Bobby Fischer's claim that there are more possible positions in chess than there are atoms in the universe is an exaggeration. While the number of possible positions in chess is indeed extremely large, it is not greater than the number of atoms in the universe.
The number of atoms in the observable universe is estimated to be around 10^80, which is an enormous number. In comparison, the number of possible chess positions is estimated to be around 10^40 to 10^50, depending on various factors such as the maximum number of moves in a game and the average branching factor of the game tree.
To put it into perspective, the estimated number of quarks in the observable universe is even greater than the number of atoms. Quarks are elementary particles that combine to form protons and neutrons, which in turn make up atomic nuclei. The exact number of quarks in the universe is difficult to determine precisely, but it is believed to be many orders of magnitude larger than the estimated number of atoms.
In summary, while the number of possible chess positions is vast, it is significantly smaller than the number of atoms in the universe and even smaller than the estimated number of quarks in the universe.