Chapter 3 Review Questions
What is an ellipse? Define its foci, semimajor axis, and eccentricity.
A special type of oval with two foci. A foci is two locations of a ellipse. A semimajor axis is half of the major axis. Eccentricity is a quantity that describes how much an ellipse is stretched out compared to a perfect circle.
What is the difference between a hypothesis and a theory in science?
A hypothesis attempts to answer questions by putting forth a plausible explanation that has yet to be rigorously tested. A theory, on the other hand, has already undergone extensive testing by various scientists and is generally accepted as being an accurate explanation of an observation.
What do we mean by a model in science? Briefly summarize the Greek geocentric model.
A model in science is a conceptual representation whose purpose is to explain and predict observed phenomena. Any of the ancient Greek models that were used to predict planetary positions under the assumption that earth lay in the center of the universe.
Why did ancient peoples study astronomy? Describe the astronomical origins of our day, week, month, and year.
Ancient people studied astronomy to keep track of time and seasons which was essential for farming. Egyptians - huge obelisks that probably served as clocks Stonehenge - helped ancient cultures mark the seasons Aztecs - Temple Mayor used to mark the seasons Anasazi - sun dagger to mark the suns position on special dates such as summer and winter solstice Greek - Metonic cycle; 19 yr. cycle on which the dates of lunar phases repeat Babylonians - predicting eclipses with the help of 18 yr. Saros cycle
What was the Copernican revolution, and how did it change the human view of the universe?
Copernican revolution The dramatic change, initiated by Copernicus, that occurred when we learned that Earth is a planet orbiting the Sun rather than the center of the universe. For the longest time we thought the all the objects in the sky revolved around us, and that the earth was the center of the universe. Copernicus discovered a simple geometric relationships that allowed him to calculate each planet's orbital period around the Sun and its relative distance from the Sun in terms of Earth-Sun distance. Resulting that the earth revolved around the sun and not us.
What do we mean by the Ptolemaic model? How did this model account for the apparent retrograde motion of planets in our sky?
Each planet moves on a small circle whose center moves around Earth on a larger circle. A planet following this circle-upon-circle motion traces a loop as seen from Earth, with the backward portion of the loop mimicking apparent retrograde motion
State and explain the meaning of each of Kepler's law of planetary motion.
Kepler's laws of planetary motion: Three laws discovered by Kepler that describe the motion of the planets around the Sun. Kepler came up with a model that could predict planetary positions with far greater accuracy than Ptolemy's Earth-centered model and summarized his findings into three laws.
Describe the three hallmarks of science and explain how we can see them in the Copernican revolution. What is Occam's Razor? Why doesn't science accept personal testimony as evidence?
Modern science seeks explanations for observed phenomena that rely solely on natural causes. Science progresses through the creation and testing of models of nature that explain the observations as simply as possible . A scientific model must make testable predictions about natural phenomena that would force us to revise or abandon the model if the predictions do not agree with observations. Each of these hallmarks is evident in the story of the Copernican revolution. The first shows up in the way Tycho's careful measurements of planetary motion motivated Kepler to come up with a better explanation for those motions. The second is evident in the way several competing models were compared and tested, most notably those of Ptolemy, Copernicus, and Kepler. We see the third in the fact that each model could make precise predictions about the future motions of the Sun, Moon, planets, and stars in our sky. When a model's predictions failed, the model was modified or ultimately discarded. Kepler's model gained acceptance in large part because its predictions were so much better than those of the Ptolemaic model in matching Tycho's observations. A principle often used in science, holding that scientists should prefer the simpler of two models that agree equally well with observations; named after the medieval scholar William of Occam (1285-1349). Science does not accept personal testimony, because there must be "No Agenda" what you may believer personal, does not have evidence to back up your allegations.
In what way is scientific thinking natural to all of us, and how does modern science build upon this everyday type of thinking?
Scientific thinking is natural to all of us because it deals with careful observations along with trial and error that we use in everyday life. Modern science differs form everyday type of thinking because they are trained to organize everyday thinking in a way that makes it easier for them to share their discoveries.
What is a lunar calendar? How can it be kept roughly synchronized with a solar calendar?
lunar calendar have 29 days and others have 30 days, so that the average matches the 29 -day lunar cycle. A 12 month lunar calendar has only 354 or 355 days, or about 11 days fewer than a calendar based on the Sun (59, 60). It's synchronized with the solar calendar by roughly synchronized with solar calendars by taking advantage of an interesting coincidence: 19 years on a solar calendar is almost precisely 235 months on a lunar calendar. As a result, the lunar phases repeat on the same dates about every 19 years (a pattern known as the Metonic cycle) (60).
