# Obsessed with Einstein

For a long time I was scared to read Einstein. Most of my physics reading was Richard Feynman's essays. I think its more to do with his life and character than the physics itself. If I remember properly I read A Brief History of Time when I was in college. That's the closest I have been to Einstein. In feb I read Hendrik Antoon Lorentz's The Einstein Theory of Relativity. It just sparked something inside me.

Since then I have read Relativity : the Special and General Theory by Albert Einstein (Guttenberg Public Domain). As I read the book I also wanted to learn the math side of it. So I followed this amazingly detailed but still simple lectures by Leonard Susskind on Modern Physics concentrating on General Relativity (Part 1, 2, 3, 4). Available on Stanford's Youtube channel. Do watch them only if you are interested in physics and maths.

### Special Theory of Relativity

We advance a step farther in our generalisation when we express the tenet thus: If, relative to K, K1 is a uniformly moving co-ordinate system devoid of rotation, then natural phenomena run their course with respect to K1 according to exactly the same general laws as with respect to K. This statement is called the principle of relativity (in the restricted sense).

Special Theory relativity in simple popular culture would be "*world is relative*". Even though its not completely wrong S.T.R is more specific and states the following two most important things

- The laws of physics are the same in any inertial reference frame
^{1}. - The speed of light in a vacuüm is the same for all observers, regardless of the motion of the light source.

Both these are easy to understand. Just watch the video below.

Interesting consequence of the second postulate is the concept of time dilation which leads to travel.

### General Theory of Relativity

“This special relativity, forming the first part of my theory, relates to all systems moving with uniform motion; that is, moving in a straight line with equal velocity. “Gradually I was led to the idea, seeming a very paradox in science, that it might apply equally to all moving systems, even of difform motion, and thus I developed the conception of general relativity which forms the second part of my theory.”

The Einstein Theory of Relativity by Hendrik Antoon Lorentz

In General Theory of Relativity (GTR) Einstein introduced gravity into the equation. He thought the Time-Space are not separate but are woven together as a fourth dimension "spacetime". This spacetime is like a stretched garment^{2} spread out where any mass can cause create dimples. These dimples are proportional to the mass. Also these dimples make other masses flow towards aka gravity. Any unsymmetric event involving massive bodies can create ripples in this spacetime garment, these ripples travel like waves and are called Gravitational waves. But it needs really huge events like Supernova to generate any measurable gravitational wave. They are very weak and difficult to measure. Hence the significance of recent detection of Gravitational Waves.

Here is another simple and yet beautiful video that explains G.T.R

The whole thing is mind-boggling and endless click spiral. I will end this blog post with this quote.

I know quite certainly that I myself have no special talent; curiosity, obsession and dogged endurance, combined with self-criticism, have brought me to my ideas.

― Albert Einstein