Winter, spring, summer, and fall—Earth experiences them all! But what about Mars? Scholars compare the planets in terms of distance, tilt, and rotation during a lesson from PBS's Space series. Great visual models of Earth and Mars, plus...

This is a plan of the church of San Ambrogio, Italy. This is an example of Italian Lombard Romanesque architecture. This church represents the "earliest [example] of the solution of the great problem which was exercising the minds of the...

This is a plan of the San Michele, Pavia, Italy. This is an example of Italian Lombard Romanesque architecture. This church represents the "earliest [example] of the solution of the great problem which was exercising the minds of the...