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Off tangent here but I thought I'd mention that yesterday a replica of a traditional Polynesian ocean-going canoe, the Hokulea, sailed into San Francisco, navig

by hbarka 3y ago

Off tangent here but I thought I'd mention that yesterday a replica of a traditional Polynesian ocean-going canoe, the Hokulea, sailed into San Francisco, navigated with non-instrument methods including star observations. https://www.sfchronicle.com/bayarea/article/hokulea-polynesian-canoe-18379540.php https://www.sfchronicle.com/bayarea/article/hokulea-polynesi... The Hokulea's maiden voyage was in 1975 and since then it has made global voyages to demonstrate and preserve ancient Polynesian wayfinding methods. Here's a video where a local news channel covered an earlier voyage of the Hokulea (2014) and summarized how the ancient sailors would have used the stars as reference points: https://youtu.be/dla3RoQo37M https://youtu.be/dla3RoQo37M

inamberclad 3y ago
That's incredible. I was just speaking with colleagues about the best conditions for surfing waves. The best waves here in California originate in storms on the opposite side of the Pacific. The waves travel thousands of miles over the course of days without appreciably dissipating.
- antod 3y ago
  For those interested... The waves do dissipate, but the dissipation and attenuation is what makes the best waves. In the storm the waves are huge and messy with all kinds of frequencies interfering with each other. Attenuation means the high frequency / small amplitude waves dissipate the quickest and the lowest frequency / high amplitude waves dissipate the slowest. By the time they've moved a long way, all that's left are the lowest frequencies which makes for a clean smooth wave. The amplitude will have reduced compared to the original storm, but that original long period is still there creating nice long gaps between the waves. This is why surfers care about the period of an incoming swell - it's a proxy for how the swell has cleaned up on it's travels. The best waves come from the biggest storms the furthest away.
KaiserPro 3y ago
Polynesian navigation is Wild. I think its well known that it almost died out, as its something that needs ideally to be taught in the (sea) field. However there are now people in their 30s who can navigate by the stars, sound, wave shape and pattern, cloud layout and birds https://manoa.hawaii.edu/exploringourfluidearth/physical/navigation-and-transportation/wayfinding-and-navigation https://manoa.hawaii.edu/exploringourfluidearth/physical/nav... Similarly there are people who can navigate the desert, even though the dunes are mostly ever shifting.
- Sharlin 3y ago
  > Similarly there are people who can navigate the desert, even though the dunes are mostly ever shifting. To be clear, most deserts don't feature dune seas at all, and even the Sahara is mostly rocky plateau, dune seas comprising about 10% of its surface area.

by hbarka 3y ago

inamberclad 3y ago

That's incredible. I was just speaking with colleagues about the best conditions for surfing waves. The best waves here in California originate in storms on the opposite side of the Pacific. The waves travel thousands of miles over the course of days without appreciably dissipating.

antod 3y ago
For those interested... The waves do dissipate, but the dissipation and attenuation is what makes the best waves. In the storm the waves are huge and messy with all kinds of frequencies interfering with each other. Attenuation means the high frequency / small amplitude waves dissipate the quickest and the lowest frequency / high amplitude waves dissipate the slowest. By the time they've moved a long way, all that's left are the lowest frequencies which makes for a clean smooth wave. The amplitude will have reduced compared to the original storm, but that original long period is still there creating nice long gaps between the waves. This is why surfers care about the period of an incoming swell - it's a proxy for how the swell has cleaned up on it's travels. The best waves come from the biggest storms the furthest away.

KaiserPro 3y ago

Polynesian navigation is Wild. I think its well known that it almost died out, as its something that needs ideally to be taught in the (sea) field. However there are now people in their 30s who can navigate by the stars, sound, wave shape and pattern, cloud layout and birds https://manoa.hawaii.edu/exploringourfluidearth/physical/navigation-and-transportation/wayfinding-and-navigation https://manoa.hawaii.edu/exploringourfluidearth/physical/nav... Similarly there are people who can navigate the desert, even though the dunes are mostly ever shifting.

Sharlin 3y ago
> Similarly there are people who can navigate the desert, even though the dunes are mostly ever shifting. To be clear, most deserts don't feature dune seas at all, and even the Sahara is mostly rocky plateau, dune seas comprising about 10% of its surface area.