As density shoots up, it ignites the fusion of oxygen. Because the threshold to fusing oxygen is crossed in a collapsing core rather than in a stable one, the ignition is explosive: fusion releases nuclear energy that heats the material further, which in turn speeds up the fusion, in a “runaway” reaction. The star can burn so much oxygen in such a short time—mere minutes—that the energy it releases is larger than the star’s entire gravitation energy. Thus, whereas typical supernovae leave behind charred remains such as a neutron star or a black hole, in this type of explosion the object completely obliterates itself. All that is left is a fast-expanding cloud, much of it made of elements that were synthesized in the fury of the deflagration.(Super Supernovae. Scientific American. June 2012.)
随着密度的激增，氧聚变最终被点燃。由于坍缩核可达到氧聚变的临界值，而稳定核达不到，因此点燃过程具有爆炸性：聚变释放的核能使材料进一步受热，反过来又加速了聚变，反应过程可以说是失控的。恒星能在如此短的时间内（仅几分钟）燃烧如此多的氧气，所产生的能量超越了恒星的总引力能。因此，尽管典型的超新星存留有烧焦的残留物，如中子星、黑洞等，但是在上述类型的爆炸过程中，天体完全自行毁灭。所剩的仅为快速膨胀的星云，其大部分的组成元素是在猛烈的爆燃过程中合成的。
Unpleasant, sure, but I now call this event serendipitous. As I rested my head back against that sanitation-paper-covered airline pillow, my midflight mind lit away to a much happier memory, one involving another big toe, yet this one belonging to a noticeably more good-humored animal than the one sitting behind me. This other toe—which felt every bit as much as its overstuffed human equivalent did, I should add—was attached to a 450-pound western lowland gorilla, with calcified gums, named King. When I was 20 and he was 27, I spent much of the summer of 1996 with my toothless friend King, listening to Frank Sinatra and the Three Tenors, playing chase from one side of his exhibit to the other, and tickling his toes. He’d lean back in his night house, stick out one huge ashen-gray foot through the bars of his cage, and leave it dangling there in anticipation, erupting in shoulder-heaving guttural laughter as I’d grab hold of one of his toes and gently give it a palpable squeeze. He almost couldn’t control himself when, one day, I leaned down to act as though I were going to bite on that plump digit. If you’ve never seen a gorilla in a fit of laughter, I’d recommend searching out such a sight before you pass from this world. It’s something that would stir up cognitive dissonance in even the heartiest of creationists.
尽管这件事情的确不愉快，但我现在认为它是一个意外收获。当我把脑袋倚靠向后休憩在包有卫生纸的航空公司枕头上时，我飞行途中的思绪飞跃到一段更美好的记忆，这段记忆有关另外一只大脚趾，它的主人可比后座那位脾气好多了。我需要补充的是，这只脚趾感觉上和肥胖人群的脚趾几乎一样，它来自于一只体重450磅、牙龈钙化、名叫“国王”的西部低地大猩猩。1996年，我20岁，“国王”27岁，那个夏天的很多时间我是同这位无牙好友一起度过的：听着Frank Sinatra和三大男高音的音乐，从展览厅的一侧追逐嬉戏到另一侧，还挠他脚趾的痒痒。在他晚上居住的小房子里，他身体向后靠，从笼子栏栅之间伸出一只灰暗色的脚，在那里满怀期待地摇晃着脚，伴随着上下起伏的肩旁，喉咙里时时发出笑声，因为这个时候我正抓住他的一只脚趾，轻轻地给它感受得到的挤压。当有一天我俯下身来装作要咬他那圆胖的脚趾，他几乎失控。如果您从未见过大猩猩开怀大笑，我建议您在离开这个世界之前找到这个情景。这种情景甚至会激起最虔诚的神创论者的认知失调。
Differences between laughing “systems” among mammals are reflected by cross-species structural differences in brain regions as well as in vocal architecture. In the same issue of Behavioural Brain Research, neuropsychologist Martin Meyer and his colleagues describe these differences in rich detail. Although brain-imaging studies of human participants watching funny cartoons or listening to jokes reveal the activation of evolutionarily ancient structures such as the amygdala and nucleus accumbens, more recently evolved, “higher-order” structures are also activated, including distributed regions of the frontal cortex. So although nonhuman primates laugh, human humor seems also to involve more specialized cognitive networks that are unshared by other species.
大脑区域和发声体系的跨物种结构性差异反映了哺乳动物发笑“系统”之间的差异。在《大脑行为研究》杂志的同一期中，神经心理学家Martin Meyer及其同事十分详细地阐述了这些差异。虽然通过志愿者观看趣味卡通或听笑话时所做的脑成像研究，发现了诸如杏仁核和伏隔核的进化上更古老的结构的激活作用（最近才进化），但同时，包括前额叶的分布式区域在内的“高阶”结构也被激活。因此，尽管除人类之外的灵长类也会发笑，但人类的幽默感似乎还涉及更加专业的认知网络，这是其他物种所不具有的。