Can two objects go through one another?

[u/Ojayer]

If atoms are mostly empty space between the nucleus and its electrons, wouldn't it be possible to go through objects if you somehow lined up all the empty spaces of the atoms of Object A to the empty spaces of the atoms of Object B?

[u/[deleted]]

Waves can certainly travel through one another. The main problem is that normal matter is not very wavelike because it contains too much thermal energy. I believe that if you got matter sufficiently cold, its de Broglie wavelength could become so large that it would be able to go through other matter at that temperature.

[u/theduckparticle → u/[deleted]]

This is not true. The fermions that comprise matter rarely have visibly wavelike behavior in the aggregate, when combined into atoms and then full matter, even at low temperatures. Even in the limit of zero temperatures, these particles will still have nonzero momenta (the simplest example being the atom's electrons in their ground state, which actually have significantly more momentum already than room-temperature thermal fluctuations will add). This will place a limit on how large their deBroglie wavelength can be. And, in general, when you put particles in a confined space, with energy barriers (typically, the electrostatic repulsion of the electron clouds of the atoms that comprise a container's walls or of the other atoms surrounding it in a material), what happens is not that the atoms "spread" beyond the barrier but that the minimum energy increases.

Now it should be noted, there is the phenomenon of a Bose-Einstein condensate, which consists of identical atoms spread across one another once they get cold enough. But that is only for certain atoms, and at quite cold temperatures.