Every day at every point on the earth's surface, atmospheric pressure rises and falls due to the thermal action of the sun and the gravitational action of the moon and sun. Why is the solar twice daily tide stronger than the corresponding lunar tide? Are the tides symmetric about the equator? In time? Do the thermal and gravitational tides interact? And can this very regular astronomical forcing give us useful information about how the atmosphere works by study of the atmospheric i.e. tidal response. These are some of the questions which as yet generally have only partial and incompletely understood theories to explain them.