If we add a line through the image and you try again, you'll notice that your brain fills in information and makes you think the line is continous instead of there being a hole in your vision.

如果我们在图片中间加上一条线，然后你再试一次，你会发现大脑得到了讯息，让你觉得这条线是连续的，而不是让你的视野中有个缺口。