In early 1902, Lieserl, daughter of Einstein and Mileva Maric, a former fellow student, was born in Hungary. Not much is known about the life of his daughter, as she was probably given up to be adopted. During this time, Albert's father fell ill and passed away. In January of 1903, Albert and Mileva marry, despite objections from both families.In 1904, the Einstein's have their first son, Hans Albert. 1905 was Einstein's "miracle year." In March of that year, he sent to the "Annalen der Physik," the leading German physics journal, a paper with a new understanding of the structure of light. He argued that light acts as though is consists of independent particles of energy. Einstein built on Max Planck's work and went beyond this. He showed that light quanta could help to explain phenomena being studied by experimental physicists; he made clear how light ejects electrons from metals. Photo from http://www.aip.org/history/einstein/

In May of 1905, Einstein submitted another paper that reinforced the kinetic energy theory. His Special Theory of Relativity was born; Einstein submitted yet another paper in June of 1905 on electromagnetism and motion. Since Galileo and Newton, physicists had known that laboratory experiments never revealed a difference between an object at rest and an object moving at a constant speed along a straight line. Objects behave the same way on a uniformly moving ship as they do on an anchored ship; this is the Principle of Relativity. However, according to the electromagnetic theory, light should not obey this principle. This theory predicted that measurements on velociy of light would show the effects of motion. Yet, no such effect had been detected in any experiments-- the velocity of light did not vary. Einstein found a way to show that the Principle of Relativity was compatible with electromagnetic threory. Einstein later remarked that reconciling these seemingly incompatible ideas required a new and careful consideration of the concept of time.