title: Why do we have to normalize the input for an artificial neural network?
body: <p>Why do we have to normalize the input for a neural network?</p>
  <p>I understand that sometimes, when for example the input values are non-numerical a certain transformation must be performed, but when we have a numerical input? Why the numbers must be in a certain interval?</p>
  <p>What will happen if the data is not normalized?</p>