title: When does Double.ToString() return a value in scientific notation?
body: <p>I assume that it has something to do with the number of leading or trailing zeroes, but I can't find anything in msdn that gives me a concrete answer.</p>
  
  <p>At what point does <code>Double.ToString(CultureInfo.InvariantCulture)</code> start to return values in scientific notation?</p>