Graphics: how to revolve earth around sun

#include 
 void init(void){
     glClearColor(0.0,0.0,0.0,0.0);
     glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
 }
 void display(void){
     glClearColor(0.05,0.05,0.5,0.0);
     glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
     glColor3f(0.03,0.05,0.09);
     glutSolidSphere(0.5,30,30);//Earth
     glMatrixMode(GL_MODELVIEW);
     glLoadIdentity();
     glTranslatef(.7,.7,.7);
     glColor3f(1.0,1.0,1.0);
     glutSolidSphere(0.2,50,50);//Sun
     glLoadIdentity();
     glFlush();

 }
int main(int argc, char **argv){
    glutInit(&argc, argv);
    glutInitDisplayMode(GLUT_SINGLE);
    glutInitWindowPosition(10,10);
    glutInitWindowSize(400,400);
    init();
    glutCreateWindow("Planets");
    glutDisplayFunc(display);
    
    glFlush();
    glutMainLoop();
}