" By dimension, we simply mean an independent direction in which, in principle, you can move; in which motion can take place. In an everyday world, we have left-right as one dimension; we have back-forth as a second one; and we have up-down as a third. "
- Brian Greene

In everyday life, we typically think about movement in terms of three primary directions: left and right, forward and backward, as well as up and down. These basic dimensions allow us to navigate through our physical world with ease, whether it's walking across a room or reaching for an object on a high shelf.

The quote delves into the concept of dimension beyond just physical movement in space. It suggests that each dimension represents an independent direction in which motion is possible. This idea can be extended metaphorically to other areas of life, such as time, where one might think about past and future as dimensions. In physics, particularly in theories like string theory, the notion of extra dimensions beyond the familiar three spatial ones offers intriguing possibilities for understanding the universe. These deeper meanings invite us to consider how we conceptualize and interact with our environment in more abstract ways.

The quote is from Brian Greene, a renowned physicist and mathematician known for his work in theoretical physics and for making complex scientific ideas accessible to the general public through books and television appearances. His contributions have helped bridge the gap between academic science and popular understanding, offering insights into topics like string theory and cosmology.