5 ms·

Can't wait for the first little green men (phosynthetic humans)

gus_massa 4y ago
There is a relevant analysis in https://what-if.xkcd.com/17/ https://what-if.xkcd.com/17/ about a "green" cow that can get energy from photosynthesis.
- cobbzilla 4y ago
  > a "green" cow that can get energy from photosynthesis Sun-fed beef?
dahfizz 4y ago
I wonder how it will change the livestock industry. Not having to feed animals alleviates the environmental concerns about eating meat, and would make meat cheaper. Hell, I would buy myself some photosynthesizing cows and pigs if I can just put them in a pen outside and not have to feed them.
- mytailorisrich 4y ago
  Considering the surface area of a cow and that they apparently ought to eat 14+kg of grass a day plus a few kg of additional feed, a photosynthetic cow would quickly starve to death if you stopped feeding it... (ignoring the still necessary mineral intake)
  - jonathankoren 4y ago
    That’s not a fair comparison. This is generating ATP directly, rather extracting sugars and whatnot the plant, most of which is indigestible waste, so it’s not like you’d need the surface area of 14 kg of grass. The real problem is that you need hemispherical hairless cows. ;)
    - TeMPOraL 4y ago
      > The real problem is that you need hemispherical hairless cows. ;) That's a good opportunity to join forces with Sabine Hossenfelder and together move some of excess funding from, say, particle physics, and allocate it to fundamental research on which all physics depends: creation of frictionless, vacuum-rated spherical cows.
    - akiselev 4y ago
      ATP requires adenine and ribose. The former requires nitrogen fixed for the grass by microorganisms and the latter requires glucose for the pentose phosphate pathway. Adenine might also be recycled by the mitochondria which would further complicate things (can ATP be sent back into the mitochondria? Can the mitochondria recycle adenine without the entire glucose/electron transport pathway?) I suspect a photosynthetic cow would still need to eat a lot of grass
      - moloch-hai 4y ago
        You process literal pounds of ADP to ATP and back to ADP, every day. If you eat fructose, you end up turning some of that into uric acid and excreting it, wastefully. It does other varied harm on its way out.
        akiselev 4y ago
        > You process literal pounds of ADP to ATP and back to ADP, every day. That's exactly my point. Some percentage of that ADP and ATP will be lost and the adenine/ribose broken down or reused for something else - cells are messy environments. Some of that will be lost permanently to waste. The more turnover in this process, the more opportunity for that loss.
k_sze 4y ago
Reminds me of "Knights of Sidonia".
zopa 4y ago
No need to wait: per Gene Wolf they’re also time travelers. They’ll come to you.
- clarionbell 4y ago
  Unless they overshoot, end up on Urth and have to wait for a guy with a spare whetstone.

There is a relevant analysis in https://what-if.xkcd.com/17/ https://what-if.xkcd.com/17/ about a "green" cow that can get energy from photosynthesis.

cobbzilla 4y ago
> a "green" cow that can get energy from photosynthesis Sun-fed beef?

dahfizz 4y ago

I wonder how it will change the livestock industry. Not having to feed animals alleviates the environmental concerns about eating meat, and would make meat cheaper. Hell, I would buy myself some photosynthesizing cows and pigs if I can just put them in a pen outside and not have to feed them.

mytailorisrich 4y ago
Considering the surface area of a cow and that they apparently ought to eat 14+kg of grass a day plus a few kg of additional feed, a photosynthetic cow would quickly starve to death if you stopped feeding it... (ignoring the still necessary mineral intake)
- jonathankoren 4y ago
  That’s not a fair comparison. This is generating ATP directly, rather extracting sugars and whatnot the plant, most of which is indigestible waste, so it’s not like you’d need the surface area of 14 kg of grass. The real problem is that you need hemispherical hairless cows. ;)
  - TeMPOraL 4y ago
    > The real problem is that you need hemispherical hairless cows. ;) That's a good opportunity to join forces with Sabine Hossenfelder and together move some of excess funding from, say, particle physics, and allocate it to fundamental research on which all physics depends: creation of frictionless, vacuum-rated spherical cows.
  - akiselev 4y ago
    ATP requires adenine and ribose. The former requires nitrogen fixed for the grass by microorganisms and the latter requires glucose for the pentose phosphate pathway. Adenine might also be recycled by the mitochondria which would further complicate things (can ATP be sent back into the mitochondria? Can the mitochondria recycle adenine without the entire glucose/electron transport pathway?) I suspect a photosynthetic cow would still need to eat a lot of grass
    - moloch-hai 4y ago
      You process literal pounds of ADP to ATP and back to ADP, every day. If you eat fructose, you end up turning some of that into uric acid and excreting it, wastefully. It does other varied harm on its way out.
      - akiselev 4y ago
        > You process literal pounds of ADP to ATP and back to ADP, every day. That's exactly my point. Some percentage of that ADP and ATP will be lost and the adenine/ribose broken down or reused for something else - cells are messy environments. Some of that will be lost permanently to waste. The more turnover in this process, the more opportunity for that loss.

k_sze 4y ago

Reminds me of "Knights of Sidonia".

zopa 4y ago

No need to wait: per Gene Wolf they’re also time travelers. They’ll come to you.

clarionbell 4y ago
Unless they overshoot, end up on Urth and have to wait for a guy with a spare whetstone.