Applications of this today: anything where there is large changes in altitude between two objects which require time synchronicity have to account for time dilation between the two time measuring devices, almost all GPS rely on such synchronicity to accurately calculate the speed direction and position of a car/plane/person etc., it was also used in the recent test at CERN where they fired neutrino’s through the Alps, due to difference in heights of the detector compared with the source of the neutrinos, there was a significant amount of time dilation that they had to account for so that there results for the neutrino’s speed would be accurate enough.

Other than those two I couldn’t find any other practical applications of this theory, but I am sure that the world of physics does have many uses for them, things to do with astronomy and such things. “Does the Inertia of a Body Depend Upon Its Energy Content”, this is the paper that led to the equation E=mc^2 which is one of the most famous, if not the most famous, equation in human history.

This equation is based upon Einstein’s investigations into the “Maxwell-Hertz equations for empty space, together with the Maxwellian expression for the electromagnetic energy of space” (Einstein 1905 [7]). Einstein then does loads of crazy maths that I don’t really understand, but basically comes to the conclusion that “The mass of a body is a measure of its energy-content; if the energy changes by L, the mass changes in the same sense by L/9 10^20” (Einstein 1905 [8]) (‘L’ is used to represent energy), I am unsure why it’s 10^20 and not 10^16 (which would be roughly the speed of light squared, but that’s the quote for you), this equation which he has written in words is just a rearrangement of E=mc^2 (it is, in his words, m=E/C^2).

This equation led to the ability for nuclear physicists to calculate the energy yield of nuclear reactions, and also allowed for more general theories of how increasing the energy of a system increases it’s mass (not through any mass being created, nor energy being created, but by the transfer of mass an energy into the respective other form).

A few examples of how changes in energy lead to changes in mass are: A spring’s mass increases whenever it is put into compression or tension. Its added mass arises from the added potential energy stored within it; The worlds official standard mass for the kilogram, made of platinum/iridium, will undergo a change in mass of 1. 5 picograms (1 picograms is equivalent to 1×10^-20 grams) if it’s temperature is raised 1 degree; The Earth itself is more massive due to its daily rotation, than it would be with no rotation.

This rotational energy {2. 14 x 10^29 J (Infranetlab 2008 [9])} represents 2. 38 billion metric tons of added mass. He also published many other papers and wrote many books too, but there isn’t the time nor the words left to go into them, I will just add that as well as his love for physics, Einstein also dabbled in philosophy, as many theoretical physicist do, and wrote a few books on it, this rewarded him with an honourary degree in philosophy.

Einstein was one of the leading figures in the World Government Movement and was offered the Presidency of Israel after WWII had ended, he declined it however. I would assume that this was for political reasons, he was a pacifist, and was against the use of atomic weapons, which the American’s used on Japan in 1945 [10]. Personally I find Einstein’s theories fascinating, and inciting of much thought. They challenge the understanding and extend the knowledge of the surrounding world.