Mastering-Physics: HW 1

Which of the following are scientific hypotheses? -Chlorophyll makes grass green. -Earth rotates about its axis because living things need an alternation of light and darkness. -Tides are caused by the Moon.

-Chlorophyll makes grass green. -Tides are caused by the Moon.

The geocentric model, in all of its complexity, survived scientific scrutiny for almost 1,400 years. However, in modern astronomy, scientists seek to explain the natural and physical world we live in as simply as possible. The complexity of Ptolemy's model was an indicator that his theory was inherently flawed. Why, then, was the geocentric model the leading theory for such a long time, even though the heliocentric model more simply explained the observed motions and brightness of the planets?

-The geocentric model conformed to both the philosophical and religious doctrines of the time. -From Earth, all heavenly bodies appeared to circle around a stationary Earth. -Ancient astronomers did not observe stellar parallax, which would have provided evidence in favor of the heliocentric model. -The heliocentric model did not make noticeably better predictions than the geocentric model.

What is the test for whether a hypothesis is scientific or not?

A hypothesis is scientific if it is possible to prove it wrong.

In daily life, we see many cases of people who are caught misrepresenting things and who soon thereafter are excused and accepted by their contemporaries. How is this different in science?

A scientist who lies in a scientific publication will suffer professional excommunication.

Briefly, what is science? Science describes the order in nature and the causes of that order. Science is a way of knowing about the world and making sense of it. Science creates testable laws and theories. All of the above.

All of the above.

One way to triangulate the distance to many remote objects, such as stars, is to observe the shifts in their location relative to more distant background objects. This apparent shifting of an object's location with respect to the background objects is known as parallax. Parallax is represented in the figure, where the top image shows the parallax shift that is observed along a baseline that runs from one side of Earth to the other. The bottom two images show what the observer sees from opposite sides of Earth. Using triangulation, the distance to the object can be calculated with simple trigonometric relations. Use the figure to determine how the measured parallax changes in each of the following situations:

As the distance to the object increases, parallax decreases. As the size of the baseline increases, parallax increases. As the distance to background objects increases, parallax remains the same.

What is the role of equations in this book?

Equations are guides to thinking and show connections between concepts.

Two competing models attempt to explain the motions and changing brightness of the planets: Ptolemy's geocentric model and Copernicus' heliocentric model. Sort the characteristics according to whether they are part of the geocentric model, the heliocentric model, or both solar system models. Drag the appropriate items to their respective bins.

Geocentric- This model is Earth-centered, Retrograde motion is explained by epicycles Heliocentric- This model is Sun-centered, Retrograde motion is explained by the orbital speeds of planets Both geocentric and heliocentric- Epicycles and deferents help explain planetary motion, Planets move in circular orbits and with uniform motion, The brightness of a planet increases when the planet is closest to Earth

Copernicus's heliocentric model and Ptolemy's geocentric model were each developed to provide a description of the solar system. Both models had advantages that made each an acceptable explanation for motions in the solar system during their time. Sort each statement according to whether it is an advantage of the heliocentric model, the geocentric model, or both. Drag the appropriate items to their respective bins.

Heliocentric- Explained planetary motions and brightness changes most simply Geocentric- Rooted in widely accepted religious beliefs regarding Earth's place in the universe Both geocentric and heliocentric- Predicted planetary positions accurately over relatively short time periods, Planetary orbits and motions based on Greek ideologies of perfect form and motion

Why are students of the arts encouraged to learn about science and science students encouraged to learn about the arts?

Knowing both the arts and sciences makes for a wholeness in the way we view the world.

Must people choose between science and religion?

No, there is no contradiction in being scientific and religious in one's thinking.

Clearly distinguish between science and technology. -Science gathers the knowledge that technology uses for practical purposes. -Technology can be helpful or harmful, while science is only helpful. -Technology solves problems, whereas science creates them. -Science is applied technology.

Science gathers the knowledge that technology uses for practical purposes.

What test can you perform to increase the chance in your own mind that you are right about a particular idea?

See if you can state the objections of your opponents to their satisfaction.

Listed following are a series of statements that each make a claim. Classify these as either testable by accepted methods of science or non-testable by accepted methods of science. Be sure to note that this question does not ask whether a statement would pass or fail a test; it only asks whether it is testable in principle.

Testable: Earth orbits the Sun every 365.25 days, Bacteria acquire resistance to antibiotics through changes in their DNA, Marcs once had liquid water on its surface, People born under the sign of Sagittarius are twice as likely to be teachers, There will be a solar eclipse next Tuesday at 11 a.m. Not Testable: Hurricane Katrina was an act of God, Vince Young is the greatest quarterback of all time

When the Sun was directly overhead in Syene, why wasn't it directly overhead in Alexandria?

The Earth is a sphere.

Why did Aristarchus choose the time of a half Moon to make his measurements for calculating the Earth -Sun distance?

The Earth, Moon, and Sun formed a right triangle at that time.

How does the Moon's diameter compare with the distance between Earth and the Moon?

The Moon's diameter is 1/110 the distance between Earth and the Moon.

What are the circular spots of light seen on the ground beneath a tree on a sunny day?

These are pinhole images of the Sun.

In daily life, people are often praised for maintaining some particular point of view, for the "courage of their convictions." A change of mind is seen as a sign of weakness. How is this different in science?

When a scientist finds evidence that contradicts a law, then the law must be abandoned.

Consider the Moon and Sun. Their angular diameters are both equal to about .5 degree. If the Sun is roughly 400 times more distant than the Moon, how much bigger is the Sun's diameter than the Moon's?

about 400 times bigger

As the distance to the object increases, parallax

decreases

As the size of the baseline increases, parallax

increases

As the distance to background objects increases, parallax

remains the same