The numbers you mentioned regarding the quantity of atoms in the world, the number of atoms in a drop of water, and the number of molecules in the oceans are all estimates that are subject to some degree of uncertainty. While these estimates are based on scientific calculations and measurements, it's important to note that they are approximations due to the vastness and complexity of the natural world.
The estimation of 1.3 x 10^50 atoms in the world is a rough estimate that considers the composition of various elements in the Earth's crust, atmosphere, and other components. However, it's worth mentioning that the Earth is just one celestial body among countless others in the universe.
Regarding the number of atoms in a drop of water, the estimate of 10^21 atoms is based on the average size of a water droplet and the known concentration of atoms in water. However, the actual number of atoms in a specific drop of water can vary based on factors like temperature, impurities, and other variables.
Similarly, the estimate of 4.7 x 10^46 molecules in the oceans takes into account the volume of the oceans and the concentration of various dissolved substances. However, it's important to remember that the composition of the oceans can vary in different locations and depths, which can affect the precise number of molecules present.
While the numbers may seem large or even incomprehensible, they are attempts to quantify the vastness and complexity of the natural world. Estimations like these provide us with a sense of scale and help scientists in their understanding of the physical properties and behaviors of matter at different levels.