Psalm 19:1-3 (NIV)
The heavens declare the glory of God; the skies proclaim the work of his hands. Day after day they pour forth speech; night after night they display knowledge. There is no speech or language where their voice is not heard.
Do you marvel at the beauty of the night sky? Do you wonder what awesome power could have hung them out there in space so far away? With the naked eye you can see about five thousand stars. With my eight inch telescope, I can see about two million. The Hubble telescope can see billions of galaxies, and each galaxy probably contains a trillion stars! David the psalmist says that we all hear the inaudible voice of the heavens and the skies proclaiming God's glory. What kind of unfathomable power and wisdom could produce such a wonderful and massive marvel as the universe!
That testimony is not enough to bring us to a saving knowledge of God but it is enough to hold us accountable to know that there is a God. I have heard the objection many times that if Jesus is the only way, isn't God unfair to hold those accountable who have never heard the gospel?
Romans 10:18 (NKJV)
But I say, have they not heard? Yes indeed: “Their sound has gone out to all the earth, And their words to the ends of the world.”
We are responsible for our unbelief, for failing to respond to the "speech" clearly spoken in the revelation of the heavens.