Chinmay's Annotated Bibliography
Source 1: British Broadcasting Corporation (BBC)
Citation of Source 1:
Ball, Philip (Dec 3, 2013). Could we harness energy from black holes? Retrieved From: <http://www.bbc.com/future/story/20131203- could-black-holes-provide-energy>
Notes of Source 1:
In this article, Ball Philip discusses the potential of humans being able to harness renewable energy from black holes. He also gives an in-depth analysis of how black holes function, and some brief but important history. Black holes are stars that have burnt out and collapsed under their own gravity. They collapse onto an infinitesimally small point in space. This is often called a singularity. In the 1970s Stephen Hawking showed that contrary to popular belief, black holes are not an infinite energy sink (infinite absorption of energy), they simply reconvert all the energy that they take in and emit it as Hawking radiation. Hawking radiation is a type of black body radiation. Black holes radiate their entire mass away (back into the universe), keeping the energy of the universe constant. Because of this newfound knowledge scientists now view black holes as energy sources instead of energy drains. This has led to them creating theories as to how we could withdraw and harness the energy released by black holes. The first method was theorized in 1983 by George Unruh and Robert Wald. They proposed lowering an energy collection device (a box) to a location close to the black hole’s event horizon. After the device was filled with energy they would pull it back up again. In principle more energy can be extracted per second from a single black hole than is radiated from all the ordinary stars in the observable universe. However, this process had many problems. Some of them were: rope stretching due to massive gravity, rope disintegrating, and the rope being able to support very little mass other than its own. The second method proposed in 1994 by Albion Lawrence and Emil Martinec tried to get rid of many of the problems which plagued the first method by trying to draw energy from the ropes itself. Their idea was to use ropes/strings and let Hawking radiation run up them like wick of an oil lamp. However this process is much slower and much less efficient.
Source 2: Universe Today
Citation of Source 2:
Anderson, Ryan (November 19, 2009). Black Hole Drive could power future Starships. Retrieved From: <http://www.universetoday.com /45571/black-hole-drive-could-power-future-starships/>
Notes of the Source 2:
In this article, Ryan Anderson discusses origins of black holes, the energy type released from black holes and their potential as an energy source. Black holes are created when large stars collapse on themselves. In recent time, we have discovered that black holes are not really black; they give of “Hawking radiation”. This means they lose energy, and therefore mass over time. The process is unique, because very large black holes release energy very slowly, while very small black holes quickly convert mass into energy – a massive amount of energy. The author discusses the work of two researchers – Lois Crane and Shawn Westmoreland. They worked out the mathematics and concluded that there is a “sweet spot” in terms of black hole size vs their radiation output. They also proposed a process to create this “sweet spot” black holes through a massive spherical gamma-ray laser in space powered by thousands of square kilometers of solar panels. The basic process would be a massive built up of energy and then a virtually instantaneous release of energy into a single point creating an artificial black hole. To harness the energy and convert it into a useable form the use of a parabolic electron – gas mirror is proposed. Theoretically speaking the energy output would not only be purely renewable energy, and the energy output could be applied to propel starships at near-light speed.
Source 3: About Education
Citation of Source 3:
Jones, Zimmerman, Andrew (2010). What is Hawking Radiation? Retrieved From: < http://physics.about.com/od/astronomy/ f/hawkrad.htm>
Notes of the Source 3:
In this article, by Andrew Zimmerman Jones, author of String Theory for Dummies, Zimmerman provides an in-depth explanation of Hawking Radiation. Before 1972, a black hole was considered to energy sink, literally absorbing all matter and energy it happened to catch in its gravitational field. However, in 1972 Israeli physicist Jacob Bekenstein suggested that black holes would have a well-defined entropy, similar to thermodynamics and heat exchange. Except in this case mass and energy were being exchanged. This would later be called black hole thermodynamics. In 1974, Stephen Hawking famously worked out the exact model for the black body emissions created by Black Holes. Hawking theorized that due to the vast amounts of energy fluctuations in the black holes event horizon; virtual particles would be generated. Virtual particles only exist for a limited time. They are predicted by the equations governing quantum physics. In specific, black holes cause the generations of particle-antiparticle pairs of virtual particles near the event horizon. Something spectacular then happens, the anti-particle falls into the black hole and the positive energy particle escapes, before the two have an opportunity to annihilate each other like in common scenarios. Since the particle that falls into the black hole has negative energy, the black hole loses mass. This is because of Einstein’s theory of relativity which states that E = mc2. This means that the black holes is losing mass. It will continue to lose mass in the form of black body radiation (energy) until it uses up all the mass it has. This theory also ensured that the total energy in the universe stayed constant. Using Stephen hawking’s theory it was found that smaller black holes emit more energy than they absorb, which results in them losing net mass. It was also found that larger black holes, specifically those which were larger than one solar mass, absorb more mass and energy than they emit through Hawking radiation.
Source 4: 123HelpMe
Citation of Source 4:
123HelpMe.com. "Black Holes: The Power Source for Future Space Travel?" Retrieved From: <http://www.123helpme.com/view.asp? id=43865>
Notes of the Source 4:
Black Holes generate energy in a number of different ways, therefore their energy can be collected in a number of different ways. Black holes are formed by matter being crushed within a certain radius (called the event horizon). Currently, scientists are optimistic about the human capture of energy of three types of black holes: Schwarzschild black holes, Newmann black holes and primordial black holes. Schwarzschild and Newmann black holes have extremely large masses, from a couple of times our Sun’s mass to several billion times more massive. However, primordial black holes are much smaller in theory and have been theorized to come into existence not due to star death like the other two, but due to the creation of the big bang. Newmann and some primordial black holes have large ellipsoids around them called the ergosphere. Once matter enters the ergoshpere it begins to rotate along with the rotation of the black holes. This creates the accretion disc. As the matter get close to the center of the black hole, it begins moving faster and faster. All of the rotation causes a build-up of static electricity, which due to the moving electric field creates a powerful magnetic field. Then the matter is pulled towards the poles and shot away from it at speeds of 90% or greater. Because of the high degree of rotation, a lot of heat through friction is generated. When objects heat up they emit radiation. Thus, a theory of energy generation is to have small primordial black holes completely covered by a sphere which is coated with energy absorbing material on the inside. Then the energy could be drawn out through wires. An added advantage of this method is great control over the food source of the black holes, which could include human garbage. Jets around the magnetic field of a black holes could also be a possible power source. This is because these jets emit a lot of high-energy radiation, including X-rays and sometimes even gamma-rays, the highest form of energy. If we could develop solar panels for these types of rays, this will become a very effective method of collecting energy from black holes. The ideal black hole for energy capture is a primordial, since black holes whose masses are greater than the mass of the earth, generate less energy than the background energy (cosmic radiation) of the universe, meaning they are energy sinks. That is, they emit energy at a slower rate than they absorb it. Therefore we would need a small primordial black hole to generate energy. One day we may be able to use particle accelerators to create black holes right here on earth.
Source 5: Mysteries of the Universe: Black Holes
Citation of Source 5:
Whiting, Jim. (2011). Mysteries of the universe: Black Holes. New York, USA. Publisher: Creative Education. Book.
Notes of the Source 5:
Black holes present a very unique problem to the physics community – they can’t be observed. To see anything, we need light. But the gravitational field near black holes is so strong that nothing, not even light can escape. Light is the fastest thing in the universe; and black holes slow down light by an immense amount of gravity. To understand this, we need an understanding of escape velocity. Escape velocity is the speed that something needs to travel at to escape the gravity of an object. Now, the interesting part is that you need more energy to escape from a lower orbit than a higher orbit. In terms of black holes, the point where light can no longer escape is called the event horizon. Before Einstein’s discovery of the theory of relativity, research into black holes was almost nil. Research started soon afterwards, but it only truly accelerated in 1971, when astronomers discovered Cygnus X-1. Cygnus X-1 is the first black hole to be properly researched and understood. The reason is because it was originally part of a two-star system, but by 1971 it had become a black hole and was ripping trails of hot gas away from its companion star HDE 226. The way scientists discovered this was because as the gas trail gets closer and closer to the event horizon of the black hole it becomes hotter and hotter, eventually becoming hot enough to generate X-Rays. A major problem that some scientists still have with black holes are its limited amount of properties. A black hole has no distinguishing properties of objects like their shape and chemical composition. Its only properties are the black holes mass, its speed of spinning and its electrical charge. Quasars are an area of continuing research and are thought to be remnants of distant and highly active galaxies and that they contain super massive black holes.
Source 6: Death by Black Hole
Citation of Source 6:
DeGrasse, Tyson. (2007). Galactic Engines. Death by Black Hole and Other Cosmic Quandaries. (pg. 268-274). New York, USA. Publisher: Norton. Book.
Notes of the Source 6:
Galaxies are in essence the fundamental organization of visible matter in the universe. There are many different types of galaxies. The can be categorized into three broad categories – spiral, elliptical or irregular. Many also have different constituents. Some have supermassive centers in their centers while others do not. Active galaxies emit an unusual amount of energy in one or more bands of light from the galaxy’s center. The royalty of active galaxies are quasars. Quasars were discovered in the early 1960s and much research work still needs to be done to unlock their secrets. Some are thousands of times as bright as the Milky Way, but their energy hails from a region smaller than the solar system. As gaseous matter funnels towards a black hole, the matter heats up and radiates incredible amounts of energy, mainly in the form of energy waves, before it descends into the event horizon of a black hole. But why do the gases radiate energy. The answer lies in Einstein’s theory of relativity. When objects fall, they gain transfer their potential energy into kinetic energy. However, when an object cannot move faster due to a certain limit imposed upon it, it starts converting the excess energy into heat and light energy. A good example, is a meteor falling in the sky. Because, a meteor cannot gain more than its terminal velocity (air resistance), it heats up. Likewise, gases cannot accelerate beyond the speed of light when being sucked into the black hole and thus convert their energy into heat (in the form of radiation, thus light) energy. When this is done on a large scale near a super massive black hole a quasar is formed. Funneling gas normally creates an opaque rotating disk before it descends through the event horizon. Thus, all black holes have spin. Quasars are thus, the ultimate royalty of active galaxies.
Source 7: Gravity's Fatal Attraction
Citation of Source 7:
Begelman, Mitchell. (2010). Gravity Triumphant. Gravity’s Fatal Attraction: Black Holes in the Universe. (pg. 1-22). New York, USA. Publisher: Cambridge University Press. Book..
Notes of the Source 7:
Gravity is the force of mutual attraction between all bodies that have mass, at least according to Newton. However, in objects like black holes, even light is attracted. Thus, even light an object without mass is effected by gravity. This is because Newton’s equations are not applicable in situations where gravitational fields are so strong. In these situations the general relativity must be used. When objects are moving at or near the speed of light, Newton’s theory of universal gravitation no longer works. Gravitational fields are manifestations of the curvature of space itself (also sometimes called space-time). Masses do not exert a gravitational pull, deflecting bodies from a straight path in Einstein’s theory of general relativity. Rather, the presence of an object with mass distorts space-time. Bodies moving through space follow the straightest path possible through space and time. So when space time is curved, the paths taken by objects become curved as well. In a simple sentence it can be summed up as – space tells matter how to move, matter tells space how to curve. Einstein’s contribution to physics is immense because of his theory of general relativity, because it required tremendous creativity to create a solution for problems that barely existed at that point in time. Black holes represent the ultimate triumph of gravity over all other forces. Gravity in a black hole is so strong that it can successfully pull light into itself, light being the fastest object in the universe.