Section 15 — The Fine-Tuning Argument: The Tilt of the Earth's Axis

The Christian Statement

The fine-tuning of the physical constants of the universe is one of the most striking discoveries of modern physics. The universe contains approximately twenty physical constants — the gravitational constant, the electromagnetic force, the strong and weak nuclear forces, the cosmological constant, and others. Each of these is calibrated to a precision that, if varied by even tiny amounts, would produce a universe incapable of supporting life of any kind.

A few examples:

• If the gravitational constant were slightly stronger, stars would burn too quickly to permit life. Slightly weaker, and they wouldn't ignite at all.
• If the cosmological constant — the energy of empty space — were larger by one part in ten to the power of 120, the universe would have expanded too fast for any structure to form.
• If the ratio of the electromagnetic force to gravity were different by one part in ten to the power of 40, stars could not exist.
• The earth's axial tilt, its distance from the sun, the size of the moon, the thickness of the earth's crust, the composition of the atmosphere — each of these is calibrated within narrow ranges that permit life.

Physicist Paul Davies writes: "The impression of design is overwhelming." Astronomer Fred Hoyle — an atheist who coined the term "Big Bang" while trying to mock the idea — said that the evidence of fine-tuning suggested "a superintellect has monkeyed with physics." He did not become a Christian. But he could not dismiss the evidence.

✖ Atheist: The anthropic principle explains this. We can only observe a universe compatible with our existence. Of course our universe permits life — we wouldn't be here to observe it if it didn't.

✔ How to respond: The anthropic principle explains why we observe a life-permitting universe rather than one we couldn't observe. It does not explain why a life-permitting universe exists at all. If I am standing before a firing squad of a hundred expert marksmen and they all miss, the anthropic principle tells me I'm not surprised I survived — I couldn't observe my death. But I'm still rationally entitled to ask why they all missed. The question of why the universe is fine-tuned at all is not answered by noting that we had to be here to observe it.