According to the prophet Joseph Smith, the spirit world is not on some distant planet or star, nor is it millions of miles from earth. The world of spirits is right here, around us. He also taught that many of the righteous spirits in the spirit world are able to observe our actions and hear our thoughts. Sometimes they are saddened by the things they see us do and think.
The best scientific explanation for two entities being in the same location where only one is able to view the other is dimensionality. Dimensionality is a Euclidian concept that refers to the number of specific points needed to define any location within space.
We live in a 3 dimensional world where we are able to define any point in our space with 3 spatial dimensions (up or down the y-axis, left of right on the x-axis, and in or out on the z-axis). In our 3rd dimension world we are able to view 1 and 2 dimensional space because they are lower than our 3rd dimension. Yet, an entity restricted to 1 or 2 dimensional space would not be able to experience our higher 3rd dimension world.
Know where this is going?
Could it be that the spirit world is in a higher 4th dimension of space? If this is true and we apply the same logic, then spirits in the 4th dimension would be able to see our 3rd dimension world, but we would not be able to see their world. All the while our two worlds could be in the same location because the 3rd dimension exists within the 4th dimension.
Here are a couple of short video clips that describe this process in greater detail. The videos describe a fictional 2 dimension world called Flat Land and its relationship to a 3 dimension world. The denizens of 2-D Flat Land are unable to “see” our 3-D world but we are able to see them because we are in a higher dimension. The first video is a comic description of Flat Land by Dr. Quantum (may be skipped). The second video is a more sophisticated but easy to follow presentation of Flat Land by Carl Sagan. Carl Sagan also gives some insight into the mind boggling essence of the 4th dimension, the possible location of the spirit world.