Around The World In ? Days

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The other day I wondered what the story “Around The World In 80 Days” would look like in the year 2024. It got me thinking, what is the definition of “Around The World”? For example, as shown in my recent blog post on my travels, I have passed through every longitude on the planet. The easiest way to confirm that is to simply show that:

Does this mean that I have been around the world? I don’t think so really. For example, if I stood on either of the North Pole or the South Pole then I would be able to cross every longitude in 10 seconds of walking. That surely doesn’t count. Now, if I went to the equator and then went all the way around the world along the equator then that would definitely count. Is there some in between solution? Can I go all the way around the world from my house? I decided that if I went from my house to my house’s antipode and back again the other way round, then that would definitely count. This immediately raises the question: “how far can I deviate from the great circle to the antipode?”

I decided to write a collection of Python scripts to show all the possible great circles from my house to my house’s antipode, then turn the line into a band with a width, and finally show all the countries that the band intersected around the world. There are an infinite number of great circles that would take me to my antipode (no matter which direction I set off from my house I would eventually arrive at my house’s antipode) - but because the Earth is not a perfect sphere, some of these great circles are longer than others:

Download:
  1. 512 px × 384 px (0.2 Mpx; 234.5 KiB)
  2. 1,024 px × 768 px (0.8 Mpx; 673.1 KiB)
  3. 2,048 px × 1,536 px (3.1 Mpx; 1.9 MiB)
  4. 2,880 px × 2,160 px (6.2 Mpx; 1.9 MiB)

If I make the journey interesting by choosing the longest pair of great circles (one to go to my house’s antipode and one to come back the other way), then the next question immediately becomes: “how much can I deviate away from the great circle?” I decided to fallback on aeroplanes - if I flew exactly along the great circle to the antipode then how much could I see along the way? The first script in the repository takes an altitude and calculates how far away the horizon is if you were in an aeroplane at that altitude. It uses this distance to set the half-width of the band. For me, my allowed deviation becomes:

Download:
  1. 512 px × 288 px (0.1 Mpx; 136.5 KiB)
  2. 1,024 px × 576 px (0.6 Mpx; 424.8 KiB)
  3. 2,048 px × 1,152 px (2.4 Mpx; 1.3 MiB)
  4. 3,840 px × 2,160 px (8.3 Mpx; 2.7 MiB)

I think that looks reasonable. I think that if I left my house and went all the way to my house’s antipode and back again without deviating from the shaded red region then no one could really say that I did not circumnavigate planet Earth. As a video, this is what my journey would look like:

Download:
  1. 512 px × 512 px (0.3 Mpx; 4.0 MiB)
  2. 1,024 px × 1,024 px (1.0 Mpx; 10.3 MiB)
  3. 2,048 px × 2,048 px (4.2 Mpx; 26.3 MiB)
  4. 3,840 px × 3,840 px (14.7 Mpx; 55.9 MiB)

… now, if only I had both the money and the time to do this adventure …