Why is the universe so big, and why is so much of it hostile to life?

Christianity and the progress of science
Christianity and the progress of science

Review: In case you need a refresher on the cosmological and fine-tuning arguments, as presented by a professor of particle physics at Stanford University, then click this link and watch the lecture.

If you already know about the standard arguments for theism from cosmology, then take a look at this post on Uncommon Descent.


In my previous post, I highlighted three common atheistic objections to to the cosmological fine-tuning argument. In that post, I made no attempt to answer these objections. My aim was simply to show that the objections were weak and inconclusive.

Let’s go back to the original three objections:

1. If the universe was designed to support life, then why does it have to be so BIG, and why is it nearly everywhere hostile to life? Why are there so many stars, and why are so few orbited by life-bearing planets? (Let’s call this the size problem.)

2. If the universe was designed to support life, then why does it have to be so OLD, and why was it devoid of life throughout most of its history? For instance, why did life on Earth only appear after 70% of the cosmos’s 13.7-billion-year history had already elapsed? And Why did human beings (genus Homo) only appear after 99.98% of the cosmos’s 13.7-billion-year history had already elapsed? (Let’s call this the age problem.)

3. If the universe was designed to support life, then why does Nature have to be so CRUEL? Why did so many animals have to die – and why did so many species of animals have to go extinct (99% is the commonly quoted figure), in order to generate the world as we see it today? What a waste! And what about predation, parasitism, and animals that engage in practices such as serial murder and infant cannibalism? (Let’s call this the death and suffering problem.)

Here’s an excerpt for the size argument:

(a) The main reason why the universe is as big as it currently is that in the first place, the universe had to contain sufficient matter to form galaxies and stars, without which life would not have appeared; and in the second place, the density of matter in the cosmos is incredibly fine-tuned, due to the fine-tuning of gravity. To appreciate this point, let’s go back to the earliest time in the history of the cosmos that we can meaningfully talk about: the Planck time, when the universe was 10^-43 seconds old. If the density of matter at the Planck time had differed from the critical density by as little as one part in 10^60, the universe would have either exploded so rapidly that galaxies wouldn’t have formed, or collapsed so quickly that life would never have appeared. In practical terms: if our universe, which contains 10^80 protons and neutrons, had even one more grain of sand in it – or one grain less – we wouldn’t be here.

If you mess with the size of the universe, you screw up the mass density fine-tuning. We need that to have a universe that expands at the right speed in order for the matter to clump together to form galaxies, stars and planets. Too fast, and you get no clumping. Too slow, and the whole thing re-collapses into a hot fireball. You need stars and planets to have a place to form life – a place with liquid water at the surface, and more.

And an excerpt for the age argument:

(a) One reason why we need an old universe is that billions of years were required for Population I stars (such as our sun) to evolve. These stars are more likely to harbor planets such as our Earth, because they contain lots of “metals” (astronomer-speak for elements heavier than helium), produced by the supernovae of the previous generation of Population II stars. According to currently accepted models of Big Bang nucleosynthesis, this whole process was absolutely vital, because the Big Bang doesn’t make enough “metals”, including those necessary for life: carbon, nitrogen, oxygen, phosphorus and so on.

Basically, you need heavy elements to make stars that burn slow and steady, as well as to make PEOPLE! And heavy elements have to be built up slowly through several iterations of the stellar lifecycle, including the right kinds of stellar death: supernovae.

Read the rest! These arguments come up all the time in debates with village atheists like Christopher Hitchens and Richard Dawkins. It’s a smokescreen they put up, but you’ve got to be able to answer it using the scientific evidence we have today. They always want to dismiss God with their personal preferences about what God should or should not do. But the real issue is the design of the cosmological constants that allow life to anywhere. That’s the part that’s designed. And that’s not a matter of personal preference, it’s a matter of mathematics and experimental science.

4 thoughts on “Why is the universe so big, and why is so much of it hostile to life?”

  1. “They always want to dismiss God with their personal preferences about what God should or should not do.”
    Yes, God’s existence is not dependent upon people’s belief or non-belief in Him. Atheists need to be reminded of this. A healthy dose of humility would help them here.

  2. By the way, someone blogged about this topic but looking at a different topic:

    Jennifer Senior of the New York Times mentioned,
    “But a powerful essay by the evolutionary biologist Matthew Cobb will make you wonder whether any form of multicellular life is far less likely than one in a billion. He points out that “there are more single-celled organisms alive on Earth than there are Earthlike planets in the observable universe”; that the number of single-celled organisms that have lived on this planet over the course of 3.8 billion years is beyond calculation; that these organisms have interacted “gazillions” of times (I love it when words of the appropriate magnitude desert even the experts). Yet we’ve never had a second instance of eukaryogenesis — that remarkable moment when one unicellular life form lodged inside another, forming something much more complex — in all this time.”

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