That's because your senses  are tuned to detect changes, not absolute measurements.

那是因为你的感官被调整来检测变化，而不是绝对测量。

If our brains could make an absolute measurement of light passing through our pupils, maybe we wouldn't be tricked by these illusions.

如果我们的大脑能够对穿过我们瞳孔的光进行绝对测量，也许我们就不会被这些错觉所欺骗。