can one compare a standard to itself over time? It seems like a paradox to me. User:Prometheus235 19:03, 16 Jun 2005 (UTC) ::Presumably because you can compare the weight of other objects over time. If you consistently find that items measured 100 years ago appeared to possess slightly greater mass than they do today, the simplest explanation is not that all of those items gained mass, but that the standard lost mass. - User:Nik42 18:25, 17 Jun 2005 (UTC) :::Also the standard has "official copies" that are stored and treated in the same manner as the standard itself. What's actually been found is that the standard is lighter in comparison to the average of these copies than it previously was. User:PakaranUser talk:Pakaran 19:12, 17 Jun 2005 (UTC)
See other meanings of words starting from letter:
K
KA | KB | KC | KD | KE | KF | KG | KH | KI | KJ | KL | KM | KN | KO | KP | KR | KS | KT | KU | KW | KX | KY | KZ |Words begining with Kilogram:
Kilogram
Kilogram
Kilogram-force
Kilogramme
Kilograms
Kilogram_per_cubic_meter
Kilogram_per_cubic_metre
Kilogram_per_metre_cubed
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