% This picture represents a three-dimentional sphere
% (C) Thiago Brevidelli
\begin{tikzpicture}[scale=0.4]
    % The cirference
    \draw (0, 0) circle (3);
            
    % The equator
    \begin{scope}
        \clip (-3, 0) rectangle (3, -3);
        \draw ellipse (3 and 1);
    \end{scope}
            
    % The equator (on the other side of the sphere)
    \begin{scope}
        \clip (-3, 0) rectangle (3, 3);
        \draw[dotted] ellipse (3 and 1);
    \end{scope}
            
    % Greenwhich
    \begin{scope}
        \clip (-3, -3) rectangle (0, 3);
        \draw ellipse (1 and 3);
    \end{scope}
            
    % Greenwhich (on the other side of the sphere)
    \begin{scope}
        \clip (3, -3) rectangle (0, 3);
        \draw[dotted] ellipse (1 and 3);
    \end{scope}
\end{tikzpicture}