How to teach physics to your dog download

Classical laws of motion govern the motion of anything large enough to see with the naked eye. Classical thermodynamics explains the physics of heating and cooling objects, and the operation of engines and refrigerators. Classical electromagnetism explains the behavior of lightbulbs, radios, and magnets.

Modern physics describes the stranger world that we see when we go beyond the everyday. This world was first revealed in experiments done in the late s and early s, which cannot be explained with classical laws of physics. New fields with different rules needed to be developed. Modern physics is divided into two parts, each representing a radical departure from classical rules.

One part, relativity, deals with objects that move very fast, or are in the presence of strong gravitational forces. The other part of modern physics is what I talk to my dog about. Modern life would be impossible without quantum mechanics. Without an understanding of the quantum nature of the electron, it would be impossible to make the semiconductor chips that run our computers.

Without an understanding of the quantum nature of light and atoms, it would be impossible to make the lasers we use to send messages over fiberoptic communication lines. Quantum physics places limits on what we can know about the universe and the properties of objects in it.

Quantum mechanics even changes our understanding of what it means to make a measurement. It requires a complete rethinking of the nature of reality at the most fundamental level. The world described in quantum theory is our world, at a microscopic scale. Quantum theory has been tested to an incredible level of precision, making it the most accurately tested theory in the history of scientific theories.

So, quantum physics is neat stuff. But what does it have to do with dogs? Dogs come to quantum physics in a better position than most humans. They approach the world with fewer preconceptions than humans, and always expect the unexpected. A dog can walk down the same street every day for a year, and it will be a new experience every day.

Every rock, every bush, every tree will be sniffed as if it had never been sniffed before. If dog treats appeared out of empty space in the middle of a kitchen, a human would freak out, but a dog would take it in stride. Indeed, for most dogs, the spontaneous generation of treats would be vindication—they always expect treats to appear at any moment, for no obvious reason.

Quantum mechanics seems baffling and troubling to humans because it confounds our commonsense expectations about how the world works. Dogs are a much more receptive audience. The everyday world is a strange and marvelous place to a dog, and the predictions of quantum theory are no stranger or more marvelous than, say, the operation of a doorknob.

Part of learning quantum mechanics is learning to think like a dog. If you can look at the world the way a dog does, as an endless source of surprise and wonder, then quantum mechanics will seem a lot more approachable. This book reproduces a series of conversations with my dog about quantum physics. Each conversation is followed by a detailed discussion of the physics involved, aimed at interested human readers. The topics range from ideas many people have heard of, like particle-wave duality chapter 1 and the uncertainty principle chapter 2 , to the more advanced ideas of virtual particles and QED chapter 9.

These explanations include discussion of both the weird predictions of the theory both practical and philosophical , and the experiments that demonstrate these predictions.

I think it needs. You need my help with the physics stuff, though. Give me an example. This covers a range from bacteria to atoms to electrons. The squirrel flees into a yard and dodges around a small ornamental maple.

You were about to run into a tree, and I stopped you. Material particles have wave nature and can diffract around objects.

I got a good running start, and I was just about to go around when you stopped me. Like I said, an interesting theory. Because I do. You see, a tree is big, and your wavelength is small. At walking speed, a twenty-kilogram dog like you has a wavelength of about meters. I can run very fast. It would take a billion years to cross the nucleus of an atom at that speed, which is way too slow to catch a bunny.

A squirrel! Quantum physics has many strange and fascinating aspects, but the discovery that launched the theory was particle-wave duality, or the fact that both light and matter have particle-like and wavelike properties at the same time. A beam of light, which is generally thought of as a wave, turns out to behave like a stream of particles in some experiments.

At the same time, a beam of electrons, which is generally thought of as a stream of particles, turns out to behave like a wave in some experiments.

Particle and wave properties seem to be contradictory, and yet everything in the universe somehow manages to be both a particle and a wave. The discovery in the early s that light behaves like a particle is the launching point for all of quantum mechanics. In order to appreciate just what a strange development this is, though, we need to talk about the particles and waves that we see in everyday life. Pretty much all the objects you see around you—bones, balls, squeaky toys—behave like particles in the classical sense, with their motion determined by classical physics.

You can multiply the mass and velocity together, to find the momentum. Momentum determines what will happen when two particles collide. When a moving object hits a stationary one, the moving object will slow down, losing momentum, while the stationary object will speed up, gaining momentum. The other notable feature of particles is something that seems almost too obvious to mention: particles can be counted.

When you have some collection of objects, you can look at them and determine exactly how many of them you have—one bone, two squeaky toys, three squirrels under a tree in the backyard. Waves, on the other hand, are slipperier. A wave is a moving disturbance in something, like the patterns of crests and troughs formed by water splashing in a backyard pond.

Waves are spread out over some region of space by their nature, forming a pattern that changes and moves over time. No physical objects move anywhere—the water stays in the pond—but the pattern of the disturbance changes, and we see that as the motion of a wave.

If you want to understand a wave, there are two ways of looking at it that provide useful information. One is to imagine taking a snapshot of the whole wave, and looking at the pattern of the disturbance in space. The other thing you can do is to look at one little piece of the wave pattern, and watch it for a long time—imagine watching a duck bobbing up and down on a lake, say.

Wavelength and frequency are related to each other—longer wavelengths mean lower frequency, and vice versa. The wave itself is a disturbance spread over space, and not a physical thing with a definite position and velocity. You can assign a velocity to the wave pattern, by looking at how long it takes one crest of the wave to move from one position to another, but again, this is a property of the pattern as a whole. Imagine that you have two different sources of waves in the same area —two rocks thrown into still water at the same time, for example.

What you get when you add the two waves together depends on how they line up. Do you have any other examples of interference? Something more. Nothing that dogs deal with on a regular basis is all that wavelike. Interference is more like putting a squirrel in the backyard, then putting a second squirrel in the backyard one second later, and finding that you have no squirrels at all.

But if you wait two seconds before putting in the second squirrel, you find four squirrels. Well, good job, then. Anyway, why are we talking about this? When are we going to talk about physics? The whole point of physics is to use math to describe the universe. Though these are both examples of wave phenomena, they appear to behave very differently. Sound waves are pressure waves in the air. When a dog barks, she forces air out through her mouth and sets up a vibration that travels through the air in all directions.

Light is a different kind of wave, an oscillating electric and magnetic field that travels through space—even the emptiness of outer space, which is why we can see distant stars and galaxies. When light waves strike the back of your eye, they get turned into signals in the brain that are processed to form an image of the world around you. The most striking difference between light and sound in everyday life has to do with what happens when they encounter an obstacle.

Light waves travel only in straight lines, while sound waves seem to bend around obstacles. The apparent bending of sound waves around corners is an example of diffraction, which is a characteristic behavior of waves encountering an obstacle. How quickly they spread depends on the wavelength of the wave and the size of the opening through On the left, a wave with a short wavelength encounters an opening much larger than the wavelength, and the waves continue more or less straight through.

On the right, a wave with a long wavelength encounters an opening comparable to the wavelength, and the waves diffract through a large range of directions. If the opening is much larger than the wavelength, there will be very little bending, but if the opening is comparable to the wavelength, the waves will fan out over the full available range.

Similarly, if sound waves encounter an obstacle like a chair or a tree, they will diffract around it, provided the object is not too much larger than the wavelength.

This is why it takes a large wall to muffle the sound of a barking dog—sound waves bend around smaller obstacles, and reach people or dogs behind them.

Sound waves in air have a wavelength of a meter or so, close to the size of typical obstacles—doors, windows, pieces of furniture. As a result, the waves diffract by a large amount, which is why we can hear sounds even around tight corners. Light waves, on the other hand, have a very short wave-length—less than a thousandth of a millimeter. A hundred wavelengths of visible light will fit in the thickness of a hair. When light waves encounter everyday obstacles, they hardly bend at all, so solid objects cast dark shadows.

A tiny bit of diffraction occurs right at the edge of the object, which is why the edges of shadows are always fuzzy, but for the most part, light travels in a straight line, with no visible diffraction.

If we look at a small enough obstacle, though, we can see unmistakable evidence of wave behavior. In an English physicist named Thomas Young did the definitive experiment to demonstrate the wave nature of light.

Young took a beam of light and inserted a card with two very narrow slits cut in it. The light passing An illustration of double-slit diffraction. On the left, the waves from two different slits travel exactly the same distance, and arrive in phase to form a bright spot.

In the center, the wave from the lower slit travels an extra half-wavelength darker line , and arrives out of phase with the wave from the upper slit. The two cancel out, forming a dark spot in the pattern. On the right, the wave from the lower slit travels a full extra wavelength, and again adds to the wave from the upper slit to form a bright spot.

At any given point, the waves from the two slits have traveled different distances, and have gone through different numbers of oscillations. At the bright spots, the two waves are in phase, and add together to give light that is brighter than light from either slit by itself.

At the dark spots, the waves are out of phase, and cancel each other out. Things stayed that way for about a hundred years. You can think of the light that goes around to the left and the light that goes around to the right of the obstacle as being like the waves from two different slits. They take different paths to their destination, and thus can be either in phase or out of phase when they arrive. You get a pattern of bright and dark spots, just like when you use slits.

I guess that makes sense. I need to talk about particles, first. I can be patient. Planck was studying the thermal radiation emitted by all objects. The emission of light by hot objects is a very common phenomenon the best-known example is the red glow of a hot piece of metal , and something so common seems like it ought to be easy to explain.

He had even discovered a formula to describe the characteristic shape of the spectrum, but was stymied when he tried to find a theoretical justification for the formula. Every method he tried predicted much more light at high frequencies than was observed. In desperation, he resorted to a mathematical trick to get the right answer. When he first made this odd assumption, Planck thought he would use it just to set up the problem, and then use a common mathematical technique to get rid of the imaginary oscillators and this extra constant h.

Much to his surprise, though, he found that his results made sense only if he kept the oscillators around—if h had a very small but nonzero value. This is a little like imagining a pond where waves can only be one, two, or three centimeters high, never one and a half or two and a quarter. The first person to talk seriously about light as a quantum particle was Albert Einstein in , who used it to explain the photoelectric effect.

The photoelectric effect is another physical effect that seems like it ought to be simple to describe: when you shine light on a piece of metal, electrons come out. This forms the basis for simple light sensors and motion detectors: light falling on a sensor knocks electrons out of the metal, which then flow through a circuit.

When the amount of light hitting the sensor changes, the circuit performs some action, such as turning lights on when it gets dark, or opening doors when a dog passes in front of the sensor. The photoelectric effect ought to be readily explained by thinking of light as a wave that shakes atoms back and forth until electrons come out, like a dog shaking a bag of treats until they fly all over the kitchen. Unfortunately, the wave model comes out all wrong: it predicts that the energy of the electrons leaving the atoms should depend on the intensity of the light—the brighter the light, the harder the shaking, and the faster the bits flying away should move.

At low frequencies, you never get any electrons no matter how hard you shake, while at high frequency, even gentle shaking produces electrons with a good deal of energy. When you get a bag with treats in it, you always shake it as fast as you can, as hard as you can. Dogs have an excellent intuitive grasp of quantum theory. For dogs, the point is to get the treats. Each photon the name now given to these particles of light has a fixed amount of energy it can provide, depending on the frequency; and some minimum amount of energy is required to knock an electron loose.

The higher the frequency, the higher the single photon energy and the more energy the electrons have when they leave, exactly as the experiments show. If the energy of a single photon is lower than the minimum energy for knocking an electron out, nothing happens, explaining the lack of electrons at low frequencies.

And yet each of those particles still has a frequency associated with it, and somehow they add up to give an interference pattern, just like a wave. Some ideas from relativity are important to quantum physics, as well. Photons have momentum because of their energy in the same way that objects have energy because of their mass. And nice job dropping an equation in there. And I am an exceptional dog. That means that the interaction between a photon of light and a stationary object ought to look just like a collision between two particles: the stationary object gains some energy and momentum, and the moving photon loses some energy and momentum.

In , Compton bounced X-rays with an initial wavelength of 0. When he looked at the X-rays that scattered off the target, he found that they had longer wavelengths, indicating that they had lost momentum X-rays bouncing off at 90 degrees from their original direction had a wavelength of 0.

This loss of momentum is exactly what should happen if light is a particle: when an X-ray photon comes in and hits a more or less stationary electron in a target, it gives up some of its momentum to the electron, which starts moving. After the collision, the photon has less momentum, and thus a longer wavelength, exactly as Compton observed.

Compton measured the wavelength at many different angles, and his results exactly fit the theoretical prediction, confirming that the shift was from collisions with electrons, and not some other effect. Einstein, Millikan, and Compton all won Nobel prizes for demonstrating the particle nature of light. The idea has a certain mathematical elegance, which was appealing to theoretical physicists even in , but it also seems like patent nonsense—solid objects show no sign of behaving like waves.

When de Broglie presented his idea as part of his Ph. Einstein proclaimed it brilliant, and de Broglie got his degree, but his idea of electrons as waves had little support until two experiments in the late s showed incontrovertible proof that electrons behaved like waves. In , two American physicists, Clinton Davisson and Lester Germer, were bouncing electrons off a surface of nickel, and recording how many bounced off at different angles.

They were surprised when their detector picked up a very large number of electrons bouncing off at one particular angle. This mysterious result was eventually explained as the wavelike diffraction of the electrons bouncing off different rows of atoms in their nickel target. Electrons reflecting from all these different rows of atoms behaved like waves.

The waves that bounced off atoms deeper in the crystal traveled farther on the way out than the ones that bounced off atoms closer to the surface. Most of the time, the reflected waves were out of phase and canceled one another out. For certain angles, though, the extra distance traveled was exactly right for the waves to add in phase and produce a bright spot, which Davisson and Germer detected as a large increase in the number of electrons reflected at that angle. The de Broglie formula for assigning a wavelength to the electron predicts the Davisson and Germer result perfectly.

An incoming electron beam dashed line passes into a regular crystal of atoms, and bits of the wave individual electrons reflect off different atoms in the crystal. Electrons reflected from deeper in the crystal travel a longer distance on the way out darker line , but for certain angles, that distance is a multiple of a full wavelength, and the waves leaving the crystal add in phase to give the bright spot seen by Davisson and Germer.

When you add the waves together, you still get a pattern of bright and dark spots, but as you use more slits, the bright spots get brighter and narrower, and the dark spots get darker and wider.

Diffraction patterns like those seen by Davisson and Germer and Thomson are an unmistakable signature of wave behavior, as Thomas Young showed in , so their experiments provided proof that de Broglie was right, and electrons have wave nature.

De Broglie won the Nobel Prize in Physics in for his prediction, and Davisson and Thomson shared a Nobel Prize in for demonstrating the wave nature of the electron. In fact, neutron diffraction is now a standard tool for determining the structure of materials at the atomic level: scientists can deduce how atoms are arranged by looking at the interference patterns that result when a beam of neutrons bounces off their sample. Knowing the structure of materials at the atomic level allows materials scientists to design stronger and lighter materials for use in cars, planes, and space probes.

Neutron diffraction can also be used to determine the structure of biological materials like proteins and enzymes, providing critical information for scientists searching for new drugs and medical treatments. The answer is the wavelength: as with the sound and light waves discussed earlier, the dramatically different behavior of dogs and electrons encountering obstacles is explained by the difference in their wavelengths.

The wavelength is determined by the momentum, and a dog has a lot more momentum than an electron. The wavelength of a pound about 20 kg dog out for a stroll, on the other hand, is about meters 0. How does that compare to the size of a tree? In , a research group at the University of Vienna headed The interference pattern produced by a beam of molecules passing through an array of narrow slits. The extra lumps to either side of the central peak are the result of diffraction and interference of the molecules passing through the slits.

Reprinted with permission from O. Nairz, M. Arndt, and A. Zeilinger, Am. Copyright , American Association of Physics Teachers. Anton Zeilinger observed diffraction and interference with molecules consisting of 60 carbon atoms bound together into a shape like a tiny soccer ball, each with a mass about a million times that of an electron. They shot these soccer-ball-shaped molecules toward a detector, and when they looked at the distribution of molecules downstream, they saw a single narrow beam.

Then they sent the beam through a silicon wafer with a collection of very small slits cut into it, and looked at the distribution of molecules on the far side of the slits. Those lumps, like the bright and dark spots seen by Thomas Young shining light through a double slit, or the electron diffraction peaks seen by Davisson and Germer, are an unmistakable signature of wave behavior. Molecules passing through the slits spread out and interfere with one another, just like light waves.

In subsequent experiments, the Zeilinger group demonstrated the diffraction of even larger molecules, adding 48 fluorine atoms to each of their original carbon-atom molecules. These molecules have a mass about three million times the mass of one electron, and stand as the current record for the most massive object whose wave nature has been observed directly. As the mass of a particle increases, its wavelength gets shorter and shorter, and it gets harder and harder to see wave effects directly.

This is why nobody has ever seen a dog diffract around a tree; nor are we likely to see it any time soon. In terms of physics, though, a dog is nothing but a collection of biological molecules, which the Zeilinger group has shown have wave properties. So, we can say with confidence that a dog has wave nature, just the same as everything else.

A squirunny. Everything in the universe is built of these quantum particles. The first law is the principle of inertia, that objects at rest tend to remain at rest, and objects in motion tend to remain in motion unless acted on by an external force.

The third law says that for every action there is an equal and opposite reaction—a force of equal strength in the opposite direction. These three laws describe the motion of macroscopic objects at everyday speeds, and form the core of classical physics. This would require two photons to hit the same electron at the same instant, and that almost never happens.

Ironically, those quotes are from the first paragraph of the paper in which he conclusively confirms the predictions of the theory. The last resistance collapsed in , when incontrovertible proof of the existence of photons was provided in an experiment by Kimble, Dagenais, and Mandel that looked at the light emitted by single atoms.

It can be as difficult to separate a physicist from a cherished model as it is to drag a dog away from a well-chewed bone. This includes the clear and sparkly things that we normally associate with the word, but also a lot of metals and other substances. Then they accidentally let air into their vacuum system.

In the process of repairing the damage, they melted the target, which recrystallized into a single large crystal, producing a single, clear diffraction pattern. Sometimes, the luckiest thing a physicist can do is to break something important. Thomson of Cambridge, won the Nobel Prize in Physics for demonstrating the particle nature of the electron. This presumably led to some interesting dinner-table conversation in the Thomson household.

Which means that when one uncertainty is small, the other must be very large. You just said. Why not? I mean, your bone has a mass of a couple hundred grams, and if I measured its velocity to within one millimeter per second, that would give an uncertainty in position of only about meters. Did you look under the TV cabinet? Sometimes it gets kicked under there. If you make a better measurement of the position, you necessarily lose information about its momentum, and vice versa.

The uncertainty principle is often presented as a statement that a measurement of a system changes the state of that system, and in this form, references to quantum uncertainty turn up in all sorts of places, from politics to pop culture to sports. Quantum uncertainty is a fundamental limit on what can be known, arising from the fact that quantum objects have both particle and wave properties. Uncertainty is also the first place where quantum physics collides with philosophy. The idea of fundamental limits to measurement runs directly counter to the goals and foundations of classical physics.

Dealing with quantum uncertainty requires a complete rethinking of the basis of physics, and leads directly to the issues of measurement and interpretation in chapters 3 and 4. This is what physicists call a semiclassical argument—the physics used is classical, with a few modern ideas added on. The idea behind the semiclassical treatment of uncertainty is familiar to any dog.

Imagine you have a bunny in the yard whose position and velocity you would like to know very well. When you attempt to make a better determination of its position by getting closer to it , you inevitably change its velocity by making it run away.

No matter how slowly you creep up on it, sooner or later, it always takes off, and you never really have a good idea of both the position and the velocity. In the collision, though, the electron acquires some momentum, leading to uncertainty in its momentum. To measure the position of an electron, you need to do something to make it visible, such as bouncing a photon of light off it and viewing the scattered light through a microscope.

But the photon carries momentum as we saw in chapter 1 [page 24] , and when it bounces off the electron, it changes the momentum of the electron. You can make the momentum change smaller by increasing the wavelength of the light decreasing the momentum that the photon has available to give to the electron , but when you increase the wavelength, you decrease the resolution of your microscope, and lose information about the position.

The real meaning of the uncertainty principle is deeper than that, though. In the microscope thought experiment illustrated above, the electron has a definite position and a definite velocity before you start trying to measure it, and still has a definite position and velocity after the measurement.

In quantum theory, however, these quantities are not defined. This fundamental uncertainty is a consequence of the dual nature of quantum particles. As we saw in the previous chapter, experiments have shown that light and matter have both particle-like and wavelike properties. The wavefunction for a particular object is a mathematical function that has some value at every point in the universe, and that value squared gives the probability of finding a particle at a given position at a given time.

So the question we need to ask is, What sort of wavefunction gives a probability distribution that has both particle and wave properties? Constructing a probability distribution for a classical particle is easy, and the result looks something like this: The probability of finding the object—say, that pesky bunny in the backyard—is zero everywhere except right at the well-defined position of the object.

Well, then, how do we draw a probability distribution with an obvious wavelength? The bunny is spread out over the entire yard, with a good probability of finding it at lots of different places. The bunny is very likely to be found in a small region of space, and the probability of finding it outside that region drops off to zero.

Inside that region, we see oscillations in the probability, which allow us to measure a wavelength, and thus the momentum. As a consequence, it also has some uncertainty in both the position and momentum of the particle. The uncertainty in position is immediately obvious on looking at the wave packet. The position as described by this wave packet is necessarily uncertain. Each of these waves represents a particular possible momentum for the bunny, so just as there are several different positions where the bunny might be found, there are also several different possible values of the momentum.

The momentum of the bunny described by this wave packet thus has some uncertainty. How do we get a wave packet by combining many waves? The way we account for that mathematically is by adding the two waves together. I was hoping for more bunnies. The wavefunction we get from adding them together the solid line in the figure has lumps in it—there are places where we see waves, and places where we see nothing.

When we square that to get the probability distribution, we get the bottom graph: The dashed curves in the top graph show the wavefunctions for the two different wavelengths shifted up so you can see them clearly. The solid curve shows the sum of the two wavefunctions. The bottom graph shows the probability distribution resulting from adding them together the square of the solid curve in the top graph. The center part of this probability distribution looks an awful lot like the wave packet we want.

Outside that region, the probability goes to zero, meaning that there are places where we have no hope of seeing a bunny at all. But we can improve the situation by adding more waves: The bottom graph is the probability distribution for a single frequency wave, with two-, three-, and five-frequency graphs above it. As we add more and more waves, the regions of high probability get narrower, and the spaces between them become wider and flatter.

What we end up with starts to looks like a long chain of wave packets. I thought we were only talking about one bunny. If we want to narrow that down to just one position for the bunny, we do it by adding together a continuous distribution of wavelengths, not just a set of regularly spaced single wavelengths.

Just take my word for it—we can make a single wave packet by summing a continuous distribution of wavelengths, with different probabilities for different wavelengths. I still want more bunnies. And if I know where it is, I can catch it! Well, each wave corresponds to a particular momentum—a different velocity for the single bunny moving through the yard. Adding these states together is the origin of the uncertainty principle. If we want a narrow and well-defined wave packet, so that we know the position of the bunny very well, we need to add together a great many waves to do that.

Each wave corresponds to a possible momentum for the bunny, though, which gives a large uncertainty in the momentum—it could be moving at any one of a large number of different speeds. On the other hand, if we want to know the momentum very well, we can use a small number of different wavelengths, but this gives us a very broad wave packet, with a large uncertainty in the position.

The bunny can only have a few possible speeds, but we can no longer say where it is with much confidence. The best we can hope to do is a single wave packet like we drew at the beginning, with a small uncertainty in the momentum and a small uncertainty in the position. Looked at in terms of wavefunctions, then, we can see that this relationship is much more than just a practical limit due to our inability to measure a system without disturbing it.

We saw in chapter 1 that quantum particles behave like particles—photons have momentum and collide with electrons in the Compton effect page We also saw that quantum particles behave like waves—electrons, atoms, and molecules diffract around obstacles and form interference patterns.

The price we pay for having both of these sets of properties at the same time is that position and momentum must always be uncertain. Not only does it change the way we look at single moving particles, but it has profound consequences for the structure of matter at the microscopic level.

Most humans, and even many dogs, picture atoms as tiny little solar systems, with negatively charged electrons orbiting a positively charged nucleus.

This picture originated with Niels Bohr in , when he proposed the first quantum model of the hydrogen atom. Electrons can never be found in an orbit with an in-between energy.

Physicists often talk about these states as if they were steps on a staircase, and the electrons were dogs looking for a place to sleep. The dog can rest comfortably on the ground floor, or on one of the steps, but any attempt to lie down halfway between two steps will end badly.

Electrons can move between the allowed states by absorbing or emitting photons of light, with the frequency of the emitted light corresponding to the difference between the energies of the two states.

The Bohr model thus solved a problem that had stymied physicists for years. When Bohr proposed the model, it was a bold break with prior physics. The fundamental problem with this picture is the same issue that leads to uncertainty. For the solar-system model to be accurate, the electron must have a well-defined position somewhere along the allowed orbit, and a well-defined momentum moving it along that orbit.

When we account for the wave nature of the electron, we are forced to discard the whole idea of electrons as planets. The different energy states correspond to different probabilities of finding the electrons at particular positions, and higherenergy states will give you a better chance of finding the electron farther from the nucleus than lower-energy states.

But for any of the allowed states, the electron could be at just about any point within a few nanometers of the nucleus. And if you get a bunch of atoms together in a solid, one electron can be shared among the whole solid. While our gadgets may be new, however, the drive to measure and master time is anything but—and in A Brief History of Timekeeping, Chad Orzel traces the path from Stonehenge to your smartphone.

Predating written language and marching on through human history, the desire for ever-better timekeeping has spurred technological innovation and sparked theories that radically reshaped our understanding of the universe and our place in it.

Orzel, a physicist and the bestselling author of Breakfast with Einstein and How to Teach Quantum Physics to Your Dog continues his tradition of demystifying thorny scientific concepts by using the clocks and calendars central to our everyday activities as a jumping-off point to explore the science underlying the ways we keep track of our time.

Ancient solstice markers which still work perfectly 5, years later depend on the basic astrophysics of our solar system; mechanical clocks owe their development to Newtonian physics; and the ultra-precise atomic timekeeping that enables GPS hinges on the predictable oddities of quantum mechanics. Along the way, Orzel visits the delicate negotiations involved in Gregorian calendar reform, the intricate and entirely unique system employed by the Maya, and how the problem of synchronizing clocks at different locations ultimately required us to abandon the idea of time as an absolute and universal quantity.

Sharp and engaging, A Brief History of Timekeeping is a story not just about the science of sundials, sandglasses, and mechanical clocks, but also the politics of calendars and time zones, the philosophy of measurement, and the nature of space and time itself. Over time, however, they discovered that Newtonian physics couldn't describe every phenomenon they observed.

They developed a new model, called quantum physics, which described the universe in a fundamentally new way, in terms of quanta and fields. Its revolutionary concepts, including wave-particle duality, randomness, and quantum jumps, are explained in this book in easy-to-follow language.

The text examines the gaps in classical physics that spurred the search for new theories, the discoveries that shaped those theories, and the scientists who developed this exciting field.

This volume also explores the ongoing ramifications of quantum physics in our lives today. Author : Hermann Wimmel Publisher: World Scientific ISBN: Category: Science Page: View: Read Now » The interpretation of quantum mechanics in this book is distinguished from other existing interpretations in that it is systematically derived from empirical facts by means of logical considerations as well as methods in the spirit of analytical philosophy, in particular operational semantics.

The new interpretation, using a two-model approach overcomes the well-known conceptional problems and paradoxes of? This interdisciplinary book should be of interest to scholars, teachers, and students in the fields of physics and philosophy of science. Author : Roger A.

Computer encryption is vital for protecting users, data, and infrastructure in the digital age. Unfortunately, many current cryptographic methods will soon be obsolete. Want to Read Currently Reading Read. Other editions. Enlarge cover. Error rating book. How to Teach Physics to Your Dog is a book that explains quantum mechanics in terms that even a dog can understand-- in fact, the dog does some of the explaining.

This describes how we know that light is a particle as well as a wave and the electron is a wave as well as a particle , and why Emmy can't use her wave nature to go around both sides of a tree at the same time.

You can also watch a dramatic reading of the dog conversation from Chapter 5, on the quantum Zeno effect:. Finally, here's a video that's not strictly book-related, but Emmy does make a couple of appearances, and it does cover some material from the book: The Bohr-Einstein debates over the philosophical implications of quantum mechanics, done with puppets. Dog puppets, because it's not easy to find a Niels Bohr puppet in the US:.

Talking to Your Human About Physics. Previews: How to Teach Physics to Your Dog How to Teach Physics to Your Dog is a book that explains quantum mechanics in terms that even a dog can understand-- in fact, the dog does some of the explaining. Once thought of as an obscure science, it reached the masses via the notion of teleportation in Star Trek and, more recently, as an integral part of the popular TV series Lost and Fringe.

Now, inspired by his hugely popular website and science blog, Chad Orzel uses his cherished mutt Emmy to explain the basic principles of quantum physics. And who better to explain the magical universe of quantum physics than a talking dog?