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michael_nielsen's profile
michael_nielsen
michael_nielsen
michael_nielsen
@michael_nielsen

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michael_nielsen

@michael_nielsen

Searching for the numinous. Co-purveyor of https://quantum.country/ 

San Francisco, CA
michaelnielsen.org
Joined July 2008

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    michael_nielsen‏ @michael_nielsen Jan 31
    • Report Tweet

    michael_nielsen Retweeted Chris Walter

    A wonderful little fact about the maximum power density inside the sun (spoiler: about the same as inside a compost pile!) ht @nattyoverhttps://twitter.com/chris_w_walter/status/1223021681918132224 …

    michael_nielsen added,

    Chris Walter @chris_w_walter
    The most surprising yet true thing anyone has ever pointed out to me on Wikipedia is that the Sun is so bright because it is so big. The power production rate is actually like a few lightbulbs in a box, or the heat from a compost pile or Lizard! From: https://en.wikipedia.org/wiki/Sun  https://twitter.com/overbye/status/1222661409277911041 … pic.twitter.com/YZqnKmchqY
    Show this thread
    9:04 AM - 31 Jan 2020
    • 44 Retweets
    • 228 Likes
    • this account is anonymous Daniel Duffy Michael Scott Rajesh Austin Moreau Goupil_des_arbres Michael Peyton Jones Jack Vader Kasia Hayden
    8 replies 44 retweets 228 likes
      1. New conversation
      2. Timothy Gowers‏ @wtgowers Jan 31
        • Report Tweet
        Replying to @michael_nielsen @nattyover

        There must be some nice scaling-law explanation for why I'd be instantly fried if I dived into the sun but not if I dived into a compost heap. If the radius of a spherical compost heap doubles, what happens to the temperature at its surface? (Is that even the right question?)

        2 replies 0 retweets 7 likes
      3. michael_nielsen‏ @michael_nielsen Jan 31
        • Report Tweet
        Replying to @wtgowers @nattyover

        Suppose you have fixed power density, and the sun is of (variable) radius r. The energy flux at the surface - the thing frying you - scales as power density * volume / surface. That's proportional to the radius. The Sun is just a really, really big compost heap!

        2 replies 3 retweets 24 likes
      4. 2 more replies
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      2. 1/(1 - 1/(1 - 1/(1 - Dan Piponi)))‏ @sigfpe Jan 31
        • Report Tweet
        Replying to @michael_nielsen @nattyover

        I usually make the comparison with the power density generated by human muscle. I guess it makes me feel like Superman or something.

        1 reply 0 retweets 1 like
      3. michael_nielsen‏ @michael_nielsen Jan 31
        • Report Tweet
        Replying to @sigfpe @nattyover

        Stronger than a shooting star! (Oops, wrong comparison...)

        0 replies 0 retweets 3 likes
      4. End of conversation
      1. New conversation
      2. David Deutsch‏ @DavidDeutschOxf Feb 1
        • Report Tweet
        Replying to @michael_nielsen @nattyover

        And a nuclear fusion reactor will have many millions of times that power per unit volume. So much for its being merely an "artificial sun"!

        1 reply 3 retweets 39 likes
      3. 2 more replies
      1. Pradyumna Singh‏ @pradyu_singh Jan 31
        • Report Tweet
        Replying to @michael_nielsen @nattyover

        Indeed, and humans typically have > 10^4x W/kg than the sun. With bacteria etc. that number gets even higher! There's a nice talk on cellular energetics by Rob Phillips:https://youtu.be/9NgT1z1Kcbs?t=285 …

        0 replies 2 retweets 6 likes
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      1. John Carlos Baez‏ @johncarlosbaez Jan 31
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        Replying to @michael_nielsen @nattyover

        I like it when on a cold day I dig into my compost pile and warm steam comes out. Now I'll think about the Sun.

        0 replies 0 retweets 11 likes
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      1. Vladbot 5013‏ @Radegund Jan 31
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        Replying to @michael_nielsen @DavidDeutschOxf @nattyover

        Maybe it's just a large collection of space reptiles.

        0 replies 0 retweets 1 like
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      1. Paul F. Dietz‏ @PaulFDietz Jan 31
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        Replying to @michael_nielsen @nattyover

        Now compute the thermal energy of a cubic meter of the Sun's core.

        0 replies 0 retweets 1 like
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