This is something I have been meaning to cover for a long while now. As I do not know the proper term for this, I simply refer to it as a "Spirit Rift" and that is when barriers between the spirit world and our material world are thinner. Some people hear that and believe that it means the two worlds may some day collide, but that is not the case and is probably impossible in the way that most people would imagine it. What it means is that spirits will have an easier time traveling here and likewise we will have an easier time contacting them. Unfortunately, the spirit world can not really be accessed by the living in the same way that the astral planes can, but many of us will still know when the barrier begins to weaken.
Many people, especially those with experience in dealing with spirits or some type of psychic talent, are sensitive to the barrier between our world and the spirit world. They will often sense when that barrier is weaker because a part of their conscious may reach out subconsciously to the spirit world. Naturally, most people will not notice that for what it is, but symptoms may include; disorientation, confusion, forgetfulness, potentially a burst of energy, and in extreme cases nausea. Many of those who have dealt with spirits before and understand them may also experience comfort, happiness, a sense of joy, etc, and if this is not expected it may further the confusion thus making the individual a little more emotional then would seem logical.
The barrier between our world and the spirit world is possibly comparable to an ocean. With an ocean the tide goes through a cycle and the waves are constantly rolling, likewise the barrier may become stronger in some points while weaker in others(like the tide) and it may seem to be constantly moving(like the waves). Mostly the barrier will be weaker in places affected by an eclipse, places with the right amount of a certain energy or set of energies, or seemingly all around the world on Halloween(when I have the money I will be doing further research on specific places affected by Halloween).
