system
Given the following post, respond as if you're commenting on Reddit:
human
Is there a theoretical maximum of magnification/zoom (for a telescope/microscope)?

Is there a phisycal limit of a  possible magnification/zoom? Or we could theoretically zoom to an atom in a grain of sand on a planet in a galaxy 1 billion light years away?

Thanks!
gpt
Yes, there is a limit given by diffraction. A single atom in a galaxy far away, even if it would be bright enough (it is not...), would lead to spot of light of finite size in the camera/eye. An atom next to it would lead to a spot that is basically identical - the shift (from a different position) is so tiny compared to the spot size that it is impossible to tell them apart.

The limit of diffraction is given by the size of the telescope (the size of the primary mirror) and the wavelength. With 10 meters diameter you can see structures twice as fine as with 5 meters diameter. Interferometry adds light from multiple telescopes and mimics a single, larger telescope, that can improve the resolution as well, especially for radio telescopes where you can combine telescopes from all over Earth.

For microscopes, the limit of diffraction does not depend on their size, but on how much solid angle they cover around the object: ideally they collect all light emitted by the object. Then they can resolve structures roughly as large as the wavelength used. There are some clever methods to see even smaller structures, but they are much more complicated.

The brightness of the source can also limit what you can see: to get an image, you need a sufficient amount of light. Smaller structures usually emit less light.