The Problem with Christians

[Angrboda]

How did the Bible know about astronomical realities?

"God asked Job “Can you bind the cluster of the Pleiades, Or loose the belt of Orion?” (Job 38:31). In the last century astrophysicists have discovered that the stars of Pleiades move in unison with each other, and are thus gravitationally bound. They have also discovered that the stars in the belt of Orion are free agents that are not gravitationally bound!6 Interestingly, the three stars that comprise Orion's belt appear to be closer  together than the outer stars in the constellation, but are actually farther apart! (they appear closer together because of the 2-D plane we see them in)." http://www.bibleevidences.com/scientif.htm

They didn't. You're back patching a modern translation onto the original words.

31 Canst thou bind the sweet influences of Pleiades, or loose the bands of Orion?
(KJV)

In Greek mythology, the Pleiades were seven sisters who were roaming free. One binds that which is free, and loosens that which binds. The verse is simply consistent with the metaphor which described each phenomena. They no more knew that the belt of Orion were free stars than that they knew the Pleiades were maidens. Moreover, you're interpreting the verse as saying that God has done these things. But it's equally within the interpretation of the verse to suggest that God could do these things if he wanted to do so. In that case, if the situation were reversed, the Pleiades free and Orion bound, you'd simply interpret the verse as God pointing out the impotence of man, and, that God knew the Pleiades were free and Orion bound. Either way, you're able to interpret the passage in your favor. Heads you win, tails I lose is not much of a miracle.