God was so happy that Abraham was willing to gut his son, he made a promise to him:
The angel of the Lord called to Abraham from heaven a second time and said, “I swear by myself, declares the Lord, that because you have done this and have not withheld your son, your only son, I will surely bless you and make your descendants as numerous as the stars in the sky and as the sand on the seashore. Your descendants will take possession of the cities of their enemies, and through your offspring all nations on earth will be blessed, because you have obeyed me.”
At that time Abraham and the Bible writers had no idea how many stars there were but God knows. With modern technology, we have a better idea of how many there are but we only know what’s in the visible universe and even that is an estimation. However, we know one thing beyond all doubt. There are many many more stars than we could ever hope to have descendants from Adam.
Let’s estimate how long the world has to exist for Abraham to reach that many descendants.
Earth is only supposed to last another 1.75 billion years. Even though homo sapiens will probably be long gone via extinction or evolutionary change, let’s assume the species will still exist (after all a lot of Christians don’t believe in evolution). Let’s figure out how many children need to be born per to reach 70 billion trillion in 1.75 billion years. So 70 billion trillion babies divided by 1.75 billion years = 40 trillion babies per year need to be born from now until the end of the earth to fulfill God’s promise.
Now I know what you’re thinking. This isn’t a true promise by God. It’s a figure of speech. But I disagree. Many Christians treat the Bible as innerant and historical. The reason these things are interesting and important is that this is a chance for God to prove he’s real and whenever God or Jesus speak in the Bible, they never seem to have any more knowledge than the person writing. I’m imagining the person writing looked up at night and knew there were a lot of stars but that given enough time and human reproduction, there could actually be enough people to match the number of “dots” they saw in the sky.