the Annenberg Foundation
the Harvard-Smithsonian Center for Astrophysics
This is Unit 3 of the free digital course "Physics for the 21st Century", aimed at secondary teachers, high school physics students, and adult learners. It explores gravity, an attractive force that acts between any objects at any distance regardless of their composition. In many ways, gravity is the dominant force in the universe. Yet, of the four forces known in nature, gravity is the weakest. The unit begins with Newton's law of universal gravitation and inertial mass, then provides an overview of general relativity, time dilation, and curved spacetime. Two chapter headings are devoted to gravitational wave detection with laser interferometers, a promising new field of astronomy.
The resource includes 3 components: written text, short video clips and animations, and an interactive web module on discovering neutrino oscillations. A Facilitator's Guide is also provided.
The video series is produced by the Harvard-Smithsonian Center for Astrophysics Science Media Group in association with the Harvard University Department of Physics. It is sponsored by Annenberg Media.
9-12: 1A/H1. Science is based on the assumption that the universe is a vast single system in which the basic rules are everywhere the same and that the things and events in the universe occur in consistent patterns that are comprehensible through careful, systematic study.
9-12: 1A/H2. From time to time, major shifts occur in the scientific view of how things work. More often, however, the changes that take place in the body of scientific knowledge are small modifications of prior knowledge. Continuity and change are persistent features of science.
9-12: 1A/H3bc. In science, the testing, revising, and occasional discarding of theories, new and old, never ends. This ongoing process leads to a better understanding of how things work in the world but not to absolute truth.
1C. The Scientific Enterprise
9-12: 1C/H6ab. Scientists can bring information, insights, and analytical skills to bear on matters of public concern. Acting in their areas of expertise, scientists can help people understand the likely causes of events and estimate their possible effects.
4. The Physical Setting
4A. The Universe
9-12: 4A/H3. Increasingly sophisticated technology is used to learn about the universe. Visual, radio, and X-ray telescopes collect information from across the entire spectrum of electromagnetic waves; computers handle data and complicated computations to interpret them; space probes send back data and materials from remote parts of the solar system; and accelerators give subatomic particles energies that simulate conditions in the stars and in the early history of the universe before stars formed.
9-12: 4F/H4. Whenever one thing exerts a force on another, an equal amount of force is exerted back on it.
4G. Forces of Nature
6-8: 4G/M1. Every object exerts gravitational force on every other object. The force depends on how much mass the objects have and on how far apart they are. The force is hard to detect unless at least one of the objects has a lot of mass.
6-8: 4G/M2. The sun's gravitational pull holds the earth and other planets in their orbits, just as the planets' gravitational pull keeps their moons in orbit around them.
9-12: 4G/H1. Gravitational force is an attraction between masses. The strength of the force is proportional to the masses and weakens rapidly with increasing distance between them.
9-12: 4G/H2a. Electric forces acting within and between atoms are vastly stronger than the gravitational forces acting between the atoms. At larger scales, gravitational forces accumulate to produce a large and noticeable effect, whereas electric forces tend to cancel each other out.
10. Historical Perspectives
10C. Relating Matter & Energy and Time & Space
9-12: 10C/H4. A decade after Einstein developed the special theory of relativity, he proposed the general theory of relativity, which pictures Newton's gravitational force as a distortion of space and time.
9-12: 10C/H5. Einstein's development of the theories of special and general relativity ranks as one of the greatest human accomplishments in all of history. Many predictions from the theories have been confirmed on both atomic and astronomical scales. Still, the search continues for an even more powerful theory of the architecture of the universe.
11. Common Themes
9-12: 11B/H1a. A mathematical model uses rules and relationships to describe and predict objects and events in the real world.
6-8: 11D/M3. Natural phenomena often involve sizes, durations, and speeds that are extremely small or extremely large. These phenomena may be difficult to appreciate because they involve magnitudes far outside human experience.
Common Core State Standards for Mathematics Alignments
High School — Functions (9-12)
Building Functions (9-12)
F-BF.4.a Solve an equation of the form f(x) = c for a simple function f that has an inverse and write an expression for the inverse.
Linear, Quadratic, and Exponential Models? (9-12)
F-LE.1.c Recognize situations in which a quantity grows or decays by a constant percent rate per unit interval relative to another.
F-LE.5 Interpret the parameters in a linear or exponential function in terms of a context.
Harvard-Smithsonian Center for Astrophysics. Physics for the 21st Century: Gravity. Annenberg Foundation, 2010. http://www.learner.org/courses/physics/unit/text.html?unit=3&secNum=0 (accessed 23 November 2014).
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