# Why does e mc squared

## Why Does E=mc²? by Brian Cox

The most accessible, entertaining, and enlightening explanation of the best-known physics equation in the world, as rendered by two of today’s leading scientists.Professor Brian Cox and Professor Jeff Forshaw go on a journey to the frontier of 21st century science to consider the real meaning behind the iconic sequence of symbols that make up Einstein’s most famous equation, E=mc2. Breaking down the symbols themselves, they pose a series of questions: What is energy? What is mass? What has the speed of light got to do with energy and mass? In answering these questions, they take us to the site of one of the largest scientific experiments ever conducted. Lying beneath the city of Geneva, straddling the Franco-Swiss boarder, is a 27 km particle accelerator, known as the Large Hadron Collider. Using this gigantic machine—which can recreate conditions in the early Universe fractions of a second after the Big Bang—Cox and Forshaw will describe the current theory behind the origin of mass.

Alongside questions of energy and mass, they will consider the third, and perhaps, most intriguing element of the equation: c - or the speed of light. Why is it that the speed of light is the exchange rate? Answering this question is at the heart of the investigation as the authors demonstrate how, in order to truly understand why E=mc2, we first must understand why we must move forward in time and not backwards and how objects in our 3-dimensional world actually move in 4-dimensional space-time. In other words, how the very fabric of our world is constructed. A collaboration between two of the youngest professors in the UK,

*Why Does E=mc2?*promises to be one of the most exciting and accessible explanations of the theory of relativity in recent years.

## Why E=mc² is wrong

As Einstein himself put it:. It followed from the special theory of relativity that mass and energy are both but different manifestations of the same thing — a somewhat unfamiliar conception for the average mind. The presence of glycoaldehydes -- a simple sugar -- in an interstellar gas cloud.

Brian Cox

## Mass–energy equivalence

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: [1]. 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. Chemical reactions , nuclear reactions , and other energy transformations may cause a system to lose some of its energy content and thus some corresponding mass , releasing it as the radiant energy of light or as thermal energy for example. A consequence of the mass—energy equivalence is that if a body is stationary, it still has some internal or intrinsic energy, called its rest energy , corresponding to its rest mass. When the body is in motion, its total energy is greater than its rest energy, and equivalently its total mass also called relativistic mass in this context is greater than its rest mass.

Many people fail to realize just how much energy there is locked up in matter. The nucleus of any atom is an oven of intense radiation, and when you open the oven door, that energy spills out; oftentimes violently. However, there is something even more intrinsic to this aspect of matter that escaped scientists for years. This seemingly simple algebraic formula represents the correlation of energy to matter energy equivalence of any given amount of mass. Many have heard of it, but not very many understand what it implies. Many people are unaware of just how much energy is contained within matter. So, for the next few minutes, I will attempt to convey to you the magnitude of your own personal potential energy equivalence.

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Let's play a game! The speed of light is just a number, right?

Did you know that you're travelling at the speed of light? Not just you: your book, your chair, the room around you, your home. In fact, everything is moving at the speed of light. Don't feel it? Don't worry, no one else did either until Albert Einstein redefined the substance of reality at the start of the 20th century. Neither Galileo, Michael Faraday, James Clerk Maxwell or Isaac Newton knew about the speed of light thing, despite laying the foundations for the insights that the Austrian patent-clerk-turned-physicist would eventually have. Let me clarify.

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.

## 4 thoughts on “Why Does E=mc²? by Brian Cox”

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Einstein's most famous equation, E = mc^2, falls into that category, stating that the energy content of a massive body is equal to that object's mass times the speed of light squared. But why are the energies of the two photons equal to the mass of the electron (and positron.

Why Does E=mc^2?

Astrophysicist Paul Sutter provides a delightful look at the science behind Einstein's famous E=mc2 equation.