Maths don't matter?

[Zaq1]

Let's assume that 250.000 couples (500.000 humans) colonized a planet far away from our beloved sun, but still within reach. Then let's go on to assume that the females among the colonists gave birth to three children on average and furthermore that the wizened lot used to be good to one another (as a rule), and also used to take care to preserving the nature of the planet, for themselves as well as future generations.

Probably the most interesting part of this intellectual experiment is the expected population development.

500.000 X 1.5 (three children per woman) = 750.000
750.000 X 1.5 (three children per woman) = 1.125.000

Total population: 500.000 (old) + 750.000 (adult) + 1.125.000 (young) = 2.375.000

Now: for religious reasons this is where I should learn to shut up and do no more thinking. The concept of people dying from old age seems to be too much for modern people. But anyway: while the old people slowly die off while the females of the younger crop continue to give birth to a now traditional average of three children, the population grows like this:

1.125.000 X 1.5 (three children per woman) = 1.687.500

Total population: 750.000 (old) + 1.125.000 (adult) + 1.687.500 (young) = 3.562.500

---

Question: "Following this formulae: how much time will it take the colony to reach 1 billion people?"

Or: "What's the actual meaning of the term population explosion?"

What's the death rate in your population Zaq?

[Richard]

You should be using the exponential growth function...

[mgopilot]

When does the average female colonist have all her children, and what is the average lifespan? What is the birthrate for replacement? (deathrate before reproduction of children)?
In this case, let's say it is a 90 year average lifespan, 30 years for the female to have 3.1 kids to counter the juvenile deathrate of .1, let's say. So the net is the same. At 16 generations times 30(480) years there would be about 1 billion, 39 million people.
Now let's get back to Earth with a real average of more like 4.5 children born per second and 3 people dying per second, and in 30 years this will be at 4 per second and 3.5 per second. Then in 45 years this will be 3 per second and 4.5 per second, and 50 years 1 per second and 10 per second. This is something like what will happen, in a classic half bell shaped curve. Dealing with just the numbers, it is less horrifying.

[Zaq1]

Originally Posted by adi

What's the death rate in your population Zaq?

Being the unassuming djinn that I am, I will cling to the childish patterns of reasoning that usually take place in all elementary school classrooms around the world. I believe that the vast majority of the little people of the planet will agree with me in thinking that people who do indeed reach the social stage of being a great-grandparent should count themselves lucky and / or in proven possession of good genes.

Sincerely: I am not trying to kid anyone with this model. It is not in any way a representation of real life or any real society, but purely and safely a theoretic formula making it possible for people to think big. I choose to call it a "humanistic approach" or even a "utopian approach" (what a shame) to founding an understanding of the reality of rapid population growth. -

I have not yet taken it upon myself to check it out but I feel confident that projected death rates for the modern world exist in other threads. This is not my object. Not now.

But yes: "I know, I know."

[Zaq1]

Originally Posted by TheRobster

You should be using the exponential growth function...

Or indeed the historic numbers approach. World population

1900: 1.500.000.000
1930: 2.000.000.000
1960: 3.000.000.000
1975: 4.000.000.000
1986: 5.000.000.000
1997: 6.000.000.000
2006: 7.000.000.000

[Zaq1]

Originally Posted by mgopilot

Now let's get back to Earth with a real average of more like 4.5 children born per second and 3 people dying per second, and in 30 years this will be at 4 per second and 3.5 per second. Then in 45 years this will be 3 per second and 4.5 per second, and 50 years 1 per second and 10 per second. This is something like what will happen, in a classic half bell shaped curve. Dealing with just the numbers, it is less horrifying.

Uhm. This thing is just one of those things that made me come to think of myself as a member of a parasitic organism, and that several years ago. -

According to this thread, births this year are approximately 2.7 times deaths.

[Richard]

Originally Posted by Zaq1

Or indeed the historic numbers approach. World population

1900: 1.500.000.000
1930: 2.000.000.000
1960: 3.000.000.000
1975: 4.000.000.000
1986: 5.000.000.000
1997: 6.000.000.000
2006: 7.000.000.000

From looking at the numbers, it's the same thing. Except the historic data is empirical rather than just theoretical.

[mgopilot]

Originally Posted by Zaq1

Or indeed the historic numbers approach. World population

1900: 1.500.000.000
1930: 2.000.000.000
1960: 3.000.000.000
1975: 4.000.000.000
1986: 5.000.000.000
1997: 6.000.000.000
2006: 7.000.000.000

2/21/06 and it is 6.54 B. 6B was reached in January of 1999. The numbers per second from "World War III: Population and the Biosphere" were approximate and from 1994. On the half bell curve line, it is past the hyperbolic to parabolic, and on the reverse parabolic, so slowing down. That is the empirical (or actual) data. We are 79% to the top of the half bell, and 44 years distant (+or -4%).