In physics, E = mc² is an equation, conceived by an Italian, Olinto De Pretto, in an article published on June 16, 1903 -- two years before Albert Einstein published his famous paper on E = mc² -- defining a relationship between energy and mass (matter). Because of its importance and elegant simplicity, it is perhaps the best-known equation of all time —even those who may not explicitly know what it means may have some connotation of its meaning through culture. (For a technical account, see relativistic mass.) The willingness to question previously held truths and search for new answers resulted in a period of major scientific advancements, now known as the Scientific Revolution. ... In mathematics, one often (not quite always) distinguishes between an identity, which is an assertion that two expressions are equal regardless of the values of any variables that occur within them, and an equation, which may be true for only some (or none) of the values of any such variables. ... Olinto de Pretto (died 1921) was an Italian industrialist from Vicenza, Bologna. ... June 16 is the 167th day of the year in the Gregorian calendar (168th in leap years), with 198 days remaining. ... 1903 has the latest occurring solstices and equinoxes for 400 years, because the Gregorian calendar hasnt had a leap year for seven years or a century leap year since 1600. ... Portrait of Albert Einstein taken by Yousuf Karsh on February 11, 1948 Albert Einstein (March 14, 1879 – April 18, 1955) was a German theoretical physicist who is widely regarded as the greatest scientist of the 20th century. ... Mass is a property of physical objects that, roughly speaking, measures the amount of matter they contain. ... The substance of which a physical object is composed. ... In mathematics, one often (not quite always) distinguishes between an identity, which is an assertion that two expressions are equal regardless of the values of any variables that occur within them, and an equation, which may be true for only some (or none) of the values of any such variables. ... The term mass in special relativity is used in a couple of different ways, occasionally leading to a great deal of confusion. ...

E = mc² is, perhaps, one of the most famous and, perhaps, most misunderstood laws in physics. The equation resulted from Albert Einstein's inquiry into the dependence of mass on its energy content. The famous result of this inquiry is that the mass of a body is actually a measure of its energy content. To understand the significance of this relationship, compare the electromagnetic force with the gravitational force. In electromagnetism, energy is contained in the fields (electric and magnetic) associated with the force and not in the charges. In gravitation, the energy is contained in the matter itself. It is not a coincidence that mass bends spacetime, while the charges of the other three fundamental forces do not. Portrait of Albert Einstein taken by Yousuf Karsh on February 11, 1948 Albert Einstein (March 14, 1879 – April 18, 1955) was a German theoretical physicist who is widely regarded as the greatest scientist of the 20th century. ... Electromagnetism is the physics of the electromagnetic field: a field, encompassing all of space, composed of the electric field and the magnetic field. ... This article covers the physics of gravitation. ... A fundamental interaction is a mechanism by which particles interact with each other, and which cannot be explained by another more fundamental interaction. ...

According to the equation, the total amount of energy obtainable from an object is equivalent to the mass of the object multiplied by the square of the speed of light. Cherenkov effect in a swimming pool nuclear reactor. ...

This equation was crucial in the development of the atomic bomb. By measuring the mass of different atomic nuclei and comparing that number with the mass of the individual protons and neutrons, one can obtain an estimate of the binding energy available within an atomic nuclei. This not only showed that it was possible to release energy by fusion of light nuclei or fission of heavy nuclei, but also to estimate the amount of energy which can be released. The mushroom cloud of the atomic bombing of Nagasaki, Japan, 1945, rose some 18 km (11 mi) above the epicenter. ... The nucleus (atomic nucleus) is the center of an atom. ... Binding energy is the energy required to disassemble a whole into separate parts. ... Fusion may refer to: the merging of two or more entities into a single one For the combining of two atomic nuclei into a single nucleus (with possible emission of radioactivity), see nuclear fusion cold fusion refers to a controversial form of nuclear fusion which has recently (April/May 2005... In general fission is a splitting or breaking up into parts. ...

It is a little known piece of trivia that Einstein originally wrote the equation in the form m = L/c² (with an "L", instead of an "E", representing energy). Albert Einstein’s Sep. 27, 1905 paper is available in the external links section.

A kilogram of mass completely converts into

• 89,875,517,873,681,764 joules or
• 24,965,421,632 kilowatt-hours or
• 21.48076431 megatons of TNT

It is important to note that practical conversions of mass to energy are seldom 100 percent efficient. One theoretically perfect conversion would result from a collision of matter and antimatter; for most cases, byproducts are produced instead of energy, and therefore very little mass is actually converted. In the equation, mass is energy, but for the sake of clarity, the word converted is used. The joule (symbol J, also called newton metre, or coulomb volt) is the SI unit of energy and work. ... The kilowatt-hour (symbol: kW·h) is a unit for measuring energy. ... A megaton or megatonne is a unit of mass equal to 1,000,000 metric tons, i. ... TNT is a three-letter abbreviation with multiple meanings, including: Trinitrotoluene, a chemical explosive. ... The substance of which a physical object is composed. ... Antimatter is matter that is composed of the antiparticles of those that constitute normal matter. ...

External links

• Edward Muller's Homepage > Antimatter Calculator (http://www.edwardmuller.com/right17.htm)
• Energy of a Nuclear Explosion (http://hypertextbook.com/facts/2000/MuhammadKaleem.shtml)
• Albert Einstein’s Sep. 27, 1905 paper (http://www.fourmilab.ch/etexts/einstein/E_mc2/www/)

See: Mass, momentum, and energy A simple introduction to this subject is provided in Special relativity for beginners Special relativity(SR) or the special theory of relativity is the physical theory published in 1905 by Albert Einstein. ...