The fine-tuning of the universe for the existence of life is fascinating to me. That’s why I was so excited to find A Fortunate Universe: Life in a Finely Tuned Cosmos, co-authored by astrophysicists Geraint Lewis and Luke Barnes, under my Christmas tree. This book provides the most up-to-date scientific evidence for the fine-tuning of the universe for life. But what is truly unique about this book is that it presents the data at a popular level so that the material is accessible to anyone interested in this topic.
As I read the book, I was awestruck by the finely-tuned constants and conditions that had to be just right to get a universe that would permit life. I’d like to give you a taste of some of this evidence. Specifically, I want to show you how the masses of three fundamental particles of the universe are set for life. If they were changed by the slightest amount, there could be no life anywhere in the universe. Unfortunately (at least for some), this requires you to understand a little particle physics.
Now stay with me. The reward at the end is worth it. Trust me. Here we go.
Particle Physics 101
Underlying all of the complexity of this universe—bees, computers, people, stars, and planets—is the simplicity of a few particles. At the most basic level, the world is built from a handful of building blocks. At one time, we believed that the smallest building blocks were atoms. However, today we know that atoms are made up of subatomic particles: neutrons, protons, and electrons. Protons, which are positively charged, and neutrons, which have no charge, compose the nucleus of the atom. Negatively charged electrons orbit the nucleus.
Are you starting to remember your high school chemistry class yet? Some of you are probably still trying to forget it.
These three particles are responsible for building the 92 naturally occurring elements, as well as the unstable elements that have been created in the laboratory. Think periodic table. For example, a stable carbon atom is made of six protons, six neutrons, and six electrons.
But this isn’t the end of the story. While electrons seem to be fundamental, neutrons and protons can be broken into smaller bits. Particle accelerators are used to smash atoms apart. In the process, scientists have discovered that protons and neutrons are made of quarks. Specifically, they are made of a combination of up quarks and down quarks. Protons are composed of two up quarks and one down quark. Neutrons are composed of two down quarks and one up quark.
These three particles—the up quark, the down quark, and the electron—make up everything we see—molecules, mice, maple trees, and the Milky Way galaxy. And each of these particles has a distinct mass. The mass of an electron is approximately 9.1 x 10-31 kg. That is extremely small. Likewise, the mass of the up quark and the down quark are approximately 4.1 x 10-30 kg and 8.5 x 10-30 kg, respectively. (Physicists prefer to use the unit MeV/c2—Mega electron volts per speed of light squared—but let’s stick with units we are all familiar with).
Changing the Masses
These numbers may not look very special, but, as Lewis and Barnes demonstrate, they are finely tuned for the existence of life. Consider how the universe would be different if the masses of the up quark and down quark were slightly different. Barnes and Lewis write, “In fact, it is rather easy to arrange for a universe to have no chemistry at all. Grab a hold of the particle mass dials and let’s create a few universes.”
So what happens if we change the masses of the three fundamental particles—the down quark, the up quark, and the electron? Let’s see.
Making a Hydrogen Universe
Lewis and Barnes describe what would happen to the universe if the mass of the down quark was increased by a factor of 3. They write,
To create a hydrogen-only universe, we increase the mass of the down quark by at least a factor of 3. Here, no neutron is safe. Even inside nuclei, neutrons decay. Once again, kiss your chemistry textbook goodbye, as we’d be left with one type of atom and one chemical reaction.
Can you even fathom this? Increase the mass by 3 times, and you construct a universe with nothing but hydrogen. No galaxies, no stars, no planets, just hydrogen atoms floating around a dark, cold, lifeless universe. But there is no reason why this mass could not have been 3 times larger, or 30 times larger, or 3000 times larger, or 300,000 times larger. You get the point. Yet, it has the right mass to get a universe that makes life possible.
Making a Neutron Universe
Lewis and Barnes describe a number of ways to create a universe that contains nothing but neutrons—no atoms or chemical reactions.
If you think the hydrogen universe is rather featureless, let’s instead increase the mass of the up quark by a factor of 6. The result is that the proton falls apart. In a reversal of what we see in our universe, the proton, including protons buried in the apparent safety of the atomic nucleus, decay into neutrons, positrons and neutrinos....
What about the other particle of everyday stuff, the electron? Since the electron (and its antiparticle, the positron) is involved in the decay of neutron and protons, it too can sterilize a universe. For example, increase its mass by a factor of 2.5, and we’re in the neutron universe again.
To help visualize how finely tuned these values are for life, consider a dartboard the size of West Virginia (approximately 630 trillion cm2). Now imagine I blindfold you and ask you to throw a dart at random towards this gigantic dartboard. Oh, and there is a catch. You have to hit the bull’s-eye (an area of about 1 cm2), or you’re dead. Your odds don’t look good.
It’s true that hitting any particular square centimeter is equally probable, but it is extremely more probable that you would hit one of the hundreds of trillions of squared centimeters that are life-prohibiting over the one squared centimeter that is life-permitting. In fact, if you hit the life-permitting bull’s-eye, most rational people would charge you with peeking—designing the outcome.
As you can see, the masses of the up quark, down quark, and electron are extremely fine-tuned for the existence of life. Not merely the existence of human life, any kind of life. These masses could have taken any number of values. Yet, they fell within the extremely narrow range of values that permits the existence of life.
This evidence should move each one of us to ask, what is the best explanation of this incredible fine-tuning? These are just three of the many values that had to be set just right to permit a universe that would allow for the existence of life. The cumulative evidence for the fine-tuning of the universe for life points persuasively to the mind of God. This universe is not merely a random, chance occurrence. No, fine-tuning points to a cosmic plan, and a cosmic plan points to a Cosmic Planner. The Apostle Paul was right: “For His invisible attributes, namely, His eternal power and divine nature, have been clearly perceived, ever since the creation of the world, in the things that have been made” (Rom. 1:20).
It is truly an exciting time to be a Christian. The science of the fine-tuning is giving us a glimpse, like never before, of the divine Architect, who thoughtfully designed this universe to support life.
 Geraint F. Lewis and Luke A. Barnes, A Fortunate Universe: Life in a Finely Tuned Cosmos (Cambridge, UK: Cambridge University Press, 2016), 48.
 Ibid., 50-51.
 Ibid., 51.
 The upper bound on the mass is the Planck Mass (1060).