Steven S. Gubser: Thunder and Lightning from Neutron Star mergers

As of late 2015, we have a new way of probing the cosmos: gravitational radiation. Thanks to LIGO (the Laser Interferometer Gravitational-wave Observatory) and its new sibling Virgo (a similar interferometer in Italy), we can now “hear” the thumps and chirps of colliding massive objects in the universe. Not for nothing has this soundtrack been described by LIGO scientists as “the music of the cosmos.” This music is at a frequency easily discerned by human hearing, from somewhat under a hundred hertz to several hundred hertz. Moreover, gravitational radiation, like sound, is wholly different from light. It is possible for heavy dark objects like black holes to produce mighty gravitational thumps without at the same time emitting any significant amount of light. Indeed, the first observations of gravitational waves came from black hole merger events whose total power briefly exceeded the light from all stars in the known universe. But we didn’t observe any light from these events at all, because almost all their power went into gravitational radiation.

In August 2017, LIGO and Virgo observed a collision of neutron stars which did produce observable light, notably in the form of gamma rays. Think of it as cosmic thunder and lightning, where the thunder is the gravitational waves and the lightning is the gamma rays. When we see a flash of ordinary lightning, we can count a few seconds until we hear the thunder. Knowing that sound travels one mile in about five seconds, we can reckon how distant the event is. The reason this method works is that light travels much faster than sound, so we can think of the transmission of light as instantaneous for purposes of our estimate.

Things are very different for the neutron star collision, in that the event took place about 130 million light years away, but the thunder and lightning arrived on earth pretty much simultaneously. To be precise, the thunder was first: LIGO and Virgo heard a basso rumble rising to a characteristic “whoop,” and just 1.7 seconds later, the Fermi and INTEGRAL experiments observed gamma ray bursts from a source whose location was consistent with the LIGO and Virgo observations. The production of gamma rays from merging neutron stars is not a simple process, so it’s not clear to me whether we can pin that 1.7 seconds down as a delay precisely due to the astrophysical production mechanisms; but at least we can say with some confidence that the propagation time of light and gravity waves are the same to within a few seconds over 130 million light years. From a certain point of view, that amounts to one of the most precise measurements in physics: the ratio of the speed of light to the speed of gravity equals 1, correct to about 14 decimal places or better.

The whole story adds up much more easily when we remember that gravitational waves are not sound at all. In fact, they’re nothing like ordinary sound, which is a longitudinal wave in air, where individual air molecules are swept forward and backward just a little as the sound waves pass them by. Gravitational waves instead involve transverse disturbances of spacetime, where space is stretched in one direction and squeezed in another—but both of those stretch-squeeze directions are at right angles to the direction of the wave. Light has a similar transverse quality: It is made up of electric and magnetic fields, again in directions that are at right angles to the direction in which the light travels. It turns out that a deep principle underlying both Maxwell’s electromagnetism and Einstein’s general relativity forces light and gravitational waves to be transverse. This principle is called gauge symmetry, and it also guarantees that photons and gravitons are massless, which implies in turn that they travel at the same speed regardless of wavelength.

It’s possible to have transverse sound waves: For instance, shearing waves in crystals are a form of sound. They typically travel at a different speed from longitudinal sound waves. No principle of gauge symmetry forbids longitudinal sound waves, and indeed they can be directly observed, along with their transverse cousins, in ordinary materials like metals. The gauge symmetries that forbid longitudinal light waves and longitudinal gravity waves are abstract, but a useful first cut at the idea is that there is extra information in electromagnetism and in gravity, kind of like an error-correcting code. A much more modest form of symmetry is enough to characterize the behavior of ordinary sound waves: It suffices to note that air (at macroscopic scales) is a uniform medium, so that nothing changes in a volume of air if we displace all of it by a constant distance.

In short, Maxwell’s and Einstein’s theories have a feeling of being overbuilt to guarantee a constant speed of propagation. And they cannot coexist peacefully as theories unless these speeds are identical. As we continue Einstein’s hunt for a unified theory combining electromagnetism and gravity, this highly symmetrical, overbuilt quality is one of our biggest clues.

The transverse nature of gravitational waves is immediately relevant to the latest LIGO / Virgo detection. It is responsible for the existence of blind spots in each of the three detectors (LIGO Hanford, LIGO Livingston, and Virgo). It seems like blind spots would be bad, but they actually turned out to be pretty convenient: The signal at Virgo was relatively weak, indicating that the direction of the source was close to one of its blind spots. This helped localize the event, and localizing the event helped astronomers home in on it with telescopes. Gamma rays were just the first non-gravitational signal observed: the subsequent light-show from the death throes of the merging neutron stars promises to challenge and improve our understanding of the complex astrophysical processes involved. And the combination of gravitational and electromagnetic observations will surely be a driver of new discoveries in years and decades to come.

 

BlackSteven S. Gubser is professor of physics at Princeton University and the author of The Little Book of String TheoryFrans Pretorius is professor of physics at Princeton. They both live in Princeton, New Jersey. They are the authors of The Little Book of Black Holes.

Everyone’s favorite genius takes the spotlight

Along with Einstein fans everywhere, we’re fairly excited to binge-watch National Geographic’s upcoming series, “Genius”, premiering Tuesday, April 25. The first episode shows a young Einstein (Johnny Flynn), poring over the nature of time, a concept well covered in our An Einstein Encyclopedia along with most any other topic that could interest an Einstein devotee, from fame, to family, to politics, to myths and misconceptions. In Genius, prepare to see a show-down between a feisty young Einstein and a particularly rigid teacher. Engrossing to watch—and bound to leave viewers wanting more. Not to worry: “Teachers, education and schools attended” are covered in depth in the Encyclopedia, as are “Rivals”.

Episode 2 of Genius promises to show Einstein embarking, after much head-butting, on a love affair with the determined Mileva Maric. Often remembered as the lone, eccentric, Princeton-based thinker, Einstein’s youthful relationship with Maric sometimes comes as a surprise even to Einstein fans. And yet in 1903, a young Albert Einstein married his confidante despite the objections of his parents. Her influence on his most creative years has given rise to much discussion—but theirs was only one of several romantic interests over the course of Einstein’s life that competed with his passion for physics. Einstein’s love life has been the subject of intense speculation over the years, but don’t believe everything you hear: “Romantic Interests: Actual, Probable, and Possible”, all included in the Encyclopedia, won’t leave you guessing.

Mileva Maric, first wife of Albert Einstein

 An Einstein Encyclopedia is the single most complete guide to Einstein’s life, perfect for browsing and research alike. Written by three leading Einstein scholars who draw on their combined wealth of expertise gained during their work on the Collected Papers of Albert Einstein, this accessible reference features more than one hundred entries and is divided into three parts covering the personal, scientific, and public spheres of Einstein’s life.

With science celebrated far and wide along with Earth Day this past weekend, what better time to get your dose of genius and #ReadUp.

 

 

PUP math editor Vickie Kearn: How real mathematicians celebrate Pi Day

Who doesn’t love Pi (aka Pie) Day? Residents here in Princeton, NJ love it so much that we spend four days celebrating. Now, to be honest, we’re also celebrating Einstein’s birthday, so we do need the full four days. I know what I will be doing on 3.14159265 but I wondered what some of my friends will be doing. Not surprisingly, a lot will either be making or eating pie. These include Oscar Fernandez (Wellesley), Ron Graham (UCSD), and Art Benjamin (who will be performing his mathemagics show later in the week). Anna Pierrehumbert (who teaches in NYC) will be working with upper school students on a pi recitation and middle school students on making pi-day buttons. Brent Ferguson (The Lawrenceville School) has celebrated at The National Museum of Mathematics in NYC, Ireland, Greece, and this year Princeton. Here he is celebrating in Alaska:

Pi

The Princeton University Math Club will be celebrating with a party in Fine Hall. In addition to eating pie and playing games, they will have a digit reciting contest. Tim Chartier (Davidson College) will be spending his time demonstrating how to estimate pi with chocolate chips while also fielding interview requests for his expert opinion on March Madness (a lot going on this month for mathematicians). Dave Richeson (Dickinson College) goes to the local elementary school each year and talks with the fifth graders about pi and its history and then eats creatively rendered pi themed pie provided by the parents.

You might be wondering why we celebrate a mathematical constant every year. How did it get to be so important? Again I went back to my pi experts and asked them to tell me the most important uses of pi. This question is open to debate by mathematicians but many think that the most important is Euler’s Identity, e(i*pi) + 1 = 0. As Jenny Kaufmann (President of the Princeton University Math Club) puts it, “Besides elegantly encoding the way that multiplication by i results in a rotation in the complex plane, this identity unites what one might consider the five most important numbers in a single equation. That’s pretty impressive!” My most practical friend is Oscar and here is what he told me: “There are so many uses for pi, but given my interest in everyday explanations of math, here’s one I like: If you drive to work every day, you take many, many pi’s with you. That’s because the circumference of your car’s tires is pi multiplied by the tires’ diameter. The most common car tire has a diameter of about 29 inches, so one full revolution covers a distance of about 29 times pi (about 7.5 feet). Many, many revolutions of your tires later you arrive at work, with lots and lots of pi’s!” Anna is also practical in that she will be using pi to calculate the area of the circular pastry she will be eating, but she also likes the infinite series for pi (pi/4 = 1 – 1/3 + 1/5 – 1/7 etc.). Avner Ash (Boston College) sums it up nicely, “ We can’t live without pi—how would we have circles, normal distributions, etc.?”

One of the most important questions one asks on Pi Day is how many digits can you recite? The largest number I got was 300 from the Princeton Math Club. However, there are quite a few impressive numbers from others, as well as some creative answers and ways to remember the digits. For example, Oscar can remember 3/14/15 at 9:26:53 because it was an epic Day and Pi Time for him. Art Benjamin can recite 100 digits from a phonetic code and 5 silly sentences. Ron Graham can recite all of the digits of pi, even thousands, as long as they don’t have to be in order. Dave Richeson also knows all of the digits of pi which are 0,1,2,3,4,5,6,7,8,and 9.

No matter how you celebrate, remember math, especially pi(e) is useful, fun, and delicious.

Vickie Kearn is Executive Editor of Mathematics at Princeton University Press.

J. Richard Gott: What’s the Value of Pi in Your Universe?

Carl Sagan’s sci-fi novel Contact famously introduced wormholes for rapid transit between the stars. Carl had asked his friend Kip Thorne to tell him if the physics of wormholes was tenable and this led Thorne and his colleagues to investigate their properties. They found that traversable wormholes required exotic matter to prop them open and that, by moving the wormhole mouths one could find general relativity solutions allowing time travel to the past. A quantum state called the Casimir vacuum whose effects have been observed experimentally, could provide the exotic matter. To learn whether such time machines could be constructible in principle, we may have to master the laws of quantum gravity, which govern how gravity behaves on microscopic scales. It’s one of the reasons physicists find these solutions so interesting.

But in Contact there is lurking yet another fantastic sci-fi idea, which gets less publicity because it was not included in the movie version. In the book, the protagonist finds out from the extraterrestrials that the system of wormholes throughout the galaxy was not built by them, but by the long gone “old ones” who could manipulate not only the laws of physics but also the laws of mathematics! And they left a secret message in the digits of pi. In his movie Pi, Darren Aronofsky showed a man driven crazy by his search for hidden meanings in the digits of pi.

This opens the question: could pi have been something else? And if so, does pi depend on the laws of physics? Galileo said: “Philosophy is written in this grand book…. I mean the universe … which stands continually open to our gaze…. It is written in the language of mathematics.” The universe is written in the language of mathematics. Nobel laureate Eugene Wigner famously spoke of the “unreasonable effectiveness of mathematics” in explaining physics. Many philosophers take the Platonic view that mathematics would exist even the universe did not. And cosmologist Max Tegmark goes so far as to say that the universe actually is mathematics.

Yet maybe it is the other way around. The laws of physics are just the laws by which matter behaves. They determine the nature of our universe. Maybe humans have simply developed the mathematics appropriate for describing our universe, and so of course it fits with what we see. The mathematician Leopold Kronecker said, “God created the integers, all the rest is the work of man.” Are the laws of mathematics discovered by us in the same way as we discover the laws of physics? And are the laws of mathematics we discover just those which would have occurred to creatures living in a universe with physics like ours? In our universe, physics produces individual identical particles: all electrons are the same for example. We know about integers because there are things that look the same (like apples) for us to count. If you were some strange creature in a fractal universe containing only one object—yourself—and you thought only recursively, you might not ever think of counting anything and would never discover integers.

What about π = 3.14159265.…? Might it have a different value in a different universe? In our universe we have a fundamental physical dimensionless constant, the fine structure constant α which is related to the square of the value of the electric charge of the proton in natural geometrical Planck units (where the speed of light is 1 and the reduced Planck constant is 1 and Newton’s gravitational constant is 1). Now 1/α = 137.035999… Some physicists hope that one day we may have a mathematical formula for 1/α using mathematical constants such as π and e. If a theory for the fine structure constant could be developed giving a value in agreement with observations but allowing it to be calculated uniquely from pure mathematics, and if more and more digits of the constant were discovered experimentally fulfilling its prediction, it would certainly merit a Nobel Prize. But many physicists feel that no such magic formula will ever be discovered. Inflation may produce an infinite number of bubble universes, each with different laws of physics. Different universes bubbling out of an original inflating sea could have different values of 1/α. As Martin Rees has said, the laws of physics we know may be just local bylaws in an infinite multiverse of universes. String theory, if correct, may eventually give us a probability distribution for 1/α and we may find that our universe is just somewhere in the predicted middle 95% of the distribution, for example. Maybe there could be different universes with different values of π.

Let’s consider one possible example: taxicab geometry. This was invented by Hermann Minkowski. Now this brilliant mathematician also invented the geometrical interpretation of time as a fourth dimension based on Einstein’s theory of special relativity, so his taxicab geometry merits a serious look. Imagine a city with a checkerboard pattern of equal-sized square blocks. Suppose you wanted to take a taxicab to a location 3 blocks east, and 1 block north of your location, the shortest total distance you would have to travel to get there is 4 blocks. Your taxi has to travel along the streets, it does not get to travel as the crow flies. You could go 1 block east, then 1 block north then 2 blocks east, and still get to your destination, but the total distance you traveled would also be 4 blocks. The distance to your destination would be ds = |dx| + |dy|, where |dx| is the absolute value of the difference in x coordinates and |dy| is the absolute value of the difference in y coordinates. This is not the Euclidean formula. We are not in Kansas anymore! The set of points equidistant from the origin is a set of dots in a diamond shape. See diagram.

Gott

Image showing an intuitive explanation of why circles in taxicab geometry look like diamonds. Wikipedia.

Now if the blocks were smaller, there would be more dots, still in a diamond shape. In the limit where the size of the blocks had shrunk to zero, one would have a smooth diamond shape as shown in the bottom section of the diagram. The set of points equidistant from the origin has a name—a “circle!” If the circle has a radius of 1 unit, the distance along one side of its diamond shape is 2 units: going from the East vertex of the diamond to the North vertex of the diamond along the diagonal requires you to change the x coordinate by 1 unit and the y coordinate by 1 unit, making the distance along one side of the diagonal equal to 2 units (ds = |dx| + |dy| = 1 + 1 units = 2 units). The diamond shape has 4 sides so the circumference of the diamond is 8 units. The diameter of the circle is twice the radius, and therefore 2 units. In the taxicab universe π = C/d = C/2r = 8/2 = 4. If different laws of physics dictate different laws of geometry, you can change the value of π.

This taxicab geometry applies in the classic etch-a-sketch toy (Look it up on google, if you have never seen one). It has a white screen, and an internal stylus that draws a black line, directed by horizontal and vertical control knobs. If you want to draw a vertical line, you turn the vertical knob. If you want to draw a horizontal line you turn the horizontal knob. If you want to draw a diagonal line, you must simultaneously turn both knobs smoothly. If the distance between two points is defined by the minimal amount of total turning of the two knobs required to get from one point to the other, then that is the “taxicab” distance between the two points. In Euclidean geometry there is one shortest line between two points: a straight line between them. In taxicab geometry there can be many different, equally short, broken lines (taxicab routes) connecting two points. Taxicab geometry does not obey the axioms of Euclidean geometry and therefore does not have the same theorems as Euclidean geometry. And π is 4.

Mathematician and computer scientist John von Neumann invented a cellular automaton universe that obeys taxicab geometry. It starts with an infinite checkerboard of pixels. Pixels can be either black or white. The state of a pixel at time step t = n + 1 depends only on the state of its 4 neighbors (with which it shares a side: north, south, east, west of it) on the previous time step t = n. Causal, physical effects move like a taxicab. If the pixels are microscopic, we get a taxicab geometry. Here is a simple law of physics for this universe: a pixel stays in the same state, unless it is surrounded by an odd number of black pixels, in which case it switches to the opposite state on the next time step. Start with a white universe with only 1 black pixel at the origin. In the next time step it remains black while its 4 neighbors also become black. There is now a black cross of 5 pixels at the center. It has given birth to 4 black pixels like itself. Come back later and there will be 25 black pixels in a cross-shaped pattern of 5 cross-shaped patterns.

Come back still later and you can find 125 black pixels in 5 cross-shaped patterns (of 5 cross-shaped patterns). All these new black pixels lie inside a diamond-shaped region whose radius grows larger by one pixel per time step. In our universe, drop a rock in a pond, and a circular ripple spreads out. In the von Neumann universe, causal effects spread out in a diamond-shaped pattern.

If by “life” you mean a pattern able to reproduce itself, then this universe is luxuriant with life. Draw any pattern (say a drawing of a bicycle) in black pixels and at a later time you will find 5 bicycles, and then 25 bicycles, and 125 bicycles, etc. The laws of physics in this universe cause any object to copy itself. If you object that this is just a video game, I must tell you that some physicists seriously entertain the idea that we are living in an elaborate video game right now with quantum fuzziness at small scales providing the proof of microscopic “pixelization” at small scales.

Mathematicians in the von Neumann universe would know π = 4 (Or, if we had a taxicab universe with triangular pixels filling the plane, causal effects could spread out along three axes instead of two and a circle would look like a hexagon, giving π = 3.). In 1932, Stanislaw Golab showed that if we were clever enough in the way distances were measured in different directions, we could design laws of physics so that π might be anything we wanted from a low of 3 to a high of 4.

Back to the inhabitants of the von Neumann universe who think π = 4. Might they be familiar with number we know and love, 3.14159265…? They might:

3.14159265… = 4 {(1/1) – (1/3) + (1/5) – (1/7) + (1/9) + …} (Leibnitz)

If they were familiar with integers, they might be able to discover 3.14159265… But maybe the only integers they know are 1, 5, 25, 125, … and 4 of course. They would know that 5 = SQRT(25), so they would know what a square root was. In this case they could still find a formula for

3.14159265. . . =
SQRT(4) {SQRT(4)/SQRT(SQRT(4))}{SQRT(4)/SQRT(SQRT(4) + SQRT(SQRT(4)))}{SQRT(4)/ SQRT(SQRT(4) + SQRT(SQRT(4) + SQRT(SQRT(4))))} …

This infinite product involving only the integer 4 derives from one found by Vieta in 1594.

There are indeed many formulas equal to our old friend 3.14159265… including a spectacular one found by the renowned mathematician Ramanujan. Though every real number can be represented by such infinite series, products and continued fractions, these are particularly simple. So 3.14159265… does seem to have a special intimate relationship with integers, independent of geometry. If physics creates individual objects that can be counted, it seems difficult to avoid learning about 3.14159265… eventually—“If God made the integers,” as Kronecker suggested. So 3.14159265… appears not to be a random real number and we are still left with the mystery of the unreasonable effectiveness of mathematics in explaining the physics we see in our universe. We are also left with the mystery of why the universe is as comprehensible as it is. Why should we lowly carbon life forms be capable of finding out as much about how the universe works as we have done? Having the ability as intelligent observers to ask questions about the universe seems to come with the ability to actually answer some of them. That’s remarkable.

UniverseGottJ. Richard Gott is professor of astrophysics at Princeton University. His books include The Cosmic Web: Mysterious Architecture of the Universe. He is the coauthor of Welcome to the Universe: An Astrophysical Tour with Neil DeGrasse Tyson and Michael A. Strauss.

Neil DeGrasse Tyson & Stephen Colbert: Make America Smart Again

On November 9, Neil DeGrasse Tyson joined Stephen Colbert on The Late Show to talk about Welcome to the Universe and to blow his own mind. Watch the clip here:

 

Even celebrities misquote Albert Einstein

Calaprice_QuotableEinstein_pb_cvrAlice Calaprice is the editor of The Ultimate Quotable Einstein, a tome mentioned time and again in the media because famous folks continue to attribute words to Einstein that, realistically, he never actually said. Presidential candidates, reality stars, and more have used social media make erroneous references to Einstein’s words, perhaps hoping to give their own a bit more credibility. From the Grapevine recently compiled the most recent misquotes of Albert Einstein by public figures and demonstrated how easy it is to use The Ultimate Quotable Einstein to refute those citations:

Albert Einstein was a wise man, even outside the science laboratory. He has inspired painters, young students and comic book creators. Even budding romantics take advice from him.

So it should come as no surprise, then, that so many people today quote Einstein. Or, to be more precise, misquote Einstein.

“I believe they quote Einstein because of his iconic image as a genius,” Alice Calaprice, an Einstein expert, tells From The Grapevine. “Who would know better and be a better authority than the alleged smartest person in the world?”

Read more here.

 

A Mere Philosopher?

The Physicist and the Philosopher by Jimena CanalesOn the 6th of April, 1922, two men met at the Société française de philosophie to discuss relativity and the nature of time. One was the winner of the previous year’s Nobel Prize in Physics, Albert Einstein, renowned for a series of extraordinary innovations in scientific theory. The other was the French philosopher, Henri Bergson. In The Physicist and the Philosopher, Jimena Canales recounts the events of that meeting, and traces the public controversy that unfolded over the years that followed. Bergson was perceived to have lost the debate and, more generally, philosophy to have lost the authority to speak on matters of science.

Perhaps the greatest evidence of that loss is that it is hard to imagine an equivalent meeting today, the great physicist and the great philosopher debating as equals. While the physical sciences enjoy unprecedented prestige and funding on university campuses, many philosophy departments face cutbacks. Yet less than a century ago, Henri Bergson enjoyed enormous celebrity. His lecture at Columbia University in 1913 resulted in the first traffic jam ever seen on Broadway. His work was translated into multiple languages, influencing not only his fellow philosophers but also artists and writers (Willa Cather named one of her characters after Bergson). His writings on evolutionary theory earned him the condemnation of the Catholic Church. Students were crowded out of his classes at the Collège de France by the curious public.

The young Bergson showed promise in mathematics, but chose instead to study humanities at the École Normale. His disappointed math teacher commented “you could have been a mathematician; you will be a mere philosopher” — a harbinger of later developments? Einstein and his supporters attacked Bergson’s understanding of relativity and asserted that philosophy had no part to play in grasping the nature of time. Bergson countered that, on the contrary, it was he who had been misunderstood, but to no avail: the Einstein/Bergson debate set the tone for a debate on the relationship between philosophy and the sciences that continues to this day. At a recent roundtable discussion hosted by Philosophy Now, biologist Lewis Wolpert dismissed philosophy as “irrelevant” to science. In this, do we hear an echo of Einstein’s claim that time can be understood either psychologically or physically, but not philosophically?

Spotlight on…Scientists

Nikola Tesla, by W. Bernard Carlson

Nikola Tesla
by W. Bernard Carlson

Genius is no guarantee of public recognition. In this post we look at the changing fortunes and reputations of three very different scientists: Alan Turing, Nikola Tesla, and Albert Einstein.

With the success of the recent movie, the Imitation Game (based on Andrew Hodges’ acclaimed biography Alan Turing: The Enigma), it’s easy to forget that for decades after his death, Turing’s name was known only to computer scientists. His conviction for homosexual activity in 1950s Britain, his presumed suicide in 1954, and the veil of secrecy drawn over his code-breaking work at Bletchley Park during the Second World War combined to obscure his importance as one of the founders of computer science and artificial intelligence. The gradual change in public attitudes towards homosexuality and the increasing centrality of computers to our daily lives have done much to restore his reputation posthumously. Turing received an official apology in 2009, followed by a royal pardon in 2013.

Despite enjoying celebrity in his own lifetime, Nikola Tesla’s reputation declined rapidly after his death, until he became regarded as an eccentric figure on the fringes of science. His legendary showmanship and the outlandish claims he made late in life of inventing high-tech weaponry have made it easy for critics to dismiss him as little more than a charlatan. Yet he was one of the pioneers of electricity, working first with Edison, then Westinghouse to develop the technology that established electrification in America. W. Bernard Carlson’s Nikola Tesla tells the story of a life that seems drawn from the pages of a novel by Jules Verne or H. G. Wells, of legal battles with Marconi over the development of radio, of fortunes sunk into the construction of grandiose laboratories for high voltage experiments.

By contrast, the reputation of Albert Einstein seems only to have grown in the century since the publication of his General Theory of Relativity. He is perhaps the only scientist to have achieved iconic status in the public mind, his face recognized as the face of genius. Children know the equation e=mc2 even though most adults would struggle to explain its implications. From the publication of the four 1905 papers onwards, Einstein’s place in scientific history has been secure, and his work remains the cornerstone of modern understanding of the nature of the universe. We are proud to announce the publication of a special 100th anniversary edition of Relativity: The Special and the General Theory, and the recent global launch of our open access online archive from the Collected Papers of Albert Einstein, the Digital Einstein Papers.

Happy Birthday Albert Einstein

“Learn from yesterday, live for today, hope for tomorrow. The important thing is to not stop questioning.” – Albert Einstein

This is a huge year for Einstein at Princeton University Press. December marked the celebrated launch of The Digital Einstein Papers, a free open-access website that puts The Collected Papers of Albert Einstein online for the very first time. Today is Albert Einstein’s 136th birthday, as well as Pi Day, which, as Steven Strogatz writes in The New Yorker, is far “more than just some circle fixation.” So once you’ve rung it in with this Pi Day recipe, you might like to check out this book list in honor of the influential scientist and writer, who fittingly enough, shares his birthday with the popular mathematical holiday. Sample chapters for several Einstein related books are linked below.

 

bookjacket

The Meaning of Relativity:
Including the Relativistic Theory of the Non-Symmetric Field (Fifth Edition)

Fifth edition
Albert Einstein
With a new introduction by Brian Greene
Chapter 1

The Collected Papers of Albert Einstein, Volume 14:
The Berlin Years: Writings & Correspondence, April 1923–May 1925

Documentary edition
Albert Einstein
Edited by Diana Kormos Buchwald, József Illy, Ze’ev Rosenkranz, Tilman Sauer & Osik Moses

Chapter 1

 

bookjacket  The Road to Relativity:
The History and Meaning of Einstein’s “The Foundation of General Relativity” Featuring the Original Manuscript of Einstein’s Masterpiece

Hanoch Gutfreund & Jürgen Renn
With a foreword by John Stachel
Released April 2015

 

bookjacket The Physicist and the Philosopher:
Einstein, Bergson, and the Debate That Changed Our Understanding of Time

Jimena Canales
Released May 2015

 

bookjacket

Philosophy of Physics:
Space and Time

Tim Maudlin
Released May 2015Introduction

 

 

Two new exhibits about Albert Einstein on Google Cultural Institute

library_quote9

Two new, expertly written and illustrated exhibits about Albert Einstein are now available for free on Google Cultural Institute. These archives feature information from the Einstein Papers Project and the Hebrew University archives.

Einstein’s Trip to the Far East and Palestine

In late 1922 and early 1923, Albert Einstein embarked on a five-and-a-half-month trip to the Far East, Palestine, and Spain. In September 1921, Einstein had been invited by the progressive Japanese journal Kaizo to embark on a lecture tour of Japan.   The tour would include a scientific lecture series to be delivered in Tokyo, and six popular lectures to be delivered in several other Japanese cities. An honorarium of 2,000 pounds sterling was offered and accepted.

Einstein’s motivation for accepting the invitation to Japan was threefold: to fulfil his long-term desire to visit the Far East, to enjoy two long sea voyages “far from the madding crowds” and to escape from Berlin for several months in the wake of the recent assassination of Germany’s Foreign Minister Walther Rathenau, who had belonged to Einstein’s circle of friends. Rathenau had been gunned down by anti-Semitic right-wing extremists in June 1922 and there was reason to believe that Einstein’s life was also at risk.

Credit: Einstein’s Trip to the Far East and Palestine

Albert Einstein German, Swiss and American?

In a letter to his superiors, the German ambassador, Constantin von Neurath, quotes from a Copenhagen newspaper: „Although a Swiss subject by birth and supposedly of Jewish origin, Einstein’s work is nevertheless an integral part of German research“.

Von Neurath uses this flawed statement with good reason: The  Swiss Jew whom he would rather disregard, unfortunately proves to be one of the few “Germans” welcome abroad.

On April 26, 1920, for example, Albert Einstein was nominated member of the  Royal Danish Academy of Sciences and Letters.

The more appreciated Einstein becomes abroad, the greater Germany’s desire to claim him as one of their own.

Credit: Albert Einstein German, Swiss and American?

On the occasion of these exhibits, Diana K. Buchwald of the Einstein Papers Project at California Institute of Technology said, “The Einstein cultural exhibit gives us a splendid glimpse into rare documents and images that tell not only the story of Einstein’s extraordinary voyage to publicize relativity in Japan in 1922, and to lay the cornerstone of the Hebrew University in Palestine in 1923, but also the dramatic trajectory of his entire life, illustrated by his colorful passports that bear testimony to the vagaries of his personal life.”

Prof. Hanoch Gutfreund, Former President, The Hebrew University of Jerusalem, Chair of the Albert Einstein Archives echoed her Buchwald’s enthusiasm noting, “The cooperation between the Google Cultural Institute, the Hebrew University of Jerusalem and the Einstein Papers Project in Caltech has produced two exhibitions exploring two specific topics on Einstein’s life and personality. Thus, Google has provided an arena, accessible to all mankind, which allows the Hebrew University to share with the general public the highlights of one of its most important cultural assets–the Albert Einstein Archives, which shed light on Einstein’s scientific work, public activities and personal life.

Learn more about Princeton University Press’s Einstein-related books, including the print editions of the Einstein Papers Project, here.

 

 

Fantasy Physics: Should Einstein Have Won Seven Nobel Prizes?

This guest post from A. Douglas Stone is part of our celebration of all things Einstein, pi, and, of course, pie this week. For more articles, please click here. Please join Prof. Stone at the Princeton Public Library on March 14 at 6 PM for a lecture about Einstein’s quantum breakthroughs.

Cross-posted with the Huffington Post.

Thanks to RealClearScience for posting about this article!!


2014-03-12-Albert_Einstein_28Nobel291.pngAlbert Einstein never cared too much about receiving awards and honors, and that included the Nobel Prizes, which were established in 1901, at roughly the same time as Einstein was beginning his research career in physics. In 1905, at the age of 25, Einstein began his ascent to scientific pre-eminence and world-wide fame with his proposal of the Special Theory of Relativity, as well as a “revolutionary” paper on the particulate properties of light, his foundational work on molecular (“Brownian”) motion, and finally his famous equation, E = mc2. In 1910, he was first nominated for the Prize and was nominated many times subsequently, usually by multiple physicists, until he finally won the 1921 Prize (awarded in 1922). Surprisingly, he did not win for his most famous achievement, Relativity Theory, which was still deemed too speculative and uncertain to endorse with the Prize. Instead, he won for his 1905 proposal of the law of the photoelectric effect—empirically verified in the following decade by Robert Millikan—and for general “services to theoretical physics.” It was a political decision by the Nobel committee; Einstein was so renowned that their failure to select him had become an embarrassment to the Nobel institution. But this highly conservative organization could find no part of his brilliant portfolio that they either understood or trusted sufficiently to name specifically, except for this relatively minor implication of his 1905 paper on particles of light. The final irony in this selection was that, among the many controversial theories that Einstein had proposed in the previous seventeen years, the only one not accepted by almost all of the leading theoretical physicists of the time was precisely his theory of light quanta (or photons), which he had used to find the law of the photoelectric effect!

In keeping with his relative indifference to such honors, Einstein declined to attend the award ceremony, because he had previously committed to a lengthy trip to Japan at that time and didn’t feel it was fair to his hosts to cancel it. Moreover, when the Prize was officially announced and the news reached him during his long voyage to Japan, he neglected to even mention the Prize in the travel diary he was keeping. He had taken one practical note of it however, in advance. When he divorced his first wife, Mileva Maric in 1919, he agreed to transfer to her the full prize money, a substantial sum, in the form of a Trust for the benefit of her and his sons, should he eventually win.

However, while Einstein himself barely dwelt at all on this honor, it is an interesting exercise to ask how many distinct breakthroughs Einstein made during his productive research career, spanning primarily the years 1905 to 1925, that could be judged of Nobel caliber, when placed in historical context and evaluated by the standards of subsequent Nobel Prize awards. Admittedly, this analysis has a bit in common with fantasy sports, in which athletes are judged and ranked by their statistical achievements and arguments are made about who was the GOAT (“greatest of all time”). Well, why not spend a few pages on this guilty pleasure, at least partly in the service of illuminating the achievements of this historic genius, even if Einstein would not have approved?

Let’s start with the Prize he did receive, which was absolutely deserved, if the committee had had the courage to write the citation, “for his proposal of the existence of light quanta.” The law of the photoelectric effect, which they cited, only makes sense if light behaves like a particle in some important respects, and that is what he proposed in 1905. This proposal came at a time when the wave theory of light was absolutely triumphant and was even enshrined in a critical technology: radio. Not a single physicist in the world was thinking along similar lines as Einstein, nor were all of the important theorists convinced by his arguments for two more decades. Nonetheless, the photon concept was unambiguously confirmed in experiments by 1925, and now is considered the paradigm for our modern quantum theory of force-carrying particles. It is the first in a family of particles known as bosons, most recently augmented by the (Nobel-winning) discovery of the Higgs particle. So the photon is a Nobel slam dunk.

We can move next to two more “no-brainers,” the two theories of relativity, the Special Theory, proposed in 1905, and the General Theory, germinated in 1907 and completed in 1915. These are quite distinct contributions. The Special Theory introduced the Principle of Relativity, that the law of physics must all be the same for bodies in uniform relative motion. An amazing implication of this statement is that time does not elapse uniformly, independent of the motion of observers, but rather that the time interval between events depends on the state of relative motion of the observer. Einstein was the first to understand and explain this radical notion, which is now well-verified by direct experiments. Moreover, Einstein’s concept of “relativistic invariance” is built into our theory of the elementary particles, and so it has had a profound impact on fundamental physics. However, here it must be noted that the equations of Special Relativity were first written down by Hendrik Lorentz, the great Dutch physicist whom Einstein admired the most of all his contemporaries. Lorentz just failed to give them the radical interpretation with which Einstein endowed them; he also failed to notice that they implied that energy and mass were interchangeable: E = mc2. There are also a few votes out there for the French mathematician, Henri Poincare, who enunciated the Principle of Relativity before Einstein, but I can’t put him in the same category as Lorentz with regard to this debate. Einstein would have been happy to share Special Relativity with Lorentz, so let’s split this one 50-50 between the two.

General Relativity on the other hand is all Albert. Like the photon, no one on the planet even had an inkling of this idea before Einstein. Einstein realized that the question of the relativity of motion was tied up with the theory of Gravity: that uniform acceleration (e.g. in an elevator in empty space) was indistinguishable from the effect of gravity on the surface of a planet. It gave one the same sense of weight. From this simple seed of an idea arose arguably the most beautiful and mathematically profound theory in all of physics, Einstein’s Field Equations, which predict that matter curves space and that the geometry of our universe is non-Euclidean in general. The theory underlies modern cosmology and has been verified in great detail by multiple heroic and diverse experiments. The first big experiment, which measured the deflection of starlight as it passed by the sun during a total eclipse, is what made Einstein a worldwide celebrity. This one is probably worth two Nobel prizes, but let’s just mark it down for one.

Here we exhaust what most working physicists would immediately recognize as Einstein’s works of genius, and we’re only at 2.5 Nobels. But it is a remarkable fact that Einstein’s work on early atomic theory, what we now call quantum theory, is vastly under-rated. This is partially because Einstein himself downplayed it due to his rejection of the final version of the theory, which he dismissed with the famous phrase, “God does not play dice.” But if one looks at what he actually did, the Nobels keep piling up.

The modern theory of the atom, quantum theory, began in 1900 with the work of the German physicist, Max Planck, who, in what he called “an act of desperation,” introduced into physics a radical notion, quantization of energy. Or so the textbooks say. This is the idea that when energy is exchanged between atoms and radiation (e.g. light), it can only happen in discrete chunks, like a parking meter that only accepts quarters. This idea turns out to be central to modern atomic physics, but Planck didn’t really say this in his work. He said something much more provisional and ambiguous. It was Einstein in his 1905 paper—but then much more clearly in a follow-up paper on the vibrations of atoms in solids in 1907—who really stated the modern principle. It is not clear if Planck himself accepted it fully even a decade after his seminal work (although he was given credit for it by the Nobel Prize committee in 1918). In contrast, Einstein boldly applied it to the mechanical motion of atoms, even when they are not exchanging energy with radiation, and stated clearly the need for a quantized mechanics. So despite the textbooks, Einstein clearly should have shared Planck’s Nobel Prize for the principle of quantization of energy. We are up to 3.0 Nobels for Big Al.

The next one in line is rarely mentioned. After Einstein proposed his particulate theory of light in 1905, he did not adopt the view that light was simply made of particles in the ordinary sense of a localized chunk of matter, like a grain of sand. Instead, he was well aware that light interfered with itself in a similar manner to water waves (a peak can cancel a trough, leading to no wave). In 1909, he came up with a mathematical proof that the particle and wave properties were present in one formula that described the fluctuations of the intensity of light. Hence, he announced that the next era of theoretical physics would see a “fusion” of the particle and wave pictures into a unified theory. This is exactly what happened, but it took fourteen years for the next advance and another three (1926) for it all to fall into place. In 1923, the French physicist Louis de Broglie hypothesized that electrons, which have mass (unlike light) and were always previously conceived of as particles, actually had wavelike properties similar to light. He freely admitted his debt to Einstein for this idea, but when he got the Nobel Prize for “wave-particle” duality in 1929, it was not shared. But it should have been. Another half for Albert, at 3.5 and counting.

From 1911 to 1915 Einstein took a vacation from the quantum to invent General Relativity, which we have already counted, so his next big thing was in 1916 (he didn’t leave a lot of dead time in those days). That was three years after Niels Bohr introduced his “solar system” model of the atom, where the electrons could only travel in certain “allowed orbits” with quantized energy. Einstein went back to thinking about how atoms would absorb light, with the benefit of Bohr’s picture. He realized that once an atom had absorbed some light, it would eventually give that light energy back by a process called spontaneous emission. Without any particular event to cause it, the electron would jump down to a lower energy orbit, emitting a photon. This was the first time that it was proposed that the theory of atoms had such random, uncaused events, a notion that became a second pillar of quantum theory. In addition, he stated that sometimes there was causal emission, that the imposition of more light could cause the atom to release its absorbed light energy in a process called stimulated emission. Forty-four years later, physicists invented a device that uses this principle to produce the purest and most powerful light sources in nature, the LASER (Light Amplified by Stimulated Emission of Radiation). The principles of spontaneous and stimulated emission introduced by Einstein underlie the modern quantum theory of light. One full Prize please—now at 4.5.

After that 1916-1917 work, Einstein had some health problems and became involved in political and social issues for a while, leading to a Nobel batting slump for a few years. (He did still collect some hits, like the prediction of gravitational waves (a double) and the first paper on cosmology and the geometry of the Universe using General Relativity (a triple)). But he came out of his slump with a vengeance in 1924 when he received a paper out of the blue from an unknown Indian, physicist Satyendranath Bose. It was yet another paper about particles of light, and although Bose did not state his revolutionary idea very clearly, reading between the lines, Einstein detected a completely new principle of quantum theory, the idea that all fundamental particles are indistinguishable. This is the standard terminology in physics, but it is actually very misleading. Here, indistinguishability is not the idea that humans can’t tell two photons apart (like identical twins); it is the idea that Nature can’t tell them apart, and in a real sense interchanging the two photons doesn’t count as a different state of light.

When Bose applied this principle to light he didn’t get anything radically new; it was just a different way of thinking about Planck’s original discovery in 1900. But Einstein then took the principle and applied it to atoms for the very first time, with amazing results. He discovered that a simple gas of atoms, if cooled down sufficiently, would cease to obey all the laws that physicists and chemist had discovered for gases over the centuries, and to which no exception had ever been found. Instead, all gases should behave like a weird liquid or super-molecule known as a Bose-Einstein condensate. But remember, Bose had no clue this would happen; he didn’t even try to apply his principle to atoms. It turns out that Einstein condensation underlies some of the most dramatic quantum effects, such as superconductivity, which is needed to make the magnets in MRI machines and has been the basis for five Nobel Prizes. No knowledgeable physicist would dispute that Einstein deserved a full Nobel Prize for this discovery, but I am sure that Einstein would have wanted to share it with Bose (who never did receive the Prize).

So we are at 5.0 “units” of Nobel Prize but seven trips to Stockholm. And this leaves out other arguably Nobel-caliber achievements (Brownian motion as well as the Einstein-Podolsky-Rosen effect, which underlies modern quantum information physics). And wait a minute—when someone shares the Nobel Prize do we refer to them as a “half- Laureate”? No way. Even scientists who get a “measly” third of a Prize are Nobel Laureates for life. Thus by the standard we apply to normal humans, Einstein deserved at least seven Nobel Prizes. So next time you make your fantasy scientist draft, you know who to take at number one.


Stone_EinsteinQuantum_jktA. Douglas Stone is author of Einstein and the Quantum: The Quest of The Valiant Swabian.

Einstein’s Real Breakthrough: Quantum Theory

Thank you to Yale University for recording this fantastic interview between A. Douglas Stone and Ramamurti Shankar.

People may be surprised to hear that Einstein could well be the father of quantum theory in addition to the father of relativity. In part this is because Einstein ultimately rejected quantum theory, but also because there is very little published evidence of his work. However, as he researched his new book Einstein and the Quantum: The Quest of the Valiant Swabian, Stone discovered letters and correspondence with other scientists that demonstrate the extent of Einstein’s influence in this area.

If you would like to learn more about Einstein’s contributions to quantum theory, grab a copy of Einstein and the Quantum which you can sample here.