Dimension

A dimension is a measurable extension in space. There are three commonly perceived dimensions, length, breadth, and width. For example a cube measuring 10 metres in each dimension will have a volume of 1000 metres squared, i.e. 10 x 10 x 10 = 1000. Since the time of Albert Einstein, it is believed by most physicists that space and time form a single entity, and that there is a fourth dimension, time itself. However, time in not measured in units of distance such as metres so this system remains incompatible with Newtonian physics. Quantum physicists propose a different theory, namely that there are more than three dimensions in space itself, perhaps as many as eleven. But dimension four and above are all curled up so tightly that they extend no further than the diameter of a sub-atomic particle, so we just don't notice them.