This back-of-the-envelope calculation appears to be off by a factor of two, which isn't bad.
http://en.wikipedia.org/wiki/World_population#Number_of_huma...
What percentage of people are alive today?
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Re: What percentage of people are alive today?
#12Re: What percentage of people are alive today?
#13[deleted]
Re: What percentage of people are alive today?
#14This back-of-the-envelope calculation appears to be off by a factor of two, which isn't bad. http://en.wikipedia.org/wiki/World_population#Number_of_huma...
this error is because of assumptions about the life expectancy, right?
Re: What percentage of people are alive today?
#15Am I the only one absolutely terrified by that number? Malthus wasn't wrong in principle, just in timescale. It's clear that technologies have improved Earth's human carrying capacity, but I don't know any method to claim that an S-shaped curve isn't inevitable. It's sounds science fiction-ey, but I don't understand how you can see data like this and then defund NASA.
You are not alone. If you want to get more scared, read http://www.amazon.com/Collapse-Societies-Choose-Fail-Succeed....
Interestingly from the population statistics alone it is possible to make an argument about the total likely future number of humans that will live. There is debate about whether the reasoning is correct, but it is at least suggestive. See http://en.wikipedia.org/wiki/Doomsday_argument for more.
Re: What percentage of people are alive today?
#16Am I the only one absolutely terrified by that number? Malthus wasn't wrong in principle, just in timescale. It's clear that technologies have improved Earth's human carrying capacity, but I don't know any method to claim that an S-shaped curve isn't inevitable. It's sounds science fiction-ey, but I don't understand how you can see data like this and then defund NASA.
I'm putting much more faith in commercial spaceflight programs (Scaled Composites, SpaceX, Armadillo) for advancing space exploration/colonization than I do in NASA. Even their early work shows that their marginal costs are many orders of magnitude less than NASA's funding. This is one of those areas where market forces will beat out the government hands down.
Re: What percentage of people are alive today?
#17i'm sure there is a more accurate prediction out there (explained in papers) by researchers who have spent way more time and effort into this subject. for us common folks, there's even a wikipedia answer:
http://en.wikipedia.org/wiki/World_population#Number_of_huma...
Re: What percentage of people are alive today?
#18Am I the only one absolutely terrified by that number? Malthus wasn't wrong in principle, just in timescale. It's clear that technologies have improved Earth's human carrying capacity, but I don't know any method to claim that an S-shaped curve isn't inevitable. It's sounds science fiction-ey, but I don't understand how you can see data like this and then defund NASA.
[deleted]
Re: What percentage of people are alive today?
#19Am I the only one absolutely terrified by that number? Malthus wasn't wrong in principle, just in timescale. It's clear that technologies have improved Earth's human carrying capacity, but I don't know any method to claim that an S-shaped curve isn't inevitable. It's sounds science fiction-ey, but I don't understand how you can see data like this and then defund NASA.
One interesting fact regarding population growth is that worldwide, having children on aggregate is a inferior good: if parts of Africa and Southeast Asia can make some significant gains in the next few decades, we will likely see population peak sometime this century.
Re: What percentage of people are alive today?
#20They never say how they estimate births_t.
We use the world population and average life expectancy to calculate births in a year. To connect these point estimates at the varying times in history we use a bounded exponential growth model for births.
I'm still not completely getting it. Let's say in some year there are a billion people alive and the average life expectancy is 50 years. How are these two pieces of information sufficient to determine how many children were born in that year?