Black holes are nothing to be afraid of

By Jon Roe

The recent completion of the Large Hadron Collider on the French-Swiss border near Geneva, Switzerland has seeped the fear of black holes from the minds of fictional space explorers into the public consciousness. This is because the high speed particle collisions in the LHC may produce tiny black holes.

These and other black holes were the subject of Tuesday’s Science Cafe, a monthly event held jointly by the University of Calgary and the Telus World of Science.

Science Cafe features presentations and discussion by experts on hot scientific topics. Dr. Warren Anderson, a visiting assistant professor from the department of physics at the University of Wisconsin-Milwaukee, and Dr. David Hobill, a U of C department of physics associate professor, held court this month.

“Are they cosmic menaces?” asked Telus World of Science astronomy producer Alan Dyer, who emceed the event. “Will they devour the galaxy? Will they devour the Earth? We’ll find out.”

The existence of black holes has been theorized since the late 1700s, when English geologist John Mitchell realized that if enough matter was concentrated in an object, light wouldn’t be able to escape the object’s orbit.

Mitchell called these objects “Dark Stars.” Later theories of gravity by Isaac Newton and Albert Einstein predicted the existence of black holes — a term popularized by a student of Einstein’s, John Wheeler.

Gravity, to Einstein, is the geometry of spacetime and black holes are like dimples in spacetime, producing extreme curvature.

“It’s sort of like the soft mattress effect,” Hobill explained.

Black holes have not been directly measured or observed, but their existence has been predicted by many different theories of gravity.

“All we can use is indirect evidence,” said Hobill.

The speed stars move around a very small object observed at the centre of our galaxy, the Milky Way, for example. The object must be heavy, up to a million times the mass of our sun, Anderson said, because of how fast the stars move, and it must be small because the stars get fairly close.

“What it is, we really don’t know yet,” said Anderson.

Einstein believed that black holes emit gravity waves and the Laser Interferometer Space Antenna satellite will detect and observe those waves, helping shed light on black holes and testing Einstein’s theory of gravity. The satellite will be launched, at the earliest, between 2018 and 2020.

Hobill and Anderson answered questions from the packed house at the Ironwood Stage and Grill in Inglewood and discussed topics ranging from science fiction to the big bang, to the LHC.

The LHC has drawn public concern since its completion last year because it may create tiny black holes. These black holes likely wouldn’t be produced under Einstein’s theory of gravity, but if the LHC did produce a black hole, it would only last for nanoseconds and would evaporate quickly.

“That would be very exciting,” said Hobill, adding that the scientists at the LHC would then look for particles the black hole would throw off as it evaporated.

These black holes are nothing to be feared, though, assured Anderson.

He then did some crude calculations, exploring what would happen if the black hole didn’t immediately evaporate. If the smallest black hole produced by Einstein’s theory was created by the LHC, it would sink to the centre of the Earth and bounce back and forth, absorbing any matter it came into contact with. But because this black hole is so small, and atoms are mostly just empty space, he calculated it would take 10 million times the age of the universe to grow to one kilogram in mass.

“We’ve covered all our bases, we don’t have to be worried about being swallowed up by a black hole,” Anderson said.

Tuesday’s event was the last Science Cafe of the 2008-09 season and was part of Calgary’s participation in celebrating 2009 as the international year of astronomy. Science Cafe will start again in September.

Leave a comment