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Anyone want to review the Relativity Lab that I made?

  1. Mar 28, 2014 #1
    Hey everyone,

    Recently I have been working on my teaching degree and doing field experience. Because relativity is part of the Georgia Science standards, I had to make a relativity lab. The experiment is actually measuring time dilation using GPS in the phones similar to Hafele–Keating experiment. I was wondering...

    If I uploaded the lab, would anyone who has expertise in general relativity be willing to do a informal review of it?
  2. jcsd
  3. Mar 28, 2014 #2


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    Sure, let's see it.
  4. Mar 28, 2014 #3
    Ok here it is attached. Also Question 3 is more an open ended question to get students to at least look up the speeds of different particles or time dilation experiments. I do actually take yes for an answer on that question even though I think personally that the answer should be no.

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    Last edited: Mar 28, 2014
  5. Mar 28, 2014 #4


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    I guess this app requires an Android phone? What do you do if your students don't have cell phones, or if they have some other kind of phone? I would like to try this myself, but I don't have that type of phone.

    I guess the phone has to have GPS -- how common is that in smart phones these days?

    The Word document has a lot of errors like this: "Error: Reference source not found. "

    In general I had a hard time following the description of the lab. Conceptually, is it as if each phone acts like a clock, and you act out the twin paradox? But in reality I assume each phone is getting its time from the GPS satellite...? It's not obvious to me that this is really an experiment that acts out the twin paradox, if the timing isn't really being done by a clock inside the phone.
  6. Mar 29, 2014 #5
    First thanks so much for reviewing!!

    In the future I am hoping that similar apps get developed on the other types of phone. However, the iphone's app that does the same thing was taken down. Most people know that app as einstien's pedometer app.

    Yes, its supposed to be, esle you phone would need wifi connection to find where you are. That is not very convenient while your driving to have to stop your car, connect to free wifi, then check your map app.

    hmm... that is odd... can you take a screenshot for me so I know which ones are acting up?

    What is just the introduction that was confusing or the procedure calculations section as well?

    If it was just the introduction, yes, I am working on that because honestly, I myself though that students might glaze over. I just cannot think of a good way to Engage them with learning about where the formula comes from. This is why I like you mention of the twin paradox. Do you know any descriptions or links of the twin paradox where one twin is sent away and they compare clocks at a distance?​
    This experiment is similar to the twin paradox if moving twin didn't return.
    The Twin Paradox, in terms of standards, is the exception (or logical contradiction) of special relativity. However, students have to understand what time dilation from special relativity is before they can understand exceptions to it. Does that make sense?​
    While based based on the information from the satellite, the time is measured by the phone(s) which treat the satellite and your the rest twin as in the same co-moving "rest" frame. Figuratively, its like your twin is at rest on the satellite. Its due to the GPS's frequency standard being pre-doppler shifted to 10.22999999543 MHz instead of 10.23 MHz. I can explain this in more detail if you would like.​

    Now in terms of making it less confusing, maybe I could have a longer introduction and engage them by talking about the twin paradox if the twin didn't return? Or should I talk about GPS first then talk about the time dilation formula? What do you think?
    Last edited: Mar 29, 2014
  7. Mar 29, 2014 #6


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    Here's an example:

    http://www.lightandmatter.com/temporary_relativity_lab_screenshot.jpg [Broken]

    This isn't quite right. The twin paradox isn't really a paradox, and it isn't an exception or a logical contradiction.
    Last edited by a moderator: May 6, 2017
  8. Mar 30, 2014 #7


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    Everything displays ok for me. I'm using MS Word 2007.

    There appears to be a missing/misplaced part of a sentence in the introduction part:
    I'm not a native speaker myself, but it doesn't sound like correct English.

    Why do you say that? You write yourself that the time correction for a fast-moving GPS satellite is mere 7 microseconds per day, which amounts to about a second per 40 years of continuous flight(SR correction only).
    You could use this fact to tie in to the twin paradox - make one twin a 'janitor' on a satellite, while the other stays on Earth. Maybe let the students calculate how much longer/shorter until retirement for the space twin.

    In comment s7 you mention a 'wavelength error' of 2km. A wavelength of what?
  9. Sep 1, 2014 #8

    I would like to know your experiment.
    Could you make it available?
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