Omniscience: n. Possessing total knowledge; knowing everything (The Free Dictionary)
The term omniscience is so vastly encompassing, it boggles the minds of those of us who have ordinary knowledge. It covers the most minute items to the greatest of all possible. Even the examples in the Bible of God's being mindful of the sparrows etc., is somewhat deceiving in that it does not express the most miniscule things. Consider the tiniest molecule in the frigid fringes of the universe. Their position, activity and purpose are covered in the term "total". The smallest algae in the depths of the sea. Not only does it cover these types of items, but it also covers the thoughts and intents of the hearts of over 7 billion humans now on the earth.
God, through his inspired prophet Isaiah, spoke the following:
"Let the wicked forsake his way, and the unrighteous man his thoughts: and let him return unto the Lord, and he will have mercy upon him; and to our God, for he will abundantly pardon. For my thoughts are not your thoughts, neither are your ways my ways, saith the Lord. For as the heavens are higher than the earth, so are my ways higher than your ways, and my thoughts than your thoughts." (Isaiah 55:7-9 KJV)
At first this statement may seem to infer that His thoughts are considerably higher than ours, but consider what He just said, "As the heavens are higher than the earth". How many light years have scientists now found the universe to extend above the earth? Check this:
According to calculations, the comoving distance (current proper distance) to particles from the CMBR, which represent the radius of the visible universe, is about 14.0 billion parsecs (about 45.7 billion light years), while the comoving distance to the edge of the observable universe is about 14.3 billion parsecs (about 46.6 billion light years), about 2% larger. (Observable universe-Wikipedia)
Now, if God's ways and thoughts are 45.7 to 46.6 billion light years higher than ours (including those of the scientists who have concluded those distances) it is easy to understand that He is vividly aware that this author is presently typing this article plus he knows exactly what each and every person on earth is thinking at this moment. How many are presently engaged in sin of some sort? We wonder, but God knows.
A preacher once spoke on this subject and he concluded that this should strike terror in every heart. I disagree with that. It should indeed strike terror in those who have not rendered obedience to Him and are currently enslaved by sin. But to those of us who have obeyed the gospel plan of salvation and are doing the very best we can to live according to his will, it is a most comforting thought. Comforting in that He makes no mistakes, but rather knows precisely what is in our hearts and when we inadvertently sin, Jesus blood continues to cleanse us.
But if we walk in the light, as he is in the light, we have fellowship one with another, and the blood of Jesus Christ his Son cleanseth us from all sin. (1 John 1:7 KJV)
The Psalmist explains God's omniscience beautifully and well, consider this in light of the above information:
O LORD, thou hast searched me, and known me. Thou knowest my downsitting and mine uprising, thou understandest my thought afar off. Thou compassest my path and my lying down, and art acquainted with all my ways. For there is not a word in my tongue, but, lo, O LORD, thou knowest it altogether. Thou hast beset me behind and before, and laid thine hand upon me. Such knowledge is too wonderful for me; it is high, I cannot attain unto it. (Psalm139:1-6 KJV)
Blessed is the nation whose God is the LORD; and the people whom he hath chosen for his own inheritance. The LORD looketh from heaven; he beholdeth all the sons of men. From the place of his habitation he looketh upon all the inhabitants of the earth. He fashioneth their hearts alike; he considereth all their works. (Psalm 33:12-15 KJV)
O LORD God, to whom vengeance belongeth; O God, to whom vengeance belongeth, shew thyself. Lift up thyself, thou judge of the earth: render a reward to the proud. LORD, how long shall the wicked, how long shall the wicked triumph? How long shall they utter and speak hard things? and all the workers of iniquity boast themselves? They break in pieces thy people, O LORD, and afflict thine heritage. They slay the widow and the stranger, and murder the fatherless. Yet they say, The LORD shall not see, neither shall the God of Jacob regard it. Understand, ye brutish among the people: and ye fools, when will ye be wise? He that planted the ear, shall he not hear? he that formed the eye, shall he not see? He that chastiseth the heathen, shall not he correct? he that teacheth man knowledge, shall not he know? The LORD knoweth the thoughts of man, that they are vanity. (Psalm 94:1-11 KJV)
And Solomon has this to say:
The eyes of the LORD are in every place, beholding the evil and the good. (Proverbs 15:3 KJV)
For those who are unconcerned that their lives are not in harmony with God's plan of salvation should give serious thought to the fact that God is privy to every action they take and every thought of their heart. Absolutely nothing is hidden from His sight. His faithful children can take comfort in those things but the day is swiftly approaching when each of us will stand before the judgment bar and all of our works will be presented to the righteous judge.
"...behold, now is the accepted time; behold, now is the day of salvation.)" (2 Corinthians 6:2 KJV)