A simple model of the overall Earth’s heat budget is derived. The Earth is assumed to be in equilibrium with the input of solar radiation balanced by the output of infrared radiation emitted by the Earth’s surface. Using this model, the Earth’s surface temperature is calculated to be cooler than in reality due to the lack of an atmosphere and the greenhouse effect in the model.
Several experiments are performed using a water tank with an input flow of water and an output flow. These experiments demonstrate the concepts of equilibrium and steady-state in system analysis and are analogous to various Earth systems; lakes and rivers and the overall heat budget of the planet. The greenhouse effect in the atmosphere is a mechanism for increasing the heat input from the sun in the overall heat budget of the Earth system.
Pressure and density decrease exponentially with altitude in the atmosphere. This leads to buoyancy effects in the atmosphere when parcels of air are heated or cooled, or raised or lowered in the atmosphere. Temperature varies in a more complicated way with altitude in the atmosphere, with several inversions which occur at the boundaries of the various layers of the atmosphere. Solar radiation interacts differently with the gases that compose each layer of the atmosphere which affects which wavelengths of radiation are able to reach the surface of the Earth.
The Perfect Gas Law relates temperature, pressure, and density of gases in the atmosphere. It can be used to demonstrate why warm air rises, cool air sinks, and helium balloons float in the air. Buoyancy forces act in fluids (both water and air) when fluid is displaced by a parcel of a fluid with a different density. A combination of buoyancy force and the relationship given in the Ideal Gas Law govern the motion of parcels of gas in the atmosphere.
Professor Freedman begins the lecture by considering the ways historians read the Confessions.In this work, St. Augustine gives unique insight into the life of an intellectual mind in Late Antiquity, into the impact of Christianity on the Roman Empire, and into the problems of early Christianity. The three major doctrinal concerns of the early Church were the problem of evil, the soul-body distinction, and issues of sin and redemption. In the Confessions, St.
The emperor Constantine’s conversion to Christianity brought change to the Roman Empire as its population gradually abandoned the old religions in favor of Christianity. The reign of Julian the Apostate, a nephew of Constantine, saw the last serious attempt to restore civic polytheism as the official religion. The Christian church of the fourth century was divided, however, by two serious heresies: Arianism and Donatism. Religious dissent led to the intervention of the emperors at church councils and elsewhere. Professor Freedman then introduces St.
Professor Freedman examines how Christianity came to be the official religion of the Roman Empire. This process began seriously in 312, when the emperor Constantine converted after a divinely inspired victory at the Battle of the Milvian Bridge. Constantine’s conversion would have seemed foolish as a political strategy since Christianity represented a completely different system of values from that of the Roman state, but not only did it prove to be a brilliant storke in aid of Constantine’s quest for power, it fundamentally changed the character of the Empire and that of the early Church.
Professor Freedman outlines the problems facing the Roman Empire in the third century. The Persian Sassanid dynasty in the East and various Germanic tribes in the West threatened the Empire as never before. Internally, the Empire struggled with the problem of succession, an economy wracked by inflation, and the decline of the local elite which had once held it together. Having considered these issues, Professor Freedman then moves on to the reforms enacted under Diocletian to stabilize the Empire.
Professor Freedman introduces the major themes of the course: the crisis of the Roman Empire, the rise of Christianity, the threats from barbarian invasions, and the continuity of the Byzantine Empire. At the beginning of the period covered in this course, the Roman Empire was centered politically, logistically, and culturally on the Mediterranean Sea. Remarkable for its size and longevity, the Empire was further marked by its tolerance.
There are other ways in which we can perceive the existence of the atmosphere, predominantly through our perceptions of pressure. Not all planets have atmospheres, and the existence of an atmosphere depends on the ability of gas molecules to remain trapped close to a planet by its gravitational force. The molecular velocity of each gas molecule depends upon its molecular weight, and must exceed the escape velocity of the planet to leave the atmosphere.
