Black Hole Muse
Edges Of Our Knowledge
Reading through Stephen Hawking’s epic book ‘A brief history of time’, I was fascinated by the intricate concepts that describe the Universe we live in. I was also fascinated by the idea that there are limits to our knowledge. Which is something I had not spent too much time thinking about before. Consider how far we have come from the days of Galileo, Newton and even Einstein.
We have built up a generational knowledge base that we can now use to predict things in the future. Like your local weather, which now includes alerts for life threatening events. Or where planetary bodies like Pluto & Mercury are going to be based on orbital mechanics. Or when our own star will turn into a red giant. This vast knowledge base has allowed us to lead lives surrounded with technological innovations and with some certainty about the future. But there have always been limits to our knowledge.
“As the area of our knowledge grows, so too does the perimeter of our ignorance.” — NDT
Even if our theory makes concrete predictions, until those predictions can be verified by repeated experiments, we can’t accept them to be conclusive. As was the case with successfully detecting long hypothesized Gravitational Waves. Janna Levin’s book “Black Hole Blues and Other Songs From Outer Space” covers the behind the scenes scientific race to detect Gravitational Waves. This fantastic book got into details of how the scientific process works with its ups & downs— brilliant insights, interdisciplinary synergies, patience, luck and good old human frailties.
It’s good to remember that science is both — a body of knowledge and a process to fill gaps in our knowledge. That process isn’t perfect, but it’s the best tool we have to keep building up our knowledge base reliably.
Black holes turned out to be one of the topics for which we have gaps in our understanding. Predicted by Einstein’s equations and now proven to exist in multiple ways, our understanding of what lies beyond a certain point goes dark; just like the black holes themselves. Our breakthrough theories in physics — Relativity and Quantum Mechanics, fall short in explaining black holes completely. Both theoretical and experimental areas of research are racing to figure out what lies beyond the event horizon.
Black Holes have become our scientific and science fiction muse.
For now our understanding of their creation goes like this — when a massive star runs out of its fuel, it collapses under its own gravitational pull into an object of immense density. How dense? If Earth was to become a black hole, it would only be the size of a plum. That’s a tremendous amount of matter squeezed into a tiny space. We already know that mass can impact the space around it. Like our Sun bending the starlight of far away stars. Similarly, black hole’s mass causes the spacetime fabric to folds into itself.
I love how physicists think about them. Light itself cannot travel outward from this gravitational well. But it doesn’t mean it’s completely dark inside, because all the light trapped inside of a black hole would make it bright. Some Black Holes can last for trillions of years. But will eventually evaporate because of Hawking radiation.
Their uniqueness and weirdness doesn’t end there. Any matter falling into the Black hole, say an unlucky astronaut, will get “Spaghettified’’; i.e they will be squeezed & stretched vertically like a spaghetti. Black Hole sizes can vary widely — the biggest one is 66 Billion times the mass of our Sun. The smallest one we know is 3.8 times the mass of our Sun. There are few ways we know they can grow — by consuming more matter around them or merging with other black holes. All of the light we see coming from Black hole is actually coming from matter going around the black hole in a region known as the accretion disks. Most things in the Universe spin, so does the black hole. As the matter around black hole rotates and spirals down, it interacts with other matter and gives out a tremendous amount of energy.
Interestingly, most galaxies have supermassive black holes at their center. Our Milky Way galaxy has a supermassive black hole called Sagittarius A* (pronounced ey-star), and it’s 4 million times the Sun’s mass. More interestingly, we don’t fully understand how supermassive black holes get that big. It’s an active field of research.
These are unique and fascinating objects. But one theory suggests maybe they are a fundamental part of nature. The black holes we see are one way for nature to create them. Nature might have more fundamental ways of creating them. Maybe that’s how we end up unifying the two great theories in physics.
We look for every opportunity to study them. As light itself cannot escape from it, we have plenty of indirect ways of detecting them. From detecting the chaos it creates in matter around its event horizon to chirps it sends out during mergers in the form of Gravitational Waves.
Event Horizon Telescope (EHT)
EHT is a planet size telescope and an epitome of scientific collaboration. It is a network of eight radio telescopes spread across continents with a single purpose, capturing the first image of black hole. We know where to begin looking, the center of the galaxies, because this region has the most accumulation of stars and usually, an active supermassive black hole. The first target for EHT was a supermassive black hole within the center of the galaxy called M87.
These radio telescopes, that are spread across the earth, had to be precisely synchronized using atomic clocks, and their data eventually combined. Scientists then had to resolve this image using computer models and prove scientific theories matched observational reality. The final image was truly a triumph for humanity as we got to look at the first image of a black hole. The team continued improving its systems and operations to reveal first image of the black hole at the heart of our own Galaxy.
Laser Interferometer Gravitational-Wave Observatory (LIGO)
Following is conversation with Prof Debarati Chatterjee about key concepts needed to understand Gravitational Waves and construction of LIGO observatory in India.
Laser Interferometer Space Antenna (LISA)
In this conversation with Dr Oliver Jennrich, we cover his path to becoming a LISA study scientist, the need for a space based detector and collaborations needed for this project.
As we improve our understanding of one of the most mysterious objects in our Universe, it’s fascinating to see science make this progress in realtime. We learn as scientists themselves learn.
One of the great endeavors of humanity guarantees nothing, but only the logical & systematic march towards verifiable findings. Going from ideas in theorists’ minds to experimentalists’ empirical reality.
An interesting take on a topic that has been shrouded in mystery of its creation and existence..The Black Holes . Inadequate knowledge through theories of Relativity and Quantum Mechanics. But a plausible explanation of Stars collapsing into a dense mass called Black Hole justifies to some extent, more knowledge will be gained through various Telescopes studying Black Holes including LIGO’S .
An interesting read..keep them coming 👍