ed by a Lambda). The purpose of this was to rectify the effects of gravity and allow the whole system to remain an eternal, static sphere. However, in 1929, Edwin Hubble confirmed that the universe is expanding. After visiting the Mount Wilson Observatory with Hubble, Einstein formally discarded the cosmological constant.
However, the concept was revisited in late 2013, when a previously undiscovered manuscript by Einstein (titled “About the Cosmological Problem“) was discovered. In this manuscript, Einstein proposed a revision of the model, in which the constant was responsible for the creation of new matter as the universe expanded – thus ensuring that the average density of the universe never changed.
This is consistent with the now-obsolete Steady State model of cosmology (proposed later in 1949) and with today’s modern understanding of dark energy. In essence, what Einstein described in many of his biographies as his “biggest blunder” would eventually come to be reassessed and considered as part of a larger mystery of the universe – the existence of invisible mass and energy that maintains the cosmological balance.
In 1915, a few months after Einstein had published his Theory of General Relativity, German physicist and astronomer Karl Schwarzschild found a solution to the Einstein field equations that described the gravitational field of a point and spherical mass. This solution, now called the Schwarzschild radius, describes a point where the mass of a sphere is so compressed that the escape velocity from the surface would equal the speed of light.
In time, other physicists came to the same conclusions independently. In 1924, English astrophysicist Arthur Eddington commented on how Einstein’s theory allows us to rule out overly large densities for visible stars, claiming that they would “produce so much curvature of the space-time metric that space would close up around the star, leaving us outside (i.e., nowhere).”
In 1931, Indian-American astrophysicist Subrahmanyan Chandrasekhar calculated, using Special Relativity, that a non-rotating body of electron-degenerate matter above a certain limiting mass would collapse in on itself. In 1939, Robert Oppenheimer and others concurred with Chandrasekhar’s analysis, claiming that neutron stars above a prescribed limit would collapse into black holes, and concluded that no law of physics was likely to intervene and stop at least some stars from collapsing to black holes.
Oppenheimer and his co-authors interpreted the singularity at the boundary of the Schwarzschild radius as indicating that this was the boundary of a bubble in which time stopped. To the outside observer, they would see the surface of the star frozen in time at the instant of collapse, but an infalling observer would have an entirely different experience.
In addition to revolutionizing our understanding of time, space, motion and gravity with his theories of special and general relativity, Einstein also made numerous other contributions to the field of physics. In fact, Einstein published hundreds of books and articles in his life, as well as more than 300 scientific papers and 150 non-scientific ones.
On December 5th, 2014, universities and archives around the world began officially releasing Einstein’s collected papers, which comprised more than 30,000 unique documents. For example, two papers which were published in 1902 and 1903 – “Kinetic Theory of Thermal Equilibrium and of the Second Law of Thermodynamics” and “A Theory of the Foundations of Thermodynamics” – dealt with the subject of thermodynamics and Brownian motion.
By definition, Brownian motion states that where a small amount of particles are oscillating with no preferred direction, they eventually spread to fill the entire medium. Addressing this from a statistical point of view, Einstein believed that the kinetic energy of oscillating particles in a medium could be imparted to larger particles, which in turn could be observed under the microscope – thus proving the existence of atoms of varying sizes.
These papers were the foundation for the