Professors, physics students, and black hole enthusiasts alike gathered for the third Natural Science and Mathematics Colloquium on Wednesday, Oct. 3. The lecture was titled, “Gravity’s Engines, or How Bubble Blowing Black Holes Rule Galaxies, Stars, and Life in the Cosmos,” and was hosted by Dr. Caleb Scharf, author of two books and director of the Columbia University Astrobiology center.
Students were excited by the lecture before it even began. “I’m excited to be here!” commented first-year Hannah Lewis. “I just really appreciate physics.”
Dr. Scharf began his lecture by commenting that science is all about stories, many of which are still being written. The story he had to tell was about black holes. “The story of black holes is one of the best stories of science.”
He started by bringing everyone back to the 1700s, in a church where a reverend named John Mitchell created the very first idea for a black hole. John Mitchell thought about the nature of light; he considered how stars could leave imprints of their properties and how light emitted contained information about its properties. Mitchell asked an important question: Could objects slow light down?
Unfortunately, despite the face that Mitchell just asked the proverbial million-dollar question, his ideas were forgotten about for 100 years. Dr. Scharf guessed as to why his ideas were forgotten – because people could not understand the importance of any of these “objects.” “If we can’t see these objects, “ Scharf imagined them asking, “why should we look for them?”
Chapter two of the story was brought up by Einstein. Einstein realized that problems could be solved if light’s speed never changed. He then came up with the idea of relativity. Light’s speed is fixed, but measurements of distance and time are flexible. He then wanted to include gravity in his theories, but it was a problem due to the fact that gravity was only known as a “mysterious force” in Newtonian terms. The gravity between two objects would change depending on the distance, but how would nature know that there was a distance between the two objects? The theories of Einstein and Newton did not mix, so Einstein decided to entirely disregard Newton and say that gravity was nothing but a “side effect.”
“Einstein was not a shrinking violet,” commented Dr. Scharf.
Scharf said to imagine a rubber sheet, and imagine dropping a ball on top of that rubber sheet. The sheet is space, and the way the ball sinks into the sheet is the effect mass has on space. Einstein used this idea to conclude that mass distorts space and gravity happens to move through the distortion.
But he had one more question: What happens to the space around the “ball?”
Chapter three of the story comes up when a German named Karl Shwaltz answers the question. He said that mass could be compressed so much that it would create a region so light – and everything else – couldn’t escape. While Einstein disagreed with Shwaltz, Shwaltz had actually come up with the first definition of a black hole. The space he described was called the “Event Horizon,” which is essentially the center of a black hole. Dr. Scharf described this area as a “tricky little place where everything vanishes.”
It took 50 more years but then “people finally convinced themselves these objects could exist,” said Scharf.
After Dr. Scharf finished the history lesson, he brought his lecture up to the more recently discovered facts about black holes.
The next chapters of the story, according to Dr. Scharf, are of the supermassive black holes. These black holes are 30 million times the mass of the sun and are the center of galaxies – including our own. These black holes can spin, and drag the fabric of space with them. “It’s like standing on a thick carpet and getting it yanked from under you.” They can also carry an electrical charge.
“A spinning, electrically charged black hole is a fearsome beast,” said Dr. Scharf.
He also commented that energy floods out of these black holes – subatomic particles forced out of the black hole before reaching event horizon. This conversion of mass to matter is the most efficient in the universe – 50 times better than nuclear fusion. This energy has an effect on the galaxies it pumps energy into; mostly, it prevents the atmosphere from cooling down, fewer stars are produced, and growth slows.
Since this has always been happening, it can be concluded that black holes play a big role in everything in the universe, and that supermassive black holes and galaxies have coevolved.
Lastly, Dr. Scharf showed a short animation of an immature star that might reach the Milky Way’s black hole in six months time, and thus make the black hole produce energy. This will not have the capacity to damage the Earth, but, “it will light up, and we will be able to watch what is going on for the first time in human history.”
A final remark was made by Dr. Scharf before dismissing the lecture, “There really are monsters under the bed – well, in the middle of the galaxy – and they are important.”
Students who attended the lecture left fascinated by the subject matter. As first-year Jacob Bernhardt remarked, “Black holes are awesome.”