### Albert Einstein

This name need not be explained. Albert Einstein is considered to be one of the best physicists in the human history.

The twentieth century has undoubtedly been the most significant for the advance of science, in general, and Physics, in particular. And Einstein is the most luminated star of the 20th century. He literally created cm upheaval by the publication, in quick succession, in the year 1905, two epoch-making papers, on the concept of the photon and on the Electrodynamics of moving bodies respectively, with yet another on the Mathematical analysis of Brownian Motion thrown in, in between.

The Electrodynamics of moving bodies was the biggest sensation and it demolished at one stroke some of the most cherished and supposedly infallible laws and concepts and gave the breathtaking new idea of the relativity of space and time.

Truly it may be said that just as the enunciation of Newton’s laws of motion heralded emancipation from the age-old Aristotelian ideas of motion, so also did Einstein’s Theory of relativity make a proclamation, loud and clear, of emancipation from the crippling bondage to luminiferous ether and the confused notions of absolute space and time.

## Einstein’s Introduction to His Concept of Relativity

As to an Introduction to the Theory of Relativity – one must read this statement what Einstein self-made to introduce the world:

I am anxious to draw attention to the fact that this theory is not speculative in origin; it owes its intention entirely to the desire to make physical theory fit observed fact as well as possible. We have here no revolutionary act but the natural continuation of a line that can be traced through centuries. The abandonment of a certain concept combed with space-time and motion hitherto treated as fundamental must not be regarded as arbitrary but only conditioned by observed facts. The law of constant velocity of light in empty space which has been confirmed by the development of the electrodynamics and optics and the equal legitimacy of all inertial systems (special theory of relativity) which was proved in a particularly incisive manner by Michelson’s famous experiment, between them made it necessary, to begin with, that the concept of time should be made relative, each inertial system being given its my special time. . . . . . . . It is , to work out the relations between general concepts and empirical facts more precisely. The fundamental principle here is that the justification for a physical concept lies exclusively in its clear and unambiguous relation to facts that can be experienced.

Feel free to ask questions, send feedback and even point out mistakes. Great conversations start with just a single word.

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## 5 comments

Albert Einstein is rightly considered one of the greatest scientists of all time, and his two theories of relativity – special and general – are the crowning glory of his scientific oeuvre. They have fundamentally reshaped our thinking of the most fundamental concepts – space, time and matter. These two theories have also withstood the test of time, and a century after they had been formulated they are still almost entirely used in their original formulations.

H. A. Lorentz was a distinguished physicist in his own right, and one of Einstein’s closest scientific and personal friends. The special kind of the coordinate transformations that characterize the special relativity have been named after him, and he is one of the first people to whom Einstein described his general theory of relativity. In that regard he is certainly one of the foremost early authorities on the subject.

This short book primarily deals with the general theory of relativity. It was written shortly after one of the most startling predictions of the general relativity – the deflection of light by the sun – was confirmed by the British astronomer Eddington. The public was immensely fascinated by this incredible phenomenon, and there was a need for an accessible and informative explanation of general relativity. Unfortunately, even though general relativity is an incredibly “beautiful” theory in its own right, the mathematical apparatus required for its full understanding is formidable. This short introduction completely sidesteps all mathematical language and presents the subject in terms of the most fundamental concepts.

It is quite remarkable that a short popular book like this one has withstood the test of time. As a college physics professor who works with general relativity I could not think of much that I would add or subtract from this book. However, this is a rather short book and if a reader would like a bit more information on the subject that is still at the level of general reader I would strongly recommend Relativity A Very Short Introduction.

What is the source of this above quote? – “I am anxious to draw attention…by Michelson’s famous experiment…that can be experienced.”

It was actually a Lecture at King’s College, London. Published in Mein Weltbild, Amsterdam: Querido Verlag, 1934. I would like to cite http://photontheory.com/Einstein/Einstein11.html

albert einstein is a good

mathematician . IHave not any word to say something.☆☆☆☆☆

am i correct

Consider a body of rest mass mo. A force F is acting on it in

X–direction. According to Newton’s second law of motion, force is

defined as the rate of change of momentum.

i.e. F = d/dt (mv) …(1)

According to the theory of relativity, both mass and velocity are

variable, therefore

F = mdv/dt + vdm/dt …(2)

If a body is displaced through a distance dx due to the force F

then, the increase in kinetic energy $dE_k$ of the body is

$$dE_k = Fdx$$

= (mdv/dt + vdm/dt ) dx

= (mdv)dx/dt + (vdm)dx/dt

$$dE_k = mv dv + v^2dm \ldots (3)$$

From Einstein’s theory of relativity

on solving we get

$$m^2c^2 – m^2v^2 = m_0^2c^2$$

Differentiating we get,

$$c^2 \cdot 2m dm – v^2 2m dm – m^2 2v dv = 0$$

$$c^2dm = mv dv + v^2 dm \ldots (4)$$

Comparing equations (3) and (4) we get,

$$dE_k = c^2 dm \ldots (5)$$

Thus the change in kinetic energy $dE_k$ is directly proportional to

the change in mass dm.

When a body is at rest, its velocity is zero and $m = m_0$. When its

velocity is v its mass becomes m. Therefore integrating equation (5)

we get

$$E_k=mc^2-m_0c^2$$

This is the relativistic formula for kinetic energy. $m_0$ is the rest

mass and $m_0c^2$ is the internal energy (rest mass energy or rest energy).

∴ Total energy = kinetic energy of the moving body

+ rest mass energy

$$E = E_k + m_0 c^2 \\

= mc^2 – m_0 c^2 + m_0 c^2$$

$$ E = mc^2$$

IF it`s correct pleace say me the mistake