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## Consequences of Special Relativity

(Lecture: 30 minutes)

- Simultaneity
- Time dilation
- Length contraction

See §2 of the text, especially §2.3.

*If you have access to the
Mechanical Universe video,
1)
there is a good animation of time dilation @ 8:00 minutes.*

### Reflections

This lecture continues the discussion of the consequences of the speed of light being constant by analyzing additional moving train examples.

The discussion of simultaneity may be combined with the previous lecture, and/or reviewed here.

The discussion of time dilation introduces a quantitative, rather than qualitative, discussion of the consequences of special relativity. However, the analogous treatment of length contraction is much less transparent. One possibility is to have students work through this argument on their own. If it is to be discussed in class, the instructor should practice the derivation beforehand to ensure it goes smoothly, and expect to spend at least an additional 10 minutes working through this example.

The video covers simultaneity and time dilation only, but is well worth making available to the class, especially as a prelude to the later excerpts from the same video which greatly enhance the transition to spacetime diagrams in a later lecture.