SCI 154EXPLORING THE UNIVERSELECTURE1Mr. Heystek Grobler – Department of Physics
Content⿌The Nature of Astronomy⿌The Nature of Science⿌The Laws of Nature⿌Numbers in Astronomy⿌Where are we in the Universe?⿌Time Scale of the Universe⿌History of Astronomy⿌Important Astronomy Discoveries2
Science and the Universe3The nature of AstronomyAstronomy is defined as the study of the objects that lie beyond ourplanet Earth and the processes by which these objects interact with oneanother.We will see, though, that it is much more. It is also humanity’s attemptto organize what we learn into a clear history of the universe, from theinstant of its birth in the Big Bang to the present moment.In considering the history of the universe, we will see again and againthat the cosmos evolves; it changes in profound ways over long periodsof time. For example, the universe made the carbon, the calcium, andthe oxygen necessary to construct something as interesting andcomplicated as you. Today, many billions of years later, the universehas evolved into a more hospitable place for life.
Science and the Universe4The nature of Astronomy
Science and the Universe5The nature of Astronomy
Science and the Universe6The nature of Science:The ultimate judge in science is always what nature itself reveals based onobservations, experiments, models, and testing. Science is not merely a body ofknowledge, but a method by which we attempt to understand nature and how itbehaves. This method begins with many observations over a period of time.From the trends found through observations, scientists can model the particularphenomena we want to understand. Such models are always approximations ofnature, subject to further testing.
Science and the Universe7The nature of Science:
Science and the Universe8The nature of Science:
Science and the Universe9The nature of Science:When they are first proposed, new models or ideas are sometimes calledhypotheses. You may think there can be no new hypotheses in a science such asastronomy—that everything important has already been learned. Nothing couldbe further from the truth.
Science and the Universe10The nature of Science:Resolving these issues will require difficult observations done at the forefrontof our technology, and all such hypotheses need further testing before weincorporate them fully into our standard astronomical models.This last point is crucial: a hypothesis must be a proposed explanation that canbe tested. The most straightforward approach to such testing in science is toperform an experiment. If the experiment is conducted properly, its resultseither will agree with the predictions of the hypothesis or they will contradict it.If the experimental result is truly inconsistent with the hypothesis, a scientistmust discard the hypothesis and try to develop an alternative. If theexperimental result agrees with predictions, this does not necessarily provethat the hypothesis is absolutely correct; perhaps later experiments will