  This paper initiates a novel research direction in the theory of Diophantine
equations: define an appropriate version of the equation's size, order all
polynomial Diophantine equations starting from the smallest ones, and then
solve the equations in that order. By combining a new computer-aided procedure
with human reasoning, we solved the Hilbert's tenth problem for all polynomial
Diophantine equations of size less than $31$, where the size is defined in
(Zidane, 2018). In addition, we solved this problem for all equations of size
equal to $31$, with a single exception. Further, we solved the Hilbert's tenth
problem for all two-variable Diophantine equations of size less than $32$, all
symmetric equations of size less than $39$, all three-monomial equations of
size less than $45$, and, in each category, identified the explicit smallest
equations for which the problem remains open. As a result, we derived a list of
equations that are very simple to write down but which are apparently difficult
to solve. As we know from the example of Fermat's Last Theorem, such equations
have a potential to stimulate the development of new methods in number theory.
