As far-fetched as it may seem that the angelic host visited Bethlehem on the night of Jesus birth riding on a section of the brightly shining crystalline firmament, we shouldn't be surprised.
The Star of Bethlehem
September 24th
It's possible that a section of the Firmament, a sphere of rigid crystal on the edge of space, may have been used to transport the host of Heaven to Earth for the birth of Jesus.