Lesson 2: Special Theory of Relativity
Albert Einstein proposed a revolutionary explanation for the failure of the Michelson-Morley experiment and called it the special theory of relativity, which has two postulates:
1. The relativity principle: all the laws of physics are valid in all inertial frames of reference.
2. The constancy of the speed of light: light travels through empty space with a speed of c=3.00 x 10^8 m/s, relative to all inertial frames of reference
The first postulate holds the implication that not only Newtonian mechanics but all laws of physics (electricity, magnetism, optics) are the same in all inertial frames. In Newtonian mechanics, while laws of motion are the same in all inertial frames, the appearance of any particular motion might change from one frame to the next. Einstein has a similar but more radical position: the changes in appearance as one moves between inertial frames travelling at high speeds with respect to each other, seem to defy common sense. Special relativity is a special case of general relativity which deals with gravitation and noninertial reference frames.
The central concept of this chapter is to understand the implications of the two postulates of special relativity.
Learning Objectives:
1. The relativity principle: all the laws of physics are valid in all inertial frames of reference.
2. The constancy of the speed of light: light travels through empty space with a speed of c=3.00 x 10^8 m/s, relative to all inertial frames of reference
The first postulate holds the implication that not only Newtonian mechanics but all laws of physics (electricity, magnetism, optics) are the same in all inertial frames. In Newtonian mechanics, while laws of motion are the same in all inertial frames, the appearance of any particular motion might change from one frame to the next. Einstein has a similar but more radical position: the changes in appearance as one moves between inertial frames travelling at high speeds with respect to each other, seem to defy common sense. Special relativity is a special case of general relativity which deals with gravitation and noninertial reference frames.
The central concept of this chapter is to understand the implications of the two postulates of special relativity.
Learning Objectives:
- Understanding that the laws of Newtonian mechanics are only valid in an inertial frame of reference and are the same in all inertial reference frames.
- Knowing that Michelson Morley's interferometer experiment proved the nonexistence of ether.
- Being able to conceptualize the implications of the two postulates of Einstein's special theory of relativity.
To introduce this lesson on the special theory of relativity, it might be a good idea to start with the historical basis of the theory and the concept of ether. I highly recommend doing the following:
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Click on the button below to be directed to a simulation of the Michelson-Morley experiment.
The following video is comprehensive and draws on applications such as the GPS system to make special relativity relevant to student's lives.
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The video below is of an appealing animation that explains all of the theories of special relativity.
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In order to have the students become involved in independent learning, have them do the following activity:
- Divide class into 5 groups and assign each group one of the following topics: the electromagnetic nature of light, ether, the Michelson-Morley experiment, the first and second postulate of special relativity.
- Book the computer lab in the library beforehand and then take students down to the library to do research on their assigned topics.
- Inform students that each group will conduct a 5 minute presentations on their topic for next class and that they should use this time to gather information and plan their presentation for the next day.
- To conclude this activity, have students fill out a handout on what they have researched thus far 10 min before the end of class and assign a mark for completion.
References
- Hirsch, A., Stewart, C., Martindale, D, & Barry, M. (2011). Nelson Physics 12. Toronto: Nelson Thomson Learning
- Rindler, W. (1991). Introduction to Special Relativity (2nd ed.). Oxford: Oxford University Press