In particle physics and string theory (M-theory), the ADD model, also known as the model with large extra dimensions (LED), is a model framework that attempts to solve the hierarchy problem. (Why is the force of gravity so weak compared to the electromagnetic force and the other fundamental forces?) The model tries to explain this problem by postulating that our universe, with its four dimensions (three spatial ones plus time), exists on a so called membrane floating in 11-dimensional space. It is then suggested that the other forces of nature (the electromagnetic force, strong interaction, and weak interaction) operate within this membrane and its four dimensions, while gravity can operate across all 11 dimensions. This would explain why gravity is very weak compared to the other fundamen