In his book, A New Earth (2005), Eckhart Tolle likens 'inner space' to the depths of our own consciousness, in which there are many 'worlds' or 'dimensions'. However, moving between dimensions of inner space is actually only a metaphor for shifts taking place in our mind and consciousness, doorways opening into different experiences of reality. This could perhaps be better understood using the analogy of a computer program. As we enter the 'program', our mind is able to shift from one level to the next by our entering in key commands (intentions), each shift being accompanied by a corresponding change in perception and our subsequent inner experiences.
To explore 'inner space' we could use a process of meditation combined with imagery and intention to create a dramatised scenario which includes symbolic portals through which we could pass from one level of the program into the next, entering ever deeper and deeper into unexplored areas of our consciousness.
A useful framework for this dramatisation would be to imagine ourselves undertaking a journey into outer space in our minds (suggesting a correspondence between inner and outer space), seeing ourselves moving out of the atmosphere of the Earth, glancing back at the planet far below, then travelling past the planets of our solar system, beyond the Sun and out into the deepest regions of outer space. Such an imaginary journey, if applied with intent and the skills of interactive visualisation, can produce many profound emotional as well as symbolic inner visual experiences and therefore have a great potential for our learning, growth and personal development.
However, if one thinks of these processes purely in terms of consciousness, then we are not really travelling in time and space at all, but rather undergoing an inner experience brought about by shifts in our perception, and simply engaging other realms or spheres of our own consciousness.