The Bible doesn’t use the word ‘eclipse’, but does describe the effects of both solar and lunar eclipses. This is a good example of how, as we understand more about the world, we understand more about the Bible as well.
A solar eclipse is when the moon blocks out the sun. A total solar eclipse is when the moon appears to completely cover the sun. Although this occurs across a relatively small area of the earth (a 100-160km wide path), there is a partial elcipse over a much wider area. In any one spot these effects (total or partial eclipse) will last for a few minutes.
A lunar eclipse is when the earth’s shadow falls on the moon. This prevents the sun’s light directly shining on the moon, is more common and lasts longer (several hours). However, the moon is usually still visible, but reddish in colour.
Both types of eclipse are accurately predicatable (and in part at least have been since the Babylonians), leading NASA to produce a 5 millennia catalog and atlas of solar eclipses.
Although the word ‘eclipse’ doesn’t occur in the Old or New Testaments the effects of what may be elcipses are mentioned. (It’s probably worth noting that the word does occur in the Apocryphal/ Deuterocanonical book Sirach 17:31)
Talking of the coming of God’s judgment the prophets use the language of the sun, moon and sometimes stars being darkened, to emphasise the seriousness and cosmic significance of the event. Therefore, whether these are direct references to eclipses or not remains debatable.
So, Isaiah 13:10
The stars of heaven and their constellations
will not show their light.
The rising sun will be darkened
and the moon will not give its light.
When I snuff you out, I will cover the heavens
and darken their stars;
I will cover the sun with a cloud,
and the moon will not give its light.
the sun and moon are darkened,
and the stars no longer shine.
‘In that day,’ declares the Sovereign Lord,
‘I will make the sun go down at noon
and darken the earth in broad daylight.
Amos was probably active as a prophet around 760/755 BC. In both 769 (on 5th May) and 762 (15th June) solar eclipses would have been visible in Judah and Israel. Although not in the path of totality for either one, both would have visible enough to be noticeable.
The language that Amos uses in this passage is matched by an earlier description of an eclipse, foud on a clay tablet in the city of Ugarit (now in Syria). This describes the eclipse of 5th March 1223 BC like this:
On the day of the new moon, in the month of Hiyar, the sun was put to shame, and went down in the daytime, with Mars in attendance.
The best description of both solar and lunar eclipses in the Bible is probably that of Joel 2:31
The sun will be turned into darkness And the moon into blood Before the great and awesome day of the LORD comes.
This describes the physical effects of both solar and lunar eclipses, while the language is also picked up in Revelation 6:12. It’s worth noting the emotional effects that even partial solar eclipses cause amongst watchers, with a noticeable drop in temperature, affects to animal (particularly bird) behaviour, and a feeling of something ‘eerie’. For a lunar eclpise, the usually white moon turning red for several hours is also an awe-inspiring sight. It’s therefore not surprising that the prophets chose to invoke this experience to give their first hearers something of an understanding of what they were talking about.
In this passage, Hezkiah is dying, prays to God for healing and is told by the prophet Isaiah that the sign that he has been healed is that the shadow will move back the ten steps it had already gone down on the stairway (2 Kings 20:11). This is the sort of phenomena that would be observable during a partial eclipse, so gives a potential basis for the miraculous sign (without making it any less of a miracle).
Eclipses were known and experienced in the ancient world as well as in the modern. Given their dramatic and awe-inspiring nature it’s not surprising that these experiences were drawn upon to describe the even more awe-inspiring experience of the coming of God.