“Do not worry about your difficulties in Mathematics. I can assure you mine are still greater.”
Mathematician: It is impossible to know precisely what Einstein meant by this quote without being able to ask him. It is often taken to mean that he did not have a strong understanding of math or that he was bad at it when he was young. It is simply wrong, however, to say that Einstein was bad at math. Some of his papers were quite mathematically sophisticated, involving advanced subjects such as stochastic differential equations and tensor calculus. What’s more, he excelled in math as a youth.
The following Einstein quote may help us gain a bit more perspective:
“Since the mathematicians have invaded the theory of relativity, I do not understand it myself anymore.”
(source: In A. Sommerfelt “To Albert Einstein’s Seventieth Birthday” in Paul A. Schilpp (ed.) Albert Einstein, Philosopher-Scientist, Evanston, 1949.)
Perhaps what Einstein meant when he claimed to have difficulties in math is that he felt as though it was a struggle to learn some of the very advanced math necessary for formulating his theories, or that (compared to mathematicians or mathematical physicists) his math skills were not exemplary. However, he certainly was far, far more gifted at math than your average person. All of this being said, the original quote was actually directed at young students, so it may have reflected little more than an attempt to encourage them to persevere despite their perceived difficulties.
Physicist: Here’s my guess. Einstein witnessed the end of what might be considered the “intuitive physics” of the 19th century and before. Most of that was his own damn fault. In 1905 (Einstein’s “miracle year“) he introduced the world to both quantum mechanics (QM) and special relativity. Up until that time (most of) modern physics was something that could be easily pictured and intuited. You can draw the trajectories of moving objects, electric and magnetic fields can be modeled using field lines, you can picture heat flowing like a fluid, etc.
Another Physicist: I am not familiar with the quote. I only have a wild guess. In the period between the publication of special relativity and general relativity he took some time to learn enough differential geometry to develop his ideas. This apparently did not come easily to him, and involved a lot of consultation with other people in Europe. He and Levi-Civita were in very frequent communication for example. So he may have been responding to someones comment of the sort we all hear that they we’re having a hard time with math.