BLACK HOLE BREAKOUT
In “Escape from a Black Hole,” Steven B. Giddings gives us a fascinating update on developments in the black hole information crisis, the seeming paradox of quantum rules and general relativity indicating that black holes destroy information despite quantum mechanics saying that information cannot be destroyed.
One thing puzzles me about his account. He explains that the three leading candidate solutions to the crisis all have the same thorny problem: they violate the principle of locality, which maintains that no influence can move across space faster than the speed of light. But I've read elsewhere that the violation of locality has already been rigorously established from both observations and theoretical analyses of quantum entanglement. If that assessment is correct, why is such violation still regarded as a problem for black hole theories? And why doesn't Giddings mention the confirmation of nonlocality in entanglement studies as helping things along for these theories?
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BRUCE ECKER New York City
GIDDINGS REPLIES: Ecker's question reflects a common misunderstanding of the precise meaning of locality in physics. It is true that quantum mechanics has properties—specifically, entanglement—that appear to represent a kind of nonlocality. This observation famously bothered Albert Einstein, who referred to its consequences as “spooky action at a distance.” But quantum field theory fully reconciles locality with quantum mechanics. Although it exhibits entanglement, the precise statement of locality is that there is no way to send a signal (meaning no way to transmit information) nonlocally—that is, faster than the speed of light. Mere quantum entanglement does not allow such signaling. It is this locality property of quantum field theory that directly conflicts with the statement that, apparently, information must escape a black hole and that prompts us to consider modifications of quantum field theory.
CONSCIOUS DISTINCTION
Christof Koch gives an interesting summary of theories of human consciousness and whether computers can attain it in “Proust among the Machines.” The popular media—including Koch, it would seem—assume that computer consciousness would be much like our own, with a desire to be free, safe and alive. But computers are so physically different from ourselves and their reason for existing so different that if they were to gain consciousness, it would be very distinct from what we experience.
Take self-driving cars, for example. Their programming, or training, is a kind of evolutionary process where the best-performing connections win out. If cars being conscious would result in better driving, then, sooner or later, it would happen. The only thing such a car would “want,” however, would be to stay on the road and not hit anything. Behavior such as admiring the scenery would not contribute to good driving and would be eliminated in the training. What would it be like to “be” such a car? The experience would be so distant from our own that we would probably not recognize it as consciousness. I expect that when truly intelligent computers arrive, we will be surrounded by artificial consciousness and not even realize it. Or maybe we already are.
PAUL COLBOURNE Ottawa
PLASTICS AND CLIMATE
In “Learning to Love Plastic” [Ventures], Wade Roush asserts that standard plastic is good for the environment because it traps carbon that would contribute to climate change and that we should thus not adopt biodegradable plastic to reduce waste. His argument is flawed in two ways.
The first is a misunderstanding of the problem, which he identifies as the carbon intensity of biodegrading plastics. The release of carbon dioxide is a natural part of biodegradation, yet Roush implies this is a problem unique to biodegradable plastics. Fallen leaves on the forest floor do the same. If anything, the problem with biodegradable plastics is that they're weaker than those derived from petrochemicals, and in the same issue of Scientific American, “Bioplastics for a Circular Economy,” by Javier Garcia Martinez, highlights efforts to strengthen biodegradable plastics as one of the “Top 10 Emerging Technologies of 2019.”
The second flaw in Roush's position is more important: he fails to recognize that we can tackle two problems at once. Biodegradable plastics are a hopeful solution to a serious problem: plastic pollution. They are not the root cause of a different but certainly more serious problem: climate change because of anthropogenic carbon emissions. Thankfully, we are developing other solutions to solve that problem that don't involve treating petrochemical plastics as carbon sinks.
ZACHARY EPSTEIN Houston, Tex.
I was appalled to see the following statement in Roush's article with no supporting documentation: “And your supposedly eco-conscious cloth grocery bag is more damaging to the environment than conventional plastic bags—unless you reuse it literally thousands of times.” This “idea” defies logic and demands evidential support. A reusable, plant-based cotton bag will most certainly degrade more quickly and with less harm than a petroleum-based plastic one.
The war to save our environment requires maximum effort on everyone's part. No effort in this regard is too small.
JAMES E. BRITSCH Santa Barbara, Calif.
ROUSH REPLIES: My column about plastic was meant to combat the idea that “biodegradable” means “safe for the environment.” Quite the reverse is true if your paramount goal is to lower greenhouse gas emissions.
Epstein is right that fallen leaves biodegrade. But if humans can avoid adding to the natural carbon cycle—in this case, by switching to nonbiodegradable bioplastic and disposing of it responsibly—then we should. Plastic pollution remains a significant problem. But the solution is to stop abandoning plastic in the environment, not to hope that it decays there.
To respond to Britsch's comment: A bag's full life-cycle impact is what counts. Reusable cotton bags often consist of cotton grown on farms in China that use enormous amounts of irrigation water and are manufactured in textile plants that run on coal-fired electricity. In a thorough 2017 report, the Canadian government corporation Recyc-Québec determined that a cotton bag must be reused between 100 and 3,000 times to bring its life-cycle impact level down to that of a conventional plastic (high-density polyethylene) bag used just once.
ERRATA
“GPS Down,” by Paul Tullis, should have indicated that the civilian and military signals sent by GPS satellites are distinguished by special bits of code, not encryption keys.
“X-ray Vision,” by Belinda J. Wilkes, incorrectly implied that the supernova that created the neutron star in the Crab Nebula occurred in the year 1054. It was first observed on Earth at that time but had occurred thousands of years earlier.
“Odd Disturbances Pierce the Universe,” by Katie Peek [Graphic Science], erroneously described the lasers in two LIGO gravitational-wave detector sites as located underground. They run in aboveground tubes 2.5 miles long.