Michael Strauss: America’s Eclipse

Welcome to the UniverseOn Monday, August 21, people all across the United States will witness one of the rarest and most spectacular of all astronomical phenomena: a total solar eclipse. This occurs when the position of the Moon and the Sun in the sky align perfectly, such that the Moon’s shadow falls onto a specific point on the Earth’s surface. If you are lucky enough to be standing in the shadow, you will see the Sun’s light completely blocked by the Moon: the sky will become dark, and the stars and planets will become visible. But because the apparent sizes of the Moon and the Sun are almost the same, and because everything is in motion—the Moon orbits Earth, and Earth rotates around its axis and orbits the Sun—the Moon’s shadow moves quickly.  During the eclipse, the Moon’s shadow will cross the United States at a speed of 1800 miles per hour, taking about 90 minutes to travel from the Pacific Coast in Oregon to touch the Atlantic in South Carolina.  This means that totality, the time when the Sun’s disk is completely covered as seen from any given spot along the eclipse path, is very brief: 2 minutes and 40 seconds at best.

If you are standing along the eclipse path, it takes about 2.5 hours for the Moon to pass across the Sun.  That is, you will see the disk of the Sun eaten away, becoming an ever-narrowing crescent. During this time, you can only look at the Sun with eclipse glasses (make sure they are from a reputable company!), which block the vast majority of the light from the Sun.  It is also fun to look at the dappled shadows underneath a leafy tree; if you look closely, you’ll see that the individual spots of light are all crescent-shaped. A bit more than an hour after the Moon begins to cover the Sun, you reach the point of totality, and the sky becomes dark. It is now safe to remove your eclipse glasses.

Experiencing a few minutes of darkness in the middle of the day is pretty cool. But what makes the eclipse really special is that with the light of the Sun’s disk blocked out, the faint outer atmosphere of the Sun, its corona, becomes visible to the naked eye. The corona consists of tenuous gas extending over millions of miles, with a temperature of a few million degrees. It is shaped by the complex magnetic field of the Sun, and may exhibit a complex arrangement of loops and filaments: indeed, observations of the solar corona during eclipses have been one of the principal ways in which astronomers have learned about its magnetic field. The sight is awe-inspiring; those who have experienced it say that it is as a life-changing experience.

As the Moon starts to move off the disk, the full brightness of the Sun becomes visible again, and you must put your eclipse glasses back on to protect your eyes. The Sun now appears as a narrow and ever-widening crescent. A bit more than an hour later, the Sun’s disk is completely uncovered.

The shadow of the Moon will be about 70 miles in diameter at any given time. That means that if you are not standing in that 70-mile-wide path as the shadow crosses the country, you will only see a partial solar eclipse, in which you will see the Sun appearing as a crescent.  Again, be sure to wear eclipse glasses to look at the Sun!

Solar eclipses happen roughly once or twice a year somewhere on Earth’s surface, but because  of the narrowness of the eclipse path, the number of people standing in the path is usually relatively small. This one, crossing the entire continental US, is special in this regard: tens of millions of people live within a few hours of the eclipse path. This promises to be the most widely seen and recorded eclipse in history! I have never seen a total eclipse of the Sun before, and am very excited to be traveling with my family to Oregon, where we have our fingers crossed for good weather. So, to all those who have the opportunity to stand in the Moon’s shadow, get yourself a pair of eclipse glasses, and prepare yourself to be awed.

Michael A. Strauss is professor of astrophysics at Princeton University. He is the coauthor (with Neil deGrasse Tyson and J. Richard Gott) of Welcome to the Universe: An Astrophysical Tour.

Anna Frebel: Solar Eclipse 2017

Next Monday, the U.S. will witness an absolutely breathtaking natural spectacle. One worthy of many tweets as it is of the astronomical kind—quite literally. I’m talking about the upcoming total solar eclipse where, for a short couple of minutes, the Moon will move directly into our line of sight to perfectly eclipse the Sun.

During the so-called “totality,” when the Sun is fully covered, everything around you will take on twilight colors. It will get cooler, the birds will become quieter, and you’ll get this eerie feeling that something is funny is going on. No wonder that in ancient times, people thought the world would end during such an event.

I have witnessed this twice before. 1999 in Munich, Germany, and 2002 in Ceduna, Australia. Like so many others, I traveled there with great anticipation to see the Sun disappear on us. In both cases, however, it was cloudy for hours before totality which caused frustration and even anxiety in the crowd. But nature happened to be kind. A few minutes before totality, the clouds parted to let us catch a glimpse. We experienced how the disk of the Sun finally fully vanished just after seeing the last little rays of light peeking through that produced a famous “diamond ring” image. We could also see the glowing corona surrounding the black Sun. All the while, nature around us transformed into what felt like a cool and breezy late summer evening. A few minutes later, everything was back to normal and the clouds covered it all once again like nothing had ever happened. The exact same cloud scenario happened both times—how lucky was that?

As for next Monday, I sincerely hope the clouds will stay home. I know so many folks who will travel from far and wide into the totality zone to experience this “Great American Eclipse.” It is actually fairly narrow, only about 100 miles wide, but stretches diagonally across the entire U.S.. For many, this will be a once in a lifetime opportunity to see such a rare event and I’m sure this experience will stay with them for years to come. It sure did for me.

I will actually not travel into the totality zone. Instead, I’ll be watching and talking about the partial eclipse that we can see up here in Massachusetts with my three year old son and his preschool class. A partial eclipse lasts for a couple of hours and occurs when the alignment between Earth, Moon, and Sun is just a bit “off.” Generally, this can happen when these three bodies are indeed not going to perfectly align. Or, when a person on Earth is close but not right in the totality zone, it causes a misalignment between the observer, the Moon, and the Sun. In both cases, the Sun is not going to get fully covered. Nevertheless, it is still a marvelous event and great for children and anyone interested to learn about solar eclipses and astronomy. And luckily enough, everyone in the U.S., Canada, and Mexico can watch a partial eclipse, no matter where you are located.

Solar eclipses don’t happen randomly. There are part of long lasting cycles that stem from the motion of the Moon around the Earth and the alignment of its orbit with respect to the Sun. This eclipse is part of the famous Saros cycle 145, and so was the 1999 eclipse I saw in Munich. It produces eclipses every 18 years, 11 days and 8h. Subsequent Saros eclipses are visible from different parts of the globe.The extra 8 hours in the cycle mean that from one eclipse to the next, the Earth must rotate an additional ~8 hours or ~120º. Hence, this eclipse is ~120º westward from continental Europe which is the continental U.S.. The next one will be visible from China in 2035. Each of the many Saros series typically lasts 12 to 13 centuries. Series 145 began in 1639 and will end in 3009 after 77 eclipses.

There are 4 to 6 total eclipses every year but not all are visible on land. Actually, from about any given point on Earth, once every 150 years an eclipse is visible. Now, it’s our turn. So if you’re not already traveling into the totality zone, make sure you still watch the partial eclipse—never without eclipse glasses, though, partial or total eclipse alike! Looking into the Sun causes serious longterm damage to your eyes but also your camera. So equip your camera with glasses, too! Alternatively, you can just watch the Sun’s shadow on a wall to observe how the Sun gets eaten away piece by piece by the incoming Moon. Ask your work if you can take a few minutes off. It’s a worthy cause. Actually, a well-timed bathroom break is almost long enough to catch totality or a glimpse of partial coverage. Eclipses are simply too rare and too beautiful to miss!

Get your eclipse glasses, rearrange your schedule (just a little bit), and make sure your kids or grandkids, friends and neighbors are seeing it too. Because, actually, the tides of the oceans on Earth are slowing down Earth’s rotation which make the Moon spiral outward and away from us by 1 inch per year. This means that the Moon will appear smaller and smaller with time, and in the far future, there won’t be any total eclipses possible anymore.

FrebelAnna Frebel is the Silverman (1968) Family Career Development Assistant Professor in the Department of Physics at the Massachusetts Institute of Technology. She has received numerous international honors and awards for her discoveries and analyses of the oldest stars. She is the author of Searching for the Oldest Stars: Ancient Relics from the Early Universe.

Welcome to the Universe microsite receives a Webby

We’re pleased to announce that the accompanying microsite to Welcome to the Universe by Neil DeGrasse Tyson, Michael A. Strauss, and J. Richard Gott has won a People’s Choice Webby in the Best Use of Animation or Motion Graphics category. Congratulations to Eastern Standard, the web designer, on a beautifully designed site.

Winning a Webby is especially gratifying because it honors how much fun we had making the site. We knew we wanted an unconventional approach that would mirror both the complexity and accessibility of the book it was meant to promote. Our wonderful in-house team and creative partners, Eastern Standard took on this challenge, and we are so happy with the results.
—Maria Lindenfeldar, Creative Director, Princeton University Press 

Creating this microsite was a wonderful experiment for us at Princeton University Press.  We wanted to explore how we, as a publisher, could present one of our major books to the public in a compelling way in the digital environment.  Ideally, we had a vision of creating a simple site with intuitive navigation that would give readers an inviting mini-tour through the topics of the book, Welcome to the Universe, by Neil deGrasse Tyson, Michael Strauss, and Richard Gott.  The animation was meant to be subtle, but meaningful, and to gently encourage user interaction, so that the focus would always remain immersing the reader in the content of the book – what we feel is the most interesting part!  We were very happy with how it turned out and now all the more thrilled and honored that the site was chosen for a Webby!
—Ingrid Gnerlich, Science Publisher, Princeton University Press

Celebration of Science: A reading list

This Earth Day 2017, Princeton University Press is celebrating science in all its forms. From ecology to psychology, astronomy to earth sciences, we are proud to publish books at the highest standards of scholarship, bringing the best work of scientists to a global audience. We all benefit when scientists are given the space to conduct their research and push the boundaries of the human store of knowledge further. Read on for a list of essential reading from some of the esteemed scientists who have published with Princeton University Press.

The Usefulness of Useless Knowledge
Abraham Flexner and Robbert Dijkgraaf

Use

The Serengeti Rules
Sean B. Carroll

Carroll

Honeybee Democracy
Thomas D. Seeley

Seeley

Silent Sparks
Sara Lewis

Lewis

Where the River Flows
Sean W. Fleming

Fleming

How to Clone a Mammoth
Beth Shapiro

Shapiro

The Future of the Brain
Gary Marcus & Jeremy Freeman

Brain

Searching for the Oldest Stars
Anna Frebel

Frebel

Climate Shock
Gernot Wagner & Martin L. Weitzman

Climate

Welcome to the Universe
Neil DeGrasse Tyson, Michael A. Strauss, and J. Richard Gott

Universe

The New Ecology
Oswald J. Schmitz

Schmitz

Welcome to the Universe microsite nominated for a Webby

We’re thrilled to announce that the microsite for Welcome to the Universe by Neil DeGrasse Tyson, Michael A. Strauss, and J. Richard Gott, designed by Eastern Standard, has been nominated for a Webby in the Best Use of Animation or Motion Graphics category. Be sure to check it out and vote for the best of the internet!

webby

 

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.

Browse Our Physics & Astrophysics 2017 Catalog

We invite you to explore our Physics & Astrophysics 2017 Catalog:

PUP will be at the 229th Meeting of the American Astronomical Society in Grapevine, Texas from January 3 to January 7. Come and visit us at booth #200! Also, follow #AAS229 and @PrincetonUnivPress on Twitter for updates and information on our new and forthcoming titles throughout the meeting.

Welcome to the Universe is a personal guided tour of the cosmos by three of today’s leading astrophysicists: Neil deGrasse Tyson, Michael A. Strauss, and J. Richard Gott. Breathtaking in scope and stunningly illustrated throughout, this book is for those who hunger for insights into our evolving universe that only world-class astrophysicists can provide.

Tyson et al Welcome to the Universe

In Fashion, Faith, and Fantasy in the New Physics of the Universe, acclaimed physicist and bestselling author Roger Penrose argues that fashion, faith, and fantasy, while sometimes productive and even essential in physics, may be leading today’s researchers astray in three of the field’s most important areas—string theory, quantum mechanics, and cosmology.

Penrose Fashion

An accessible blend of narrative history and science, Strange Glow describes mankind’s extraordinary, thorny relationship with radiation, including the hard-won lessons of how radiation helps and harms our health. Timothy Jorgensen explores how our knowledge of and experiences with radiation in the last century can lead us to smarter personal decisions about radiation exposures today.

Jorgensen Strange Glow

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Exclusive interview with Neil deGrasse Tyson, Michael A. Strauss, and J. Richard Gott on their NYT bestseller, Welcome to the Universe

UniverseWe’re thrilled to announce that Welcome to the Universe, a guided tour of the cosmos by three of today’s leading astrophysicists, recently made the New York Times extended bestseller list in science. Inspired by the enormously popular introductory astronomy course that Neil deGrasse Tyson, Michael A. Strauss, and J. Richard Gott taught together at Princeton, this book covers it all—from planets, stars, and galaxies to black holes, wormholes, and time travel. The authors introduce some of the hot topics in astrophysics in today’s Q&A:


What is the Cosmic Perspective?

NDT: A view bigger than your own that offers a humbling, yet enlightening, and occasionally empowering outlook on our place as humans in time, space, on Earth and in the Universe. We devote many pages of Welcome to the Universe to establishing our place in the cosmos – not only declarations of that place, but also the reasons and the foundations for how we have come to learn how we fit in that place. When armed with a cosmic perspective, many earthly problems seem small, yet you cultivate a new sense of belonging to the universe. You are, in fact, a participant in the great unfolding of cosmic events.

What are some of the takeaways from the book?

NDT: If you read the entire book, and if we have succeeded as authors, then you should walk away with a deep sense of the operations of nature, and an appreciation for the size and scale of the universe; how and why planets form; how and why we search for planets orbiting around other stars, and alien life that may thrive upon them; how and why stars are born, live out their lives and die; what galaxies are and why they are the largest organizations of stars in the universe; the large scale structure of galaxies and space-time; the origins and future of the universe, Einstein’s relativity, black holes, and gravitational waves; and time travel. If that’s not enough, you will also learn about some of the continued unsolved mysteries in our field, such as dark matter, dark energy, and multiverses.

This book has more equations than do most popular books about astrophysics.  Was that a deliberate decision?

MAS: Yes.  The book’s subtitle is “An Astrophysical Tour,” and one of our goals in writing it was to show how observations, the laws of physics, and some high school mathematics can combine to yield the amazing discoveries of modern astrophysics: A Big Bang that happened 13.8 billion years ago (we show you how that number is determined), the dominant role dark matter has in the properties of galaxies (we tell you how we came to that conclusion), even the fact that some planets orbiting other stars have conditions conducive for liquid water to exist on their surface, thought to be a necessary prerequisite for life. Our goal is not just to present the wonders of the universe to the reader, but to have the reader understand how we have determined what we know, and where the remaining uncertainties (and there are plenty of them!) lie.

So your emphasis is on astrophysics as a quantitative science, a branch of physics?

MAS:  Yes.  We introduce the necessary physics concepts as we go: we do not expect the reader to know this physics before they read the book.  But astrophysicists are famous (perhaps notorious!) for rough calculations, “to astrophysical accuracy.”  We also lead the reader through some examples of such rough calculations, where we aim to get an answer to “an order of magnitude.”  That is, we’re delighted if we get an estimate that’s correct to within a factor of 2, or so.  Such calculations are useful in everyday life, helping us discriminate the nonsensical from the factual in the numerical world in which we live.

Can you give an example?

MAS: Most people in everyday discourse don’t think much about the distinction between “million,” “billion,” “trillion,” and so on, hearing them all as “a really big number,” with not much difference between them.  It is actually a real problem, and the difference between Federal budget items causing millions vs. billions of dollars is of course huge.  Our politicians and the media are confusing these all the time.  We hope that the readers of this book will come away with a renewed sense of how to think about numbers, big and small, and see whether the numbers they read about in the media make sense.

Is time travel possible?

JRG: In 1905 Einstein proved that time travel to the future is possible. Get on a rocket and travel out to the star Betelgeuse 500 light-years away and return at a speed of 99.995 % the speed of light and you will age only 10 years, but when you get back it will be the year 3016 on Earth. Even though we have not gone that fast or far, we still have time travelers among us today. Our greatest time traveler to date is the Russian cosmonaut Gennady Padalka, who by virtue of traveling at high speed in low Earth orbit for 879 days aged 1/44 of a second less than if he had stayed home. Thus, when he returned, he found Earth to be 1/44 of a second to the future of where he expected it to be. He has time traveled 1/44 of a second to the future. An astronaut traveling to the planet Mercury, living there for 30 years, and returning to Earth, would time travel into the future by 22 seconds. Einstein’s equations of general relativity, his theory of curved spacetime to explain gravity, have solutions that are sufficiently twisted to allow time travel to the past. Wormholes and moving cosmic strings are two examples. The time traveler can loop back to visit an event in his own past. Such a time machine cannot be used to journey back in time before it was created. Thus, if some supercivilization were to create one by twisting spacetime in the year 3000, they might use it to go from 3002 back to 3001, but they couldn’t use it go back to 2016, because that is before the time loop was created. To understand whether such time machines can be realized, we may need to understand how gravity works on microscopic scales, which will require us to develop a theory of quantum gravity. Places to look for naturally occurring time machines would be in the interiors of rotating black holes and at the very beginning of the universe, where spacetime is strongly curved.

Do we live in a multiverse?

JRG: A multiverse seems to be a natural consequence of the theory of inflation. Inflation explains beautifully the pattern of slightly hotter and colder spots we see in the Cosmic Microwave Background Radiation. It explains why the universe is so large and why it is as smooth as it is and still has enough variations in density to allow gravity to grow these into galaxies and clusters of galaxies by the present epoch. It also explains why the geometry of the universe at the present epoch is approximately Euclidean. Inflation is a period of hyperactive accelerated expansion occurring at the beginning of our universe. It is powered by a large vacuum energy density and negative pressure permeating empty space that is gravitationally repulsive. The universe doubles in size about every 3 10-38 seconds. With this rate of doubling, it very quickly grows to enormous size: 1, 2, 4, 8, 16, 32, 64, 128, 256, 512, 1024… That explains why the universe is so large. When the high density vacuum state decays, it doesn’t do so all at once. Like water boiling in a pot, it does not turn into steam all at once, but should form bubbles. Each expanding bubble makes a universe. The inflationary sea should expand forever, creating an infinite number of bubble universes, ours being one of them. Other distant bubble universes are so far away, and the space between us and them is expanding so fast, that light from them may never reach us. Nevertheless, multiple universes seem a nearly inevitable consequence of inflation.

What discovery about the universe surprises or inspires you the most?

JRG: Perhaps the most amazing thing about the universe is that it is comprehensible to intelligent, carbon-based life forms like ourselves. We have been able to discover how old the universe is (13.8 billion years) and figure out many of the laws by which it operates. The object of this book is to make the universe comprehensible to our readers.

Don’t miss this C-Span video on the book, in which the authors answer questions about the universe, including how it began and the likelihood of intelligent life elsewhere.

Neil deGrasse Tyson is director of the Hayden Planetarium at the American Museum of Natural History. He is the author of many books, including Space Chronicles: Facing the Ultimate Frontier, and the host of the Emmy Award–winning documentary Cosmos: A Spacetime Odyssey. Michael A. Strauss is professor of astrophysics at Princeton University. J. Richard Gott is professor of astrophysics at Princeton University. His books include The Cosmic Web: Mysterious Architecture of the Universe (Princeton).

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:

 

Bird Fact Friday – To migrate long distances, birds follow the stars

From page 46 of Bird Brain:

There are a number of tools that birds use when migrating long distances. For example, one way that nocturnal birds find their way is by using the stars to navigate. Experiments with migratory birds in planetariums have found that birds learn celestial maps based on the position of certain major constellations, and their position relative to the poles. When exposed to a simulation of the northern hemisphere sky in the spring, birds will orient north, and vice versa.

Bird Brain
An Exploration of Avian Intelligence
Nathan Emery
With a foreword by Frans de Waal
Introduction

EmeryBirds have not been known for their high IQs, which is why a person of questionable intelligence is sometimes called a “birdbrain.” Yet in the past two decades, the study of avian intelligence has witnessed dramatic advances. From a time when birds were seen as simple instinct machines responding only to stimuli in their external worlds, we now know that some birds have complex internal worlds as well. This beautifully illustrated book provides an engaging exploration of the avian mind, revealing how science is exploding one of the most widespread myths about our feathered friends—and changing the way we think about intelligence in other animals as well.

Bird Brain looks at the structures and functions of the avian brain, and describes the extraordinary behaviors that different types of avian intelligence give rise to. It offers insights into crows, jays, magpies, and other corvids—the “masterminds” of the avian world—as well as parrots and some less-studied species from around the world. This lively and accessible book shows how birds have sophisticated brains with abilities previously thought to be uniquely human, such as mental time travel, self-recognition, empathy, problem solving, imagination, and insight.

Written by a leading expert and featuring a foreword by Frans de Waal, renowned for his work on animal intelligence, Bird Brain shines critical new light on the mental lives of birds.

The companion website to Welcome to the Universe launches today

Welcome to the UniverseWe’re thrilled to launch this beautiful companion website to the highly anticipated new book, Welcome to the Universe by Neil DeGrasse Tyson, Michael Strauss, and Richard Gott.

If you’ve ever wondered about the universe and our place in it, then this elegant mini-tour of the cosmos is for you. Divided into three parts called ‘Stars, Planets and Life,’ ‘Galaxies,’ and ‘Einstein and the Universe,’ the site is designed to take you on a journey through the major ideas in Welcome to the Universe. We hope you learn something new and exciting about outer space. If you find something interesting and would like to share, please do! The site is set up to make sharing interesting tidbits on social media easy. Want to learn more? The site also includes information on where to learn more about each topic. Keep an eye out for the book in October 2016.

 

Welcome to the Universe: An Astrophysical Tour by Neil deGrasse Tyson, Michael A. Strauss & J. Richard Gott from Princeton University Press on Vimeo.

Women in Science: Who are they at Princeton University Press?

Women have made great strides in STEM fields, but there are still far too few women in science—a situation that remains both complex and troubling. Here at Princeton University Press, we are proud to publish numerous important books in the sciences by women, on topics ranging from de-extinction, to primitive stars, to fireflies. If you’re interested in learning more about the lives and ideas of #WomenInScience, DiscovHer—a site dedicated to showcasing these remarkable people—has put together a great list of blogs for you to follow. And check out some of the most fascinating PUP authors and their books here:

Shapiro Jacket Beth Shapiro, an evolutionary biologist
and pioneer in “ancient DNA” research, shows how
de-extinction might change the future of
conservation in
How to Clone a Mammoth.
The Cosmic Cocktail What is the universe made of?
Acclaimed theoretical physicist Katherine Freese
shares the most cutting edge research aimed at
answering that question in
The Cosmic Cocktail.
Frebel Anna Frebel, who discovered several of the oldest
and most primitive stars, tells the story of the
research behind stellar archeology in
Searching for the Oldest Stars.
Lewis Have you ever been curious about the fireflies
that light up our summer nights? Noted
biologist and firefly expert Sara Lewis
answers all your questions and
more in Silent Sparks.
5-9 Fairbairn_Odd Daphne J. Fairbairn, a professor of biology,
shows that the differences between men and
women are negligible when compared with
differences between males and
females in the animal kingdom in
Odd Couples.
Hough

Delve into the fascinating world of
earthquake prediction in
Predicting the Unpredictable by
seismologist Susan Elizabeth Hough.