Genesis describes a firmament dividing the waters below from the waters above. Christians have believed that this firmament is literally a dome or bowl which separates the sky from the earth. Christians have believed God affixed the stars, the sun, and the moon to this firmament. Of course, we now know that there is no such thing - yet some Christians insist on clinging to the idea that the Bible is completely and literally true.
Read Article: Errors in Genesis About the a Firmament in Heaven