This effect, known as gravitational redshift, is not specific to black holes. 这种称做重力红移的效应，并不是黑洞所特有。
The redshift caused by the expansion is often confused with the more familiar redshift generated by the Doppler effect. 膨胀所造成的红移，常会和我们比较熟悉的都卜勒效应所产生的红移搞混。
