In Genesis 15, God invites Abram to count the stars. “Look toward heaven and count the stars, if you are able to count them.…So shall your descendants be” (Genesis 15:5). The implication is clear enough: the stars are too many for Abram to count, and his descendants will likewise be an innumerable multitude. And the crux of the story: Abram believed God, and “the LORD reckoned it to him as righteousness” (Genesis 15:6).

What happens in this story is that God makes a connection between the trustworthiness of his promise and the vastness of creation. Abram is beginning to question and doubt, to speak up to God about the fact that he has no child. Earlier God had promised to make Abram a “great nation,” blessing him and making his name great, and in response Abram had left his home and family and set out for the land God would show him (Genesis 12:1-4). But now, in Genesis 15, we see Abram beginning to doubt. He knows a great nation must start with children, and he’s growing older with not even one child to speak of. He asks God, “What will you give me, for I continue childless?” (Genesis 15:2). It’s in answer to this question that God shows Abram the sky and tells him to count the stars. “So shall your descendants be.” By using the night sky as a demonstration of what’s possible, God joins his promise to the immensity of the created world–and invites Abram to trust in him as the one who made it all.

That is what lies at the heart of this encounter between Abram and God, which makes it more than a simple repetition of God’s earlier promise. Abram asks God for reassurance, and God shows him that the universe far surpasses Abram’s ability to comprehend it or account for it. Abram must trust that the one who made it all is the one who is speaking to him. If Abram can believe this, then he can believe it’s possible for God to multiply his descendants on that same immense scale. If Abram can’t believe this, then it doesn’t matter what else God shows him or tells him or guarantees for him. Abram can’t envision how it will happen, any more than he is able to number the stars. But he doesn’t have to. He just has to trust the Creator.

Reading this story, I can’t help but wonder if Abram gave it a shot. Did he try to count the stars? And if so, how long was it before he gave up? Did he get up to 100? 1,000? Did he notice that the stars moved as the night went on, complicating his task? Did he discover that the sun would come up before he finished, and that it would take him many nights to count them all? Did he know, could he have known, that if he went past the equator he would begin to see other stars as he traveled through the southern hemisphere? Did he consider that the band of light, the Milky Way, was the light of many thousands of distant stars blurring together? I wonder if Abram looked up and knew immediately the implications of God’s rhetorical device, or if it was Abram’s own efforts that convinced him something much, much greater than himself must have set all those stars in the sky.

I don’t know how long Abram tried to count the stars, but astronomy kept at it. Astronomers since before Abram have not just counted the stars, but cataloged them, tracked them, measured their movements. It turns out that there are less than ten thousand stars visible to the naked eye, less than five thousand if you count only those visible from one hemisphere. But far from diminishing the scope of God’s promise, astronomy has revealed that it continually grows, staying ahead of our ability to perceive, understand, or imagine.

Today we can see farther than Abram could see as he looked up at the night sky. For most of human existence we could only look at the stars with the naked eye, but then Galileo turned a telescope toward the heavens. Suddenly more stars came into view. In the hundreds of years since Galileo, telescopes got bigger. Then they got much bigger. Then we launched them into space for a view uninhibited by earth’s atmosphere. Instruments now detect radio waves, microwaves, x-rays, and other forms of light that we cannot see. Cutting-edge research detects gravity waves, a way of perceiving things in the heavens that doesn’t even depend on the spectrum of light. We have done our best to count the stars using all these instrument and more, and the number just keeps growing. We know that the Milky Way is a galaxy that contains a hundred billions of stars, and that it’s just one of billions, maybe trillions, of galaxies that themselves contain hundreds of billions of stars. Not to mention whatever lies beyond the observable universe, too far for its light to have reached us.

The more we see, the greater becomes our appreciation for the vastness of God’s promise to Abram and, by extension, the other promises in Scripture. These promises are underwritten by the Creator of the whole immense universe, that which is seen and unseen. Of course, that doesn’t guarantee anything. We still have to believe, to have faith, to trust as Abram did. But if we have such faith, learning about the heavens cannot help but cause it to grow.