“The infinite! No other question has ever moved so profoundly the spirit of man.”[David Hilbert]

David Hilbert was a German mathematician. He is recognized as one of the most influential and universal mathematicians of the 19th and early 20th centuries. Hilbert discovered and developed a broad range of fundamental ideas in many areas, from number systems to geometry and extended mathematics to mathematical physics—he was the first to discover the invariant theory.

In 1900, Hilbert gave a massive homework assignment to all mathematicians across the world—a list of 23 mathematical problems, many of them still unsolved today. A physicist also gave his colleagues some ambitious homework. Einstein predicted Gravitational Waves 100 years ago, and their existence has now been confirmed.

Hilbert and Einstein traveled in the same circles. Both German living and working before WWI, the mathematician and physicist interests aligned on the theory of general relativity. In 1915, Hilbert came very close to publishing the equation, but experts have proven that his theory, “is not generally covariant,” the critical ingredient for the theory's success.

Einstein ended up finding the correct form of the equations, because physics was at the heart of relativity theory and Einstein excelled at physical insights and visualization of thought experiments. He had already viewed gravity as a field of spacetime, which could be deformed and pulled by the time he started thinking about the equations. Einstein's theory of general relativity predicted that the space-time around Earth would be not only warped but also twisted by the planet's rotation.

As was the case when Nobel Prize winner (chemistry) Marie Curie was denied a seat in the French Academy of Sciences and Einstein sent a letter of support, he also wrote a sensitive note to Hilbert seeking to put disagreements behind and to rekindle their friendship. It says:

There was a moment in which something like as irritation came between us, the origin of which I no longer want to analyze. I have fought against the bitterness which it provoked in me, and have succeeded completely in doing so. I again think of you with unclouded friendship, and I ask you to do the same for me. It is really a pity if companions such as we are, who have managed to forge a path aside from the pettiness of this world, could find anything other than joy in each other's company.

It's an act of humility and kindness and an example of how when we focus on relationships we can be hard on issues, yet soft on people.