When we speak of darkness, we are referring that light in the midst of darkness shines. The Bible says that in the beginning of creation, that darkness covered the whole earth.
1 In the beginning God created the heavens and the earth.
2 Now the earth was formless and empty, darkness was over the surface of the deep, and the Spirit of God was hovering over the waters.
3 And God said, “Let there be light,” and there was light.
4 God saw that the light was good, and he separated the light from the darkness.
5 God called the light “day,” and the darkness he called “night.” And there was evening, and there was morning—the first day.
Here we see that the earth was covered by darkness, and if the earth was covered by darkness it was because nothing was seen. Everything was dark.