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  • 13 Comments
Joined 2 years ago
Cake day: June 4th, 2023
  • cosmic_skillet@lemmy.mltoShowerthoughts@lemmy.world•Swimming...
    1·
    2 years ago

    Hmm, I guess, sort of… The details in animal locomotion are really interesting and the gist of it is that there are different kinds of “swimming” and different kinds of “flying” and while some of these share similar mechanics, not all do.

    As a quick example, there are some fish that power their swimming mostly with drag. With this kind of swimming they push their fins backwards on the power stroke, propelling themselves forwards by generating a lot of drag in the water. Then they need to retract their fins, and to minimize drag they might collapse the fin so it has a small area and produces less backwards thrust.

    A duck’s foot works the same way. When pushing back the foot is splayed out, allowing the webbing to maximize drag. When retracting the foot it collapses down, to minimize drag. This kind of swimming is mechanically different from most forms of flying.

    Contrast this with the fins of sharks that lay flat and have a single leading edge that cuts through the water. These fins work by creating lift and don’t get pushed and pulled through the water. This is also how penguin wings work and why it’s often said they “fly” through the water. So this kind of swimming is very much like flying.

    In the air, wings generally need to generate lift to keep the animal airborne, while this isn’t strictly necessary under water. Also water is very dense, so many animals generate a good deal of thrust by undulating their bodies and rear fins. This isn’t generally very effective in air.

    Here’s a good Wikipedia article about this kind of stuff:

    https://en.wikipedia.org/wiki/Aquatic_locomotion

  • cosmic_skillet@lemmy.mltoWorld News@lemmy.ml•Fukushima fish with 180 times legal limit of radioactive cesium fuels water release fears
    5·
    2 years ago

    This article is not clear. I’m not sure if this issue is directly related to the planned waste water release since that hasn’t happened yet. Here’s a few scenarios off the top of my head:

    1. Ground & rainwater continue to seep into the power plant and become contaminated. Maybe some of this water is not collected and instead flows out into the breakwater, continuously carrying additional contamination with it. In this case the release or non-release of the separately stored & treated water is not related to this issue.

    2. The stored water is leaking out and contaminating the breakwater area. In this case the contamination could indicate that releasing this water is a bad idea because it will release more Cs contamination. Or maybe not, because I don’t think the currently stored water has been treated yet for release. The treatment plans for the stored water includes filtering out Cs.

    3. The contamination in the breakwater is leftover from the initial disaster a decade ago and not new. Cs-137 has a half life of ~30 years, so most of it would still be around and it’s known that a lot of this stuff got into the seabed sediment in the area. In this case it again would not be an indication about anything related to the planned water release.

    4. Some other scenario.

    Unfortunately there’s just not enough information in this article to say for certain what the origin of the Cs contamination is and what consequences that holds.