国家地理:送给外星人的地图(5)

Appropriately, Dad's pulsar map looks like a fancy asterisk¹, a radial explosion of hatched lines that intersect at our solar system's location. Briefly², here's how his map works:

父亲的脉冲星地图，看起来很像一个漂亮的星号，影线呈放射状散开，在我们太阳系的位置相交。简单地说，他的地图是这样用的：

Each of the lines connect Earth to a pulsar. The hatch marks are binary³ numbers that reveal the pulsar's rotation⁴ rate (at the time the map was designed), and line lengths are roughly proportional to distance. Some of the pulsars parked on Dad's map -- for example, the Crab⁵ and Vela -- sit in the centers of beautiful nebulae created during the pulsars' violent formations. Presumably, any civilizations sharp enough to detect and snare⁶ a quiet interstellar spacecraft would know about pulsars. And by matching the rotation periods on the map with stellar signposts in the sky, aliens could find their way to Earth relatively⁷ easily.

每条影线都将地球与一颗脉冲星连接起来。影线标记表示的是脉冲星自转速率的二进制数字（在地图绘制时），影线的长度大致与距离成比例。我父亲地图上的一些脉冲星，落位于脉冲星剧烈形成时所创造出的美丽星云中央。据推测，任何能够敏锐地侦测并拦截安静的星际飞船的文明，都应该对脉冲星有所了解。通过将地图上的自转周期与天空中的指路星体一比照，外星人就可以相对容易地找到通往地球的路。

In addition, because the energy we see from pulsars comes from their spin and they slow down over time, Dad's map also points to Earth in the fourth dimension. By calculating the difference between the observed and coded rotation periods -- a difference that will be apparent after thousands of years -- aliens could figure out how long ago the map was made.

此外，由于我们从脉冲星观测到的能量来自于它们的自转，而且随着时间的推移它们转速会变慢，因此父亲的地图也标记出了地球在第四维度。通过计算观测到的自转周期和地图标记的自转周期之间的差异--这种差异在几千年后才会显现出来，外星人就能知道这幅地图是在多久以前绘制的。

1 asterisk   

n.星号，星标

参考例句：

• The asterisk refers the reader to a footnote.星号是让读者参看脚注。
• He added an asterisk to the first page.他在第一页上加了个星号。

2 briefly   

adv.简单地，简短地

参考例句：

• I want to touch briefly on another aspect of the problem.我想简单地谈一下这个问题的另一方面。
• He was kidnapped and briefly detained by a terrorist group.他被一个恐怖组织绑架并短暂拘禁。

3 binary   

adj.二，双；二进制的；n.双(体)；联星

参考例句：

• Computers operate using binary numbers.计算机运行运用二进位制。
• Let us try converting the number itself to binary.我们试一试，把这个数本身变成二进制数。

4 rotation   

n.旋转；循环，轮流

参考例句：

• Crop rotation helps prevent soil erosion.农作物轮作有助于防止水土流失。
• The workers in this workshop do day and night shifts in weekly rotation.这个车间的工人上白班和上夜班每周轮换一次。

5 crab   

n.螃蟹，偏航，脾气乖戾的人，酸苹果；vi.捕蟹，偏航，发牢骚；vt.使偏航，发脾气

参考例句：

• I can't remember when I last had crab.我不记得上次吃蟹是什么时候了。
• The skin on my face felt as hard as a crab's back.我脸上的皮仿佛僵硬了，就象螃蟹的壳似的。

6 snare   

n.陷阱，诱惑，圈套；（去除息肉或者肿瘤的）勒除器；响弦，小军鼓；vt.以陷阱捕获，诱惑

参考例句：

• I used to snare small birds such as sparrows.我曾常用罗网捕捉麻雀等小鸟。
• Most of the people realized that their scheme was simply a snare and a delusion.大多数人都认识到他们的诡计不过是一个骗人的圈套。

7 relatively   

adv.比较...地，相对地

参考例句：

• The rabbit is a relatively recent introduction in Australia.兔子是相对较新引入澳大利亚的物种。
• The operation was relatively painless.手术相对来说不痛。