绕日而行可以说是2017年里一段难忘的旅程了。
撰文\播音：史蒂夫·米尔斯基（Steve Mirsky）
翻译：陈美娟
审校：张清越
Happy New Year! And if you’ve been away from work for a few days, you deserve some time off. After all, you’ve traveled far. Even if you just stayed at home. According to NASA, just by being on the planet Earth in the last year, you’ve zipped about 584 million miles around the sun. At an average speed of about 67,000 miles per hour. [Siren sound.] Hey, I wasn’t speeding—in my inertial reference frame.
如果你已经甩开工作好几天了的话，我只能说你确实该缓缓身子了。毕竟，今年你已经“转”了这么远。就算你只是待在家里也算。NASA（美国国家航空航天局）的报告显示，光是去年一年，身在地球上的你就已经以平均每小时六万七千米的速度绕着太阳转了五亿八千四百多万米了。【警笛响起——】嗐，我可是一直照着惯性参照系算的，一点没超速。
Of course, the trip was not a perfect circle. As Kepler showed, the Earth’s orbit is an ellipse, with the sun at one of the two focal points. He also figured out the planet goes faster when it’s at perihelion, nearer the sun, than when it’s at aphelion, its farthest distance. Which would explain why summer seems to zip by, except that the seasons are a function of the tilt of the Earth’s axis, not its different distances from the sun. And the Earth rotated 365 and a quarter times during its sweep around the sun. The trip took 8,766 hours. Or 525,960 minutes. Or 31,557,600 seconds. Tick tock.
当然啦，这趟旅程没按着完美的正圆形轨道在走。开普勒证明过，地球的绕日轨道是个椭圆形，太阳刚好位于其中一个焦点上。他还指出，地球在位于接近太阳的近日点处的速度比在离太阳最远的的远日点的速度更快。这就可以解释除了季节的变化对地轴倾斜程度有影响外，为什么夏天的日子看起来飞逝而过，而这却不是由地球离太阳的远近决定的。地球绕日一周要365又四分之一天。这是8766个小时。也就是31,557,600秒。嘀嗒一下，秒奔千里。
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