According to this book the universe has multi dimensions (10 according to hyperspace theory). Just as a square living in a two dimensional paper cannot visualize or think about a three dimensional world, we human beings may not be able to visualze multi dimensions, though it can be represented mathematically.
After reading that, I just related it with Yoga Vasishta, an ancient Indian Spiritual Text which describes various levels of conciousness and various dimensions of the universe. According to Kaku, the radius of next dimension is much smaller than the planck's constant, so that it is almost impossible to find it.
This resembled me the 'Sukshma loka' (subtle world) in Yoga Vasishta, where the conciousness can enter.
Indian Vedanta and culture is so deep and vast, and the ancient Rishis experimented various possiblities of human conciousness through techniques like meditation, and explored the universe in various ways. Yoga Vasishta even discusses techniques like Time Travel (Akshagamana) - and explains how human conciousness and mind can be fine tuned to attain such realms.
According to Vedanta, the whole nature (observing phenomena) is part of the self (observer), and there is no duality between the two (Advaita). According to Kaku, the String theory describes that the whole matter is nothing much vibration of energy.
Science knows that the base or substratum of matter is energy. Vendanta goes further - it explains the whole matter as vibration in the level of energy (much before Einstien), and continues further, to explain that the substratum or base of whole energy is conciousness (Prajna).
And Vedanta concludes that the Prajna is the divine (Prajnanam Brahma), and all beings are just the manifestation of the same conciousness (Aham Brahmasmi, That-tvam Asi).
And, Vedanta explains that the maximum possibility of Human life is to realize this conciousness- to be one with it. This can be experienced by anyone, by controlling his mind, like various masters at various ages did (Krishna, Buddha, Nabi, Jesus, Guru Gobind etc)
May be science is coming closer to reality.. Who knows.