Toys, Entropy, and the Laws of the Universe

My two-year-old son is quickly learning one of the most basic and frustrating facts of life: it is far easier to make a mess than it is to clean it up.

Spreading toys around several rooms requires nothing more than removing them from their box, taking them to some seemingly random place to play with, quickly losing interest, and then returning to the box to repeat the process. But he never plays with them all in the same place, so the house is strewn about with toys.

Of course, it’s fun for him. But when my wife or I get sick of the mess and ask him to put everything back, well, so much for the fun part. Putting everything back is harder than spreading it all around. The latter happens without thinking, but the former requires some serious thought. And we usually wind up using more physical effort to clean up a mess than to make one.

That’s the second law of thermodynamics for you.

OK, the analogy isn’t perfect. This famous physical principle simply says that a quantity called entropy within a closed system will tend to stay the same or increase with time, but never decrease.

Entropy is commonly described as a measure of the degree of disorder in a system. From a statistical perspective, the entropy of a closed system will increase because the number of disordered states far outnumber the ordered ones, so it is far more likely for a physical system to evolve into one of the former than the latter. Another way of putting it is that even though energy itself is conserved (the first law of thermodynamics), the forms of energy that tend to become more and more common are more disordered and less useful for doing work. (Confused? This TED-Ed video might help.)

Going back to my son and his toys, there are far more ways for them to be strewn about than there are for them to be stored in the box. And even though the entropy of the room appears to go down when he (or more likely one of us) puts them back in the box, the process requires expending physical and mental energy, which generates heat. And this form of energy is far more disordered than its previous state stored in our cells, and compensates for the order created by putting the toys back in the box.

Given the laws of physics, a world without the increase of entropy would be utterly boring. It would mean that everything would be in equilibrium and in its most disordered state. Everything would be a uniform cosmic soup of particles and fields whizzing around randomly. The fact that we can even observe the second law in action is because there are huge reservoirs of ordered energy in the universe which can be used for work and converted into heat. Among others, the physicist Roger Penrose has pointed out that the universe began in the Big Bang with an astonishingly low entropy, which has been the catalyst for the development of ordered structures from clusters of galaxies, stars, planets, and life on Earth.

Second law = very good

As a Christian, I see the second law as part of God’s “very good” creation. The manifestation of the increase of entropy implies that God endowed the universe in the beginning with extensive potential for the growth and development of all of its wonders. But there is another, more unfortunate, consequence of the second law: because energy is continuously being transferred into forms that are more disordered and less useful for work, this inevitably leads eventually to decay and death.

Why would God make such a world, instead of one where energy was transferred from one useful form into another all of the time? Revelation, the last book of the Bible, seems to suggest that one day the world will be like that, since it will endure forever in the intimate energy-giving presence of God. So why not start with that now and skip this current part, with all of the death, decay, and suffering?

This is the age-old question of “theodicy”: if God is all-good and all-powerful, why is there so much evil and death in the cosmos? The Bible explains much of the world’s evil in terms of the sinful choices of beings like ourselves, but that still leaves open the question why destructive things—hurricanes, forest fires, earthquakes, things incapable of “sin”—have been going on for billions of years, even before humans were in the picture.

I won’t pretend to be able to solve the problem of evil in my lifetime, let alone in a blog post. But based on the Bible, on the discoveries of science, and on my own life experience, God seems to prefer to work by process. These processes often seem slow and require many steps, and often the expenditure of great energy. But in the end, they allow us to look back, see what happened, and learn from it.

Thanks to the finite speed of light, we can look out into space and back into time and see the slow, laborious process—and all of its intricacy—that led to us being here. And I can look back on my own life and see how God was slowly shaping me through my experiences, especially the difficult ones, to build character and faith to (hopefully, at least) better serve my fellow men and women.

This is not to minimize the very real and painful suffering of sickness and death, which often seem to have no reason—and for which trying to give a logical explanation would be insensitive, even cruel. In such times, I’ve realized that the death of Jesus himself was God’s strange and unexpected way of redeeming the world—by subjecting himself to the law of decay, which gives me hope for the future.

So I’ll keep letting my son “increase the entropy” of our small piece of the universe. But I’ll also eventually ask him to impose some order on the room again, even if the entropy of the universe will still increase.

I hope that such a simple task will lay the foundation for a lifelong pursuit of character-building in the face of struggles—and for looking forward to the day when God finally brings his order to the world.

John ZuHone is an astrophysicist at the Harvard-Smithsonian Center for Astrophysics.