Albert Einstein is revered with reason as one of the greatest physicists that ever lived and his two most famous theories, special and general relativity, have surpassed every single test we have thrown at them. If your hypothesis goes against Einstein’s idea, the odds are not in your favor, but he didn’t always get things right.

It would be inhuman to be constantly correct and biases and his personal view of the world influenced the great scientist just as much as they influence us all. We are probably luckier that our work has not had the same level of scrutiny. So what have been Einstein's biggest science mistakes?

A Big Mistake But Maybe Not A Terrible One

Einstein and most of the scientists at the time believed that the universe was static. It had always been like this and it never changed, at least on large scales. But Einstein's laws of general relativity made a crucial prediction about our universe, it had to change. It was either expanding or contracting and you could not keep it still. This was a philosophical clash and to solve it Einstein added an extra parameter to the equation: the cosmological constant.

Within two decades, the evidence that the universe was expanding started coming in. He then decided to abandon the cosmological constant, calling it his “biggest blunder”. Jump forward to 1998 and astronomers discover that the universe is expanding with an acceleration and the best way to describe it in the equation of general relativity is to add a cosmological constant term, also known as dark energy. This is different from Einstein’s one but the underlying mathematics is the same. So maybe it wasn’t such a grave error after all.

What He Meant By Quantum Mechanics

Quantum mechanics with relativity is the cornerstone of how we understand the world and Einstein was one of the co-founders of this field. But he did not like the view that many other scientists had at the time. And he was dead wrong.

The accepted view of quantum mechanics, known as the Copenhagen interpretation, sees the world as probabilistic and made up of physical systems that don’t have defined properties before you measure them. Einstein was an unmovable determinist and could not accept this view. He gave his own spin to the theory by speculating about the existence of hidden variables. This was put in theoretical jeopardy in the 1960s when Bell’s theorem was formulated, a theorem that has been tested many times, passing without fail.  

Nuclear Energy

Einstein was a member of the Manhattan Project that was responsible for the development of nuclear weapons for the United States during World War II. And his most famous equation, E=mc2, underlies the principle of converting matter into energy, extracting it from the nucleus of atoms, for example. And yet, a bit more than a decade before the first nuclear test, he did not believe it was possible to actually split the atom.

“There is not the slightest indication that [nuclear energy] will ever be obtainable. It would mean that the atom would have to be shattered at will,” Einstein told the Pittsburgh Post-Gazette on December 29, 1934.

The first sustaining chain reaction that allowed scientists to create a controlled release of nuclear energy was obtained in 1942. This was called the atomic pile, the precursor to what we now call the nuclear reactor, by Italian physicist Enrico Fermi and his team at the University of Chicago.

Theory Of Everything

Until his dying day, Einstein worked tirelessly trying to combine quantum mechanics and relativity into a single coherent system that could explain every object and every phenomenon in the universe. He, unfortunately, failed at it, and on top of that, he didn’t even get close to the final theory. That was not his fault as he was missing a lot of knowledge about the universe that we now have. For example, he didn’t know about the existence of the weak and strong nuclear forms (at least not in their current definition).

But extra knowledge doesn’t mean we are any closer to finding this theory of everything. Several hypotheses have been put forward, like string theory or quantum gravity, but we haven’t found any definitive proof for either. Or it's something else.