John said:
OK David.
Name your 5 main differences that preclude the comparison.
Please.
John
The most important differences are due to scale:
On the astronomic scale, gravity is by far the dominant effect. On the
atomic scale, the electromagnetic force is dominant (and also weak and
strong nuclear forces, when you get within the nucleus). These are very
different types of forces, leading to very different patterns.
On the atomic scale, quantum mechanics rules - on the astronomic scale,
relativity rules. One day, someone will figure out a successful and
consistent big toe, but even then the two theories will be very good
approximations in all but the most extreme cases. Among the differences
caused by this, it is not hard to find out where a given star is (or at
least, where it was), whereas it doesn't even make sense to ask where a
particular orbital electron is.
Atoms interact with their environment in many ways, such as partnerships
with neighbouring atoms, or electrons jumping between orbits. Galaxies,
to a large extent, are independent - their relations to other galaxies
are mostly minor due to the distances involved.
Atoms have a core that is totally different in character to the orbitals
- galaxies have no well-defined core, but simply a denser central region.
Atoms come in specific discrete sizes, all with the same spherical shape
(when isolated). Galaxies come in a wide range of shapes and sizes.
Looking at the similarities between galaxies (or more commonly, solar
systems) and atoms can be illustrative at a basic level, but the
similarities end quickly. It's like comparing a bacteria to a person,
and describing the nucleus as the "brain", and flagela as the "arms".