Has Stephen Hawking solved the mystery of black holes?
Dr. Don Lincoln is a senior physicist at Fermilab who does research using the Large Hadron Collider. He has written numerous books and produces a series of science education videos. He is the author of, most recently, “The Large Hadron Collider: The Extraordinary Story of the Higgs Boson and Other Things that Will Blow Your Mind.” Follow him on Facebook. The opinions expressed in this commentary are solely those of the author.
Black holes have a way of capturing our imagination. That’s why when Stephen Hawking recently talked about them the media went wild.
But what was he really saying? Was it a breakthrough moment?
At the Hawking Radiation Conference organized by Laura Mersini-Houghton, a professor of physics at the University of North Carolina, 32 eminent physicists gathered to discuss outstanding issues involved with apparent contradictions in our current understanding of the theories of relativity and quantum mechanics. The convergence of the two take us to the inner workings of black holes.
Black holes are ravenous monsters of the cosmos, constantly reaching out and gobbling nearby mass as they grow larger and larger. The poster child of Einstein’s theory of relativity, black holes exert such a strong gravitational force that not even light can escape, and they are able to distort the very fabric of space and slow the passage of time. These are very real objects.
And yet they embody a very significant mystery. Black holes are said to absorb matter and never let it go. The matter simply disappears inside the black hole. But matter is more than, well, matter. It is information. For instance, if I have a single atom of hydrogen, I have a proton and electron. That’s matter. But there is also information in how they are connected. Are they near one another, or far apart?
The information component is even more important in, say, a piece of fruit. While I might tell you just how many protons, neutrons and electrons exist in an apple, without the information that tells you how they arranged, it wouldn’t have the apple’s tart taste. In fact, it wouldn’t be an apple at all. Ultimately, it is information that is at the heart of theÂ mystery.
According to the rules of quantum mechanics, information should never be lost, not even if it gets sucked inside the black hole. This is because of two premises: causality and reversibility. Taken together, it means that effects have causes, and those causes can be undone.
For example, you can break a glass and then find all the pieces and glue it back together. Yet, these two premises don’t hold for a classical black hole, in which the information is permanently and irreversibly lost as it enters the black hole.
Note that information being lost isn’t the same as matter being lost. In the 1970s, Hawking postulated what is now called Hawking radiation, which in principle, cause black holes eventually to evaporate as the radiation carries away energy. However, Hawking radiation should be completely independent of the matter absorbed by a black hole. So, information really does appear to be lost, in complete contradiction of quantum theory.
This is where Hawking’s announcement comes in. He is saying that he can solve the conundrum.
He is countering the claim that the black hole gobbles and destroys the information by positing that the information never actually falls into the black hole. Instead, the information is held on the black hole’s surface — the event horizon.
This is an intriguing thought and is analogous to how holograms are made. Holograms are two-dimensional sheets of, for example, plastic that can make three-dimensional images. All of the information of three dimensions is encoded in the two dimensional plastic. (By the way, there are some who hypothesize that our entire universe is a hologram!)
It is difficult to properly evaluate Hawking’s announcement. The claim as it has been described is not very precise. There is no paper published on the idea, nor has the idea passed peer review. In fact, scientists who attended the conference are still trying to absorb the idea and to cast it in a mathematical language so that the implication can be assessed.
Hawking developed this concept in collaboration with Malcolm Perry of Cambridge University and Andrew Stromberg of Harvard University. They plan to submit a paper in a month or so. That’s when the real evaluation of the proposal can begin.
While everyone would much prefer to hear about a definitive advancement in science, the actual process of developing scientific ideas can be both intellectually stimulating and thoroughly messy.
Stephen Hawking’s new ideas are certainly interesting and may point us in the right direction. But we will have to wait a bit longer to solve the enigma of what happens when information confronts a black hole. Sit tight, we’re on a very long journey.