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Science Friday: US Pop. = pi | Earth, in 100 million years | Top 10 facts about the solar system | Sun is a 'perfect circle'

Math Nerds Rejoice As U.S. Population Hits 314.159 Million

    From the department of utterly meaningless yet charmingly geeky milestones (it’s a larger department than you might think) comes word that the United States’ population on Tuesday hit 314,159,265, according to the Census Bureau’s population clock. As all math geeks know, that’s pi times 10 to the eighth, rounded to the nearest whole number.

    Pi, for those who have forgotten or repressed their middle-school geometry lessons, is the ratio of a circle’s circumference to its diameter. The census bureau, bless its heart, saw fit to put out a brief news release marking the occasion. It reported that we reached the milestone shortly after 2:29 p.m. eastern today. The timing is not precise, since the population clock is an estimate rather than an exact count. (It assumes one birth every eight seconds, one death every 14 seconds, and one net migrant every 46 seconds.) But pi is an irrational number anyway, so who cares.


    Earth's landmasses were not always what they are today. Continents formed as Earth's crustal plates shifted and collided over long periods of time. This video shows how today's continents are thought to have evolved over the last 600 million years, and where they'll end up in the next 100 million years. Paleogeographic Views of Earth's History provided by Ron Blakey, Professor of Geology, Northern Arizona University.

Ten things you may not know about the solar system

    My friend and colleague Dr. Victor Andersen of the Community College of Aurora, CO gave a talk called “Ten Things You May Not Know About the Solar System,” a bit in the sense of David Letterman’s Top Ten List. I thought it was a great talk and so decided to give my own commentary on Victor’s list. While the list is Victor’s, any errors are purely my own.

    So here we go:

    10 ) The hottest planet isn’t closest to the sun

    Many people know that Mercury is the closest planet to the sun, well less than half of the Earth’s distance. It is no mystery, therefore, why people would assume that Mercury is the hottest planet. We know that Venus, the second planet away from the sun, is on the average 30 million miles farther from the sun than Mercury. The natural assumption is that being farther away, it must be cooler. But assumptions can be dangerous. For practical consideration, Mercury has no atmosphere, no warming blanket to help it maintain the sun’s heat. Venus, on the other hand, is shrouded by an unexpectedly thick atmosphere, about 100 times thicker than our own on Earth. This in itself would normally serve to prevent some of the sun’s energy from escaping back into space and thus raise the overall temperature of the planet. But in addition to the atmosphere’s thickness, it is composed almost entirely of carbon dioxide, a potent greenhouse gas. The carbon dioxide freely lets solar energy in, but is far less transparent to the longer wavelength radiation emitted by the heated surface. Thus the temperature rises to a level far above what would be expected, making it the hottest planet. In fact the average temperature on Venus is about 875 degrees F, hot enough to melt tin and lead. The maximum temperature on Mercury, the planet closer to the sun, is about 800 degrees F. In addition, the lack of atmosphere causes Mercury’s surface temperature to vary by hundreds of degrees, whereas the thick mantle of carbon dioxide keeps the surface temperature of Venus steady, hardly varying at all, anywhere on the planet or any time of day or night!

    9 ) Pluto is smaller than the USA

    The greatest distance across the contiguous United States is nearly 2,900 miles (from Northern California to Maine). By the best current estimates, Pluto is just over 1400 miles across, less than half the width of the U.S. Certainly in size it is much smaller than any major planet, perhaps making it a bit easier to understand why a few years ago it was “demoted” from full planet status. It is now known as a “dwarf planet.”


The Sun is Just 0.0007% Away From Being a Perfect Sphere

    Trying to draw a circle is really hard. You’re normally better off overturning a cup or bottle cap or finding something else to trace. It turns out, though, that the best tracing tool you could find has been hanging overhead all your life.

    “The Sun,” says the Guardian, “is the most perfectly round natural object known in the universe.”

    The Sun was long thought to be a little bit squat, being fatter at the equator than elsewhere. That is, until Jeffrey Kuhn and others published their study. The Guardian:

    The sun doesn’t bulge much at all. It is 1.4m kilometres across, but the difference between its diameter at the equator and between the poles is only 10 kilometres.