Cosmic Space

Black hole’s shadow boosts the case for relativity

The first-ever picture of a black hole is the gift that keeps on giving — in the form of new insights into the dynamics behind the mysterious phenomenon and new evidence that Albert Einstein was right.

The validity of Einstein’s theory of general relativity has been proven time and time again over the course of the past century. But physicists keep coming up with new ideas for tweaking the theory’s equations in unorthodox ways.

To figure out how much leeway there could be for variations on Einstein’s theme, researchers took a closer look at the supermassive black hole at the center of the galaxy M87.

M87’s black hole, which lies about 55 million light-years from Earth, was featured in a history-making close-up last year, produced by a radio astronomy collaboration known as the Event Horizon Telescope. The achievement is likely to win the EHT collaboration a Nobel Prize as soon as next week.

The team behind the relativity-checking research, published this week in Physical Review Letters, measured the size of the black hole’s shadow — that is, the dark central region from which light rays can’t escape, due to the gravitational pull of a singularity that’s 6.5 billion times as massive as our sun.

The predicted size of the shadow could vary, depending on which theory of gravity you go with. But in M87’s case, the size matched up precisely with Einstein’s theory.

“Using the gauge we developed, we showed that the measured size of the black hole shadow in M87 tightens the wiggle room for modifications to Einstein’s theory of general relativity by almost a factor of 500, compared to previous tests in the solar system,” the University of Arizona’s Feryal Özel, a senior member of the EHT collaboration, said in a news release.

“Many ways to modify general relativity fail at this new and tighter black hole shadow test,” Özel said.

The Event Horizon Telescope’s findings add to a bonanza of black hole data from the Laser Interferometer Gravitational-wave Observatory, or LIGO, and Europe’s VIRGO detector.

“Together with gravitational-wave observations, this marks the beginning of a new era in black hole astrophysics,” said lead study author Dimitrios Psaltis, a University of Arizona astronomer who recently finished his stint as the EHT collaboration’s project scientist.

And the EHT isn’t stopping with last year’s image. Just last month, the collaboration unveiled a “movie” that shows a wobbling pattern of emissions from the surroundings of M87’s black hole. The analysis of black hole dynamics over time, published in The Astrophysical Journal, was created by feeding more than a decade’s worth of observations into a computer model.

Eight observatories around the world contributed to the initial round of observations for the Event Horizon Telescope project. For the EHT’s next campaign in 2021, there’ll be three more observatories on the case, in Arizona, Greenland and France.

The added capacity should result in higher-fidelity images — not only of M87’s black hole, but also of Sagittarius A*, the supermassive black hole at the center of our own Milky Way galaxy.

Up-close views of black holes could well shine a light on another prediction made by general relativity, known as the no-hair theorem. This theorem states that the characteristics of black holes are completely determined by their mass, spin and electrical charge.

If the theorem is correct, all black holes with the same values for those three attributes would be identical to each other. Any other distinguishing characteristics for black holes and their history — their “hair,” metaphorically speaking — would disappear forever inside the black hole’s event horizon.

In a theoretical paper that was published months after the death of British physicist Stephen Hawking, he and three co-authors argued that black holes might be surrounded by a distinctive kind of “soft hair” that’s left behind as they evolve. This would have deep implications for general relativity, and for a long-running, almost metaphysical debate over what happens when something falls into a black hole.

Was Einstein right, or was Hawking? Thanks to gravitational-wave detectors and the Event Horizon Telescope, we could well find out.

Flash interactive: Putting Einstein to the test

Lessons learned from Einstein’s ‘Genius’

Geoffrey Rush as Einstein
An elderly Albert Einstein, played by Geoffrey Rush, blows out a candle on a birthday cake in the final episode of National Geographic Channel’s “Genius” TV series. (National Geographic Channel Photo)

Don’t expect to hear a lot about relativity in the final chapter of Albert Einstein’s life story, as told tonight in the season finale of National Geographic Channel’s “Genius” TV series.

But do expect to see a lot about the humanitarian – and all-too-human – side of the 20th century’s best-known scientist.

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Einstein’s love life vs. his love of physics

'Genius' TV show
Albert Einstein and his wife, Mileva Maric (played by Johnny Flynn and Samantha Colley) look over a scientific paper in “Genius,” a TV series on the National Geographic Channel. (NGC via YouTube)

National Geographic Channel’s “Genius” TV series on Albert Einstein spends almost as much time on the famous physicist’s love life as it does on his theory of relativity – and his most recent biographer, Walter Isaacson, says that’s just as it should be.

“In my biography, I begin and end by saying there’s a ‘unified field theory’ that connects Einstein’s personality with his physics, and the genius of the TV series ‘Genius’ is that it shows this,” said Isaacson, who has written biographies of Benjamin Franklin and Steve Jobs as well as “Einstein: His Life and Universe.”

Isaacson said the series’ fourth episode, airing tonight, illustrates that point. It focuses on Einstein’s “miracle year” of 1905, when he laid out not just one but four groundbreaking scientific papers, including the theory of special relativity.

But it also dwells on Einstein’s tempestuous relationship with his first wife, Serbian-born physicist Mileva Maric, who helped him with his math.

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‘Genius’ spices up Einstein’s tale for TV

Geoffrey Rush as Einstein
Geoffrey Rush, who plays the older Albert Einstein in “Genius,” re-enacts a cllassic picture of the world-famous physicist. (National Geographic Photo / Dusan Martincek)

There have been plenty of TV documentaries about Albert Einstein, but almost none of them begin with a political assassination and a sex scene. “Genius” does.

The 10-part docudrama series, premiering April 25 on the National Geographic Channel, goes where few accounts of the physicist’s life have gone before.

Executive producer Ron Howard told The Associated Press that the series’ eyebrow-raising first scenes “fulfilled the desire to announce to audiences right away that we weren’t approaching it in an entirely straightforward, traditional and academic way.”

“We were looking for the drama in the story and willing to deal with Einstein, warts and all,” Howard said.

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Are you getting paid more than Einstein?

Image: Albert Einstein
Albert Einstein works at the blackboard during a lecture in 1921. (F. Schmutzer via Wikipedia)

This week’s Parade magazine lets you compare your pay with the annual earnings of a Seattle bridge operator ($53,575) or a Baltimore street-corner astronomer ($6,423). But how does your salary stack up against what Albert Einstein or Marie Curie made back in the day?

Stephen Pritchard, a content marketer for a London-based job search site called Adzuna, calculated the inflation-adjusted salaries for Einstein, Curie and nine other famous scientists. The results suggest that Isaac Newton should have asked for a raise.

“it’s worth bearing in mind that these reported salaries come from different stages in the scientists’ careers,” Pritchard wrote in a blog posting. “Einstein’s genius was well-established when he arrived at Princeton University, for example, while Newton was almost 20 years away from publishing his theory on gravity. And of course, while it’s interesting to compare the salaries of some of history’s great scientists, stating how much money from the 17th century is worth in the 21st century has its problems.”

Check out the infographic on GeekWire.


General relativity gets a 100th birthday party

Image: Albert Einstein
Albert Einstein works at the blackboard during a lecture in Vienna in 1921. (F. Schmutzer via Wikipedia)

This week’s 100th anniversary of Albert Einstein’s general theory of relativity is a geeky cause for celebration, but what’s arguably the concept’s toughest test has just gotten under way.

General relativity was a follow-up to special relativity, Einstein’s big idea from a decade earlier. Back in 1905, he worked out a way to explain why the speed of light is constant, regardless of an observer’s point of view: It’s because space and time are not inflexible metrics, but interrelated dimensions that are measured differently depending on your perspective.

Special relativity explained a lot of the weirdness that physicists were puzzling over at the time, but the theory applied only to “special” conditions that didn’t involve acceleration – for example, how things fall in a gravitational field. On Nov. 25, 1915, Einstein laid out how the interplay of space and time gives rise to gravity and the fabric of the cosmos.

The theory passed its first big test in 1919, when observations during a total solar eclipse were found to be more consistent with Einstein’s view of gravity than with Isaac Newton’s. General relativity has been passing tests ever since. For example, if we didn’t take relativistic effects into account, our GPS readings would seem out of whack.

This week is prime time for centennial retrospectives on the theory and its implications. Here are a few to keep you entertained.

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