The earth’s atmosphere is just right to support life. For example, the distance from the sun. We are just the right distance from the sun for us to live. If the earth were much closer to the sun, most water on the earth would boil. If the earth were much farther away, the water would mostly freeze, and we couldn’t survive in the earth’s environment.
Let’s talk a little more about water. Almost all molecules are heaviest in their solid form. But unlike most molecules, water is lighter in its solid form. That is why ice floats. If water got heavier in its solid form, ice would sink to the bottom of its container. This would cause a problem for lakes in the winter. If water in lakes froze from the bottom up, many lakes would freeze solid and kill most of their life. It seems like water itself was designed to make this world a better place to live.
Another example is the “weak force” of an atom. If this “weak force” was altered in its value by 1 in 10100 that would prevent a life-permitting universe. One more example: If the gravitational constant differed by 1 in 1060 life could not exist. William Lane Craig points out in his book On Guard that to have an accuracy of one part in 1060 is like firing a bullet to the other side of the observable universe (20 billion light-years away) and hitting a one-inch target. So the chances that there is no intelligence involved to design it the way it is are very remote. Dr. Craig uses the following lottery illustration to explain the odds: Let’s say that there are billions of billions of white ping-pong balls mixed together with one black ping-pong ball, and there’s a chute that will allow one ping-pong ball out of the mix. If the one that comes down the chute is black, you are allowed to live (in a life-permitting universe); if white, you die. Sure, some ball will be picked, but what are the odds of the black one being picked? And if the black one is picked five times in a row, everyone would recognize it didn’t happen by chance.
I’ll put this another way with a reference to the state lottery. Even though the odds of being picked for a mega million jackpot is extremely low (like about 1 in 300,000,000), it is true that someone will be picked. But if the same person was picked five times in a row, you would know that it was rigged—that there is no way that it happened by chance. Theoretically, there’s a chance that the same person could be picked 5 times in a row, but there is so little chance for that to occur, that if it happened you would be foolish to think that the selection process was fair. That’s how it is with the universe.
The universe is so fine-tuned, with so many factors at once needing to be in place for the universe to be life-permitting, we know that it could not be by chance. In that sense, the universe is “rigged” for human life—intelligence is certainly involved to account for a life-permitting universe.
An atheist might object that there could be an infinite number of universes and therefore you would expect our universe to be among the universes. But these other universes have never been observed. There is no evidence or proof of a multiverse. This proposal is only speculated to try to get around the force of the fine-tuning argument.