For the past few decades, black holes have been at the center of a paradoxical problem — a problem famed physicist Stephen Hawking now believes he’s solved. Even if you don’t follow astronomy or physics closely, you’re likely familiar with the concept of black holes. Black holes, which are formed by the collapse of super-massive stars, are areas of gravitation so intense that nothing, not even light, can escape. As an object approaches a black hole, it is stretched and compressed beyond recognition, until it passes through the event horizon and… well, we don’t know what happens inside the event horizon of a black hole.
Here’s the problem that Hawking thinks he may have solved. In 1974, Hawking proved that black holes do emit particles, in the form of so-called Hawking radiation. That means that over time — an absolutely fantastic amount of time — black holes evaporate. But if a black hole can evaporate, what happens to the information about the material it once absorbed?
To understand this in the physical world, consider the drought afflicting much of the American southwest. As reservoirs fall, garbage, old vehicles, and even entire towns becomes visible. The “information,” in this case, is disclosed as the reservoir evaporates. Remember, though — a black hole is an area of such intense gravity that nothing can escape, including information about what it previously digested. If the information disappears with the black hole, that violates quantum mechanics. If the information doesn’t escape, that also violates the laws of quantum mechanics. It’s a problem.
Here’s Hawking’s new solution(s). At a conference sponsored by the KTH Royal Institute of Technology this week, he proposed one of two answers. First, it’s possible that the physical material (information) swallowed by the black hole never actually enters it at all. Instead, it’s smashed into the point of no return and encoded as a two-dimensional hologram.
“The information is not stored in the interior of the black hole as one might expect, but in its boundary — the event horizon,” he said. Working with Cambridge Professor Malcolm Perry (who spoke afterward) and Harvard Professor Andrew Stromberg, Hawking formulated the idea that information is stored in the form of what are known as super translations.
“The idea is the super translations are a hologram of the ingoing particles,” Hawking said. “Thus they contain all the information that would otherwise be lost.”
The information stored in these holograms is then emitted in the form of quantum fluctuations, though the data is so scrambled as to be useless for all intents and purposes. To return to our real-world analogy, imagine feeding a car through a crusher, industrial wood chipper, and coffee grinder. Even if you captured every bit of fluid, metal shavings, and tattered upholstery released at every stage of this process, there’s no way to reconstitute two tons of finely-ground Volvo into a vehicle.
The advantage of this theory is that it doesn’t violate quantum mechanics. The disadvantage is that it’s rather boring.
Hawking’s other proposed option is that black holes might serve as gateways into other universes. “The existence of alternative histories with black holes suggests this might be possible,” Hawking said. “The hole would need to be large and if it was rotating it might have a passage to another universe. But you couldn’t come back to our universe.
“So although I’m keen on space flight, I’m not going to try that.”
White holes and alternate universes
One theory is that inside every black hole is another universe — and that the if you could pass through the event horizon of the black hole, you’d be emitted by an object called a white hole on the other side. A white hole is a theoretical structure (none are known to exist, though they don’t violate any of the known laws of physics) that emit matter and energy, but cannot ever be reached from the outside. I’m not going to pretend to understand the physics much past that, except to note that there’s no known way for a white hole to form, no white holes have ever been observed to exist, and white holes don’t form when stars collapse.
According to some theories, a white hole, rather than the Big Bang, might have been responsible for the birth of our own universe. This is, as you might expect, rather difficult to test directly.
The chance that we’ll ever answer the question pro or con is quite low. Not only are we fresh out of black holes in this neck of the woods, the gravitational fields surrounding them would destroy any scientific instrument package we could build. Even if the alternate universe theory is true, what a white hole emits is a blast of energy — not a probe, and certainly not a human being.
