THE DEMOGRAPHIC FATE OF intelligent SPECIES: April 2015

Tuesday, April 7, 2015

More Earth-like planets across the universe than grains of sand on Earth's beaches?

Earth as a grain of sand
We used to think of Earth as the center of the universe, with the Sun circling around it... Turned out it's the other way around, the solar system has 7 other planets beside ours. 30 years ago, we knew no other star with planets apart from our Sun. Now we have identified hundreds in just a tiny corner of our Milky Way galaxy. Given the estimated size of the observable universe - 200 billion galaxies times 200 billion stars per galaxy, it's possible that there might be more Earthy planets out there than sands on our beaches. Could we really be alone?


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A new study combines exoplanet data from the Kepler Space Telescope with a new version of a 250-year-old method for determining orbital periods and positions of planets. The research calculates that in our galaxy alone, there could be billions of planets hosting liquid water, habitable conditions and perhaps even life.
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Digging deeper into the data, the researchers looked at how many planets were likely to be in the habitable zone where conditions to support liquid water and life might exist. They found an average of one to three planets in the habitable zone in each planetary system. Extrapolate those calculations further, and you arrive at the conclusion that if the math holds, there may be billions of habitable planets in the Milky Way, which is itself just one of billions of galaxies.
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Should these calculations hold up -- and the researchers behind them encourage astronomers to check to see whether the planets they predict are actually there to help bolster their case -- it means that the chances of our planet being the universe's only potentially habitable rock that actually hosts life would be not one in a million, one in a billion or even one in a trillion -- but one in a sextillion. (In case this is your first time seeing that word, a sextillion is a one with 21 zeroes behind it.)

Actually, if the estimates of 40 billion Earth-sized planets in habitable zones of sun-like or red dwarf stars in the Milky Way and the estimate of the 100 billion to 200 billion galaxies in the universe are accurate -- and if the average galaxy has roughly the same number of Earth cousins as the Milky Way, then the chances that we are the only planet with life are more like one in 6 sextillion.
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Jason Marshall, aka "The Math Dude," has calculated that there are roughly 5 sextillion grains of sand on all our planet's beaches combined. So take every grain of sand on every beach on Earth and you can begin to be able to actually visualize how many planets we're talking about.
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