The equation e mc2 relates energy and
E=mc²: A Biography of the Worlds Most Famous Equation by David BodanisE=mc². Just about everyone has at least heard of Albert Einsteins formulation of 1905, which came into the world as something of an afterthought. But far fewer can explain his insightful linkage of energy to mass. David Bodanis offers an easily grasped gloss on the equation. Mass, he writes, is simply the ultimate type of condensed or concentrated energy, whereas energy is what billows out as an alternate form of mass under the right circumstances.
Just what those circumstances are occupies much of Bodaniss book, which pays homage to Einstein and, just as important, to predecessors such as Maxwell, Faraday, and Lavoisier, who are not as well known as Einstein today. Balancing writerly energy and scholarly weight, Bodanis offers a primer in modern physics and cosmology, explaining that the universe today is an expression of mass that will, in some vastly distant future, one day slide back to the energy side of the equation, replacing the dominion of matter with a great stillness--a vision that is at once lovely and profoundly frightening.
Without sliding into easy psychobiography, Bodanis explores other circumstances as well; namely, Einsteins background and character, which combined with a sterling intelligence to afford him an idiosyncratic view of the way things work--a view that would change the world. --Gregory McNamee
In the equation, the increased relativistic mass m of a body times the speed of light squared c 2 is equal to the kinetic energy E of that body. In physical theories prior to that of special relativity, mass and energy were viewed as distinct entities. Furthermore, the energy of a body at rest could be assigned an arbitrary value. In special relativity, however, the energy of a body at rest is determined to be m c 2. The mass-energy relation, moreover, implies that, if energy is released from the body as a result of such a conversion, then the rest mass of the body will decrease. Such a conversion of rest energy to other forms of energy occurs in ordinary chemical reactions , but much larger conversions occur in nuclear reactions. This is particularly true in the case of nuclear fusion reactions that transform hydrogen to helium , in which 0.
Einstein deriving special relativity, for an audience, in For hundreds of years, there was an immutable law of physics that was never challenged: that in any reaction occurring in the Universe, mass was conserved. That no matter what you put in, what reacted, and what came out, the sum of what you began with and the sum of what you ended with would be equal. But under the laws of special relativity, mass simply couldn't be the ultimate conserved quantity, since different observers would disagree about what the energy of a system was. A nuclear-powered rocket engine, preparing for testing in
It's the world's most famous equation, but what does it really mean? Under the right conditions, energy can become mass, and vice versa. We humans don't see them that way—how can a beam of light and a walnut, say, be different forms of the same thing? So why would you have to multiply the mass of that walnut by the speed of light to determine how much energy is bound up inside it? The reason is that whenever you convert part of a walnut or any other piece of matter to pure energy, the resulting energy is by definition moving at the speed of light.
In physics , mass—energy equivalence states that anything having mass has an equivalent amount of energy and vice versa, with these fundamental quantities directly relating to one another by Albert Einstein 's famous formula: . Similarly, anything having energy exhibits a corresponding mass m given by its energy E divided by the speed of light squared c 2. Because the speed of light is a very large number in everyday units, the formula implies that even an everyday object at rest with a modest amount of mass has a very large amount of energy intrinsically.
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