The final scientific paper written by beloved theoretical physicist Stephen Hawking has been published posthumously by colleagues from Cambridge and Harvard.
Titled "Black Hole Entropy and Soft Hair," the paper discussed a concept called "the information paradox," which Professor Hawking spent decades of his life pondering. The researchers, including co-author Malcolm Perry, reportedly completed the study days before Hawking's death in March.
The paper is now online via the pre-print resource arxiv.org.
The Information Paradox
The information paradox is a puzzle that comes from the combination of Albert Einstein's theory on general relativity and quantum mechanics. In the 1970s, Hawking proposed that black holes also have temperature and leak quantum particles. Eventually, black holes will evaporate, leaving a vacuum that is the same everywhere else.
However, according to physics, information is never lost. So where exactly do all the matter that a black hole has consumed go?
"The difficulty is that if you throw something into a black hole it looks like it disappears," explained Perry. "How could the information in that object ever be recovered if the black hole then disappears itself?"
Hawking and his colleague made an attempt to solve the puzzle. They argued that some information from the black hole can be preserved before it completely disappears.
In 2016, the scientists proposed the idea of "soft hairs," photons and gravitons that escape from a black hole's event horizon or the point at which nothing — not even light — could escape. The study claims that some information from the black hole might be recorded by photons.
The idea relies on entropy or the measure of internal disorder. When matter gets pulled into a black hole, its temperature changes. Because entropy is affected by temperature, specifically heat, scientists can use its changes through stored information by photons.
This is the third in a series of studies that discuss black hole information paradox. However, Perry said that the study does not completely answer the puzzle.
"We don't know that Hawking entropy accounts for everything you could possibly throw at a black hole," he said, "so this is really a step along the way."
Stephen Hawking's Death
Hawking passed away on March 14 in his home in Cambridge, United Kingdom. He was known for his work on black holes and general relativity as well as his best-selling books, including A Brief History of Time.
At 21, he was diagnosed with a rare form of motor neurone disease that strapped him in a wheelchair for most of his life. His ashes were buried at the Westminster Abbey alongside Charles Darwin and Isaac Newton.
