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Black Holes Explained

Black Holes Explained

Professor Alex Filippenko Ph.D.
University of California, Berkeley
Course No.  1841
Course No.  1841
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Course Overview

About This Course

12 lectures  |  30 minutes per lecture

Imagine a region in space where the force of gravity is so strong that nothing—not even light—can escape. A region with physical conditions so extreme that they have not yet been reproduced in any terrestrial laboratory. A region so dense that an object as tiny as a walnut would have the same mass as our entire planet.

This phenomenon—first formed in the equations of Einstein and popularized in the stories of science-fiction authors—is a black hole: one of the most exotic, mind-boggling, and profound subjects in astrophysics.

Black holes are at the heart of some of the most intriguing phenomena in the universe. Not only that, they are ideal gateways to fundamental and cutting-edge concepts in astronomy, including the following:

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Imagine a region in space where the force of gravity is so strong that nothing—not even light—can escape. A region with physical conditions so extreme that they have not yet been reproduced in any terrestrial laboratory. A region so dense that an object as tiny as a walnut would have the same mass as our entire planet.

This phenomenon—first formed in the equations of Einstein and popularized in the stories of science-fiction authors—is a black hole: one of the most exotic, mind-boggling, and profound subjects in astrophysics.

Black holes are at the heart of some of the most intriguing phenomena in the universe. Not only that, they are ideal gateways to fundamental and cutting-edge concepts in astronomy, including the following:

  • General relativity: Einstein's general theory of relativity provides the framework for understanding black holes, in which the warping of both space and time is so great that they are effectively cut off from the rest of the universe.
  • Monsters at the heart of galaxies: Detailed studies of the centers of galaxies reveal that supermassive black holes are common, with masses of millions to billions of suns. Nearly every large galaxy has one.
  • Wormholes: According to general relativity, black holes may be connected to passages through space-time known as wormholes. The jury is still out on whether they exist and whether they would allow time travel and trips to other universes.
  • Is the universe like a hologram? Quantum theory suggests that information is not lost inside a black hole but instead is encoded around it like a hologram—a phenomenon that may characterize the universe as a whole!

Indeed, the idea that the universe itself has properties similar to black holes shows that these objects play a pivotal role at all scales: from the truly cosmic to the subatomic realm, where theory suggests the existence of mini-black holes that may have been created in the aftermath of the big bang and that could be produced in the latest generation of particle accelerators.

Nearly everyone has heard of black holes, but few people outside of complex scientific fields understand their true nature and their implications for our universe. Black Holes Explained finally makes this awe-inspiring cosmological subject graspable, with 12 lavishly illustrated lectures by veteran Great Courses Professor Alex Filippenko, a distinguished astronomer and award-winning teacher at the University of California, Berkeley.

Travel into a Black Hole

No movie, novel, or other fictional treatment of black holes matches Professor Filippenko's absorbing presentation of the actual science behind these amazing objects. In Lectures 8 and 9 he uses computer simulations created by fellow astronomers to conduct a virtual tour around and into a supermassive black hole, and then through a wormhole to another universe. Among the features you investigate are these:

  • Einstein ring: As you approach a black hole, the starlight behind it spectacularly bends in a kaleidoscopic effect called gravitational lensing. This phenomenon can produce a series of halos known as Einstein rings.
  • Photon sphere: Closer to a black hole, you come to a zone where an object must orbit at the speed of light to avoid falling in. Here, light can move in circular orbits and, in principle, you can look forward and see the back of your head.
  • Event horizon: Continuing your plunge, you reach a boundary called the event horizon. Once you cross it, you can't return. Anyone watching from outside sees time come to a standstill, as you appear to stop and motionlessly fade from view.
  • Singularity: After crossing the event horizon, you are only a minute away from the singularity, the hypothetical point of infinite density. Powerful tidal forces squeeze and stretch your body, until you are ultimately crushed to oblivion.

Mission Invisible

Recently elected to the prestigious National Academy of Sciences, Dr. Filippenko has devoted much of his research career to black holes, discovering some of the best evidence for the existence of stellar-mass black holes in the Milky Way Galaxy, and participating in studies of supermassive black holes using the Hubble Space Telescope.

Drawing on extensive graphics, including hundreds of stunning astronomical images, Dr. Filippenko shows how scientists have been able to read the evidence to surmise a great deal about objects that are inherently invisible. Among the most dramatic clues are high-energy beams of radiation that were first detected by spy satellites in the 1960s. These powerful "gamma-ray bursts" were long a mystery, but they are now thought to be the dying gasps of massive stars in distant galaxies, collapsing to form black holes.

Dr. Filippenko also dispels several myths about black holes, such as that they are "cosmic vacuum cleaners," drawing in matter from afar with irresistible force. In fact, if the sun were compressed to form a black hole, there would be no effect on the orbits of the planets. Similarly, fears that mini-black holes created by particle accelerators will grow and devour the Earth have no basis in physics.

In popular usage, a black hole is a place of utter emptiness. But in this engaging course, you learn about how there is much more to them than that. Astronomers have brought black holes out of the shadows to reveal that they are a widespread and vital phenomenon in the universe with unexpected implications for all scales of reality. Black holes are intriguingly counterintuitive, gratifyingly comprehensible, and surprisingly relevant to our overall understanding of the universe—as you will discover in Black Holes Explained.

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12 Lectures
  • 1
    A General Introduction to Black Holes
    Widely featured in novels, movies, and other media, black holes are not just entertaining plot devices, they're real. Learn how the idea of black holes was proposed more than two centuries ago, and how more recently Einstein's general theory of relativity gave a firm theoretical basis for them. x
  • 2
    The Violent Deaths of Massive Stars
    Discover how black holes can form from stars that are much more massive than the sun. After exhausting their nuclear fuel, these behemoths end in a colossal explosion called a supernova, leaving behind a superdense neutron star, or in some cases something even denser: a black hole. x
  • 3
    Gamma-Ray Bursts—The Birth of Black Holes
    Trace the story of gamma-ray bursts. Long a mystery, these intense eruptions of high-energy radiation from random spots in the sky are now thought to be associated with the formation of black holes in distant galaxies. Their visibility from so far away means they are truly titanic explosions. x
  • 4
    Searching for Stellar-Mass Black Holes
    If black holes emit no light, how are they detected? Investigate the different clues that establish strong evidence for black holes. For example, a star orbiting an unseen object that exceeds the 3-solar-mass limit for neutron stars is probably circling a black hole. x
  • 5
    Monster of the Milky Way and Other Galaxies
    This lecture presents the most compelling evidence to date for black holes—found in the core of most galaxies. There, stars and gas clouds typically orbit at high speeds, signaling the presence of a central, supermassive black hole, millions to billions of times the mass of the sun. x
  • 6
    Quasars—Feasting Supermassive Black Holes
    Quasars are another astronomical mystery explained by black holes. Explore the history of these star-like objects that long baffled astronomers, until observers realized they were seeing matter falling into supermassive black holes during the early era of galaxy formation. x
  • 7
    Gravitational Waves—Ripples in Space-Time
    Gravity waves are an unexplored new window for studies of black holes. Learn how these hard-to-detect vibrations are the predicted ripples in the fabric of space-time that should result from violent phenomena such as the merging of two black holes. x
  • 8
    The Wildest Ride in the Universe
    What happens if you fall into a black hole? Take a wild ride into the supermassive black hole at the center of the Milky Way Galaxy with a vivid computer simulation showing the strange effects you would experience before being crushed to incredible density. x
  • 9
    Shortcuts through the Universe and Beyond?
    Mathematically, black holes seem to connect our universe with others through a gateway called an Einstein-Rosen bridge—nicknamed a wormhole by physicist John Wheeler, who also coined the term black hole. See a computer simulation of what passage through a wormhole would be like. x
  • 10
    Stephen Hawking and Black Hole Evaporation
    Learn why black holes may not be completely black. In 1975, physicist Stephen Hawking showed that they can evaporate via a quantum tunneling process, giving off a slow trickle of quantum particles before eventually ending in an explosion of gamma rays. x
  • 11
    Black Holes and the Holographic Universe
    The "no-hair" theorem says that black holes are utterly simple and preserve almost no information about what went into them. Discover why some physicists believe that the supposedly lost information is contained just outside the black hole in a form that resembles a hologram—and that the universe as a whole may display the same property. x
  • 12
    Black Holes and the Large Hadron Collider
    Professor Filippenko closes by looking at the possibility that a new particle accelerator called the Large Hadron Collider will produce microscopic black holes. Discover why there is no danger that they will devour the Earth, and why there is no risk from any known black holes in space. x

Lecture Titles

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Alex Filippenko
Ph.D. Alex Filippenko
University of California, Berkeley

Dr. Alex Filippenko is Professor of Astronomy and the Richard and Rhoda Goldman Distinguished Professor in the Physical Sciences at the University of California, Berkeley. He earned his B.A. in Physics from the University of California, Santa Barbara, and his Ph.D. in Astronomy from the California Institute of Technology.

Dr. Filippenko's research accomplishments, documented in more than 500 scientific publications and 600 abstracts and astronomical circulars, are among the most highly cited in the world. Science magazine credited two international teams of astronomers (on which he was the only coauthor contributing to both teams) with the top "Science Breakthrough of 1998" for research on exploding stars (supernovae), which shows that the universe is expanding at an accelerating rate, propelled by mysterious "dark energy." Professor Filippenko received a share of the 2007 Gruber Cosmology Prize for this discovery, work that went on to receive the 2011 Nobel Prize in Physics. Professor Filippenko also leads the world's most successful robotic search for exploding stars.

Dr. Filippenko was elected in 2009 to the National Academy of Sciences, one of the highest honors accorded to a U.S. scientist. He has also been recognized with several major awards, including the 2010 Richard H. Emmons Award for excellence in the teaching of college-level introductory astronomy for non-science majors from the Astronomical Society of the Pacific, the 2007 Richtmyer Memorial Award of the American Association of Physics Teachers, the 1997 Robert M. Petrie Prize of the Canadian Astronomical Society, and the 1992 Newton Lacy Pierce Prize of the American Astronomical Society. He was a Guggenheim Fellow in 2001 and a Phi Beta Kappa Visiting Scholar in 2002.

In 2006, he was honored nationally as the "Outstanding Doctoral and Research Universities Professor of the Year" by the Carnegie Foundation for the Advancement of Teaching and the Council for Advancement and Support of Education.

At UC Berkeley, Dr. Filippenko's teaching awards include the Donald S. Noyce Prize for Excellence in Undergraduate Teaching in the Physical Sciences and the Distinguished Teaching Award. He was also voted the Best Professor on Campus nine times in student polls.

Dr. Filippenko is coauthor of The Cosmos: Astronomy in the New Millennium, now in its 4th edition (2013), and winner of the 2001 Texty Excellence Award for best new textbook in the physical sciences. He has played a prominent role in numerous television documentaries, including about 40 episodes spanning six seasons of The Universe on The History Channel.

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Rated 4.7 out of 5 by 79 reviewers.
Rated 5 out of 5 by True to Its Title The course title is Black Holes Explained and the lectures deliver that. Black Holes Explained provides a conceptual understanding of how black holes likely form, what their properties are and how they interact with the rest of the cosmos. The student should keep in mind that much of the explanation is based on theoretical projections not all of which have been or may ever be verified with data. Dr. Filippenko does point this out, but the student should take note. The course is largely conceptual with few equations or mathematics. This will appeal to the layperson. But the conceptual discussion has sufficient depth that those with a scientific bent will also gain much from this course. The bibliography and websites contained in the course guide provide opportunity for the student to explore beyond the lectures to whatever depth they seek. Dr. Filippenko is a very good lecturer. He is enthusiastic, energetic and knowledgeable. He clearly enjoys being a bit of a showman. He goes to great lengths to try to simplify his explanations using analogies a lay person can relate to. He appropriately uses voice inflection and body language to emphasize points. He cracks a lot of corny jokes, a few of which are funny, but many seemed aimed at high school or even junior high students. He tends to overuse popular cartoons and other such caricatures of black holes but in between explanations of demanding concepts these diversions give one's mind a break. He also goes to great lengths at multiple times to explain why we are in no real danger from black holes swallowing us up; not something that has kept me up at night but he seems to think people are concerned about this. I have a physics (not astrophysics) background yet I found many things in this course that were new and fascinating. For example, short duration Gamma Ray Burst signify the birth of a black hole, neutron stars must exceed 3 solar masses to collapse to a black hole, black holes at the center of galaxies are supermassive and the size of the "bulge" in a galaxy's center is proportional to the black hole mass, quasars only exist in the far reaches of the universe and thus are phenomena from the early universe, the merger of black holes and/or neutron stars with themselves or with each other should result in gravitation waves providing insight to quantum gravity, and Hawking radiation results when particle pairs separate at an event horizon leading ultimately to the evaporation of the black hole. The debate between Leonard Susskind (and others) and Stephen Hawking about whether or not information is lost when particles enter a black hole is fascinating. Perhaps its not quite up there with the Bohr-Einstein debates in terms of drama and impact, but it is another example of the philosophical disagreements in theoretical physics. Lectures 9, 10, and 11 which highlight the Susskind-Hawking debates are technically and conceptually the most challenging but Dr. Fillipenko makes them understandable. The accompanying course guide is excellent. The lecture summaries capture most of the key points from the lectures. The glossary and bibliography/websites are extensive. The timeline of discovery and the biographical notes of the principal scientists both add value to the guide. For those of us who are more mathematically inclined, a relevant equations to each lecture section, ala in Dr. Whittle's Cosmology course, would have been a welcome, nice to have, addition. Other than a bit of an overdose of cornball jokes and popular culture items, my only criticism of this 2009 course is that a few things are dated. For example, while Lecture 8, "The Wildest Ride" spent an entire lecture explaining what would happen should we fall in a black hole i.e. "spaghettification". Since then a new, equally plausible theory has emerged that proposes that we would incinerate at the event horizon as we fell into the hole. Neither scenario is cheery. The other, very recent (March 2014), news is that the BICEP-2 detector in Antarctica does seem to have detected gravitation waves, though this awaits confirmation. All in all, I would highly recommend this course to anyone interested in learning about black holes, whether one's background is in science or not. June 17, 2014
Rated 4 out of 5 by Zard Review of Black Holes OK, I tried. I am a student of history by inclination, choice and passion but I do have an interest in Astronomy. I have no training in the sciences but I do enjoy reading about Astronomy, Paleontology, Archeology and a few other subjects but no formal training and again, history is my passion. I bought this course because I am fascinated about Black Holes and I enjoyed the lecture and I REALLY ENJOYED Professor Alex Filippenko. He loves this subject and passion for it is a mild description of the intensity of his loving of it. He is engaging, interesting, passionate, funny and has great jokes, cartoons and graphics. The short comings are all on me. As much as he tried to keep it simple it is a complicated subject. I did fine with the first 6 of 12 lectures but then lost it in the next 5 lectures but enjoyed the last lecture. To put it mildly you have to stay focused on the lectures and cannot wander for a moment. But even with that it got a little too deep for me. That is not his fault or the subjects but mine, I am a lightweight when it comes to this stuff. Still I have no regrets in buying or watching this course and will re-watch it over the years. There is a lot in it. It is not quite the same thing but somewhat similar to reading a history book on a subject that I am really interested in but the writer goes into great detail to make and/or prove their points. I am interested in the view at 20,000 feet, not at ground level. I want the gist of it, the overall picture, the broad brushstrokes, not the details. I leave that to the historians. I am not a historian. Just an avid fan of history. Bottom line, I liked the course and it stretched me. That is OK but I got a little lost. Not the fault of the teacher, just me. I would recommend the course but with reservations based on my shortcomings. August 7, 2014
Rated 3 out of 5 by Not for everyone Contrary to what most of the other reviewers say, I had to force myself to continue watching this course. I'm sure it was a case of my interest level. Even though I have a science background I found this course much, much too detailed for my taste. Of course, this may be exactly what you want. In addition to my getting bogged down with the detail, I had a problem with Professor Filippenko's delivery -- he never moved from behind his standing desk and even he commented frequently on his bad jokes. However, it was clear that he loves his topic. The graphics in the course were very good and the almost 12 pages of the Glossary definitely helped me in understanding all that Professor Filippenko was describing. June 4, 2014
Rated 5 out of 5 by Black Holes Explained Enjoyed the style and subject matter of the course. Dr Filipenko is a exciting instructor September 5, 2013
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