听力文摘：残留的光线

Afterglow 夕照，晚霞

Here's an experiment you can try: look at something bright relative to its surroundings, such as a lamp or a sunny window, for ten seconds without blinking. Then shut your eyes and cover them over with your hands.

你可以尝试这样的试验：不眨眼盯着看相对周围而言光亮的东西十秒钟，比如，一盏灯或洒满阳光的窗户；接着闭上眼睛且双手蒙住。

You will find that the lamp or window still seem to be hovering¹ in front of you, quite visible at first and only gradually fading away. Yet your eyes are closed and your hands are blocking them completely — so where is the light coming from?

你会发现那盏灯或窗户依旧浮现在眼前，最开始清晰得很，又慢慢消失。可是，你不是闭眼了吗？况且双手不是严实地蒙住了吗？那么，光线从何而来？

The answer is that the afterglow light you see isn't really light at all. It's the result of residual² activity of the nerve cells on the back of your eye, called the retina. In sensory³ psychology⁴ this effect is called a "positive afterimage".

答案是残留的余光根本不是真正的光芒。其实这是视网膜（眼后的神经细胞）的痕迹作用。感官心理学将这种现象称作“正后像”。

You can think of it as something like the vibration⁵ of a string after it has been struck. The player's finger is taken away, and yet the sound continues, because the energy she or he put into the string takes a little while to dissipate.

你可以将“正后像”视为拨动后琴弦的振动。弹琴者手指离开了琴，而琴音依旧。因为琴弦上的能量需要点时间消退。

It's a similar situation with your eyes. In order to respond usefully to such a relatively⁶ faint signal as light, the cells in the retina need to be very sensitive. Over-stimulate them and some will continue responding for a couple of seconds after the stimulus⁷ is removed.

视觉的情况也类似，视网膜细胞的感光十分敏感以便及时感知像光线般微弱的信号。受到过度刺激的视网膜细胞，部分在刺激后持续反应。

Of course, the only thing we ever "see", really, is the activation⁸ of our retinal cells — that's what our brains interpret as light from the outside world. So for as long as it takes for them to calm down, you will continue to see a faint glow of light — even though nothing is there.

当然，唯一我们“看到”的是视网膜细胞的激活也就是大脑解读的：外界的光线。所以，只要刺激后需要时间平复，你就能持续看到微弱的灯光，虽然，实际上并不存在。

1 hovering   

鸟( hover的现在分词 )； 靠近（某事物）； （人）徘徊； 犹豫

参考例句：

• The helicopter was hovering about 100 metres above the pad. 直升机在离发射台一百米的上空盘旋。
• I'm hovering between the concert and the play tonight. 我犹豫不决今晚是听音乐会还是看戏。

2 residual   

adj.复播复映追加时间；存留下来的，剩余的

参考例句：

• There are still a few residual problems with the computer program.电脑程序还有一些残留问题。
• The resulting residual chromatism is known as secondary spectrum.所得到的剩余色差叫做二次光谱。

3 sensory   

adj.知觉的，感觉的，知觉器官的

参考例句：

• Human powers of sensory discrimination are limited.人类感官分辨能力有限。
• The sensory system may undergo long-term adaptation in alien environments.感觉系统对陌生的环境可能经过长时期才能适应。

4 psychology   

n.心理，心理学，心理状态

参考例句：

• She has a background in child psychology.她受过儿童心理学的教育。
• He studied philosophy and psychology at Cambridge.他在剑桥大学学习哲学和心理学。

5 vibration   

n.颤动，振动；摆动

参考例句：

• There is so much vibration on a ship that one cannot write.船上的震动大得使人无法书写。
• The vibration of the window woke me up.窗子的震动把我惊醒了。

6 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。

7 stimulus   

n.刺激，刺激物，促进因素，引起兴奋的事物

参考例句：

• Regard each failure as a stimulus to further efforts.把每次失利看成对进一步努力的激励。
• Light is a stimulus to growth in plants.光是促进植物生长的一个因素。

8 activation   

n. 激活，催化作用

参考例句：

• A computer controls the activation of an air bag.电脑控制着气囊的启动。