Image: Photograph by Timothy Archibald
In Brief
Who
LEONARD SUSSKIND
Vocation | Avocation
Theoretical physicist, known especially for pioneering string theory, black hole physics and the multiverse
Where
Stanford University
Research Focus
What is the deep nature of physical reality?
Big Picture
We may never be able to grasp that reality. The universe and its ingredients may be impossible to describe unambiguously.
More In This Article
Stanford University physicist Leonard Susskind revels in discovering ideas that transform the status quo in physics. Forty years ago he co-founded string theory, which was initially derided but eventually became the leading candidate for a unified theory of nature. For years he disputed Stephen Hawking’s conjecture that black holes do not merely swallow objects but grind them up beyond recovery, in violation of quantum mechanics. Hawking eventually conceded. And he helped to develop the modern conception of parallel universes, based on what he dubbed the “landscape” of string theory. It spoiled physicists’ dream to explain the universe as the unique outcome of basic principles.
Physicists seeking to understand the deepest levels of reality now work within a framework largely of Susskind’s making. But a funny thing has happened along the way. Susskind now wonders whether physicists can understand reality.
This article was originally published with the title Bad Boy of Physics.
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34 Comments
Add CommentIn this intriguing Q&A, “Leonard Susskind insists that reality may forever be beyond reach of our understanding. One thing that led him to this conclusion is his principle of black hole complementary, which holds that there is an inherent ambiguity in the fate of objects that fall into a black hole. From the point of view of the falling object itself, it passes without incident through the hole’s perimeter and is destroyed when it reaches the hole’s singularity. From the vantage point of an external observer, the falling object is incinerated at the event horizon”. I tend not to agree with this line of reasoning. It seems clear that what physically happens is that the object passes without incident through the hole’s perimeter. The apparent ambiguity stems from the fact that – according to general relativity – the passage of time differs in the frame of reference of the falling object and that of the external observer. Actually, what happens is that from the vantage point of the external observer, the falling object appears “frozen in time” when it arrives at the event horizon (and permanently disappear from view upon expansion of said horizon). However, one should not conclude from this that the falling object has an ambiguous fate. The event is merely observed in a different way depending on the observer’s frame of reference.
Reply | Report Abuse | Link to thisAntirealists such as Niels Bohr, who said that mental images are fraught with peril and that scientists should confine themselves to making and testing empirical predictions, are ironically very similar to Benedictine monks who follow the Rule of Benedict from like 500 AD. One phrase from the Rule comes to mind: Conversatio morum, or in one translation, continuous openness to change or growth. Meditative, wordless, image- and concept-free prayer is perhaps more empirical than science, as it is also free of predictions. It is freely open to what is -- or isn't.
Reply | Report Abuse | Link to thisPlease, what is the empirical evidence which indicates that the universe is at least 1000 times bigger in volume than we can possibly observe?
Reply | Report Abuse | Link to thisThe BIG BANG was the start of the black hole that we are inside. Each back hole that we observe contains a universe similar to ours. And our black hole/universe in inside another black hole/universe. It's TURTLES not only all the way DOWN but all the way UP as well.
Reply | Report Abuse | Link to thisConsidering black hole complementarity, I looked a bit deeper into the black hole information loss paradox. From a theoretical point of view, there seem to be different opinions on whether information is preserved or lost when the information-carrying system crosses the event horizon of a black hole (and finally hits its singularity). It seems experimental data is the only way out of this discussion. Should the LHC be capable of producing microscopic black holes, an interesting experiment could be to create a pair of entangled particles and to perform a measurement on one of them in order for their wavefunction to (apparently) collapse (at least for the measured quantity). The next step is to contact the first particle with an LHC synthesized microscopic black hole. If information is destroyed within said black hole, the second particle is expected to return to a state of superposition and should therefore show clear quantum effects. If information is preserved within said black hole, the second particle is expected to remain in its collapsed state (at least for the measurement quantity). Such an experiment may possibily even be performed with a black hole model system.
Reply | Report Abuse | Link to this"Please, what is the empirical evidence which indicates that the universe is at least 1000 times bigger in volume than we can possibly observe?"
Reply | Report Abuse | Link to thisThere are several lines of evidence. They involve the details of the distribution of mass in the universe and its (in)homogeneity at different scales, the power spectrum and spacial distribution of variations in the cosmic microwave background, etc. All of these lines of evidence indicate that when we point our telescopes at the edge of what we can see we're nowhere near looking at the edge of what IS.
It is truly amazing how "far" one can get without ever generating a single scientific prediction that is prior, feasible, quantitative, non-adjustable and unique to "string/M theory".
Reply | Report Abuse | Link to thisIt really defines our era in theoretical physics, eh?
Robert L. Oldershaw
http://www3.amherst.edu/~rloldershaw
Isn't it kind of naive to make these proclamations that things "will forever be beyond reach of our understanding". That just smacks of naive, unimaginative and close-minded thinking to me.
Reply | Report Abuse | Link to thisI found the recent article about the "physics of intelligence" to be of about the same caliber. This was really a disappointing issue of SA for me.
I liken humans intending to psychologically understand reality as trying to do weather modelling on a five dollar calculator sold in college bookshops.
Reply | Report Abuse | Link to thisSolving the problem "What is reality?" using quantum computers is not so much the answer solved in hours instead of millenniums, if our biological brains in this newly evolving life form we call "human" cannot grasp the results! In our present state of intelligence and consciousness, it will take an amount of linear time exceeding a human lifespan to fully comprehend the truth about reality as it relates to science, physics, and our own consciousness as intelligent life forms.
Along the lines of what I just said, I loved the famous "answer to everything" riddle in a dark-humored sci-fi movie that humorously but poignantly addresses the issues raised by Loenard Susskind. As some may recall in the Hitchhiker's Guide to the Galaxy, a must-see for it's thought provoking British humor, a group of hyper-intelligent pan-dimensional beings demand to learn "the Ultimate Answer to the Ultimate Question of Life, The Universe, and Everything" from the supercomputer, Deep Thought, specially built for this purpose. It takes Deep Thought 7.5 million years to compute and check the answer, which turns out to be 42. The Ultimate Question itself? Deep Thought admits that after all this geologic time, the question remains unknown.
Reply | Report Abuse | Link to thisOn the origin of black holes and their internal structure… part 1/2
Reply | Report Abuse | Link to thisIn the context of black hole complementarity, an intriguing question pops up: is a growing black hole observable by an external observer?
According to general relativity, from the vantage point of an external observer, material approaching a black hole slows down. It takes an infinite amount of time for said material to reach the event horizon and it will never - from the vantage point of an external observer - actually reach the singularity inside. An external observer will therefore never observe a growing black hole, i.e. he will never observe the expansion of its event horizon.
So, if the growth of a black hole cannot be observed by an external observer, why do we observe black holes with different equivalent solar masses?
My personal opinion on the matter is that since the gravitational collapse of a massive star can never be perfectly centrosymmetrical, the formation of every observable macroscopic black hole must inevitably start with the formation of a large number of microscopic black holes (that originate at highest density positions within the collapsing star). From the vantage point of an external observer, the diameter of the event horizon of each of said microscopic black holes must inevitably remain constant from the moment that said diameter is infinitesimal larger than the diameter of its singularity. Said microscopic black holes then clutter together under their own gravity and form a macroscopic black hole. Said formation is complete - from the vantage point of an external observer - when the distance between the event horizons of the constituent microscopic black holes becomes infinitesimal small (which takes an infinite amount of time).
On the origin of black holes and their internal structure… part 2/2
Reply | Report Abuse | Link to thisThis line of reasoning has some consequences:
1) For the event horizon of a macroscopic black hole to have a finite, non-zero, diameter, the event horizons of its constituent microscopic black holes must have a finite, non-zero diameter. Since said diameter of the event horizon of said microscopic black holes is only infinitesimal larger than the diameter of their singularity, it follows that the singularity itself must have a finite, non-zero, diameter. In other words, the singularity cannot be a mathematical point.
2) A model of a macroscopic black hole based on a single singularity in the center surrounded by a single event horizon seems inadequate. Instead, a black hole should be modelled as a closed-packed lattice of microscopic black holes.
3) According to the model above, a macroscopic black hole is in principle transparent: by carefully navigating through the closed-packed lattice and avoiding crossing an event horizon, one can in principle enter the macroscopic hole at one side an leave it at the other side.
It would be interesting to know the authors opinion about these issues.
Beyond Susskind/Hawking's black hole analysis concluding our species cognitive limitations in the sensory/computational resolution capacities is self-evident common sense. Human existential reality is a hybrid mixture of empirical observations and inferential metaphysical logic to extend our search for meaningful adaptive solutions beyond the ontological measurement. Barring a genetic mutation, the search for noumenal reality is a journey along an asymptotic sinuous trail. Because reality is in the brain we need to factor in the emotional substratum inexorably coloring the most objective/rational effort to be truthful. We are the resultant of a continuing, ongoing genetic and memetic effort to preserve and maintain a biopsychosocial equilibrium as a strategy for survival in our biospherical ecosystem. But, we preserve a free will that liberates us from unconscious genetic,subconscious memetic and conscious emotional controls. We love poems about genesis and destinies and elaborate models, the hallmark of our frustrating human experience. Dr.d
Reply | Report Abuse | Link to thisIn our modern world case at least one candidate "ultimate question" seems reasonable. Its brief form would be something like "why (human) consciousness" (meaning the "strong", practically unlimited, version of the latter capable of catching the detailed material structure of more than one universe). It's not new (gave rise to all big religions, in particular), but it's today that it becomes "very intriguing" again, just at this time of ultimate technical power and equally ultimate spiritual and intellectual misery (we agree on your estimate of real official science "power", it's just that notorious "42" :)). Although it may be less evident for many, now this "ultimately philosophical" question becomes also the most practically important one, in the sense "so what to do with all of it now and where to go" or even "how to survive (and what for exactly)", beyond trivial impasses of the official agenda, of course. Yet less trivial (but provable), all modern hard practical problems can only be resolved "together" with the "ultimate" one.
Reply | Report Abuse | Link to thisYou mention the difficulty of such or similar problems, but the truth is that nobody even tries to tackle it, seriously and in a balanced way, beyond the evident extremes of traditional religion, politics, philosophy and that always "calculating", oversimplified science (within its grossly deficient abstract "models" imposed as the unique ever possible answer and "objective" approach).
So instead of wasting the last world's resources on all those obviously destructive enterprises, why not to engage a much cheaper but deeper analysis of all "difficult" and "ultimate" modern problems within a logical, "science-like" approach but avoiding the ultimate simplification (and unfortunately corruption) of evidently bankrupt official schemes ?
In case somebody can find a practical possibility for it, I don't think that nontrivial "ultimate" answers to their respective questions will be missing. "Eyes wide open" would imply real interactivity providing a new, sensible input to all those eyes that want to be open, http://sites.google.com/site/unifiedcomplexity/ . Or else, let it be like it is and remain with their 42 lies, delirious "landscapes", war of civilisations and financial crises...
He's completely right. We don't perceive reality, we just have a mental construct of what our senses feel. Also, the Heisenberg's undetermination principle opens the way to the multiverses: if some matter is tuned to a certain quantum configuration, and other matter to a different one, they can co-exist in the same physical place with little or no interaction or cross-talk one to the other. This can even open the way to a material explanation for some elusive phenomena such as ghosts. Are ghostbusters a feasible fact ?
Reply | Report Abuse | Link to thisGodel was the first who claimed that we can not define (or fully describe) our world while we are being inside. This is the same argument that we can not define what a human being is without referring to all the other creatures. Hence, there is no hope to ever be able to grasp our world to its wholeness. However what we can do is to limit the unknowable (virtual) part to its physical edges and try to understand how it is interconnected with our "physical" reality.
Reply | Report Abuse | Link to thisBlack Hole is the virtual part (idol) of its complementary universe and we simply can not see inside as "reality" jumps from "real" to "virtual" by passing its horizon from outside to inside. However this does not imply that we can have multi-Universes as the Universe is one that includes many sub-Universes. Black Hole's Horizon accommodates the whole information of any included event (object) in a kind of a "radial projection".
I like to think of our body of knowledge as a balloon. What we know is inside the balloon, what we do not know, but can imagine is represented by the outside surface of the balloon. The infinite space beyond the outside of the balloon is what we do not know, but more importantly is what we have little to no framework to be able to learn, yet. When we learn something new, it is like a puff of air inside the balloon. What we know increases, but the outside surface of the balloon increases as well, and as the cube of what we have learned
Reply | Report Abuse | Link to thisThere is no "infinite" space beyond the outside ... as Universe is no unlimited (in space and in time). When our knowledge increases (in real framework) the inside increases but the outside "decreases" in "real" framework (or "increases" in "virtual" framework). This means that the whole remains "constant". The proportion between "real and "virtual" changes and not the whole amount of information.Even-more, when "real" part of an object's reality becomes bigger than its "virtual" reality then object jumps into the "virtual" reality (it passes the other side of horizon). It is worth mentioning that "virtual" part is the "idol" of the "real" one. In other words, all parameters that increase in "real" framework decrease in "virtual" framework according to the "real" reality or all parameters that decrease in "real" framework increase in "virtual" framework according to the "virtual" reality.
Reply | Report Abuse | Link to thisLike any human Leonard Susskind has the freedom of thought, his view of reality is one of 6 billion, I myself pose thge following questions:
Reply | Report Abuse | Link to this1. Who or what provides the energy to let strings vibrate ??? (for me the main question)
2. Gravity is a force that we cannot yet explain, it seems to me the result of collapsed wave function (particles), because the pure wave function is a way to say that a particle can emerge everywhere where it will be "observed"; and waves cannot produce gravity...
3. at the event horizon of the black hole the force of gravity is so strong that nothing can return back, this means that the black hole must be filled with particles (and not waves/possibillities, for else there is no gravity), not being able to return does not mean that time is standing still for the object itself (subjective velocity of light) or that it has to move at the speed of light (for exemple Hawking radiation : if the counterparticle is on the event horizon it does not have the speed of light).
4. In my opinion there are no "singulairities" not in the "center" of a black hole nor at the beginning of our Universe (I hate the word Big Bang, there was no one to hear it), the smallest units in our universe are the Planck units (10^-33cm) beyond this border there is no longer causality, string theorsts use this border to let vibrate their strings , I use it (which in deed can not be proved also) as a door to the "non causal total simultaneity" (not te be mixed with the absolute simultaneity of Einstein which is happening in the causal deterministic time), so this being the origin of paralel worlds is partly true, it is not their origin, they are ALL TOGETHER present wit all the possible space/time moments.
5. Our Consciousness is able to recognise and combine in this total simultaneity planck units of space/time to LIFE LINES (they "exist" without time causality). So every moment of your life is in the fridge of total simultaneity. (reincarnation is the sensibility for other life lines, ghosts are also your ability (or not) to read life lines of dthe dead, going back in time and killing your grandfather brings you in a paralel world and not back in the world where you do not exist, etc etc
freedom of thinking
Wilhelmus
Is Dr. Susskind saying anything new about reality that wasn't said by Immanuel Kant near the end of the eighteenth century? Kant maintained, and idealists after him, that the human mind is conditioned by a priori constructs including time, space and causality that preclude our ever knowing "Das-Ding-an-Sich" or "the-thing-in-itself." If I'm wrong, perhaps someone can tell me how Susskind's views differ from or add significantly to Kant's, other than to help confirm them with modern scientific theory.
Reply | Report Abuse | Link to thisWith all due respect to physicist Leonard Susskind, The issue is not of one of scientific explanation but one of contaminated perceptions. We can no more perceive our physical reality than a fish can until it is taken out of its watery environment. The reality we seek has to take into account our universe in which time and space are relativity compressed into an inaccessible quantum state. That is like trying to catch up with a photon and exam it once it is created. Our visible universe's reality is not accessible for those seeking to explore it from outside our universe's barriers. Dr Leonard Susskind I ask you where is the edge of our universe? You can not catch up with that universal barrier edge and exam it any more than you can catch up and exam the escaping photon.
Reply | Report Abuse | Link to thisCosmology mathematical proofs supporting contemporary theories are effective in formulating predictions just as were the pre Copernicus math predictions of lunar and solar eclipses. They predicted well but did not know what was out there. Lesson learned: mathematical proofs alone may not represent what is out there without representative observations from outside our universe's relativity barriers.
Dr Leonard Susskind perhaps our observations are dealing with the observed effects of near parallel universes which may be more intrusive than parallel ones.
Ernest Bellantoni
Good comment RIOLDERSHAW (comment 7). Like you, I have become uncomfortable with how far theory has gone without any kind of experimental evidence or verifiable predictions. I'm not saying that string theory or M-theory is wrong. No one knows. They may ultimately turn out to be a final description of reality. But we all need to take step back. Many times in the past, pretty theories have turned out to be wrong.
Reply | Report Abuse | Link to thisFor whatever it is worth, my advice is to stay scientifically skeptical of the multi-verse, M-theory, string theory, and a lot of the current physics fads. In the absence of evidence they are no better than fancy fantasies.
Always wrong in every way.
Reply | Report Abuse | Link to thisProf. Susskind is correct. When you have two equal aspects of a binary -- such as wave-particle -- it isn't either or, it is either and.
Reply | Report Abuse | Link to thisHeisenberg's electronic microscope thought experiment demonstrated how nature prevents us from perceiving both complimentary aspects of the wave-particle binary at the same time.
For a fictional take on what kind of "reality" this might yield, see http://donnee.com/true-nature-of-existence.htm
Enjoy.
I was shocked when I read in “Bad Boys of Physics” that Mr. Susskind was not cut out to be an engineer because his professor in the engineering college told him : “you’re exceptionally smart. You should become a scientist”. Smart in this context means good in math ( Mr. Susskind claims: “I was very good in math” ).
Reply | Report Abuse | Link to thisMath is the fundamental tool and language in science and engineering. But the ideas, the imagination are triggering the century compiled collective knowledge and power in this symbolic language. Good scientists as well as good engineers generate original ideas and have imagination. The difference is that scientists discover the new and engineers create the new (a definition by Niels Bohr). There is another difference: scientists are in a much better position because if they fail with a particular theory they have a good excuse “Oh, doesn’t matter, we learn from our failures”…And they continue with the next idea. Except for the fund managers who pay for their scientific projects, few others care. If an engineer creates a flop he simply will be fired.
If you read this text and if you agree with me, what do you think? Who is smarter: me, the electronic engineer or Mr. Susskind, the theoretical physicist?
Peter Grigorov
I was shocked when I read in “Bad Boys of Physics” that Mr. Susskind was not cut out to be an engineer because his professor in the engineering college told him : “you’re exceptionally smart. You should become a scientist”. Smart in this context means good in math ( Mr. Susskind claims: “I was very good in math” ).
Reply | Report Abuse | Link to thisMath is the fundamental tool and language in science and engineering. But the ideas, the imagination are triggering the century compiled collective knowledge and power in this symbolic language. Good scientists as well as good engineers generate original ideas and have imagination. The difference is that scientists discover the new and engineers create the new (a definition by Niels Bohr). There is another difference: scientists are in a much better position because if they fail with a particular theory they have a good excuse “Oh, doesn’t matter, we learn from our failures”…And they continue with the next idea. Except for the fund managers who pay for their scientific projects, few others care. If an engineer creates a flop he simply will be fired.
If you read this text and if you agree with me, what do you think? Who is smarter: me, the electronic engineer or Mr. Susskind, the theoretical physicist?
Peter Grigorov
How can man find reality?Everything in the Creation is changing ,everything observable changes but what is the nature of the observer that witnesses the change? That is the unchangeable reality.It can't be investigated or held but it can be known.Once known all is known and playing scientific sandcastles can then become fun again.
Reply | Report Abuse | Link to thisUntil we go beyond seeking the cause in the effect the big scientific questions will never be answered .Investigating the reaction of various radio components does not show the location of the voice.
We need more "bad boys" like Bohr and Susskind
Reply | Report Abuse | Link to thisAristotele and Aquino said we should believe only what we observe by our senses or deduce deduce logically from observations by our senses .
Reply | Report Abuse | Link to thisFrom this we may conclude in reality is no place for empirism or quanta . This conclusion is confirmed by the experiments of the LHC.
To understand this article can the author or somebody else tell me what is object falling in the black hole?Is it composed of molecules or is it pure spirit ?
Reply | Report Abuse | Link to thisBig mouths.Science of Everything.Multiple Uninerses. Octonions when quaternions are finished etc.Learned discussions about non-existing entities.Why not use all that science to explain realities .Atomic spectra are of our time and dimension,when spectra were discovered about 1860 scientists agreed there is a link between atomic structures and spectra.Until now this real link between real things was not found. Benedict humility is more wise here than a big mouth.
Reply | Report Abuse | Link to thisThe question has now become "why is the answer 42?":-)
Reply | Report Abuse | Link to thisIf the Big Banged in all directions of which we are only one then the Bang must be the center of a sphere of observable matter, meaning of course that the universe diameter is at least twice as big as the radius we have measured.
Reply | Report Abuse | Link to thisA respected lecturer's video showed two moving five man teams passing a basket ball between their members, and asked the medical audience to count the number of passes that transpired between the moving white team members during a short period of time. The correct number was found by the audience's diligent attention to the problem. The next question was "how many people saw the gorilla in the scene"? --- Dead silence. He ran the video again in slower motion. Guess what! a black gorilla comes into the scene, stops in the middle and dances for the camera. The proverbial elephant in the middle of the room?
Reply | Report Abuse | Link to thisA bigger elephant of course is the ETHER dancing for attention while the Susskinds and the Hawkings develop theories to prove that the ball can only bounce between team members and occasionally vanish but still be retrievable etc, etc by rewinding the camera.
When their theories die of their own complexity and absurd magic, they fall back on the time honored cop out of "lets face it we may never be able to resolve problems which are beyond human (their?)understanding."
"The Dynamic Ether" on the other hand, presents an ether which redirects the cosmic questions, and comes up with some logical answers well within any body's understanding.