POST AP 02: SR Vis

I hope you enjoyed your very first Rock Opera... for some folks it can be something of an (how shall I say....)

Acquired Taste?

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As is sometimes the case, I had a bit of an ulterior motive in having you folks do that, what might that have been? <please discuss>

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So... along those lines, I have a VERY cool activity for you today, but it's gonna start out a little *ahem* different. Please roll with it.

To wit:

Let's arrange seats back to back in a circle

After each prompt you'll move from inner to outer.

The outer person ALWAYS talks, the inner person ALWAYS listens. The inner person (so to speak) can ask very brief (less than 10 words please) clarifying questions only.

If we have an odd number of students today, we'll swap out a person each round to be the prompter. If we have an even number, I'll do the prompting.

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Using simple images from his day-to-day life and nothing more than basic high school algebra, Einstein was able to formulate a powerful relationship between time and the speed of light (c).

Let's recap:

A passenger onboard a train watches a single photon move from a flashlight to the ceiling.

An observer outside watches the train go by at .90 c

The observer also watches the photon move from the flashlight to the ceiling of the train compartment where the passenger is seated.

Work with your group to see if you discern the radical departure that Einstein embarked upon in this thought experiment.

Answer: This thought experiment offers the very radical suggestion that the speed of light is constant in both reference frames.

• Have a conversation and see if you can suggest how keeping c constant in BOTH reference frames would impact displacement calculations in each reference frame?

• What does the passenger see the photon do (draw and label a sketch)?
• Using the most simple rate equation, how would the passenger calculate the displacement for that photon moving from a flashlight to the roof of the cabin?

Now let's switch to the observer in a different frame of reference (watching the train go by from outside the train) and let's say the train is moving at .90 c:

• What does the observer see the photon do (draw and label a sketch)?
• Using the most simple rate equation, how would the observer calculate the displacement for that photon moving from a flashlight to the roof of the cabin?
• How does that observer calculate the displacement of that train during that same?

Here is another amazing insight that Einstein obtained: He related all three of those displacements to determine a relationship between time inside, time outside and the speed of the train:

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