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Stephen Hawking thought black holes were 'hairy'. New study suggests he was right.
The outer edges of a black hole might be "fuzzy" instead of neat and smooth.
- A recent study analyzed observations of gravitational waves, first observed in 2015.
- The data suggests, according to the researchers, that black holes aren't bounded by smooth event horizons, but rather by a sort of quantum fuzz, which would fit with the idea of Hawking radiation.
- If confirmed, the findings could help scientists better understand how general relativity fits with quantum mechanics.
What's it like on the outer edges of a black hole?
This mysterious area, known as the event horizon, is commonly thought of as a point of no return, past which nothing can escape. According to Einstein's theory of general relativity, black holes have smooth, neatly defined event horizons. On the outer side, physical information might be able to escape the black hole's gravitational pull, but once it crosses the event horizon, it's consumed.
"This was scientists' understanding for a long time," Niayesh Afshordi, a physics and astronomy professor at the University of Waterloo, told Daily Galaxy. The American theoretical physicist John Wheeler summed it up by saying: "Black holes have no hair." But then, as Afshordi noted, Stephen Hawking "used quantum mechanics to predict that quantum particles will slowly leak out of black holes, which we now call Hawking radiation."
ESO, ESA/Hubble, M. Kornmesser
In the 1970s, Stephen Hawking famously proposed that black holes aren't truly "black." In simplified terms, the theoretical physicist reasoned that, due to quantum mechanics, black holes actually emit tiny amounts of black-body radiation, and therefore have a non-zero temperature. So, contrary to Einstein's view that black holes are neatly defined and are not surrounded by loose materials, Hawking radiation suggests that black holes are actually surrounded by quantum "fuzz" that consists of particles that escape the gravitational pull.
"If the quantum fuzz responsible for Hawking radiation does exist around black holes, gravitational waves could bounce off of it, which would create smaller gravitational wave signals following the main gravitational collision event, similar to repeating echoes," Afshordi said.
Credit: NASA's Goddard Space Flight Center/Jeremy Schnittman
A new study from Afshordi and co-author Jahed Abedi could provide evidence of these signals, called gravitational wave "echoes." Their analysis examined data collected by the LIGO and Virgo gravitational wave detectors, which in 2015 detected the first direct observation of gravitational waves from the collision of two distant neutron stars. The results, at least according to the researchers' interpretation, showed relatively small "echo" waves following the initial collision event.
"The time delay we expect (and observe) for our echoes ... can only be explained if some quantum structure sits just outside their event horizons," Afshordi told Live Science.
Afshordi et al.
Scientists have long studied black holes in an effort to better understand fundamental physical laws of the universe, especially since the introduction of Hawking radiation. The idea highlighted the extent to which general relativity and quantum mechanics conflict with each other.
Everywhere — even in a vacuum, like an event horizon — pairs of so-called "virtual particles" briefly pop in and out of existence. One particle in the pair has positive mass, the other negative. Hawking imagined a scenario in which a pair of particles emerged near the event horizon, and the positive particle had just enough energy to escape the black hole, while the negative one fell in.
Over time, this process would lead black holes to evaporate and vanish, given that the particle absorbed had a negative mass. It would also lead to some interesting paradoxes.
For example, quantum mechanics predicts that particles would be able to escape a black hole. This idea suggests that black holes eventually die, which would theoretically mean that the physical information within a black hole also dies. This violates a key idea in quantum mechanics which is that physical information can't be destroyed.
The exact nature of black holes remains a mystery. If confirmed, the recent discovery could help scientists better fuse these two models of the universe. Still, some researchers are skeptical of the recent findings.
"It is not the first claim of this nature coming from this group," Maximiliano Isi, an astrophysicist at MIT, told Live Science. "Unfortunately, other groups have been unable to reproduce their results, and not for lack of trying."
Isi noted that other papers examined the same data, but failed to find echoes. Afshordi told Galaxy Daily:
"Our results are still tentative because there is a very small chance that what we see is due to random noise in the detectors, but this chance becomes less likely as we find more examples. Now that scientists know what we're looking for, we can look for more examples, and have a much more robust confirmation of these signals. Such a confirmation would be the first direct probe of the quantum structure of space-time."
- Did a lab-made black hole just prove Hawking radiation? - Big Think ›
- Is the universe a hologram? Black holes may one day tell us. - Big ... ›
- Black hole photo: NASA astronomer explains the event horizon - Big ... ›
- Extreme black holes may have "hair," find scientists - Big Think ›
A leading British space scientist thinks there is life under the ice sheets of Europa.
- A British scientist named Professor Monica Grady recently came out in support of extraterrestrial life on Europa.
- Europa, the sixth largest moon in the solar system, may have favorable conditions for life under its miles of ice.
- The moon is one of Jupiter's 79.
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A tourist generally has an eye for the things that have become almost invisible to the resident.
A large new study puts caffeine-drinking moms on alert.
- Neuroregulating caffeine easily crosses the placental barrier.
- A study finds that the brains of children born to mothers who consumed coffee during pregnancy are different.
- The observed differences may be associated with behavioral issues.
A large study of nine- and ten-year-old brains<img type="lazy-image" data-runner-src="https://assets.rebelmouse.io/eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9.eyJpbWFnZSI6Imh0dHBzOi8vYXNzZXRzLnJibC5tcy8yNTY3NzIyOC9vcmlnaW4uanBnIiwiZXhwaXJlc19hdCI6MTY1MDk5MjQ0N30.UCu1Ygfi_rmO-xLpW-KOgCX-MJ3bfqjzfIVg4Kmcr9w/img.jpg?width=980" id="d2e15" class="rm-shortcode" data-rm-shortcode-id="c96aa86f8dbe08aa8536502ac1769497" data-rm-shortcode-name="rebelmouse-image" data-width="1440" data-height="960" />
Credit: myboys.me/Adobe Stock<p>For the study, its authors analyzed brain scans of 9,000 nine and ten-year-olds. Based on their mothers' recollections of their coffee consumption during pregnancy, the researchers found that children of coffee drinkers had clear changes in the manner in which white brain matter tracks were organized. These are the pathways that interconnect brain regions.</p><p>According to Foxe, "These are sort of small effects, and it's not causing horrendous psychiatric conditions, but it is causing minimal but noticeable behavioral issues that should make us consider long-term effects of caffeine intake during pregnancy."</p><p>Christensen says that what makes this finding noteworthy is that "we have a biological pathway that looks different when you consume caffeine through pregnancy."</p><p>Of children with such pathway differences, Christensen says, "Previous studies have shown that children perform differently on IQ tests, or they have different psychopathology, but that could also be related to demographics, so it's hard to parse that out until you have something like a biomarker. This gives us a place to start future research to try to learn exactly when the change is occurring in the brain."</p><p>The study doesn't claim to have determined exactly <em>when</em> during development these changes occur, or if caffeine has more of an effect during one trimester or another.</p><p>Foxe cautions, "It is important to point out this is a retrospective study. We are relying on mothers to remember how much caffeine they took in while they were pregnant."</p><p>So as if being pregnant wasn't difficult enough, it sounds like the most conservative and safe course of action for expectant mothers is to forgo those revitalizing cups of Joe and switch to decaf or some other uncaffeinated form of liquid comfort. We apologize on behalf of science.</p>