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Meaningness's profile
David Chapman
David Chapman
David Chapman
@Meaningness

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David Chapman

@Meaningness

Better ways of thinking, feeling, and acting—around problems of meaning and meaninglessness; self and society; ethics, purpose, and value.

meaningness.com/about-my-sites
Joined September 2010

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    1. David Chapman‏ @Meaningness 20 Aug 2018
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      Very roughly how many water molecules would you guess there are in a single cell? Within a couple of orders of magnitude? I got it quite wrong.

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    2. David Chapman‏ @Meaningness 20 Aug 2018
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      I guessed off-hand “a billion” which I think was just my brain’s way of saying “wow, a really big number!” But it’s WAY too small.

      3 replies 0 retweets 7 likes
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    3. David Chapman‏ @Meaningness 20 Aug 2018
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      There’s a bunch of different numbers you can find on the web. Some of them are definitely way off. But there’s a wide range of values that seem reasonable (to me) because cells vary in size over several orders of magnitude.

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    4. David Chapman‏ @Meaningness 20 Aug 2018
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      A water molecule is roughly 3Å (I remembered this!). An Å is 10^-10m (I remembered this too!) How big is a cell? (I didn’t remember this, if I ever knew!) 10μ is too small and 100μ is too big (although for a Fermi estimate, but might be reasonable).

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    5. David Chapman‏ @Meaningness 20 Aug 2018
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      So call it 30μ, i.e. 3*10^-5. Then the ratio of linear dimensions is 10^5, or volumetrically 10^15. But water isn’t the whole of the cell, so less than that. Maybe 10^14. This is larger than most numbers I found on the web, but not way off.

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    6. David Chapman‏ @Meaningness 20 Aug 2018
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      Several tweeps did estimates based on total mass of human body divided by the number of cells, and came up with similar numbers. I wouldn’t have thought of that approach!

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    7. David Chapman‏ @Meaningness 20 Aug 2018
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      I think my original guess was dumb in an interesting way. 10^9 is the cube of only 10^3. Would it be reasonable for a cell to be 10^3 water molecules across? If you think about all the stuff that’s crammed into a cell, made of proteins, and proteins are WAY bigger—no, not 10^3.

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    8. David Chapman‏ @Meaningness 20 Aug 2018
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      The lesson for me is that cubing numbers makes them grow faster than I realized at a gut level. “Polynomial algorithms are fast!” is not so true for O(n^3).

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      David Chapman‏ @Meaningness 20 Aug 2018
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      Apparently there are on the order of 10^8 protein molecules per cell, which sounds like an awful lot until you take the cube root, to get a few hundred, which seems plausible if you think of all the organelles, made of protein, that have to fit in there.

      1:47 PM - 20 Aug 2018
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      • Derek. JUST "Derek. JUST "Derek. JUST "Derek. JUST
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