An atom only appears in a particular place if you measure it.
In other words an atom is everywhere until an act of observation happens.
The act of perception creates the Universe.

If it were necessary to give all parts of the world a completely quantum-mechanical description, a person trying to apply quantum theory to the process of observation would be faced with an insoluble paradox. This would be so because he would then have to regard himself as something connected inseparably with the rest of the world.

What sees is all there is.