The Big Bang Theory: A history of the Universe starting from a singularity and expanding ever since. Credit: grandunificationtheory.com
How was our Universe created? How did it come to be the seemingly infinite place we know of today? And what will become of it, ages from now? These are the questions that have been puzzling philosophers and scholars since the beginning the time, and led to some pretty wild and interesting theories. Today, the consensus among scientists, astronomers and cosmologists is that the Universe as we know it was created in a massive explosion that not only created the majority of matter, but the physical laws that govern our ever-expanding cosmos. This is known as The Big Bang Theory.
For almost a century, the term has been bandied about by scholars and non-scholars alike. This should come as no surprise, seeing as how it is the most accepted theory of our origins. But what exactly does it mean? How was our Universe conceived in a massive explosion, what proof is there of this, and what does the theory say about the long-term projections for our Universe?
The basics of the Big Bang theory are fairly simple. In short, the Big Bang hypothesis states that all of the current and past matter in the Universe came into existence at the same time, roughly 13.8 billion years ago. At this time, all matter was compacted into a very small ball with infinite density and intense heat called a Singularity. Suddenly, the Singularity began expanding, and the universe as we know it began.
In science fiction, wormholes are a method often used to travel great distances across space. Are these magic bridges really possible?
With all my enthusiasm for humanity’s future in space, there’s one glaring problem. We’re soft meat bags of mostly water, and those other stars are really really far away. Even with the most optimistic spaceflight technologies we can imagine, we’re never going to reach another star in a human lifetime.
Reality tells us that even the most nearby stars are incomprehensibly far away, and would require vast amounts of energy or time to make the journey. Reality says that we’d need a ship that can somehow last for hundreds or thousands of years, while generation after generation of astronauts are born, live their lives and die in transit to another star.
Science fiction, on the other hand, woos us with its beguiling methods of advanced propulsion. Crank up the warp drive and watch the stars streak past us, making a journey to Alpha Centauri as quick as a pleasure cruise.
You know what’s even easier? A wormhole; a magical gateway that connects two points in space and time with one another. Just align the chevrons to dial in your destination, wait for the stargate to stabilize and then just walk… walk! to your destination half a galaxy away.
Yeah, that would be really nice. Someone should really get around to inventing these wormholes, ushering in a bold new future of intergalactic speedwalking. What are wormholes, exactly, and how soon until I get to use one?.
A wormhole, also known as an Einstein-Rosen bridge is a theoretical method of folding space and time so that you could connect two places in space together. You could then travel instantaneously from one place to another.
We’ll use that classic demonstration from the movie Interstellar, where you draw a line from two points, on a piece of paper and then fold the paper over and jab your pencil through to shorten the journey. That works great on paper, but is this actual physics?
As Einstein taught us, gravity isn’t a force that pulls matter like magnetism, it’s actually a warping of spacetime. The Moon thinks it’s just following a straight line through space, but it’s actually following the warped path created by the Earth’s gravity.
And so, according to Einstein and physicist Nathan Rosen, you could tangle up spacetime so tightly that two points share the same physical location. If you could then keep the whole thing stable, you could carefully separate the two regions of spacetime so they’re still the same location, but separated by whatever distance you like.
Climb down the gravitational well of one side of the wormhole, and then instantaneously appear at the other location. Millions or billions of light-years away. While wormholes are theoretically possible to create, they’re practically impossible from what we currently understand.
Albert Einstein, pictured in 1953. Photograph: Ruth Orkin/Hulton Archive/Getty Images Ruth Orkin/Getty
The first big problem is that wormholes aren’t traversable according to General Relativity. So keep this in mind; the physics that predicts these things, prohibits them from being used as a method of transportation. That’s a pretty serious strike against them.
Second, even if wormholes can be created, they’d be completely unstable, collapsing instantly after their formation. If you tried to walk into one end, you might as well be walking into a black hole.
Third, even if they are traversable, and can be kept stable, the moment any material tried to pass through – even photons of light – that would make them collapse.
There’s a glimmer of hope, though, because physicists still haven’t figured out how to unify gravity and quantum mechanics.
This means that the Universe itself might know things about wormholes that we don’t understand yet. It’s possible that they were created naturally as part of the Big Bang, when the spacetime of the entire Universe was tangled up in a singularity.
Astronomers have actually proposed searching for wormholes in space by looking for how their gravity distorts the light from stars behind them. None have turned up yet.
One possibility is that wormholes appear naturally like the virtual particles that we know exist. Except these would be incomprehensibly small, on the Planck scale. You’re going to need a smaller spacecraft.
Artist illustration of a spacecraft passing through a wormhole to a distant galaxy. Image credit: NASA.
One of the most fascinating implications of wormholes is that they could allow you to actually travel in time.
Here’s how it works. First, create a wormhole in the lab. Then take one end of the wormhole, put it on a spacecraft and fly away at a significant percentage of the speed of light, so that time dilation takes effect.
For the people on the spacecraft, just a few years will have occurred, while it could have been hundreds or even thousands for the folks back on Earth. Assuming you could keep the wormhole stable, open and traversable, then traveling through it would be interesting.
If you passed in one direction, you’d not only move the distance between the wormholes, but you’d also be transported to the time that the wormhole is experiencing. Go one direction and you move forward in time, go the other way: backwards in time.
Some physicists, like Leonard Susskind think this wouldn’t work because this would violate two of physics most fundamental principles: local energy conservation and the energy-time uncertainty principle.
Unfortunately, it really seems like wormholes will need to remain in the realm of science fiction for the foreseeable future, and maybe forever. Even if it’s possible to create wormholes, then you’ve got the keep them stable and open, and then you’ve got to figure out how to allow matter into them without collapsing. Still, if we could figure it out, that’d make space travel very convenient indeed.
If you could set up two ends of a wormhole to anywhere in the Universe, where would they be? Tell us your ideas in the comments below.
In honor of Dr. Stephen Hawking, the COSMOS center will be creating the most detailed 3D mapping effort of the Universe to date. Credit: BBC, Illus.: T.Reyes
When we think of major figures in the history of science, many names come to mind. Einstein, Newton, Kepler, Galileo – all great theorists and thinkers who left an indelible mark during their lifetime. In many cases, the full extent of their contributions would not be appreciated until after their death. But those of us that are alive today are fortunate to have a great scientist among us who made considerable contributions – Dr. Stephen Hawking.
Considered by many to be the “modern Einstein”, Hawking’s work in cosmology and theoretical physics was unmatched among his contemporaries. In addition to his work on gravitational singularities and quantum mechanics, he was also responsible for discovering that black holes emit radiation. On top of that, Hawking was a cultural icon, endorsing countless causes, appearing on many television shows as himself, and penning several books that have made science accessible to a wider audience.
Early Life:
Hawking was born on January 8th, 1942 (the 300th anniversary of the death of Galileo) in Oxford, England. His parents, Frank and Isobel Hawking, were both students at Oxford University, where Frank studied medicine and Isobel studied philosophy, politics and economics. The couple originally lived in Highgate, a suburb of London, but moved to Oxford to get away from the bombings during World War II and give birth to their child in safety. The two would go on to have two daughters, Philippa and Mary, and one adopted son, Edward.
The family moved again in 1950, this time to St. Albans, Hertfordshire, because Stephen’s father became the head of parasitology at the National Institute for Medical Research (now part of the Francis Crick Institute). While there, the family gained the reputation for being highly intelligent, if somewhat eccentric. They lived frugally, living in a large, cluttered and poorly maintained house, driving around in a converted taxicab, and constantly reading (even at the dinner table).
Stephen Hawking as a young man. Credit: gazettereview.com
Education:
Hawking began his schooling at the Byron House School, where he experienced difficulty in learning to read (which he later blamed on the school’s “progressive methods”.) While in St. Albans, the eight-year-old Hawking attended St. Albans High School for Girls for a few months (which was permitted at the time for younger boys). In September of 1952, he was enrolled at Radlett School for a year, but would remain at St. Albans for the majority of his teen years due the family’s financial constraints.
While there, Hawking made many friends, with whom he played board games, manufactured fireworks, model airplanes and boats, and had long discussions with on subjects ranging from religion to extrasensory perception. From 1958, and with the help of the mathematics teacher Dikran Tahta, Hawking and his friends built a computer from clock parts, an old telephone switchboard and other recycled components.
Though he was not initially academically successfully, Hawking showed considerable aptitude for scientific subjects and was nicknamed “Einstein”. Inspired by his teacher Tahta, he decided to study mathematics at university. His father had hoped that his son would attend Oxford and study medicine, but since it was not possible to study math there at the time, Hawking chose to study physics and chemistry.
Stephen Hawking (holding the handkerchief) and the Oxford Boat Club. Credit: focusfeatures.com
In 1959, when he was just 17, Hawking took the Oxford entrance exam and was awarded a scholarship. For the first 18 months, he was bored and lonely, owing to the fact that he was younger than his peers and found the work “ridiculously easy”. During his second and third year, Hawking made greater attempts to bond with his peers and developed into a popular student, joining the Oxford Boat Club and developing an interest in classical music and science fiction.
When it came time for his final exam, Hawking’s performance was lackluster. Instead of answering all the questions, he chose to focus on theoretical physics questions and avoided any that required factual knowledge. The result was a score that put him on the borderline between first- and second-class honors. Needing a first-class honors for his planned graduate studies in cosmology at Cambridge, he was forced to take a via (oral exam).
Concerned that he was viewed as a lazy and difficult student, Hawking described his future plans as follows during the viva: “If you award me a First, I will go to Cambridge. If I receive a Second, I shall stay in Oxford, so I expect you will give me a First.” However, Hawking was held in higher regard than he believed, and received a first-class BA (Hons.) degree, thus allowing him to pursue graduate work at Cambridge University in October 1962.
Hawking on graduation day in 1962. Credit: telegraph.co.uk
Hawking experienced some initial difficulty during his first year of doctoral studies. He found his background in mathematics inadequate for work in general relativity and cosmology, and was assigned Dennis William Sciama (one of the founders of modern cosmology) as his supervisor, rather than noted astronomer Fred Hoyle (whom he had been hoping for).
In addition, it was during his graduate studies that Hawking was diagnosed with early-onset amyotrophic lateral sclerosis (ALS). During his final year at Oxford, he had experienced an accident where he fell down a flight of stairs, and also began experiencing difficulties when rowing and incidents of slurred speech. When the diagnosis came in 1963, he fell into a state of depression and felt there was little point in continuing his studies.
However, his outlook soon changed, as the disease progressed more slowly than the doctors had predicted – initially, he was given two years to live. Then, with the encouragement of Sciama, he returned to his work, and quickly gained a reputation for brilliance and brashness. This was demonstrated when he publicly challenged the work of noted astronomer Fred Hoyle, who was famous for rejecting the Big Bang theory, at a lecture in June of 1964.
Stephen Hawking and Jane Wilde on their wedding day, July 14, 1966. Credit: telegraph.co.uk
When Hawking began his graduate studies, there was much debate in the physics community about the prevailing theories of the creation of the universe: the Big Bang and the Steady State theories. In the former, the universe was conceived in a gigantic explosion, in which all matter in the known universe was created. In the latter, new matter is constantly created as the universe expands. Hawking quickly joined the debate.
Hawking became inspired by Roger Penrose’s theorem that a spacetime singularity – a point where the quantities used to measure the gravitational field of a celestial body become infinite – exists at the center of a black hole. Hawking applied the same thinking to the entire universe, and wrote his 1965 thesis on the topic. He went on to receive a research fellowship at Gonville and Caius College and obtained his PhD degree in cosmology in 1966.
It was also during this time that Hawking met his first wife, Jane Wilde. Though he had met her shortly before his diagnosis with ALS, their relationship continued to grow as he returned to complete his studies. The two became engaged in October of 1964 and were married on July 14th, 1966. Hawking would later say that his relationship with Wilde gave him “something to live for”.
Scientific Achievements:
In his doctoral thesis, which he wrote in collaboration with Penrose, Hawking extended the existence of singularities to the notion that the universe might have started as a singularity. Their joint essay – entitled, “Singularities and the Geometry of Space-Time” – was the runner-up in the 1968 Gravity Research Foundation competition and shared top honors with one by Penrose to win Cambridge’s most prestigious Adams Prize for that year.
In 1970, Hawking became part of the Sherman Fairchild Distinguished Scholars visiting professorship program, which allowed him to lecture at the California Institute of Technology (Caltech). It was during this time that he and Penrose published a proof that incorporated the theories of General Relativity and the physical cosmology developed by Alexander Freidmann.
Based on Einstein’s equations, Freidmann asserted that the universe was dynamic and changed in size over time. He also asserted that space-time had geometry, which is determined by its overall mass/energy density. If equal to the critical density, the universe has zero curvature (i.e. flat configuration); if it is less than critical, the universe has negative curvature (open configuration); and if greater than critical, the universe has a positive curvature (closed configuration)
According to the Hawking-Penrose singularity theorem, if the universe truly obeyed the models of general relativity, then it must have begun as a singularity. This essentially meant that, prior to the Big Bang, the entire universe existed as a point of infinite density that contained all of the mass and space-time of the universe, before quantum fluctuations caused it to rapidly expand.
Per the Friedmann equations, the geometry of the universe is determined by its overall mass/energy density, and can have either flat, negative, or positive curvature. Credit: NASA/GSFC
Also in 1970, Hawking postulated what became known as the second law of black hole dynamics. With James M. Bardeen and Brandon Carter, he proposed the four laws of black hole mechanics, drawing an analogy with the four laws of thermodynamics.
These four laws stated that – for a stationary black hole, the horizon has constant surface gravity; for perturbations of stationary black holes, the change of energy is related to change of area, angular momentum, and electric charge; the horizon area is, assuming the weak energy condition, a non-decreasing function of time; and that it is not possible to form a black hole with vanishing surface gravity.
In 1971, Hawking released an essay titled “Black Holes in General Relativity” in which he conjectured that the surface area of black holes can never decrease, and therefore certain limits can be placed on the amount of energy they emit. This essay won Hawking the Gravity Research Foundation Award in January of that year.
In 1973, Hawking’s first book, which he wrote during his post-doc studies with George Ellis, was published. Titled, The Large Scale Structure of Space-Time, the book describes the foundation of space itself and the nature of its infinite expansion, using differential geometry to examine the consequences of Einstein’s General Theory of Relativity.
Hawking was elected a Fellow of the Royal Society (FRS) in 1974, a few weeks after the announcement of Hawking radiation (see below). In 1975, he returned to Cambridge and was given a new position as Reader, which is reserved for senior academics with a distinguished international reputation in research or scholarship.
The mid-to-late 1970s was a time of growing interest in black holes, as well as the researchers associated with them. As such, Hawking’s public profile began to grow and he received increased academic and public recognition, appearing in print and television interviews and receiving numerous honorary positions and awards.
In the late 1970s, Hawking was elected Lucasian Professor of Mathematics at the University of Cambridge, an honorary position created in 1663 which is considered one of the most prestigious academic posts in the world. Prior to Hawking, its former holders included such scientific greats as Sir Isaac Newton, Joseph Larmor, Charles Babbage, George Stokes, and Paul Dirac.
His inaugural lecture as Lucasian Professor of Mathematics was titled: “Is the end in sight for Theoretical Physics”. During the speech, he proposed N=8 Supergravity – a quantum field theory which involves gravity in 8 supersymmetries – as the leading theory to solve many of the outstanding problems physicists were studying.
Hawking’s promotion coincided with a health crisis which led to Hawking being forced to accept some nursing services at home. At the same time, he began making a transition in his approach to physics, becoming more intuitive and speculative rather than insisting on mathematical proofs. By 1981, this saw Hawking begin to focus his attention on cosmological inflation theory and the origins of the universe.
Inflation theory – which had been proposed by Alan Guth that same year – posits that following the Big Bang, the universe initially expanded very rapidly before settling into to a slower rate of expansion. In response, Hawking presented work at the Vatican conference that year, where he suggested that their might be no boundary or beginning to the universe.
During the summer of 1982, he and his colleague Gary Gibbons organized a three-week workshop on the subject titled “The Very Early Universe” at Cambridge University. With Jim Hartle, an American physicist and professor of physics at the University of California, he proposed that during the earliest period of the universe (aka. the Planck epoch) the universe had no boundary in space time.
In 1983, they published this model, known as the Hartle-Hawking state. Among other things, it asserted that before the Big Bang, time did not exist, and the concept of the beginning of the universe is therefore meaningless. It also replaced the initial singularity of the Big Bang with a region akin to the North Pole which (similar to the real North Pole) one cannot travel north of because it is a point where lines meet that has no boundary.
This proposal predicted a closed universe, which had many existential implications, particularly about the existence of God. At no point did Hawking rule out the existence of God, choosing to use God in a metaphorical sense when explaining the mysteries of the universe. However, he would often suggest that the existence of God was unnecessary to explain the origin of the universe, or the existence of a unified field theory.
In 1982, he also began work on a book that would explain the nature of the universe, relativity and quantum mechanics in a way that would be accessible to the general public. This led him to sign a contract with Bantam Books for the sake of publishing A Brief History of Time, the first draft of which he completed in 1984.
After multiple revisions, the final draft was published in 1988, and was met with much critical acclaim. The book was translated into multiple languages, remained at the top of bestseller lists in both the US and UK for months, and ultimately sold an estimated 9 million copies. Media attention was intense, and Newsweek magazine cover and a television special both described him as “Master of the Universe”.
Further work by Hawking in the area of arrows of time led to the 1985 publication of a paper theorizing that if the no-boundary proposition were correct, then when the universe stopped expanding and eventually collapsed, time would run backwards. He would later withdraw this concept after independent calculations disputed it, but the theory did provide valuable insight into the possible connections between time and cosmic expansion.
During the 1990’s, Hawking continued to publish and lecture on his theories regarding physics, black holes and the Big Bang. In 1993, he co-edited a book with Gary Gibbons on on Euclidean quantum gravity, a theory they had been working on together in the late 70s. According to this theory, a section of a gravitational field in a black hole can be evaluated using a functional integral approach, such that it can avoid the singularities.
It was also in 1990s that major developments happened in Hawking’s personal life. In 1990, he and Jane Hawking commenced divorce proceedings after many years of strained relations, owing to his disability, the constant presence of care-givers, and his celebrity status. Hawking remarried in 1995 to Elaine Mason, his caregiver of many years.
Stephen Hawking lectured regularly throughout the 90s, many of which were collected and published in “The Nature of Space and Time” in 1996. Credit: educatinghumanity.com
In the 2000s, Hawking produced many new books and new editions of older ones. These included The Universe in a Nutshell (2001), A Briefer History of Time (2005), and God Created the Integers (2006). He also began collaborating with Jim Hartle of the University of California, Santa Barbara, and the European Organization for Nuclear Research (CERN) to produce new cosmological theories.
Foremost of these was Hawking’s “top-down cosmology”, which states that the universe had not one unique initial state but many different ones, and that predicting the universe’s current state from a single initial state is therefore inappropriate. Consistent with quantum mechanics, top-down cosmology posits that the present “selects” the past from a superposition of many possible histories.
In so doing, the theory also offered a possible resolution of the “fine-tuning question”, which addresses the possibility that life can only exist when certain physical constraints lie within a narrow range. By offering this new model of cosmology, Hawking opened up the possibility that life may not be bound by such restrictions and could be much more plentiful than previously thought.
In 2006, Hawking and his second wife, Elaine Mason, quietly divorced, and Hawking resumed closer relationships with his first wife Jane, his children (Robert, Lucy and Timothy), and grandchildren. In 2009, he retired as Lucasian Professor of Mathematics, which was required by Cambridge University regulations. Hawking has continued to work as director of research at the Cambridge University Department of Applied Mathematics and Theoretical Physics ever since, and has made no indication of retiring.
“Hawking Radiation” and the “Black Hole Information Paradox”:
In the early 1970s, Hawking’s began working on what is known as the “no-hair theorem”. Based on the Einstein-Maxwell equations of gravitation and electromagnetism in general relativity, the theorem stated that all black holes can be completely characterized by only three externally observable classical parameters: mass, electric charge, and angular momentum.
In this scenario, all other information about the matter which formed a black hole or is falling into it (for which “hair’ is used as a metaphor), “disappears” behind the black-hole event horizon, and is therefore preserved but permanently inaccessible to external observers.
In 1973, Hawking traveled to Moscow and met with Soviet scientists Yakov Borisovich Zel’dovich and Alexei Starobinsky. During his discussions with them about their work, they showed him how the uncertainty principle demonstrated that black holes should emit particles. This contradicted Hawking’ second law of black hole thermodynamics (i.e. black holes can’t get smaller) since it meant that by losing energy they must be losing mass.
What’s more, it supported a theory advanced by Jacob Bekenstein, a graduate student of John Wheeler University, that black holes should have a finite, non-zero temperature and entropy. All of this contradicted the “no-hair theorem” about black boles. Hawking revised this theorem shortly thereafter, showing that when quantum mechanical effects are taken into account, one finds that black holes emit thermal radiation at a temperature.
From 1974 onward, Hawking presented Bekenstein’s results, which showed that black holes emit radiation. This came to be known as “Hawking radiation”, and was initially controversial. However, by the late 1970s and following the publication of further research, the discovery was widely accepted as a significant breakthrough in theoretical physics.
However, one of the outgrowths of this theory was the likelihood that black holes gradually lose mass and energy. Because of this, black holes that lose more mass than they gain through other means are expected to shrink and ultimately vanish – a phenomena which is known as black hole “evaporation”.
In 1981, Hawking proposed that information in a black hole is irretrievably lost when a black hole evaporates, which came to be known as the “Black Hole Information Paradox”. This states that physical information could permanently disappear in a black hole, allowing many physical states to devolve into the same state.
This was controversial because it violated two fundamental tenets of quantum physics. In principle, quantum physics tells us that complete information about a physical system – i.e. the state of its matter (mass, position, spin, temperature, etc.) – is encoded in its wave function up to the point when that wave function collapses. This in turn gives rise to two other principles.
The first is Quantum Determinism, which states that – given a present wave function – future changes are uniquely determined by the evolution operator. The second is Reversibility, which states that the evolution operator has an inverse, meaning that the past wave functions are similarly unique. The combination of these means that the information about the quantum state of matter must always be preserved.
By proposing that this information disappears once a black evaporates, Hawking essentially created a fundamental paradox. If a black hole can evaporate, which causes all the information about a quantum wave function to disappear, than information can in fact be lost forever. This has been the subject of ongoing debate among scientists, one which has remained largely unresolved.
However, by 2003, the growing consensus among physicists was that Hawking was wrong about the loss of information in a black hole. In a 2004 lecture in Dublin, he conceded his bet with fellow John Preskill of Caltech (which he made in 1997), but described his own, somewhat controversial solution to the paradox problem – that black holes may have more than one topology.
In the 2005 paper he published on the subject – “Information Loss in Black Holes” – he argued that the information paradox was explained by examining all the alternative histories of universes, with the information loss in those with black holes being cancelled out by those without. As of January 2014, Hawking has described the Black Hole Information Paradox as his “biggest blunder”.
Other Accomplishments:
In addition to advancing our understanding of black holes and cosmology through the application of general relativity and quantum mechanics, Stephen Hawking has also been pivotal in bringing science to a wider audience. Over the course of his career, he has published many popular books, traveled and lectured extensively, and has made numerous appearances and done voice-over work for television shows, movies and even provided narration for the Pink Floyd song, “Keep Talking”.
Stephen Hawking’s theories on black holes became the subject of television specials, such as “Stephen Hawking’s Universe” on PBS. Credit: discovery.com
A film version of A Brief History of Time, directed by Errol Morris and produced by Steven Spielberg, premiered in 1992. Hawking had wanted the film to be scientific rather than biographical, but he was persuaded otherwise. In 1997, a six-part television series Stephen Hawking’s Universe premiered on PBS, with a companion book also being released.
In 2007, Hawking and his daughter Lucy published George’s Secret Key to the Universe, a children’s book designed to explain theoretical physics in an accessible fashion and featuring characters similar to those in the Hawking family. The book was followed by three sequels – George’s Cosmic Treasure Hunt (2009), George and the Big Bang (2011), George and the Unbreakable Code (2014).
Since the 1990s, Hawking has also been a major role model for people dealing with disabilities and degenerative illnesses, and his outreach for disability awareness and research has been unparalleled. At the turn of the century, he and eleven other luminaries joined with Rehabilitation International to sign the Charter for the Third Millennium on Disability, which called on governments around the world to prevent disabilities and protect disability rights.
Professor Stephen Hawking participating in a zero-gravity flight (aka. the “Vomit Comet”) in 2007. Credit: gozerog.com
Motivated by the desire to increase public interest in spaceflight and to show the potential of people with disabilities, in 2007 he participated in zero-gravity flight in a “Vomit Comet” – a specially fitted aircraft that dips and climbs through the air to simulate the feeling of weightlessness – courtesy of Zero Gravity Corporation, during which he experienced weightlessness eight times.
In August 2012, Hawking narrated the “Enlightenment” segment of the 2012 Summer Paralympics opening ceremony. In September of 2013, he expressed support for the legalization of assisted suicide for the terminally ill. In August of 2014, Hawking accepted the Ice Bucket Challenge to promote ALS/MND awareness and raise contributions for research. As he had pneumonia in 2013, he was advised not to have ice poured over him, but his children volunteered to accept the challenge on his behalf.
During his career, Hawking has also been a committed educator, having personally supervised 39 successful PhD students.He has also lent his name to the ongoing search for extra-terrestrial intelligence and the debate regarding the development of robots and artificial intelligence. On July 20th, 2015, Stephen Hawking helped launch Breakthrough Initiatives, an effort to search for extraterrestrial life in the universe.
Also in 2015, Hawking lent his voice and celebrity status to the promotion of The Global Goals, a series of 17 goals adopted by the United Nations Sustainable Development Summit to end extreme poverty, social inequality, and fixing climate change over the course of the next 15 years.
President Barack Obama talks with Stephen Hawking in the Blue Room of the White House before a ceremony presenting him and 15 others the Presidential Medal of Freedom, August 12th, 2009. Credit: Pete Souza/White House photo stream
Honors and Legacy:
As already noted, in 1974, Hawking was elected a Fellow of the Royal Society (FRS), and was one of the youngest scientists to become a Fellow. At that time, his nomination read:
Hawking has made major contributions to the field of general relativity. These derive from a deep understanding of what is relevant to physics and astronomy, and especially from a mastery of wholly new mathematical techniques. Following the pioneering work of Penrose he established, partly alone and partly in collaboration with Penrose, a series of successively stronger theorems establishing the fundamental result that all realistic cosmological models must possess singularities. Using similar techniques, Hawking has proved the basic theorems on the laws governing black holes: that stationary solutions of Einstein’s equations with smooth event horizons must necessarily be axisymmetric; and that in the evolution and interaction of black holes, the total surface area of the event horizons must increase. In collaboration with G. Ellis, Hawking is the author of an impressive and original treatise on “Space-time in the Large.
Other important work by Hawking relates to the interpretation of cosmological observations and to the design of gravitational wave detectors.
Peter Higgs and Stephen Hawking visiting the “Collider” exhibition at London’s Science Museum in 2013, in honor of the discovery of the Higgs Boson. Credit: sciencemuseum.org.uk
In 1975, he was awarded both the Eddington Medal and the Pius XI Gold Medal, and in 1976 the Dannie Heineman Prize, the Maxwell Prize and the Hughes Medal. In 1977, he was appointed a professor with a chair in gravitational physics, and received the Albert Einstein Medal and an honorary doctorate from the University of Oxford by the following year.
In 1981, Hawking was awarded the American Franklin Medal, followed by a Commander of the Order of the British Empire (CBE) medal the following year. For the remainder of the decade, he was honored three times, first with the Gold Medal of the Royal Astronomical Society in 1985, the Paul Dirac Medal in 1987 and, jointly with Penrose, with the prestigious Wolf Prize in 1988. In 1989, he was appointed Member of the Order of the Companions of Honour (CH), but reportedly declined a knighthood.
In 1999, Hawking was awarded the Julius Edgar Lilienfeld Prize of the American Physical Society. In 2002, following a UK-wide vote, the BBC included him in their list of the 100 Greatest Britons. More recently, Hawking has been awarded the Copley Medal from the Royal Society (2006), the Presidential Medal of Freedom, America’s highest civilian honor (2009), and the Russian Special Fundamental Physics Prize (2013).
Stephen Hawking being presented by his daughter Lucy Hawking at the lecture he gave for NASA’s 50th anniversary. Credit: NASA/Paul Alers
Also in 2008, while traveling to Spain, Hawking received the Fonseca Prize – an annual award created by the University of Santiago de Compostela which is awarded to those for outstanding achievement in science communication. Hawking was singled out for the award because of his “exceptional mastery in the popularization of complex concepts in Physics at the very edge of our current understanding of the Universe, combined with the highest scientific excellence, and for becoming a public reference of science worldwide.”
Multiple films have been made about Stephen Hawking over the years as well. These include the previously mentioned A Brief History of Time, the 1991 biopic film directed by Errol Morris and Stephen Spielberg; Hawking, a 2004 BBC drama starring Benedict Cumberbatch in the title role; the 2013 documentary titled “Hawking”, by Stephen Finnigan.
Most recently, there was the 2014 film The Theory of Everything that chronicled the life of Stephen Hawking and his wife Jane. Directed by James Marsh, the movie stars Eddie Redmayne as Professor Hawking and Felicity Jones as Jane Hawking.
Death:
Dr. Stephen Hawking passed away in the early hours of Wednesday, March 14th, 2018 at his home in Cambridge. According to a statement made by his family, he died peacefully. He was 76 years old, and is survived by his first wife, Jane Wilde, and their three children – Lucy, Robert and Tim.
When all is said and done, Stephen Hawking was the arguably the most famous scientist alive in the modern era. His work in the field of astrophysics and quantum mechanics has led to a breakthrough in our understanding of time and space, and will likely be poured over by scientists for decades. In addition, he has done more than any living scientist to make science accessible and interesting to the general public.
Stephen Hawking holding a public lecture at the Stockholm Waterfront congress center, 24 August 2015. Credit: Public Domain/photo by Alexandar Vujadinovic
To top it off, he traveled all over the world and lectured on topics ranging from science and cosmology to human rights, artificial intelligence, and the future of the human race. He also used the celebrity status afforded him to advance the causes of scientific research, space exploration, disability awareness, and humanitarian causes wherever possible.
In all of these respects, he was very much like his predecessor, Albert Einstein – another influential scientist-turned celebrity who was sure to use his powers to combat ignorance and promote humanitarian causes. But what was especially impressive in all of this is that Hawking has managed to maintain his commitment to science and a very busy schedule while dealing with a degenerative disease.
For over 50 years, Hawking lived with a disease that doctor’s initially thought would take his life within just two. And yet, he not only managed to make his greatest scientific contributions while dealing with ever-increasing problems of mobility and speech, he also became a jet-setting personality who travelled all around the world to address audiences and inspire people.
His passing was mourned by millions worldwide and, in the worlds of famed scientist and science communicator Neil DeGrasse Tyson , “left an intellectual vacuum in its wake”. Without a doubt, history will place Dr. Hawking among such luminaries as Einstein, Newton, Galileo and Curie as one of the greatest scientific minds that ever lived.
Albert Einstein in 1947. Credit: Library of Congress
At the end of the millennium, Physics World magazine conducted a poll where they asked 100 of the world’s leading physicists who they considered to be the top 10 greatest scientist of all time. The number one scientist they identified was Albert Einstein, with Sir Isaac Newton coming in second. Beyond being the most famous scientist who ever lived, Albert Einstein is also a household name, synonymous with genius and endless creativity.
As the discoverer of Special and General Relativity, Einstein revolutionized our understanding of time, space, and universe. This discovery, along with the development of quantum mechanics, effectively brought to an end the era of Newtonian Physics and gave rise to the modern age. Whereas the previous two centuries had been characterized by universal gravitation and fixed frames of reference, Einstein helped usher in an age of uncertainty, black holes and “scary action at a distance”.
Have you heard that black holes destroy any information that goes into them? Why is this such a big problem for physics?
In my day, things were simple. Robot dogs had wheels and laser noses. School was uphill both ways. Unwanted children removed themselves from lawns, and we didn’t need those horrible electrified tentacle arms. The cut of my jib was completely beyond reproach. Nathan Fillion was the captain of the Serenity all day, every day. … And black holes were holes that were black. By that I mean black holes would compress matter and energy into an infinitely dense singularity, and didn’t create a seemingly insurmountable information paradox. Yep, those were the good ole’ days.
But those days are over. Now it’s all 50 shades of grey, with the laws of physics bending under other laws of physics. “Hashtag not my Christian”. What I’m talking about is the black hole information paradox.
First, let’s talk information. When physicists talk information, they’re on about the specific state of every single particle in the Universe: mass, position, spin, temperature, you name it. The fingerprint that uniquely identifies each one, and the probabilities for what they’re going to do in the Universe. You can change atoms, crush them together, but the quantum wave function that describes them must always be preserved.
Quantum physics allows you to run the whole Universe forwards and backwards, as long as you reverse everything in your math: charge, parity and time. Here’s the important part. The big brains tell us information must live on, no matter what. Think about it like energy. You can’t destroy energy, all you can do is transform it.
Now, the black hole recap. Naturally formed when the largest stars, those with more than 20 times the mass of the Sun, collapse violently and explode. Here the density of matter is so high, the escape velocity exceeds the speed of light. The fancy ones have a super-heated accretion disk of matter swirling around the black hole event horizon, where even light can be pulled into orbit.
Here, we get one of the strangest side effects from Relativity: time dilation. Imagine a clock falling towards a black hole, moving deeper into the gravity well. It would appear to slow as it got closer to the black hole, and eventually freeze at the edge of the event horizon. Photons from the clock would stretch out, and the color of the clock would redshift. Eventually, it fades away as the photons stretched out beyond what our eyes can detect.
If you could stare at the black hole for billions of years, you would see everything it ever collected, stuck to the outside like flypaper. You could point out the clock, the Titanic, the Ranger, and USS Cygnus, and theoretically, you could identify the quantum state of every single particle and photon that went into the black hole. Since they’re going to take an infinite length of time to disappear completely, everything’s fine.
Black hole with disc and jets visualization courtesy of ESA
Their information is preserved forever on the surface of the black hole. They’re all totally dead, but their information, their precious precious quantum information, is totally safe.
If you could unravel a black hole, you could get at all the quantum information describing everything the black hole ever consumed. And least, that’s how it was in the good old days.
But in 1975, Hawking dropped a bombshell. He realized black holes have a temperature, over vast periods of time, they would evaporate away until there was nothing left. releasing their mass and energy back into the Universe. Unsurprisingly known as Hawking Radiation.
But this… idea created a paradox. The information about what went into the black hole is preserved by time dilation, but with the mass itself of the black hole evaporating. Eventually, it will completely disappear, and then, where does our information go? That information which can’t be destroyed…?
This is strictly not cricket, and puzzled astronomers. They’ve been working for decades to resolve it. There’s a fun stack of options here:
Black holes don’t evaporate at all, and Hawking was wrong.
Information within the black hole somehow leaks back out while Hawking radiation is escaping.
The black hole holds it all in until the very end, and as the final two particles evaporate, all the information is suddenly released back into the Universe.
It all goes into the teeniest possible bits and nothing is lost OR The information is compressed into a microscopic space, which remains after the black hole itself has evaporated.
An artist’s representation showing outflow from a supermassive black hole inside the middle of a galaxy. Credit: NASA/CXC/M.Weiss
And maybe, physicists will never figure it out. Hawking recently proposed a new idea to resolve the black hole information paradox. He has suggested that there’s a way that new Hawking radiation could be imprinted by the information of new matter falling into the black hole.
So, the information of everything falling in is preserved by the outgoing radiation, returning it to the Universe and resolving the paradox. This is a hunch, since Hawking radiation itself has never been detected. We are decades away from knowing if this is in the right direction, or even if there’s a way to resolve the paradox.
In situations like this that we’re reminded how little about the Universe we really understand. Some aspect of our understanding of this whole process is unclear, and it’ll take much more detective work and experimentation to get closer to the truth.
What information would like to be destroyed from the Universe forever? Tell us all your secrets in the comments below.
Is our 13.8 billion year old universe actually in its death throes?
Poor Universe, its demise announced right in it’s prime. At only 13.8 billion years old, when you peer across the multiverse it’s barely middle age. And yet, it sadly dwindles here in hospice.
Is it a Galactus infestation? The Unicronabetes? Time to let go, move on and find a new Universe, because this one is all but dead and gone and but a shell of its former self.
The news of imminent demise was recently broadcast in mid 2015. Based on research looking at the light coming from over 200,000 galaxies, they found that the galaxies are putting out half as much light as they were 2 billion years ago. So if our math is right, less light equals more death.
So tell it to me straight, Doctor Spaceman(SPAH-CHEM-AN), how long have we got? Astronomers have known for a long time that the Universe was much more active in the distant past, when everything was closer and denser, and better. Back then, more of it was the primordial hydrogen left over from the Big Bang, supplying galaxies for star formation. Currently, there are only 1 to 3 new stars formed in the Milky Way every year. Which is pretty slow by Milky Way standards.
Not even at the busiest time of star formation, our Sun formed 5 billion years ago. 5 billion years before that, just a short 4 billion after the Big Bang, star formation peaked out. There were 30 times more stars forming then, than we see today.
When stars were formed actually makes a difference. For example, the fact that it took so long for our Sun to form is a good thing. The heavier elements in the Solar System, really anything higher up the periodic table from hydrogen and helium, had to be formed inside other stars. Main sequence stars like our own Sun spew out heavier elements from their solar winds, while supernovae created the heaviest elements in a moment of catastrophic collapse. Astronomers are pretty sure we needed a few generations of stars to build up enough of the heavier elements that life depends on, and probably wouldn’t be here without it.
Even if life did form here on Earth billions of years ago, when the Universe was really cranking, it would wish it was never born. With 30 times as much star formation going on, there would be intense radiation blasting away from all these newly forming stars and their subsequent supernovae detonations. So be glad life formed when it did. Sometimes a little quiet is better.
So, how long has the Universe got? It appears that it’s not going to crash together in the future, it’s just going to keep on expanding, and expanding, forever and ever.
Our eyes would never see the Crab Nebula as this Hubble image shows it. Image credit: NASA, ESA, J. Hester and A. Loll (Arizona State University)
In a few billion years, star formation will be a fraction of what it is today. In a few trillion, only the longest lived, lowest mass red dwarfs will still be pushing out their feeble light. Then, one by one, galaxies will see their last star flicker and fade away into the darkness. Then there’ll only be dead stars and dead planets, cooling down to the background temperature of the Universe as their galaxies accelerate from one another into the expanding void.
Eventually everything will be black holes, or milling about waiting to be trapped in black holes. And these black holes themselves will take an incomprehensible mighty pile of years to evaporate away to nothing.
So yes, our Universe is dying. Just like in a cheery Sartre play, it started dying the moment it began its existence. According to astronomers, the Universe will never truly die. It’ll just reach a distant future when there’s so little usable energy, it’ll be mostly dead. Dead enough? Dead inside.
As Miracle Max knows, mostly dead is still slightly alive. Who knows what future civilizations will figure out in the googol years between then and now.
Too sad? Let’s wildly speculate on futuristic technologies advanced civilizations will use to outlast the heat death of the Universe or flat out cheat death and re-spark it into a whole new cycle of Universal renewal.
We talk about stellar mass and supermassive black holes. What are the limits? How massive can these things get?
Without the light pressure from nuclear fusion to hold back the mass of the star, the outer layers compress inward in an instant. The star dies, exploding violently as a supernova.
All that’s left behind is a black hole. They start around three times the mass of the Sun, and go up from there. The more a black hole feeds, the bigger it gets.
Terrifyingly, there’s no limit to much material a black hole can consume, if it’s given enough time. The most massive are ones found at the hearts of galaxies. These are the supermassive black holes, such as the 4.1 million mass nugget at the center of the Milky Way. Astronomers figured its mass by watching the movements of stars zipping around the center of the Milky Way, like comets going around the Sun.
There seems to be supermassive black holes at the heart of every galaxy we can find, and our Milky Way’s black hole is actually puny in comparison. Interstellar depicted a black hole with 100 million times the mass of the Sun. And we’re just getting started.
The giant elliptical galaxy M87 has a black hole with 6.2 billion times the mass of the Sun. How can astronomers possibly know that? They’ve spotted a jet of material 4,300 light-years long, blasting out of the center of M87 at relativistic speeds, and only black holes that massive generate jets like that.
Most recently, astronomers announced in the Journal Nature that they have found a black hole with about 12 billion times the mass of the Sun. The accretion disk here generates 429 trillion times more light than the Sun, and it shines clear across the Universe. We see the light from this region from when the Universe was only 6% into its current age.
Somehow this black hole went from zero to 12 billion times the mass of the Sun in about 875 million years. Which poses a tiny concern. Such as how in the dickens is it possible that a black hole could build up so much mass so quickly? Also, we’re seeing it 13 billion years ago. How big is it now? Currently, astronomers have no idea. I’m sure it’s fine. It’s fine right?
We’ve talked about how massive black holes can get, but what about the opposite question? How teeny tiny can a black hole be?
An illustration that shows the powerful winds driven by a supermassive black hole at the centre of a galaxy. The schematic figure in the inset depicts the innermost regions of the galaxy where a black hole accretes, that is, consumes, at a very high rate the surrounding matter (light grey) in the form of a disc (darker grey). At the same time, part of that matter is cast away through powerful winds. (Credits: XMM-Newton and NuSTAR Missions; NASA/JPL-Caltech;Insert:ESA)
Astronomers figure there could be primordial black holes, black holes with the mass of a planet, or maybe an asteroid, or maybe a car… or maybe even less. There’s no method that could form them today, but it’s possible that uneven levels of density in the early Universe might have compressed matter into black holes.
Those black holes might still be out there, zipping around the Universe, occasionally running into stars, planets, and spacecraft and interstellar picnics. I’m sure it’s the stellar equivalent of smashing your shin on the edge of the coffee table.
Astronomers have never seen any evidence that they actually exist, so we’ll shrug this off and choose to pretend we shouldn’t be worrying too much. And so it turns out, black holes can get really, really, really massive. 12 billion times the mass of the Sun massive.
What part about black holes still make you confused? Suggest some topics for future episodes of the Guide to Space in the comments below.
NGC 1300, a spiral, barred galaxy viewed nearly face-on by the Hubble Space Telescope. Credit: NASA/ESA/Hubble
For millennia, human beings have stared up at the night sky and stood in awe of the Milky Way. Today, stargazers and amateur astronomers continue in this tradition, knowing that what they are witnessing is in fact a collection of hundreds of millions of stars and dust clouds, not to mention billions of other worlds.
But one has to wonder, if we can see the glowing band of the Milky Way, why can’t we see what lies towards the center of our galaxy? Assuming we are looking in the right direction, shouldn’t we able to see that big, bright bulge of stars with the naked eye? You know the one I mean, it’s in all the pictures!
Unfortunately, in answering this question, a number of reality checks have to be made. When it is dark enough, and conditions are clear, the dusty ring of the Milky Way can certainly be discerned in the night sky. However, we can still only see about 6,000 light years into the disk with the naked eye, and relying on the visible spectrum. Here’s a rundown on why that is.
Size and Structure:
First of all, the sheer size of our galaxy is enough to boggle the mind. NASA estimates that the Milky Way is between 100,000 – 120,000 light-years in diameter – though some information suggests it may be as much as 150,000 – 180,000 light-years across. Since one light year is about 9.5 x 1012km, this makes the diameter of the Milky Way galaxy approximately 9.5 x 1017 – 1.14 x 1018 km in diameter.
To put that in layman’s terms, that 950 quadrillion (590 quadrillion miles) to 1.14 quintillion km (7oo septendecillion miles). The Milky Way is also estimated to contain 100–400 billion stars, (although that could be as high as one trillion), and may have as many as 100 billion planets.
At the center, measuring approx. 10,000 light-years in diameter, is the tightly-packed group of stars known as the “bulge”. At the very center of this bulge is an intense radio source, named Sagittarius A*, which is likely to be a supermassive black hole that contains 4.1 million times the mass of our Sun.
We, in our humble Solar System, are roughly 28,000 light years away from it. In short, this region is simply too far for us to see with the naked eye. However, there is more to it than just that…
Radio image of the night sky. Credit: Max Planck Institute for Radio Astronomy, generated by Glyn Haslam.
Low Surface Brightness:
In addition to being a spiral barred galaxy, the Milky Way is what is known as a Low Surface Brightness (LSB) galaxy – a classification that refers to galaxies where their surface brightness is, when viewed from Earth, at least one magnitude lower than the ambient night sky. Essentially, this means that the sky needs to be darker than about 20.2 magnitude per square arcsecond in order for the Milky Way to be seen.
This makes the Milky Way difficult to see from any location on Earth where light pollution is common – such as urban or suburban locations – or when stray light from the Moon is a factor. But even when conditions are optimal, there still only so much we can see with the naked eye, for reasons that have much to do with everything that lies between us and the galactic core.
Dust and Gas:
Though it may not look like it to the casual observer, the Milky Way is full of dust and gas. This matter is known as as the interstellar medium, a disc that makes up a whopping 10-15% of the luminous/visible matter in our galaxy and fills the long spaces in between the stars. The thickness of the dust deflects visible light (as is explained here), leaving only infrared light to pass through the dust.
This dazzling infrared image from NASA’s Spitzer Space Telescope showing hundreds of thousands of stars crowded into the swirling core of our spiral Milky Way galaxy. Credit: NASA/JPL-Caltech
This makes infrared telescopes like the Spitzer Space Telescope extremely valuable tools in mapping and studying the galaxy, since it can peer through the dust and haze to give us extraordinarily clear views of what is going on at the heart of the galaxy and in star-forming regions. However, when looking in the visual spectrum, light from Earth, and the interference effect of dust and gas limit how far we can see.
Limited Instrumentation:
Astronomers have been staring up at the stars for thousands of years. However, it was only in comparatively recent times that they even knew what they were looking at. For instance, in his book Meteorologica, Aristotle (384–322 BC) wrote that the Greek philosophers Anaxagoras (ca. 500–428 BCE) and Democritus (460–370 BCE) had proposed that the Milky Way might consist of distant stars.
However, Aristotle himself believed the Milky Way was be caused by “the ignition of the fiery exhalation of some stars which were large, numerous and close together” and that these ignitions takes place in the upper part of the atmosphere. Like many of Aristotle’s theories, this would remain canon for western scholars until the 16th and 17th centuries, at which time, modern astronomy would begin to take root.
Meanwhile, in the Islamic world, many medieval scholars took a different view. For example, Persian astronomer Abu Rayhan al-Biruni (973–1048) proposed that the Milky Way is “a collection of countless fragments of the nature of nebulous stars”. Ibn Qayyim Al-Jawziyya (1292–1350) of Damascus similarly proposed that the Milky Way is “a myriad of tiny stars packed together in the sphere of the fixed stars” and that these stars are larger than planets.
Persian astronomer Nasir al-Din al-Tusi (1201–1274) also claimed in his book Tadhkira that: “The Milky Way, i.e. the Galaxy, is made up of a very large number of small, tightly clustered stars, which, on account of their concentration and smallness, seem to be cloudy patches. Because of this, it was likened to milk in color.”
Despite these theoretical breakthroughs, it was not until 1610, when Galileo Galilei turned his telescope towards the heavens, that proof existed to back up these claims. With the help of telescopes, astronomers realized for the first time that there were many, many more stars in the sky than the ones we can see, and that all of the ones that we can see are a part of the Milky Way.
Over a century later, William Herschel created the first theoretical diagram of what the Milky Way (1785) looked like. In it, he described the shape of the Milky Way as a large, cloud-like collection of stars, and claimed the Solar System was close to the center. Though erroneous, this was the first attempt at hypothesizing what our cosmic backyard looked like.
It was not until the 20th century that astronomers were able to get an accurate picture of what our Galaxy actually looks like. This began with astronomer Harlow Shapely measuring the distributions and locations of globular star clusters. From this, he determined that the center of the Milky Way was 28,000 light years from Earth, and that the center was a bulge, rather than a flat area.
This annotated artist’s conception illustrates our current understanding of the structure of the Milky Way galaxy. Image Credit: NASA
In 1923, astronomer Edwin Hubble used the largest telescope of his day at the Mt. Wilson Observatory near Pasadena, Calif., to observe galaxies beyond our own. By observing what spiral galaxies look like throughout the universe, astronomers and scientists were able to get an idea of what our own looks like.
Since that time, the ability to observe our galaxy through multiple wavelengths (i.e. radio waves, infrared, x-rays, gamma-rays) and not just the visible spectrum has helped us to get an even better picture. In addition, the development of space telescopes – such as Hubble, Spitzer, WISE, and Kepler – have been instrumental in allowing us to make observations that are not subject to interference from our atmosphere or meteorological conditions.
But despite our best efforts, we are still limited by a combination of perspective, size, and visibility barriers. So far, all pictures that depict our galaxy are either artist’s renditions or pictures of other spiral galaxies. Until quite recently in our history, it was very difficult for scientists to gauge what the Milky Way looks like, mainly because we’re embedded inside it.
To get an actual view of the Milky Way Galaxy, several things would need to happen. First, we would need a camera that worked in space that had a wide field of view (aka. Hubble, Spitzer, etc). Then we’d need to fly that camera to a spot that’s roughly 100,000 light years above the Milky Way and point it back at Earth. With our current propulsion technology, that would take 2.2 billion years to accomplish.
Milky Way in infrared. Image credit: COBE
Fortunately, as noted already, astronomers have a few additional wavelengths they can use to see into the galaxy, and these are making much more of the galaxy visible. In addition to seeing more stars and more star clusters, we’re able to see more of the center of our Galaxy as well, which includes the supermassive black hole that has been theorized as existing there.
For some time, astronomers have had name for the region of sky that is obscured by the Milky Way – the “Zone of Avoidance“. Back in the days when astronomers could only make visual observations, the Zone of Avoidance took up about 20% of the night sky. But by observing in other wavelengths, like infrared, x-ray, gamma rays, and especially radio waves, astronomers can see all but about 10% of the sky. What’s on the other side of that 10% is mostly a mystery.
In short, progress is being made. But until such time that we can send a ship beyond our Galaxy that can take snapshots and beam them back to us, all within the space of our own lifetimes, we’ll be dependent on what we can observe from the inside.
And be to sure to check out Universe Today’s interview with Dr. Andrea Ghez, Professor of Astronomy at UCLA, talking about what is at the center of our Galaxy.
Black Holes? Dark Energy? Dark Matter? Alien Life? What are the biggest mysteries that still exist out there for us to figure out?
“The more I learn, the more I realize how much I don’t know.” These are the words of Albert Einstein. I assume he was talking about Minecraft, but I guess it applies to the Universe too.
There are many examples: astronomers try to discover the rate of the expansion of the Universe, and learn a dark energy is accelerating its expansion. NASA’s Cassini spacecraft finally images Saturn’s moon Iapetus, and finds a strange equatorial ridge – how the heck did that get there? Did the Celestials forget to trim it when it came out of the packaging?
There have always been, and, let’s go as far as to say that there always will be, mysteries in astronomy. Although the nature of the mysteries may change, the total number is always going up.
Hundreds of years ago, people wanted to know how the planets moved through sky (conservation of angular momentum), how old the Earth was (4.54 billion years), or what kept the Moon from flying off into space (gravity). Just a century ago, astronomers weren’t sure what galaxies were (islands of stars), or how the Sun generated energy (nuclear fusion). And just a few decades ago, we didn’t know what caused quasars (feeding supermassive black holes), or how old the Universe was (13.8 billion years). Each of these mysteries has been solved, or at least, we’ve a got a pretty good understanding of what’s going on.
Science continues to explore and seek answers to the mysteries we have, and as it does it opens up new brand doors. Fortunately for anyone who’s thinking of going into astronomy as a career, there are a handful of really compelling mysteries to explore right now:
Is the Universe finite or infinite? We can see light that left shortly after the Big Bang, 13.8 billion years in all directions. And the expansion of the Universe has carried these regions more than 45 billion light-years away from us. But the Universe is probably much larger than that, and may be even infinite.
Images from the Hubble Space Telescope showing a gravitational lensing effect. Credit: NASA/ESA.
What is dark matter? Thanks to gravitational lensing, astronomers can perceive vast halos of invisible material around all galaxies. But what is this stuff, and why doesn’t it interact with any other matter?
What is dark energy? When trying to discover the expansion rate of the Universe, astronomers discovered that the expansion is actually accelerating? Why is this happening? Is something causing this force, or do we just not understand gravity at the largest scales?
There are supermassive black holes at the heart of pretty much every galaxy. Did these supermassive black holes form first, and then the galaxies around them? Or was it the other way around?
The Big Bang occurred 13.8 billion years ago, and the expansion of the Universe has continued ever since. But what came before the Big Bang? In fact, what even caused the Big Bang? Has it been Big Bangs over and over again?
The Universe 590 million years after the Big Bang. Credit: Alvaro Orsi, Institute for Computational Cosmology, Durham University.
Are we alone in the Universe? Is there life on any other world or star system? And is anyone out there we could talk to?
Shortly after the Big Bang, incomprehensible amounts of matter and antimatter annihilated each other. But for some reason, there was a slightly higher ratio of matter – and so we have a matter dominated Universe. Why?
Is this the only Universe? Is there a multiverse of universes out there? How do I get to the Whedonverse?
In the distant future, after all the stars are dead and gone, maybe protons themselves will decay and there will be nothing left but energy. Physicists haven’t been able to catch a proton decaying yet. Will the ever?
And these are just some of the big ones. There are hundreds, thousands, millions of unanswered questions. The more we learn, the more we discover how little we actually understand.
Whenever we do a video about concepts in astronomy where we have a basic understanding, like gravity, evolution, or the Big Bang, trolls show up and say that scientists are so arrogant. That they think they know everything. But scientists don’t know everything, and they’re willing to admit when something is a mystery. When the answer to the question is: I don’t know.
What’s your favorite unanswered question in space and astronomy? Give us your best mystery in the comments below.
How small do black holes get? Could you carry one around in your pocket? Does that even like a sane thing to do?
I’m pleased to announce that the Large Hadron Collider, the enormous particle accelerator in Europe has begun operations again with twice the colliding power. Smashing atoms with 15 Tera-electron volts.
The LHC double-down has a laundry list of science to get done, like determining the nature of dark matter, searching for particles to confirm the theory of supersymmetry, and probing the Universe for extra dimensions. One of its tasks will be to search for Hawking Radiation, the stream of particles that come out of black holes as they evaporate.
So, in order to watch them evaporate, the LHC is going to try and create little tiny black holes. We only know one natural process for creating black holes: the death of massive stars as supernova. Oh, and whatever it took to make supermassive black holes – that’s still pretty much a mystery.
As a side note, we are going to be supermassively embarrassed if it turns out they’re created by species messing with forces far beyond their comprehension by doubling the power at their biggest particle accelerator, and turning their region of the Universe into a giant mess. Clean up, aisle Milky Way.
Apparently, you could get a black hole of any size, even microscopic. If you took the mass of the Earth, compressed it down to the size of a marble, it would become a black hole. A black hole with the mass of the Earth.
The only place this might have been possible was at the very beginning of the Universe, shortly after the Big Bang. When the Universe was unimaginably hot and dense, there were tiny fluctuations of density, nooks in spacetime where tiny black holes might have formed. Maybe they don’t exist at all, the conditions of the early Universe didn’t bring them about. It’s just a theory. A theory that the Large Hadron Collider will try to confirm or deny.
Artist illustration of a black hole. Image credit: NASA
The important question is, will it kill us all? Could a black hole fall out of the experiment, and roll down into the sewer drain. Chewing its way down into the center of the Earth, gobbling away the core of the planet, eventually creating an Earth-massed black hole?
Here’s the good news. The less massive, the hotter it is, and the faster it evaporates. Microscopic black holes would evaporate in a faction of a second. Any that the LHC could create, would disintegrate in a faction of a second. In fact, they should be gone in 10^-27 seconds.
So it turns out, you could put a black hole in your pocket. An Earth-mass black hole would fit nicely in your pocket. An Earth’s worth of gravity, however, could prove problematic.
Fortunately, there’s no natural process that can create these objects, and any black holes that we could create would be gone before you could get them anywhere near a pocket. So, you should probably stop thinking of it in terms of one of Lord Nibbler’s doodies.
What would you do with a pocket-sized black hole? Tell us in the comments below.
