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An asteroid is hurtling toward Earth. A big, bad one.
Maybe not kill-all-the-dinosaurs bad, but at least kill-everyone-in-California-and-wipe-out-Japan-with-a-tsunami bad. Yuri, a physicist prodigy from Russia, has been recruited to aid NASA as they calculate a plan to avoid disaster. The good news is Yuri knows how to stop the asteroid--his research in antimatter will probably win him a Nobel prize if there's ever another Nobel prize awarded.
But the trouble is, even though NASA asked for his help, no one there will listen to him. He's seventeen, and they've been studying physics longer than he's been alive. Then he meets (pretty, wild, unpredictable) Dovie, who lives like a normal teenager, oblivious to the impending doom. Being with her, on the adventures she plans when he's not at NASA, Yuri catches a glimpse of what it means to save the world and live a life worth saving. Prepare to laugh, cry, cringe, and have your mind burst open with the questions of the universe.
How did you approach the research process for your story? What resources did you turn to? What roadblocks did you run into? How did you overcome them? What was your greatest coup, and how did it inform your manuscript?
Research was a huge part of writing Learning to Swear in America. The book is about an incoming asteroid, and the main character, Yuri, is a physics genius. I’m not.
I knew I didn’t want the book to be science-free. I mean, how could it be? It would be like a biography of a poet that doesn’t talk about the poetry—it would be missing a crucial element.
A physician friend told me about a Morbidity & Mortality meeting he attended as a young doctor. The physician in charge strode out onto the stage and wrote on the marker board:
I didn’t know enough.
Bad stuff happens.
I was lazy.
The man turned to the assembled doctors and said, “The first two will happen. You will have patients die for both those reasons.”
Then he slammed the side of his fist against the board and roared, “But by God it better never be because you were too lazy to Do. Your. Job.”
That’s how I felt about approaching research for Learning to Swear. I didn’t know enough. I would make mistakes. But it wouldn’t be for lack of trying.
I read Neil deGrasse Tyson, Brian Greene, Michio Kaku, and articles written by astrophysicists—for astrophysicists. You can find science simplified for the average educated reader—the basics on asteroids, for example. But if you want simplified information on spectral analysis? Forget it.
NASA’s website has all sorts of tables about asteroids, and it was a go-to source—until I discovered that the government shutdown also shuttered NASA. It was inconvenient not to be able to access information on which I was used to relying. It was chilling to realize that the people who usually stand sentry for Earth had been pulled in.
I should mention that a physicist who’s involved in security issues read for me—this is Dr. Robert August—and did me a world of good. Not only did he help me get the equipment right, but he corrected me on little cultural things. For example, he said that the computer programmers would have the name of their favorite pizza place written on their marker board. I included that.
Almost everything in the scenes with the programmers came from information Bob shared. He’s been in these kind of meetings, so that was incredibly helpful.
My biggest problem—outside of lack of background knowledge—was that I had envisioned exacerbating the problem mid-book by having the asteroid’s speed increase, so that it would arrive sooner than they expected.
Then I discovered this would violate the laws of nature.
Stupid laws of nature. By this point I had half the book written, and knew I had to find another way to make it harder for Yuri to stop the asteroid.
So I ate a lot of mint chocolate chip ice cream and did more reading—and somewhere in the tiny print I found my answer.
I did a little happy dance, and my husband asked why. “I found a way for an asteroid to smash the Earth, and we couldn’t do anything to stop it!”
He gave me a very strange look.
As a teacher-author, how do your two identities inform one another? What about being a teacher has been a blessing to your writing?
Learning to Swear in America is based on an Immanuel Kant quote:
"Do what is right, though the world should perish."
I teach college history, and we talk about Kant as part of the Enlightenment. That quote is one that hooked my imagination—I remember walking across the college parking lot thinking, Yeah, but what if the world really would perish? What then?
This book is the outgrowth of my conversation with Kant about that.
So I think being an instructor is helpful in several ways. First, history is narrative--essentially I tell stories to my students. Some of them are pretty good!
Charlemagne and Pope Adrian I.
I look at the names in my lectures—the Gracchi, Charlemagne, George Washington—and I’m so grateful that I get to share their stories with my students. What a privilege!
Also—what good practice in storytelling. I get to see immediately when the students’ attention flags.
Second, I come in contact with interesting material all the time, through reading in support of my day job, and even through my own lectures—like the Kant quote.
In fact, the main character of my next book was inspired by an historical figure—but I’m not saying who it is.
My first degree was in mathematics, where I specialised in mathematical physics. That meant studying notions of mass, weight, length, time, and so on. After that, I took a master’s and a PhD in statistics. Those eventually led to me spending 11 years working at the Institute of Psychiatry in London, where the central disciplines were medicine and psychology. Like physics, both medicine and psychology are based on measurements.
Suppose you had to explain to someone, who did not already know, what it means to say that time passes. What might you say? Perhaps you would explain that different times are arranged in an ordered series with a direction: Monday precedes Tuesday, Tuesday precedes Wednesday, and so on.
Independence Day is here; this weekend fireworks will light up the sky around the nation in celebration. But…how are fireworks made? And…who thought to send brightly colored explosions into the sky?
For Arbordale celebration and science go hand in hand, so here is a quick history chemistry and physics lesson in fireworks!
History
The Chinese were experimenting with exploding tubes of bamboo as early as 200 B.C., but it wasn’t until 900 A.D. that Chinese chemists found a mix that when stuffed in bamboo and thrown in a fire produced a loud bang. Over the next several hundred years experimentation lead to the first rockets, but as fire power began to fly in the air, celebrations also began to light up the sky.
Soon firework technology began to spread across Europe to Medieval England. The popularity of celebrating war victories and religious ceremonies with fireworks displays grew. The Italian pyrotechnic engineers are first credited with adding color to their fireworks in the 1830’s. The Europeans brought their knowledge of fireworks to America, and the first recorded display was in Jamestown in 1608.
John Adams predicted that fireworks would be part of the Fourth of July celebrations on July 3, 1776 with a letter to Abigail Adams where he said, “I am apt to believe that it will be celebrated by succeeding generations as the great anniversary festival. It ought to be commemorated, as the Day of Deliverance by solemn Acts of Devotion to God Almighty. It ought to be solemnized with Pomp and Parade, with Shews, Games, Sports, Guns, Bells, Bonfires and Illuminations from one End of this Continent to the other from this Time forward forever more.”
And so on the first anniversary of the country and each year we celebrate with Pomp and Parade, ending the day with Illuminations!
The Science
The Chinese put bamboo in the fire and the air pocket would make a bang when it was heated to a certain temperature. Today we have much better technology and fireworks are a little more complicated. The basic science has not changed, but the delivery methods have gotten much more accurate and high tech giving celebrators a bigger better show.
We know a tube is our vehicle, but how does it travel to the sky?
A mix of combustible solid chemicals is packed into the tube, along with neatly arranged metals. The metals determine the color (copper=blue/green, calcium=red), and the arrangement determines shape (circle, smiley faces, stars).
When the heat activates the chemicals, the excitement begins. The reaction is started by either fire or electricity through a fuse. As the heat begins to travel into the tube the chemicals become activated that reaction produces other chemicals such as smoke and gasses. The chemical reaction creates the release of energy; the energy is converted into the heat, light, sound and movement that we see up in the sky.
Physics takes over!
The Conservation of Energy Law says that the chemical energy packed inside that tube is equal to the energy of the released plus the energy left after the reaction. A professional firework in a large tube packed with chemicals creates a much bigger light show and bang than a tiny firecracker that jumps with a small bang.
The fireworks fly because of Newton’s Third Law. “For every action, there is an equal and opposite reaction” When the gasses are released from the chemical reaction they shoot down with force cause the firework to lift up into the air.
Finally, Why are fireworks always symmetrical?
Conservation of Momentum says that momentum must be the same before and after the explosion. In other words, when the explosion occurs the movement must be balanced.
Now that you have learned a little about the science behind fireworks enjoy watching them on this Independence Day. But remember, fireworks are dangerous and best left to the professionals!
When I first heard the suggestion that religion is primitive science, I put it down to ignorance on the part of people who had not studied these things. Having not studied religion, they did not understand what our ancestors’ religious statements were really doing.
Planet Earth doesn’t have ‘a temperature’, one figure that says it all. There are oceans, landmasses, ice, the atmosphere, day and night, and seasons. Also, the temperature of Earth never gets to equilibrium: just as it’s starting to warm up on the sunny-side, the sun gets ‘turned off’; and just as it’s starting to cool down on the night-side, the sun gets ‘turned on’.
Describing the very ‘beginning’ of the Universe is a bit of a problem. Quite simply, none of our scientific theories are up to the task. We attempt to understand the evolution of space and time and all the mass and energy within it by applying Albert Einstein’s general theory of relativity. This theory works extraordinarily well. But when we’re dealing with objects that start to approach the infinitesimally small – elementary particles such as quarks and electrons – we need to reach for a completely different structure, called quantum theory.
There was much more to Max Planck than his work and research as an influential physicist. For example, Planck was an avid musician, and endured many personal hardships under the Nazi regime in his home country of Germany.
Albert Einstein’s greatest achievement, the general theory of relativity, was announced by him exactly a century ago, in a series of four papers read to the Prussian Academy of Sciences in Berlin in November 1915, during the turmoil of the First World War. For many years, hardly any physicist—let alone any other type of scientist—could understand it.
November 2015 marks the 100th anniversary of Albert Einstein's general theory of relativity. This theory is one of many pivotal scientific discoveries that would drastically influence our understanding of the world around us.
This is the continuation of the story about the origin of the Germanic word for man. Last week I left off after expressing great doubts about the protoform that connected man and guma and tried to defend the Indo-European girl from an unpronounceable name. As could be expected, in their attempts to discover the origin of man etymologists cast a wide net for words containing m and n.
Oxford is thrilled to welcome Dr. Kathy Battista as the new Editor in Chief of the Benezit Dictionary of Artists. Get to know Dr. Battista with our Q/A session.
What is all around us, terrifies a lot of people, but adds enormously to the quality of life? Answer: chemistry. Almost everything that happens in the world, in transport, throughout agriculture and industry, to the flexing of a muscle and the framing of a thought involves chemical reactions in which one substance changes into another.
This November marks the 100th anniversary of Albert Einstein completing his masterpiece of general relativity, an idea that would lead, one world war later, to his unprecedented worldwide celebrity. In the run-up to what he called “the most valuable discovery of my life,” he worked within a new sort of academic comfort.
Sturdy idiophone ubiquitous among dress shoe-wearing cultures. Rising to prominence during 15th century England, the shoehorn has today become one of the most widely used instruments in the world. This notoriety had lead many scholars to suggest that the shoehorn stands as Britain's crowning contribution to contemporary music culture.
Few elementary mathematical ideas arouse the kind of curiosity and astonishment among the uninitiated as does the idea of the “imaginary numbers”, an idea embodied in the somewhat mysterious number i. This symbol is used to denote the idea of , namely, a number that when multiplied by itself yields -1. How come?
The discovery of water on Mars has been claimed so often that I’d forgive anyone for being skeptical about the latest announcement. Frozen water, ice, has been proven on Mars in many places, there are lots of ancient canyons hundreds of kilometres long that must have been carved by rivers, and much smaller gullies that are evidently much younger.
The history of modern Crystallography is intertwined with the great discoveries’ of William Lawrence Bragg (WLB), still renowned to be the youngest Nobel Prize in Physics. Bragg received news of his Nobel Prize on the 14th November 1915 in the midst of the carnage of the Great War. This was to be shared with his father William Henry Bragg (WHB), and WHB and WLB are to date the only father and son team to be jointly awarded the Nobel Prize.
NASA’s New Horizons probe swept past Pluto and its moons at 17 km per second on 14 July. Even from the few close up images yet beamed back we can say that Pluto’s landscape is amazing. Charon, Pluto’s largest moon, is quite a sight too, and I’m glad that I delayed publication of my forthcoming Very Short Introduction to Moons so that I could include it.
Within a year, we have been able to see our solar system as never before. In November 2014, the Philae Probe of the Rosetta spacecraft landed on the halter-shaped Comet 67P/Churyumov-Gerasimenko. In April 2015, the Dawn spacecraft entered orbit around the largest of the asteroids, Ceres (590 miles in diameter), orbiting between Mars and Jupiter. And in July, the New Horizons mission made the first flyby of the dwarf planet Pluto, making it the most distant solar-system object to be visited. Other spacecraft continue to investigate other planets.
Writing a book is an unnatural act of communication.Writing a book is an unnatural act of communication. Speaking to a person, or even to an audience, is an interaction. Very different styles are suited to an expert, a curious layperson, or a student on assignment... or to a one-on-one, a salon, or a lecture theater. When we [...]
0 Comments on You Are… Who? as of 7/15/2015 8:45:00 PM
Fin de siècle Hungary was a progressive country. It had limited sovereignty as part of the Austro-Hungarian dual monarchy, but industry, trade, education, and social legislation were rapidly catching up with the Western World. The emancipation of Jews freed tremendous energies and opened the way for ambitious young people to the professions in law, health care, science, and engineering (though not politics, the military, and the judiciary). Excellent secular high schools appeared challenging the already established excellent denominational high schools.
Galileo and some of his contemporaries left careful records of their telescopic observations of sunspots – dark patches on the surface of the sun, the largest of which can be larger than the whole earth. Then in 1844 a German apothecary reported the unexpected discovery that the number of sunspots seen on the sun waxes and wanes with a period of about 11 years.
Initially nobody considered sunspots as anything more than an odd curiosity. However, by the end of the nineteenth century, scientists started gathering more and more data that sunspots affect us in strange ways that seemed to defy all known laws of physics. In 1859 Richard Carrington, while watching a sunspot, accidentally saw a powerful explosion above it, which was followed a few hours later by a geomagnetic storm – a sudden change in the earth’s magnetic field. Such explosions – known as solar flares – occur more often around the peak of the sunspot cycle when there are many sunspots. One of the benign effects of a large flare is the beautiful aurora seen around the earth’s poles. However, flares can have other disastrous consequences. A large flare in 1989 caused a major electrical blackout in Quebec affecting six million people.
Interestingly, Carrington’s flare of 1859, the first flare observed by any human being, has remained the most powerful flare so far observed by anybody. It is estimated that this flare was three times as powerful as the 1989 flare that caused the Quebec blackout. The world was technologically a much less developed place in 1859. If a flare of the same strength as Carrington’s 1859 flare unleashes its full fury on the earth today, it will simply cause havoc – disrupting electrical networks, radio transmission, high-altitude air flights and satellites, various communication channels – with damages running into many billions of dollars.
There are two natural cycles – the day-night cycle and the cycle of seasons – around which many human activities are organized. As our society becomes technologically more advanced, the 11-year cycle of sunspots is emerging as the third most important cycle affecting our lives, although we have been aware of its existence for less than two centuries. We have more solar disturbances when this cycle is at its peak. For about a century after its discovery, the 11-year sunspot cycle was a complete mystery to scientists. Nobody had any clue as to why the sun has spots and why spots have this cycle of 11 years.
A first breakthrough came in 1908 when Hale found that sunspots are regions of strong magnetic field – about 5000 times stronger than the magnetic field around the earth’s magnetic poles. Incidentally, this was the first discovery of a magnetic field in an astronomical object and was eventually to revolutionize astronomy, with subsequent discoveries that nearly all astronomical objects have magnetic fields. Hale’s discovery also made it clear that the 11-year sunspot cycle is the sun’s magnetic cycle.
Sunspot 1-20-11, by Jason Major. CC BY-NC-SA 2.0 via Flickr.
Matter inside the sun exists in the plasma state – often called the fourth state of matter – in which electrons break out of atoms. Major developments in plasma physics within the last few decades at last enabled us to systematically address the questions of why sunspots exist and what causes their 11-year cycle. In 1955 Eugene Parker theoretically proposed a plasma process known as the dynamo process capable of generating magnetic fields within astronomical objects. Parker also came up with the first theoretical model of the 11-year cycle. It is only within the last 10 years or so that it has been possible to build sufficiently realistic and detailed theoretical dynamo models of the 11-year sunspot cycle.
Until about half a century ago, scientists believed that our solar system basically consisted of empty space around the sun through which planets were moving. The sun is surrounded by a million-degree hot corona – much hotter than the sun’s surface with a temperature of ‘only’ about 6000 K. Eugene Parker, in another of his seminal papers in 1958, showed that this corona will drive a wind of hot plasma from the sun – the solar wind – to blow through the entire solar system. Since the earth is immersed in this solar wind – and not surrounded by empty space as suspected earlier – the sun can affect the earth in complicated ways. Magnetic fields created by the dynamo process inside the sun can float up above the sun’s surface, producing beautiful magnetic arcades. By applying the basic principles of plasma physics, scientists have figured out that violent explosions can occur within these arcades, hurling huge chunks of plasma from the sun that can be carried to the earth by the solar wind.
The 11-year sunspot cycle is only approximately cyclic. Some cycles are stronger and some are weaker. Some are slightly longer than 11 years and some are shorter. During the seventeenth century, several sunspot cycles went missing and sunspots were not seen for about 70 years. There is evidence that Europe went through an unusually cold spell during this epoch. Was this a coincidence or did the missing sunspots have something to do with the cold climate? There is increasing evidence that sunspots affect the earth’s climate, though we do not yet understand how this happens.
Can we predict the strength of a sunspot cycle before its onset? The sunspot minimum around 2006–2009 was the first sunspot minimum when sufficiently sophisticated theoretical dynamo models of the sunspot cycle existed and whether these models could predict the upcoming cycle correctly became a challenge for these young theoretical models. We are now at the peak of the present sunspot cycle and its strength agrees remarkably with what my students and I predicted in 2007 from our dynamo model. This is the first such successful prediction from a theoretical model in the history of our subject. But is it merely a lucky accident that our prediction has been successful this time? If our methodology is used to predict more sunspot cycles in the future, will this success be repeated?
Headline image credit: A spectacular coronal mass ejection, by Steve Jurvetson. CC-BY-2.0 via Flickr.
Modern science has introduced us to many strange ideas on the universe, but one of the strangest is the ultimate fate of massive stars in the Universe that reached the end of their life cycles. Having exhausted the fuel that sustained it for millions of years of shining life in the skies, the star is no longer able to hold itself up under its own weight, and it then shrinks and collapses catastrophically unders its own gravity. Modest stars like the Sun also collapse at the end of their life, but they stabilize at a smaller size. But if a star is massive enough, with tens of times the mass of the Sun, its gravity overwhelms all the forces in nature that might possibly halt the collapse. From a size of millions of kilometers across, the star then crumples to a pinprick size, smaller than even the dot on an “i”.
What would be the final fate of such massive collapsing stars? This is one of the most exciting questions in astrophysics and modern cosmology today. An amazing inter-play of the key forces of nature takes place here, including gravity and quantum forces. This phenomenon may hold the secrets to man’s search for a unified understanding of all forces of nature, with exciting implications for astronomy and high energy astrophysics. Surely, this is an outstanding unresolved mystery that excites physicists and the lay person alike.
The story of massive collapsing stars began some eight decades ago when Subrahmanyan Chandrasekhar probed the question of final fate of stars such as the Sun. He showed that such a star, on exhausting its internal nuclear fuel, would stabilize as a “White Dwarf”, about a thousand kilometers in size. Eminent scientists of the time, in particular Arthur Eddington, refused to accept this, saying how a star can ever become so small. Finally Chandrasekhar left Cambridge to settle in the United States. After many years, the prediction was verified. Later, it also became known that stars which are three to five times the Sun’s mass give rise to what are called Neutron stars, just about ten kilometers in size, after causing a supernova explosion.
But when the star has a mass more than these limits, the force of gravity is supreme and overwhelming. It overtakes all other forces that could resist the implosion, to shrink the star in a continual gravitational collapse. No stable configuration is then possible, and the star which lived millions of years would then catastrophically collapse within seconds. The outcome of this collapse, as predicted by Einstein’s theory of general relativity, is a space-time singularity: an infinitely dense and extreme physical state of matter, ordinarily not encountered in any of our usual experiences of physical world.
Cradle of stars, photo by Scott Cresswell CC-by-2.0 via Flickr
As the star collapses, an ‘event horizon’ of gravity can possibly develop. This is essentially ‘a one way membrane’ that allows entry, but no exits permitted. If the star entered the horizon before it collapsed to singularity, the result is a ‘Black Hole’ that hides the final singularity. It is the permanent graveyard for the collapsing star.
As per our current understanding of physics, it was one such singularity, the ‘Big Bang’, that created our expanding universe we see today. Such singularities will be again produced when massive stars die and collapse. This is the amazing place at boundary of Cosmos, a region of arbitrarily large densities billions of times the Sun’s density.
An enormous creation and destruction of particles takes place in the vicinity of singularity. One could imagine this as ‘cosmic inter-play’ of basic forces of nature coming together in a unified manner. The energies and all physical quantities reach their extreme values, and quantum gravity effects dominate this regime. Thus, the collapsing star may hold secrets vital for man’s search for a unified understanding of forces of nature.
The question then arises: Are such super-ultra-dense regions of collapse visible to faraway observers, or would they always be hidden in a black hole? A visible singularity is sometimes called a ‘Naked Singularity’ or a ‘Quantum Star’. The visibility or otherwise of such super-ultra-dense fireball the star has turned into, is one of the most exciting and important questions in astrophysics and cosmology today, because when visible, the unification of fundamental forces taking place here becomes observable in principle.
A crucial point is, while gravitation theory implies that singularities must form in collapse, we have no proof the horizon must necessarily develop. Therefore, an assumption was made that an event horizon always does form, hiding all singularities of collapse. This is called ‘Cosmic Censorship’ conjecture, which is the foundation of current theory of black holes and their modern astrophysical applications. But if the horizon did not form before the singularity, we then observe the super-dense regions that form in collapsing massive stars, and the quantum gravity effects near the naked singularity would become observable.
“It turns out that the collapse of a massive star will give rise to either a black hole or naked singularity”
In recent years, a series of collapse models have been developed where it was discovered that the horizon failed to form in collapse of a massive star. The mathematical models of collapsing stars and numerical simulations show that such horizons do not always form as the star collapsed. This is an exciting scenario because the singularity being visible to external observers, they can actually see the extreme physics near such ultimate super-dense regions.
It turns out that the collapse of a massive star will give rise to either a black hole or naked singularity, depending on the internal conditions within the star, such as its densities and pressure profiles, and velocities of the collapsing shells.
When a naked singularity happens, small inhomogeneities in matter densities close to singularity could spread out and magnify enormously to create highly energetic shock waves. This, in turn, have connections to extreme high energy astrophysical phenomena, such as cosmic Gamma rays bursts, which we do not understand today.
Also, clues to constructing quantum gravity–a unified theory of forces, may emerge through observing such ultra-high density regions. In fact, the recent science fiction movie Interstellar refers to naked singularities in an exciting manner, and suggests that if they did not exist in the Universe, it would be too difficult then to construct a quantum theory of gravity, as we will have no access to experimental data on the same!
Shall we be able to see this ‘Cosmic Dance’ drama of collapsing stars in the theater of skies? Or will the ‘Black Hole’ curtain always hide and close it forever, even before the cosmic play could barely begin? Only the future observations of massive collapsing stars in the universe would tell!
And the prices for the first 3 installments will still stay nice and low until next week, so if you haven’t read Parallelogram 1, 2, or 3 yet, you can scoop them up at a bargain!
0 Comments on Because Waiting Is So Boring as of 1/17/2015 8:23:00 AM
A previous blog post, Patterns in Physics, discussed alternative “representations” in physics as akin to languages; an underlying quantum reality described in either a position or a momentum representation. Both are equally capable of a complete description, the underlying reality itself residing in a complex space with the very concepts of position/momentum or wave/particle only relevant in a “classical limit”. The history of physics has progressively separated such incidentals of our description from what is essential to the physics itself. We will consider this for time itself here.
Thus, consider the simple instance of the motion of a ball from being struck by a bat (A) to being caught later at a catcher’s hand (B). The specific values given for the locations of A and B or the associated time instants are immediately seen as dependent on each person in the stadium being free to choose the origin of his or her coordinate system. Even the direction of motion, whether from left to right or vice versa, is of no significance to the physics, merely dependent on which side of the stadium one is sitting.
All spectators sitting in the stands and using their own “frame of reference” will, however, agree on the distance of separation in space and time of A and B. But, after Einstein, we have come to recognize that these are themselves frame dependent. Already in Galilean and Newtonian relativity for mechanical motion, it was recognized that all frames travelling with uniform velocity, called “inertial frames”, are equivalent for physics so that besides the seated spectators, a rider in a blimp moving overhead with uniform velocity in a straight line, say along the horizontal direction of the ball, is an equally valid observer of the physics.
Einstein’s Special Theory of Relativity, in extending the equivalence of all inertial frames also to electromagnetic phenomena, recognized that the spatial separation between A and B or, even more surprisingly to classical intuition, the time interval between them are different in different inertial frames. All will agree on the basics of the motion, that ball and bat were coincident at A and ball and catcher’s hand at B. But one seated in the stands and one on the blimp will differ on the time of travel or the distance travelled.
Even on something simpler, and already in Galilean relativity, observers will differ on the shape of the trajectory of the ball between A and B, all seeing parabolas but of varying “tightness”. In particular, for an observer on the blimp travelling with the same horizontal velocity as that of the ball as seen by the seated, the parabola degenerates into a straight up and down motion, the ball moving purely vertically as the stadium itself and bat and catcher slide by underneath so that one or the other is coincident with the ball when at ground level.
Hourglass, photo by Erik Fitzpatrick, CC-BY-2.0 via Flickr
There is no “trajectory of the ball’s motion” without specifying as seen by which observer/inertial frame. There is a motion, but to say that the ball simultaneously executes many parabolic trajectories would be considered as foolishly profligate when that is simply because there are many observers. Every observer does see a trajectory, but asking for “the real trajectory”, “What did the ball really do?”, is seen as an invalid, or incomplete, question without asking “as seen by whom”. Yet what seems so obvious here is the mistake behind posing as quantum mysteries and then proposing as solutions whole worlds and multiple universes(!). What is lost sight of is the distinction between the essential physics of the underlying world and our description of it.
The same simple problem illustrates another feature, that physics works equally well in a local time-dependent or a global, time-independent description. This is already true in classical physics in what is called the Lagrangian formulation. Focusing on the essential aspects of the motion, namely the end points A and B, a single quantity called the action in which time is integrated over (later, in quantum field theory, a Lagrangian density with both space and time integrated over) is considered over all possible paths between A and B. Among all these, the classical motion is the one for which the action takes an extreme (technically, stationary) value. This stationary principle, a global statement over all space and time and paths, turns out to be exactly equivalent to the local Newtonian description from one instant to another at all times in between A and B.
There are many sophisticated aspects and advantages of the Lagrangian picture, including its natural accommodation of basic conservation laws of energy, momentum and angular momentum. But, for our purpose here, it is enough to note that such stationary formulations are possible elsewhere and throughout physics. Quantum scattering phenomena, where it seems natural to think in terms of elapsed time during the collisional process, can be described instead in a “stationary state” picture (fixed energy and standing waves), with phase shifts (of the wave function) that depend on energy, all experimental observables such as scattering cross-sections expressed in terms of them.
“The concept of time has vexed humans for centuries, whether layman, physicist or philosopher”
No explicit invocation of time is necessary although if desired so-called time delays can be calculated as derivatives of the phase shifts with respect to energy. This is because energy and time are quantum-mechanical conjugates, their product having dimensions of action, and Planck’s quantum constant with these same dimensions exists as a fundamental constant of our Universe. Indeed, had physicists encountered quantum physics first, time and energy need never have been invoked as distinct entities, one regarded as just Planck’s constant times the derivative (“gradient” in physics and mathematics parlance) of the other. Equally, position and momentum would have been regarded as Planck’s constant times the gradient in the other.
The concept of time has vexed humans for centuries, whether layman, physicist or philosopher. But, making a distinction between representations and an underlying essence suggests that space and time are not necessary for physics. Together with all the other concepts and words we perforce have to use, including particle, wave, and position, they are all from a classical limit with which we try to describe and understand what is actually a quantum world. As long as that is kept clearly in mind, many mysteries and paradoxes are dispelled, seen as artifacts of our pushing our models and language too far and “identifying” them with the underlying reality that is in principle out of reach.
In the last of the Physics Project Lab blog posts, Paul Gluck, co-author of Physics Project Lab, describes how to create and investigate the domino effect…
Many dominoes may be stacked in a row separated by a fixed distance, in all sorts of interesting formations. A slight push to the first domino in the row results in the falling of the whole stack. This is the domino effect, a term also used in figuratively in a political context.
You can use this amusing phenomenon to carry out a little project in physics. Instead of dominoes it’s preferable to use units that are uniformly smooth on both sides, say for example building blocks for kids. Chuildren’s building blocks usually come in sets of 100, 200 or 280 blocks.
The blocks are stacked in a perfect straight line, absolutely uniformly spaced. To ensure this, lay them along the extended metal strip of a builder’s ruler several meters long, fixed at both ends. A non polished wooden floor is a suitable surface, since its roughness is enough to prevent any sliding of the blocks while falling.
What is interesting to measure and correlate in your experimentation? You want to measure the speed of the pulse when the first block is given a reproducibly slight push. In other words, you must measure the total length of the stack, as well as the time between the beginning of the fall of the first block and the fall of the last one. The speed will then be the total distance divided by the time elapsed.
Domino Rally, by mikeyp2000. CC-BY-NC-2.0 via Flickr.
There are several questions you can ask and investigate. First, how does the spacing between the blocks affect the pulse speed? Second, for the same spacing, how do the pulse speeds compare between two cases: the first, with the regular blocks, and the second when you double the height of each block (by sticking two blocks on top of each other to form a single block)? Third, for large numbers of units N in the stack, does the speed depend on the number of units (say when N = 100 and when N = 200)? Finally, does the speed vary for small numbers of units in the stack, say for values between 5 and 15?
For fair comparison between the various cases, you must devise a way to give the slight initial push reproducibly. One way you can arrange this is by releasing a pendulum above the first block and releasing it from a fixed distance so that at the end of its swing the bob just touches the first block, causing it to fall.
For time measurements you need a stopwatch. Be aware that you have a reaction time between when you perceive any event and the pressing of the stopwatch – this can be anything from 0.1 to 0.3 seconds. So repeat each measurement a number of times and take the average. If you have access to two photogates in a physics lab, you can devise a more accurate way of measuring the pulse speed. Actuate the first one by the beginning of the fall of the first block, the second one by the fall of the last one. Couple the two photogates by a circuit that triggers measuring the time when the first brick starts to fall and stops measuring it when the second block falls. You can also video the whole event and analyze the clip frame-by-frame to calculate times.
Happy tinkering!
We hope you have enjoyed the Physics Project Lab series. Have you tried this experiment or any of the other experiments at home? Tell us how it went to get the chance to win a free copy of ‘Physics Project Lab’. We’ll pick our favourite descriptions on 9th January.
Although we rarely stop to think about the origin of the elements of our bodies, we are directly connected to the greater universe. In fact, we are literally made of stardust that was liberated from the interiors of dying stars in gigantic explosions, and then collected to form our Earth as the solar system took shape some 4.5 billion years ago. Until about two decades ago, however, we knew only of our own planetary system so that it was hard to know for certain how planets formed, and what the history of the matter in our bodies was.
Then, in 1995, the first planet to orbit a distant Sun-like star was discovered. In the 20 years since then, thousands of others have been found. Most planets cannot be detected with our present-day technologies, but estimates based on those that we have observed suggest that almost every star in the sky has at least one extrasolar planet (or exoplanet) orbiting it. That means that there are more than 100 billion planetary systems in our Milky Way Galaxy alone! Imagine that: astronomers have gone from knowing of 1 planetary system to some 100 billion, in the same decades in which human genome scientists sequenced the 6 billion base-pairs that lie at the foundation of our bodies. How many of these planetary systems could potentially support life, and would that life use a similar code?
Exoplanets are much too far away to be actually imaged, and they are way too faint to be directly observed next to the bright glow of the stars they orbit. Therefore, the first exoplanet discoveries were made through the gravitational tug on their central star during their orbits. This pull moves the star slightly back and forth. Only relatively heavy, close-in planets can be detected that way, using the repeating Doppler shifts of their central star’s light from red to blue and back. Another way to find planets is to measure how they block the light of their central star if they happen to cross in front of it as seen from Earth. If they are seen to do this twice or more, the temporary dimmings of their star’s light can disclose the planet’s size and distance to its star (basically using the local “year” – the time needed to orbit its star – for these calculations). If both the gravitational tug and the dimming profile can be measured, then even the mass of the planet can be estimated. Size and mass together give an average density from which, in turn, knowledge of the chemical composition of that planet comes within reach.
Star trails, by MLazarevski. CC-BY-ND-2.0 via Flickr.
With the discoveries of so many planets, we have realized that an astonishing diversity exists: hot Jupiter-sized planets that orbit closer to their star than Mercury orbits the Sun, quasi-Earth-sized planets that may have rain showers of molten iron or glass, frozen planets around faintly-glowing red dwarf stars, and possibly some billions of Earth-sized planets at distances from their host stars where liquid water could exist on the surface, possibly supporting life in a form that we might recognize if we saw it.
Guided by these recent observations, mega-computers programmed with the laws of physics give us insight into how these exo-worlds are formed, from their initial dusty disks to the eventual complement of star-orbiting planets. We can image the disks directly by focusing on the faint infrared glow of their gas and dust that is warmed by their proximity to their star. We cannot, however, directly see these far-away planets, at least not yet. But now, for the first time, we can at least see what forming planets do to the gas and dust around them in the process of becoming a mature heavenly body.
A new observatory, called ALMA, working with microwaves that lie even beyond the infrared color range, has been built in the dry Atacama desert in Chili. ALMA was pointed at a young star, hundreds of light years away. Its image of that target star, LH Tauri, not only shows the star itself and the disk around it, but also a series of dark rings that are most likely created as the newly forming planets pull in the gas and dust around them. The image is of stunning quality: it shows details down to a resolution equivalent to the width of a finger seen at a distance of 50 km (30 miles).
At the distance of LH Tauri, even that stunning imaging capability means that we can see structures only if these are larger than about the distance of the Sun out to Jupiter, so there is a long way yet to go before we see anything like the planet directly. But we will observe more of these juvenile planetary systems just past the phase of their birth. And images like that give us a glimpse of what happened in our own planetary system over 4.5 billion years ago, before the planets were fully formed, pulling in the gases and dust that we now live on, and that ultimately made their way to the cycles of our own planet, to constitute all living beings on Earth.
What a stunning revolution: from being part of the only planetary system we knew of, we have been put among billions and billions of neighbors. We remember Galileo Galilei for showing us that the Sun and not the Earth was the center of the solar system. Will our society remember the names of those who proved that billions of planets exist all over the Galaxy?
Headline image credit: Star shower, by c@rljones. CC-BY-NC-2.0 via Flickr.
John Adams predicted that fireworks would be part of the Fourth of July celebrations on July 3, 1776 with a letter to Abigail Adams where he said, “I am apt to believe that it will be celebrated by succeeding generations as the great anniversary festival. It ought to be commemorated, as the Day of Deliverance by solemn Acts of Devotion to God Almighty. It ought to be solemnized with Pomp and Parade, with Shews, Games, Sports, Guns, Bells, Bonfires and Illuminations from one End of this Continent to the other from this Time forward forever more.”
metals. The metals determine the color (copper=blue/green, calcium=red), and the arrangement determines shape (circle, smiley faces, stars).
Conservation of Momentum says that momentum must be the same before and after the explosion. In other words, when the explosion occurs the movement must be balanced.
This is the continuation of the story about the origin of the Germanic word for man. Last week I left off after expressing great doubts about the protoform that connected man and guma and tried to defend the Indo-European girl from an unpronounceable name. As could be expected, in their attempts to discover the origin of man etymologists cast a wide net for words containing m and n.
The post You’ll be a man, my son. Part 2 appeared first on OUPblog.
Oxford is thrilled to welcome Dr. Kathy Battista as the new Editor in Chief of the Benezit Dictionary of Artists. Get to know Dr. Battista with our Q/A session.
The post Meet Dr. Kathy Battista, Benezit’s new Editor in Chief appeared first on OUPblog.