Arctic sea ice appears likely to reach a record minimum extent this year; as Greg Laden says, “It is almost like the Earth is warming up or something.” The lowest extent of Arctic sea ice on record (since observations began in 1979) occurred in 2012, the second-lowest in 2007, and the third-lowest in 2015. On Stoat, William M. Connolley says it’s currently at an “all-time low for the time of year, but only just, which is better than its been for the last few months.” While the fate of the entire human race may hinge on the effects of global warming, Connolley also has $10,000 on the line. Will the extent of sea ice drop below 3.1 million square kilometers this September? And will we experience ice-free Arctic summers in the near future?
Coldness can manifest where you least expect it: on a planet rapidly warmed by the combustion of fossil fuel, or in the heart of a star 250 times as massive as our own. On Greg Laden’s Blog, Greg explains that an apparent “recovery” of Arctic sea ice from its historic low in 2012 does not invalidate the long-term trend. Greg also explains this year’s legacy of extreme weather, such as snow in Cairo, writing that when there is less difference in temperature between equatorial and polar regions, “the jet streams get all wiggly and cause northerly air to reach far to the south in some places and southerly air to reach farther north in other places.” Meanwhile, on Starts With a Bang, Ethan Siegel explores the different fates awaiting stars of different sizes. When a star like our own runs out of fuel and begins to collapse, it blows off its outer layers and leaves behind a neutron star or small black hole. Bigger stars, however, start producing antimatter, which lowers the pressure in the star and generates gamma rays that heat up the core even further. These stars end in a pair-instability supernova, which “not only destroys the outer layers of the star, but the core as well, leaving absolutely nothing behind!” But in the biggest stars in the universe, gamma rays cause photodisintegration, which cools down the interior of the star and allows all its mass to collapse into a black hole. The earliest of these massive black holes probably seeded the centers of galaxies, which now contain millions of solar masses.