Monday, December 12, 2011

Two-thirds of the people who have ever reached 65 are alive today

Can the above statement really be true? First of all, the common statement: "more people are alive today than have ever lived" is false. According to wolfram alpha, there have been about 100 billion people ever.

There is a possibility that we are are reaching older ages with the technology available to us today, and therefore the statement might be "more" true. I wouldn't discredit it right away, but I think it might be a little bit exaggerated, given facts such as:

In the United States the proportion of people aged 65 or older increased from 4% in 1900 to about 12% in 2000. [Citation] And in the entire world we are sitting at ~ 7.9% of 65 and older currently. So this would mean we have about 550 million seniors. This would require that out of the other 100 billion people who are not living anymore, only 250 million of them could have reached age 65. While this seems small, we have to look at what life expectancy has been historically. Curves of life expectancy in the past have looked like this:

The life expectancy curve is essentially unchanging, until the development of science and technology, and then it explodes. This gives more possibility to the "0.25% chance of reaching age 65" that is a requirement for the 2/3 statement. So as a whole, it may be viable but I would probably feel more comfortable with a statement such as "Most likely, 1/3 of the people who have reached 65 are alive today."

Finally, it is important to note that huge infant mortality rates were a large part of low life expectancy in the past. There is an interactive graph that showed age breakdown for each year, here. This graph represents some amusing data points, such as the claim that it’s impossible to die between the ages of 20 and 26.

Sunday, December 11, 2011

Lunar Eclipse

You may have noticed, with Saturday's total lunar eclipse, a dark patch that became visible around the moon. This is caused by the Earth's shadow. The shadow, which includes the atmosphere, suppresses the Rayleigh and Mie scattering components in the atmosphere and causes a local darkening. (The Rayleigh effect is the same effect that causes the sky to turn red at sunset.) While this is actually happening all the time, it is only so pronounced when seen against a low light background.

Monday, December 5, 2011

Zebra Coloration

Zebras have one of the coolest fur colorings/configurations in the animal kingdom. A common theory is that the stripes of a zebra make it blend in with the heard, confusing predators, which is a cool and easy-to-apply concept. However, the real magic comes with the colors themselves.

What scientists discovered is that the sunlight beating down and being absorbed by the black stripes creates a big difference in surface temperature from the white stripes, which reflect most of that light, staying much cooler.

Body temperature has an optimum value. Any extant species will likely have a method in place for maintaining this temperature. Unless a species' climate changes significantly (especially for cold blooded animals) either in a given location or due to a migration, there is no evolutionary pressure to develop a new method.

As a result of these differences in temperature—and thus, pressure—on the fur of the zebras, a mini weather current is formed on the surface of the skin. This keeps a constant airflow over the animal, keeping it cooler in the extreme heat of its environment. Pretty cool huh?

Sunday, December 4, 2011

2011: World’s 10th warmest year, warmest year with La Niña on record, second-lowest Arctic sea ice extent

The World Meteorological Organization released today their 2011 analysis, in a document titled, “Provisional Statement of the Status of the Global Climate.” In summary, it stated that 2011 was the world’s 10th warmest year, the warmest year with La Niña on record, and the second-lowest Arctic sea ice extent. Major weather events have included severe drought, then flood, in east Africa, and major floods in south-east Asia. However, it’s been a below average year with regards to tropical cyclone activity. Normal years have an average of 84 tropical cyclones, but -- as of November 22 -- there had only been 69 tropical cyclones in 2011.

The World Meteorological Organization is the UN’s voice on weather, climate, and water and issues a yearly report after collecting data. Climate data is gathered from networks of land-based weather and climate stations, ships and buoys, as well as satellites. However, since the year is obviously not completed yet, final updates and reports for the current year will be published in the annual WMO Statement on the Status of the Global Climate, which will come out in March 2012. The current press release can be read on the World Meteorological Organization's website.