Cat,
Regading "unperceived dimensions": Even just expanding "time" along with "space" seems to be beyond our current intellectual capabilities. "Time" might be at least part of our perception of "flatness" that is actually more difficult to imagine than we can grasp. For instance, we do not believe that it can be "traveled" in both directions. We do not associate an equivalent to "mass" for time, such that changing the speed or direction of its passage can be accomplished with applications of energy. Yet, we have equations that seem to equate time to a dimension. We just don't seem to be able to get a physical handle on it, nor a conceptual handle, either.
Regading "unperceived dimensions": Even just expanding "time" along with "space" seems to be beyond our current intellectual capabilities. "Time" might be at least part of our perception of "flatness" that is actually more difficult to imagine than we can grasp. For instance, we do not believe that it can be "traveled" in both directions. We do not associate an equivalent to "mass" for time, such that changing the speed or direction of its passage can be accomplished with applications of energy. Yet, we have equations that seem to equate time to a dimension. We just don't seem to be able to get a physical handle on it, nor a conceptual handle, either.