Even geniuses can be wrong. Albert Einstein was probably the scientist who contributed the most to modern physics and science, but also to his own relativity theory could be hiding what he himself called “his biggest mistake”.
In 1915, Einstein published General Relativity, expanding on his earlier theory of special (or special) relativity. As of today, this is the most complete theory we have for describing gravity. But there was a problem with this description.
At the time, in fact, most physicists he believed that the universe was static; it had always looked that way, and it stood to reason that it wouldn’t change on a large scale. But when the equations of the theory were applied to our galaxy, something strange happened – this one it seemed to collapse in on itself into a single point.
Obviously it is not what we observe in reality and to resolve this discrepancy, our beloved physicist had to insert an additional parameter to his theory: the cosmological constant.
This constant (indicated by the Greek letter lambda) however was not based on any scientific observations; this generated skepticism in the physicists of the time, and when years later it was demonstrated that the Universe was not static, but in expansion, the cosmological constant became useless, leading Einstein to admit that it was a mistake.
However, the story does not end here, because when it was discovered – at the end of the 1900s – that the expansion of the Universe was accelerating, everything changed again. A mysterious force, which we call today dark energyis responsible for acceleration and the best way to describe it is precisely the cosmological constant that Einstein initially inserted.
In short, it can be said that Einstein’s greatest mistake was to believe he was wrong.