# Albert Einstein happy birthday doc

Albert Einstein was born 134 years ago, he has changed the world with his theories about time, matter and gravity.

Albert Einstein (1879-1955) was born in Germany and immediately demonstrate his curiosity and passion for math and physics. It is completely false the legend about his difficulties in math. Even though he didn’t have the required minimum age, he has tried the entrance examination for the Swiss Federal Polytechnic in Zurich but he failed. A year later, in 1896 he entered the Polytechnic of Zurich to study physics and mathematics.

In 1900 he obtained his diploma but not the expected teaching position and  then he got a job as a patent examiner. Far away from the academic world, Einstein started the revolution. In 1905, the so called “annus mirabilis”, he wrote 4 papers contibuiting heavily on the foundation of modern physics.

The first paper is about the photoelectric effect, he explain the phenomenon introducing the concept of  “quanta” of the electromagnetic field, the so called photons. Einstein imagined that light could be made by quanta, something like a particle, whose energy depends only on its frequency and then he solved the puzzle. This idea, coming also from the imagination of Max Planck, was central to the early development of quantum mechanics.

The second one was about Brownian motion, in other words the chaotic motion of particle suspended in a stationary liquid. His explanation gives an important empirical evidence of the atomic theory supporting the ideas of statistical physics, firstly developed by Ludwig Boltzmann.

The third paper is on the electrodynamics of moving bodies, in which he introduced the special relativity. Introducing two simple concepts, the equivalence of stationary observer and the costant speed of light, Einstein has turned upside down our concept of time and space.

Finally, in the fourth paper he stated the famous equivalence beetwen mass and energy, summarized in the “pop” formula:

$E=mc^2$

After his PhD in 1905, he began his academic carrer. In 1909 Einstein became professor at the University of Zurich, then in 1914 was in Berlin, where he would remain until 1933, when he renounced German citizenship and moved to Princeton, U.S.: these were the terrible years of Hitler’s dictature and the beginning of the madness.

In these years he developed, together with mathematician Marcel Grossmann, the general theory of relativity. He extended the space-time concepts to non-inertial reference frame, discovering the intrinsic connection between space-time and gravitational field. Unlike his previous discoveries, in which he stood on the shoulders of giants, the theory of general relativity was essentially a journey of a single man.

Einstein’s last efforts were about the unification of general relativity and quantum mechanics, a still unresolved problem today.

Happy Birthday doc !