São José dos Campos, 2017/08/29

About this measurement

  • Method: Shadow tracking with toothpick and printed protractor
  • Tracker: Tony Lâmpada
  • Location: São José dos Campos — Brazil (-23.10º, -45.5º)
  • Date and Timezone: 2017, Aug 29, GMT-3

Evidence produced

As you can see the measurements didn’t apply much rigorous techniques. A cracker was used to hold the toothpick in place, made vertically level without the use of any instrument. My compass was pointing at 342º seems to be off from true north by 12º (I still don’t understand what’s up with that, maybe something weird with the magnetic field in my house?). Anyway on that first picture, true North is at 354º (See second picture with solar noon at 12:07). I decided to keep the sheet alignet with the angles of the house and then account for that -6º different when computing the results.

Raw data and spreadsheet

Complete spreadsheet (google docs)

Comparison with predictive models

Data interpretation

Well, seems like the old fashioned shadows are more accurate than our electronic devices. Can’t say I’m that surprised.

It’s almost a perfect fit with the globe model. Maybe a more precise measurements process will yield results that are even closer to the blue curve.


Shadow behaviour can be perfectly predicted by the globe model, in São José dos Campos, on Aug 29. But that’s still a long way from “anywhere anytime”.

Also, the data here is provided by me and it can be argued that I had every intention to prove the globe all along (which is true) — so I understand if these results are challenged based on the grounds that I am biased as a tracker.

Science is made with repeatable, measurable, observable and testable evidence from independent sources. We need more.

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