Over the past ninety years we have come to understand and appreciate the world, the universe which embraces it, and their emergence and development in completely new ways. Thanks to astronomy and physics - particularly to the speciality known as cosmology - we now know that the universe we inhabit began expanding and cooling from an extremely hot and dense, homogeneous, simple state about 13.7 billion years ago. That initial state, often now referred to as the Planck era, was so extreme that our current physics is completely unable to describe it. Space and time as we know them had not yet emerged, and the fundamental forces of gravity, electromagnetism, and the strong and weak nuclear interactions were undoubtedly unified, and thus indistinguishable from one another. Only a thorough and complete quantum description of reality, including space-time and gravity - a quantum cosmology - would be adequate. That is something we do not yet possess, although many people are expending tremendous efforts to develop the components of such a description by exploring superstrings, loop-quantum gravity and non-commutative geometry, as well as exploiting semi-classical approaches to quantizing space-time, gravity and the universe itself.
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