Dear physics,(adsbygoogle = window.adsbygoogle || []).push({});

I'm new to the site. I found it reading this topic:

https://www.physicsforums.com/showthread.php?t=145043

I wonder if we could manage to answer, if some not critical precision, the question of:

How many people can live confortably, eating only potatos, in earth?

As of a first estimation, also used to set an example and the conditions, I'll try to answer. Please, help me correct the estimations, many of them I got from not so trusted sites.

1. How much power we need to function?

2. How much power the earth can give?

3. How much people can live with that?

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1. From the link above, considering 2000 Kcal per day as a good consumption, we can reach that a human being is like a 100 Watt lamp.

(more details on the link)

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2. Now, to estimate how much the earth can give, we need a lot of assumptions, each one must be checked and corrected if you find it wrong. Thanks.

First, lets talk about potatos. I found that a large potato (300g) has approximately 250 cal.

It takes 20 weeks to grow from seed. And some estimate that 6m x 6m can produce 200Kg of potatos.

That makes ~19 potatos per m^2. That makes 5.7Kg per grow per m^2, or 41g per day per m^2, or still 35 calories per m^2 per day.

Now, arable land. This google us to wikipedia, and they estimate 14000 km^2 of arable land, and 50000 km^2 of agricultural land. I'm not sure the difference, though I read the description. But I believe its safe to sum them. So we have 64 thousand km^2 to plant our potatos. That gives us 2600 gigacalories per day.

So the earth can produce 127 bilions Watts from potatos.

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Now using 100 Watts per person, every one eating his 8 potatos per day at lunch and dinner, the maximum confortable population would be only 1 billion 300 millions.

And here, looking this number, I think there should be serious problems with this estimation!

Please, any lights to share?

Thanks,

Beco.

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# Maximum population for 2000 Kcal per day

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