Jeff answers questions from the popular magazine Christianity Today
Original Interview: How Black Holes Radiate God’s Glory | Christianity Today
INTERVIEW BY DANIEL SILLIMAN
There has been a burst of research on black holes in recent days. Three scholars from Norway, Brazil, and Canada say they’ve found the “smoking gun for the quantum structure of black hole horizons” in gravitational wave echoes. NASA’s Chandra X-ray Observatory reports evidence black holes are devouring thousands of stars. And two more scholars from the United Kingdom and the United States have proposed that “quantum hair” can resolve the black hole paradox first described by theoretical physicist Stephen Hawking.
According to Reasons to Believe astrophysicist Jeff Zweerink, the new research raises new questions, showing us that “the more we learn, the more we realize how much more there is to learn.” CT asked him why physics isn’t finished and what that can teach Christians who, like the psalmist, “consider your heavens, the work of your fingers” (Ps. 8:3).
What do black holes tell us about God?
It’s not like, “Black holes, therefore God.” But the theory of the universe that we have—the theory that said black holes should exist before anyone knew to even think about them—is predicated on the idea that our universe ought to be understandable. It ought to be coherent. It ought to be the same out in the distant reaches of the universe as it is here.
That points to the Creator. That tells us something about the Creator.
Look at how we get to black holes in the first place. Albert Einstein, back in 1915, recognized that as you move through the universe, from big stuff to small stuff and very fast stuff to very slow stuff, the laws of physics seemed to change. The way electromagnetism behaved was different from the way gravity behaved, and Einstein looked at that and said that doesn’t make sense. The laws of physics ought to be the same no matter how you look at them.
It was that philosophical idea that led him to develop his general theory of relativity. And if general relativity is right, then there should be these things called black holes.
The insight or genius of general relatively is that space and time, instead of being abstractions or kind of empty spaces, are now understood as these dynamic quantities. As energy moves through space and time, it actually warps space and time, and they could become so warped that they would rupture. If you get a star that’s massive enough, the gravitational pull is so strong that it collapses on itself and that’s a black hole. So people started thinking about black holes theoretically and eventually found evidence. We even found that in the center of our galaxy there is this massive black hole.
The connection here is that when we look at creation, we expect to see an orderly, coherent creation. For Einstein, it is a philosophical idea that ultimately derives from the notion that there is a unified order. And that’s what you would expect if there is a God who created it.
My basic understanding is that a black hole is a very dense star, a collapsed star, with a gravitational pull so powerful that even light, instead of just shining past, is locked into an orbit. How does that happen?
Take something like the earth. The earth is round because of gravity. Gravity wants to pull everything to the center, so it pulls all the atoms it can reach inward, but the atoms are all negatively charged, so when the atoms get close enough together, the electrons on those atoms repel one another. Gravity pulls them, but electromagnetic force pushes out.
Now imagine we added more mass. It gets a little bigger. But add more and more mass; eventually the gravitational pull would get strong enough it would overcome that electromagnetic force and pull those atoms closer together. That’s a white dwarf.
Now if you keep adding mass, it will get more gravitational attraction. And eventually you overcome the Pauli exclusion principle that says two electrons can’t exist in the same place; you’re going to push all the electrons into the protons to make neutrons. It’s going to collapse further until you’re pushing neutrons together, and that a neutron star.
If you continue to add matter, eventually what will happen is it will collapse down to where all of the mass is concentrated into a point, and there you have a black hole.
Essentially, keep adding mass until there’s nothing that can keep it from collapsing—until there’s no volume—and all of the mass is concentrated into this point and the gravitational pull is so strong that even light can’t escape. That’s the recipe for making a black hole.
Sometimes when people talk about black holes, there’s a kind of reverence. It goes even beyond awe. Why do you think that is?
For me personally, it’s that black holes are so beyond what I could fathom, so far beyond what I could even comprehend experiencing. We’re confronted in a small way with what it would be like to experience something infinitely bigger than us.
When I stand here on the surface of the earth, the gravitational pull on my feet is a little bit larger than the gravitational pull on my head, but it’s no big deal. But if I were falling feet first into a black hole, the gravitational pull on my feet would become so much larger than what’s on my head that it will actually rip every atom apart and the atoms will spiral into the black hole.
If Christianity is correct, one of the things that is true is that we as humans are designed to worship. And when you see things like black holes that are so much bigger and more powerful than us, it’s a very natural response to be moved to worship.
A lot of people are fascinated by black holes because they’re these weird objects in the universe. But they also present problems for scientists. Why do scientists have to grapple with black holes?
General relativity is an incredibly successful theory. It has passed every experimental test we’ve thrown at it. Quantum mechanics is the same. It’s incredibly good at describing the universe. But when it comes to black holes, they’re giving us different answers. So we need to dig deeper.
Quantum mechanics says that information cannot be destroyed. But general relatively says that a black hole can only have three properties: mass, charge, and spin. It’s just the nature of the way black holes work, those are the only three properties.
Say you have a star that is made out of pumpkin pie and you’ve got a star that is made up of hydrogen. If they each collapse and form a black hole, and they both reduce to mass, spin, and charge, then they’re going to look identical. Does that mean you’ve lost all the information that could tell you that one was originally made out of hydrogen and the other pumpkin pie?
Stephen Hawking identified this as a big problem in the 1970s. The way we’re looking at black holes, all this information is getting destroyed, and a fundamental rule of quantum mechanics is you can’t destroy information. That information has to be somewhere.
This is where we get the idea of Hawking radiation as a potential solution to this problem.
There was recently a new discovery—I’m not sure whether to call it a discovery or an argument—about Hawking radiation. Can you tell us about that?
There are multiple solutions that have been proposed, but this is a novel one. It’s another idea for how Hawking radiation could work. In this study, the scientists are saying a mechanism called “quantum hair” could explain how the information inside the black hole is connected to the radiation in the quantum state outside the horizon of the gravitational field.
Basically, if the gravity gives off bits of information—if the information could be encoded in the gravitation, then it could be radiated off—and not lost in the black hole. Theoretically, in principle, it seems that the information is there to extract. Because of the way gravity is quantized, it’s giving off information about the black hole.
If that’s right, that leads to a new level of complexity. It would allow us to reconcile this discrepancy in what we know now, and we’d be able to explain it, but then it has implications for how things work, and that will open up a whole new set of questions.
Historically, physicists have sometimes talked like they’re almost done. Like we’re just about to have a complete picture of the physical structure of the universe and there will be nothing more to know. And Christians who promote “God of the gaps” theories try to hurry that process along. But it doesn’t seem like we’re going to be finished with physics very soon.
Every time we solve one of these big questions and put the answer out there, we run into a whole new set of questions that we didn’t know existed! Compare our understanding of the universe now to when Isaac Newton was talking about his theory of gravity. We know so much more about what’s going on than we did back then. But there are also so many more questions that we don’t have answers to.
It’s almost like, the more we learn, the more we realize how much more there is to learn. You can start to see that we will never exhaust this. We’re going to be able to study creation forever. There will be new questions that we haven’t even thought to ask.
And this, again, points to the Creator. That’s where I see a connection to theology. Because that same thing is true about studying God’s revelation and Scripture and God. We’ve got a lot of the big picture in place, but there are also new questions and we will never be done. We will never exhaust the subject. That moves me personally to awe and to want to worship.