• 1 Post
  • 58 Comments
Joined 4 年前
cake
Cake day: 2020年7月18日

help-circle





  • Xavienth@lemmygrad.mltoScience Memes@mander.xyzStress
    link
    fedilink
    English
    arrow-up
    2
    ·
    1 个月前

    A successful organism would not have evolved to highly express cortisol to weed itself out in the case that it has a stressful life. It makes no sense for an organism to evolve a trait that makes it at best equally likely and at worst less likely to reproduce.

    The reason we release excess cortisol in modern life is because our bodies did not evolve for constantly present stressors, they evolved to be stressed in a situation, run away from the tiger, and then you’re good.











  • Xavienth@lemmygrad.mltoScience Memes@mander.xyz#justposeidonthings
    link
    fedilink
    English
    arrow-up
    3
    arrow-down
    1
    ·
    2 个月前

    It’s less the result of a sensible system of units (like how 1 L of water ideally weighs 1 kg), and more fortunate happenstance in this case.

    The formula for hydrostatic pressure* is:

    ∆P= ρ·g·∆h

    where ∆P is the difference in pressure across the difference in height ∆h, ρ is the density of the liquid (~1000 kg/m³ for water, slightly more for sea water), and g is the acceleration due to gravity.

    So the reason it works out nicely is because g is a little bit less than a nice factor of ten (9.8 m/s²), and the density of sea water is a little bit more than a nice factor of ten (typically 1025 kg/m³), and 1 atm also happens to be almost a nice factor of ten (101,325 Pa). That’s why the difference between the approximation and the actual* is less than a percent.

    *This assumes a constant density of the liquid, which for water is reasonable, however different depths can have different salinities and temperatures in layers which change the density by less than a percent. Additionally, this assumes a constant acceleration due to gravity. At depth, the acceleration due to gravity can be higher, but this also has an effect that amounts to less than a percent even at the deepest point in the ocean.