I'm just preparing myself to write an essay on Relativity , and I'm wondering how to begin. Before Einstein , there was Newton . Newton's Universe is the universe of common sense. Before I can discuss Einstein's Universe I need to describe what existed before. The Newtonian Universe makes the following assumptions.
Time is constant and absolute, the same for all observers.
There is no limit to how fast something can go. Matter and energy are two separate phenomena. The mass and length of a body are fixed. The problem with Relativity is that it violates all of the above common-sense ideas. Because of that, many people have problems believing Relativity rather than understanding it.