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On September 17th, 1998 the Ithaca Journal ran its first "Ask A Scientist!" article in which Professor Neil Ashcroft , who was then the director of CCMR, answered the question "What is Jupiter made of?" Since then, we have received over 1,000 questions from students and adults from all over the world. Select questions are answered weekly and published in the Ithaca Journal and on our web site. "Ask A Scientist!" reaches more than 21,000 Central New York residents through the Ithaca Journal and countless others around the world throught the "Ask a Scientist!" web site.

Across disciplines and across the state, from Nobel Prize winning scientist David Lee to notable science education advocate Bill Nye, researchers and scientists have been called on to respond to these questions. For more than seven years, kids - and a few adults - have been submitting their queries to find out the answer to life's everyday questions.

Previous Week's Question Published: 6 December, 2000 Next Week's Question
Global population growth not always a constant rate
Question
How much does the population grow a minute?

Question
This is a good question. Now get ready for a barrage of numbers! According to the U.S. Census Bureau there are 249 births and 103 deaths per minute on average in the world. This gives a net growth rate of 146 people every minute, or over 77 million people per year. To put this in perspective, every three hours the world's population increases by about the number of people that live in Ithaca!

The world now contains over 6 billion people, a mark passed in 1999. Currently our population is increasing at a rate of about 1.25% per year. But this growth rate is not steady. In the past, the growth rate was very low and sometimes there was a decline in the world population due to plagues and things like that. It wasn't until the 20th century that the growth rate exceeded, on average, 1% per year.

Two thousand years ago there were about 200 to 400 million people in the world. About 500 AD the population was about 200 million. It increased to 400 million by 1200 AD and reached 800 million around 1750 AD. The 1 and 2 billion marks were passed around 1810 AD and 1925 AD respectively. Estimating the world population in early times is not easy, so some of the numbers above are a bit uncertain. However, the trend is very clear. The time to double the world population has been decreasing, meaning that the growth rate has been increasing.

Projecting the future is even more difficult, but some estimates are that the world will have over 9 billion people by the year 2050. These estimates assume a decrease in the rate of population growth over what we have today. Indeed the growth rate has been decreasing somewhat in recent years. Let us hope that the decrease continues, for an overpopulated world will have grave consequences. As the population increases, the problems of food production, water supply, energy production, ecological destruction, etc. become more prominent.

You can find more about the world population at the U.S. Census Bureau web site: www.census.gov

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