John Wheeler’s famous comment “John Wheeler “Black holes have no hair” on Black Holes might have set the ball rolling that information within these infinitely densely packed invisible objects is lost forever. However, over the years the view about Black Holes is changing with significant contributions by scientists. Three laureates won the Nobel Prize for Physics in 2020 for their discoveries in explaining the most exotic phenomena in the Universe, Black Holes. This year, the Nobel Prize was awarded to Sir Roger Penrose (one-half) for his work on understanding mathematically that black holes are a direct consequence of Albert Einstein’s General Theory of Relativity and jointly to Reinhard Genzel and Andrea Ghez (other half) for their work on supermassive Black Hole Sagittarius A*.
Stephen Hawking is perhaps the most well known scientist whose contribution in understanding the mysteries behind this invisible objects is timeless. Black Holes; The BBC Reith Lectures, is a wonderful primer on understanding the working of Black Hole from a layman’s perspective. The book is based on two fifteen minutes talk by Stephen Hawking about his lifetime work on this subject with add on notes by David Shukman. Stephen’s work in understanding characteristics of Black Hole is of paramount importance today. His research brings a fresh perspective to the long-held view that no matter can escape black holes. Famous for espousing black holes to remit radiation aptly termed as Hawking radiation, understanding the workings of Black Holes could change our understanding of our Universe especially in the quantum mechanics. The book is fantastic assimilation of the scientist’s lectures on this subject. Pic Goodreads
# Understanding Black Holes
Black holes are known to record only mass, state of rotation and the electric charge. Black holes are formed when giant stars collapse under their mass after exhausting their nuclear fuel and compress to an infinitesimally single point. This point of singularity is what Stephen Hawking spent most of his time researching. The density of the black holes in unimaginably high that even light cannot escape it. The gravity of black holes sucks everything inside once an object crosses the event horizon and it is assumed that space and time do not exist at the center of a black hole.
Stars over their billions of years of existence, use the nuclear fusion process to convert hydrogen to helium to support itself from collapsing against its gravity. The fusion process is the prime source of energy in this world when one or more nuclei combine to form one or more different atoms along with the generation of subatomic particles. When the nuclear process is exhausted, the stars collapse under its gravity and contract to work white dwarfs and neutron stars. Based on the game-changing research by scientists S Chandrashekar and Lev Landau, the maximum mass of a white dwarf is 1.4 times the mass of the Sun. However, this doesn’t explain what happens to massive stars with mass greater than 1.4 times than that of our Sun at the end of their time. What lies ahead leads to the realms of Black Holes and Singularity where laws of physics don’t apply diverging from Einstein’s theory of general relativity. Ironically, Roger Penrose won the prize for his seminal work that proved Black Holes are a direct consequence of Albert Einstein’s general theory of relativity.
“John Wheeler coined the term Black Hole in 1967”
“Einstein himself did not believe that stars could collapse under their weight and in 1939 published a paper in the journal Annals of Mathematics titled On a Stationary System with Spherical Symmetry Consisting of Many Gravitating Masses wherein he discredited the existence of black holes. Stephen Hawking credits John Wheeler, an American scientist whose work in the late 1950 and 60’s emphasized their existence and importance within the cosmos. Roger Penrose, ground-breaking work which laid out the mathematical evidence towards Black Hole formation and his 1965 article on this topic remains according to the Nobel committee the most significant contribution to the general theory of relativity since Einstein.”
# Singularity, the beginnings of this Universe
“Black Holes are formed when extremely large stars collapse to form invisible dense objects, bringing us to the concept of singularity. Consider a star twice the mass of our Sun compressed to a very small size. The largest known black hole is 500 trillion km away, 40 billion km across which is 3 million times the size of the Earth but with a mass of 6.5 billion times of Earth. These are supersized black holes, where both Reinhard Genzel and Andrea Ghez jointly won the Nobel prize for their work on understanding the largest known Black Hole within our galaxy, Sagittarius A*of size four million times of that our Sun. Working for nearly three decades, their findings have helped in determining solid evidence of the presence of supermassive black hole at the center of our galaxy. Their breakthrough contribution lies in designing new tools, structuring new techniques to map with precision the movement of stars around the Black Hole laying down evidence of a super heavy invisible object pulling stars around itself at breath-taking speeds.”
Interestingly, today, scientists believe black holes are at the center of all galaxies within the Cosmos taking the number to billions. Read about other Nobel Prizes for 2020 here.
# Black Holes: The BBC Reith Lectures revisited; Event Horizon: Hotel California & You can never leave but you just might
Compare it as a metaphor to the Eagles evergreen song Hotel California “We are programmed to receive. You can check out any time you like, But you can never leave”
Black Holes that have event horizon are not visible while naked singularities are without one and visible. Event Horizon is a boundary around the back hole where the gravity is so high that it sucks anything within its presence, even photons. Once inside the event horizon, you can never leave. Hence black holes are not visible but can be indirectly detected through its pull-on neighboring celestial objects.
A fascinating read, Black Holes, a pocket-sized dynamo traces the evolution of the theoretical framework of Black Holes within the parlance of the scientific community backed by easy to understand examples. Examples of a canoe falling over the edge of Niagara fall akin to entering the event horizon and the causality between an increase in the area of the event horizon when additional matter enters the horizon and Sir Newton’s second law of thermodynamics of entropy, are winners simplifying a seemingly complex concept. However, the triumph of Hawking’s two lectures lies in the explanation on how information is preserved within the black holes. Recall that Heisenberg theory of uncertainty delves that in sub atomic states i.e. the quantum level its difficult to precisely predict both the speeds and positions of the particles. Yet knowing the Quantum State, one can predict with certain degree of accuracy both speeds and positions. Understanding gravitation as a weak force in our Universe could well be due to multiple dimensions, as proposed by Super String theory with gravity seeping into other dimensions is a thought provoking knowhow. Brian Greene, the well know Physicist is a huge advocate of this scientific reasoning.
Whether, Black Holes work as time warps sending matter to another dimension unknown hitherto to humans only time will tell but the recent award towards work related to Black Holes is a step in a forward direction. It’s a significant step to understand the origins of this Universe giving credence to multiverse theory and parallel universes. In a nutshell, Hawking’s Nobel Prize one day could be in practically proving that one can leave the black hole. The answer is how soon can this be done. Deciphering laws governing information within the black holes could lead to a framework which better fuses both the gravitational and quantum aspects of theory paving the way for buildup for a United Theory of laws governing physics.
Time is endless. There is no beginning of time and no end of time.