Radioactive Decay Quotes

What is it that you contain? The dead. Time. Light patterns of millennia opening in your gut. Every minute, in each of you, a few million potassium atoms succumb to radioactive decay. The energy that powers these tiny atomic events has been locked inside potassium atoms ever since a star-sized bomb exploded nothing into being. Potassium, like uranium and radium, is a long-lived radioactive nuclear waste of the supernova bang that accounts for you. Your first parent was a star.

The air around you is filled with floating atoms, sliding down the Earth's spacetime curve. Atoms first assembled in the cores of long-dead stars. Atoms within you, everywhere, disintegrating in radioactive decays. Beneath your feet, the floor - whose electrons refuse to let yours pass, thus making you able to stand and walk and run. Earth, your planet, a lump of matter made out of the three quantum fields known to mankind, held together by gravity, the so-called fourth force (even though it isn't a force), floating within and through spacetime.

with the weak force controlling radioactive decay, the strong force binding the atomic nucleus, the electromagnetic force binding molecules, and gravity binding bulk matter.

the weak force controlling radioactive decay, the strong force binding the atomic nucleus, the electromagnetic force binding molecules, and gravity binding bulk matter.

I listen to a radio segment about scientists measuring the radioactive decay after such large-scale catastrophes as September 11 or the 2003 tsunami in Indonesia. It turns out that nuclear decay, which is, if not a constant, as close to such a thing as we can get, inexplicably increases after these events. As if contingent matter echoed or shadowed or even shared our sufferings (and our joys?). As if creation itself cried out with us.

[T]he probabilistic nature of the Schrödinger equation, which predicts only the likelihood of different experimental outcomes, leaves it offering no reason why one specific outcome is observed instead of another. In effect, it says that quantum events (the radioactive decay of an atom, say) happen for no reason.

Had she not been an immigrant, she might have enjoyed being a mom. 'Raising you took half my life,' she would say. 'You're living proof of where that half of my life went.' Chemists know this already. All elements on the periodic table decay. And in one half life, half the original element, called the parent nucleus, decays to a different element, for the daughter nucleus. No son nucleus, of course. No son could ever be a by-product of radioactive decay.

What can I say about my first real relationship, the one I had with Raylan Thompson? That he was charming, and easy on the eyes... a brave military man like my father. However, if I was being honest with myself, he wasn’t my Pierre Curie or Frederic Joliot. I never felt the way the songs say you’re supposed to feel if you love someone. Sure, I really liked him, but I always knew I could live without him. Our relationship was unstable, like radioactive decay, or boron- 7—a substance that didn’t last, as though it had never been there at all.

What can I say about my first real relationship, the one I had with Raylan Thompson? That he was charming, and easy on the eyes... a brave military man like my father. However, if I was being honest with myself, he wasn’t my Pierre Curie or Frederic Joliot. I never felt the way the songs say you’re supposed to feel if you love someone. Sure, I really liked him, but I always knew I could live without him. Our relationship was unstable, like radioactive decay, or boron- 7—a substance that didn’t last, as though it had never been there at all.

radioactive elements decayed into other elements—that one day you had an atom of uranium, say, and the next you had an atom of lead. This was truly extraordinary. It was alchemy, pure and simple; no one had ever imagined that such a thing could happen naturally and spontaneously.

Everyone should be very grateful radioactivity exists at all. It can kill you, yes, but without it you wouldn't have been born in the first place. On Earth, deep under your feet, our planet happens to contain many atoms that do decay, all the time. Less so now than in the past, but still, Earth's mantle is radioactive. When atoms decay there, the particles they emit bump into their neighbours and generate heat, the very heat that contributes to keeping our planet warm. Without radioactivity, there would be no seismic or volcanic activity. The surface of the Earth would have been dead cold billions of yeras ago. Life as we know it would probably not exist at all.

Imagine a cat, a vial of poison, and a radioactive source in a sealed box. If an internal sensor registers radioactivity, like an atom decaying, the vial is broken, releasing a poison that kills the cat. The atom has an equal chance of decaying or not decaying. It’s an ingenious way of linking an outcome in the classical world, our world, to a quantum-level event. The Copenhagen interpretation of quantum mechanics suggests a crazy thing: before the box is opened, before observation occurs, the atom exists in superposition—an undetermined state of both decaying and not decaying. Which means, in turn, that the cat is both alive and dead. And only when the box is opened, and an observation made, does the wave function collapse into one of two states. In other words, we only see one of the possible outcomes. For instance, a dead cat. And that becomes our reality. But then things get really weird. Is there another world, just as real as the one we know, where we opened the box and found a purring, living cat instead? The Many-Worlds interpretation of quantum mechanics says yes. That when we open the box, there’s a branch. One universe where we discover a dead cat. One where we discover a live one. And it’s the act of our observing the cat that kills it—or lets it live. And then it gets mind-fuckingly weird. Because those kinds of observations happen all the time. So if the world really splits whenever something is observed, that means there’s an unimaginably massive, infinite number of universes—a multiverse—where everything that can happen will happen.

On that fateful morning in April 1986, the explosion that blew off the reactor lid also dislodged special serpentine sand and concrete from within the thick walls surrounding the RBMK. In that same moment, a powerful shock wave forced the entire bottom half of the core assembly - including the lower biological shield - downward by several meters, into the space below. Over the following week, intense heat from the fire and radioactive decay increased until it reached temperatures sufficient to melt the fuel assembly, which poured out and bonded with the sand/concrete mix to form a kind of radioactive lava called corium. This lava then oozed through pipes, ducts and cracks in the damaged structure to the rooms beneath. The Elephant’s Foot was one offshoot of this lava, which had cooled into a glassy form. Melted fuel vacating the exposed reactor like this is probably what caused the sudden drop in temperature and emission levels in early May, 1986. A molten core is capable of burning through 30cm of concrete within hours, hence the scramble to prevent this from happening.246

I came into the room, which was half dark, and presently spotted Lord Kelvin in the audience and realised that I was in for trouble at the last part of my speech dealing with the age of the earth, where my views conflicted with his. To my relief, Kelvin fell fast asleep, but as I came to the important point, I saw the old bird sit up, open an eye and cock a baleful glance at me! Then a sudden inspiration came, and I said Lord Kelvin had limited the age of the earth, provided no new source (of energy) was discovered. That prophetic utterance refers to what we are now considering tonight, radium! Behold! the old boy beamed upon me.

Quantum physics speaks in chance, with the syntax of uncertainty. You can know the position of an electron but you cannot know where its going, or where it is by the time you register the reading. John went blind. Or you can know it's direction, but you cannot know it's position. Heinz Formaggio at Light Box read my Belfast papers and offered me a job. The particles in the atoms of the brain of that young man who pulled me out of the bath of the taxi in London were configured so that he was there, and able to, and willing to. Even the most complete knowledge of a radioactive atom will not tell you when it will decay. I don't know when the Texan will be here. Nowhere does the microscopic world stop and the macroscopic world begin.

Not only the iron on Earth, but also the iron in the entire Solar System, comes from outer space, since the temperature in the Sun is inadequate for the formation of iron. The Sun has a surface temperature of 6,000 degrees Celsius (11,000oF), and a core temperature of approximately 20 million degrees (36 million degrees Fahrenheit). Iron can only be produced in much larger stars than the Sun, where the temperature reaches a few hundred million degrees. When the amount of iron exceeds a certain level in a star, the star can no longer accommodate it, and it eventually explodes in what is called a "nova" or a "supernova." These explosions make it possible for iron to be given off into space.40 One scientific source provides the following information on this subject: There is also evidence for older supernova events: Enhanced levels of iron-60 in deep-sea sediments have been interpreted as indications that a supernova explosion occurred within 90 light-years of the sun about 5 million years ago. Iron-60 is a radioactive isotope of iron, formed in Allah's Miracles in the Qur'an 85 supernova explosions, which decays with a half life of 1.5 million years. An enhanced presence of this isotope in a geologic layer indicates the recent nucleosynthesis of elements nearby in space and their subsequent transport to the earth (perhaps as part of dust grains).41 All this shows that iron did not form on the Earth, but was carried from supernovas, and was "sent down," as stated in the verse. It is clear that this fact could not have been known in the 7th century, when the Qur'an was revealed. Nevertheless, this fact is related in the Qur'an, the word of Allah, Who encompasses all things in His infinite knowledge.

How does one power a spacecraft that will be traveling for at least a decade on a journey so far from the Sun that our star shines there at less than a thousandth of its brightness at Earth? Solar arrays won’t work that far from the Sun, and no battery is powerful and light enough to do the job of powering a decade-long mission. But the radioactive decay of plutonium (an element that was discovered in 1940 and was named for Pluto) passively generates heat without fail—and that heat can be turned into electricity. For this reason, plutonium-fueled nuclear batteries have been the power supplies of choice for deep-space interplanetary missions to the most distant planets from the Sun.

radioactive Rubidium-87, containing 37 protons (and 50 neutrons), can change or decay to strontium, which has 38 protons. These two elements can be thought of as a radiochemical system. When

Right about here every discussion of quantum epistemology invokes Schrödinger’s cat, a thought experiment that Schrödinger proposed in 1935 to illustrate the bewilderments of quantum superpositions. Put a pellet inside a box, he said, along with a radioactive atom. Arrange things so that the pellet releases poison gas if and only if the atom decays. Radioactive decay is a quantum phenomenon, and hence probabilistic: a radioactive atom has a finite probability of decaying in a certain window of time. In thirty minutes, an atom may have a 50 percent chance of decaying—not 70 percent, not 20 percent, but precisely 50 percent. Now put a cat in the box, and seal it in what Schrödinger called a “diabolical device.” Wait a while. Wait, in fact, a length of time equal to when the atom has a fifty-fifty chance of decaying. Is the cat alive or dead? Quantum mechanics says that the creature is both alive and dead, since the probability of radioactive decay and hence release of poison gas is 50 percent, and the possibility of no decay and a safe atmosphere is also 50 percent. Yet it seems absurd to say that the cat is part alive and part dead. Surely a physical entity must have a real physical property (such as life or death) ? If we peek inside the box, we find that the cat is alive or dead, not some crazy superposition of the two states. Yet surely the act of peeking should not be enough to turn probability into actuality? According to Bohr’s Copenhagen Interpretation, however, this is precisely the case. The wave function of the whole system, consisting of kitty and all the rest, collapses when an observer looks inside. Until then, we have a superposition of states, a mixture of atomic decay and atomic intactness, death and life. Observations, to put it mildly, seem to have a special status in quantum physics. So long as the cat remains unobserved, its wave function encodes equal probabilities of life and death. But then an observation comes along, and bam—the cat’s wave function jumps from a superposition of states to a single observed state. Observation lops off part of the wave function. The part corresponding to living or deceased, but not the other, survives.

Applying quantum theory to the brain means recognizing that the behaviors of atoms and subatomic particles that constitute the brain, in particular the behavior of ions whose movements create electrical signals along axons and of neurotransmitters that are released into synapses, are all described by Schródinger wave equations. Thanks to superpositions of possibilities, calcium ions might or might not diffuse to sites that trigger the emptying of synaptic vesicles, and thus a drop of neurotransmitter might or might not be released. The result is a whole slew of quantum superpositions of possible brain events. When such superpositions describe whether a radioactive atom has disintegrated, we say that those superpositions of possibilities collapse into a single actuality at the moment we observe the state of that previously ambiguous atom. The resulting increment in the observer’s knowledge of the quantum system (the newly acquired knowledge that the atom has decayed or not) entails a collapse of the wave functions describing his brain.

The weak nuclear force is the mechanism of interaction between subatomic particles that is responsible for the radioactive decay of atoms.

As in Schrödinger’s cat, the famous thought experiment. Imagine a cat, a vial of poison, and a radioactive source in a sealed box. If an internal sensor registers radioactivity, like an atom decaying, the vial is broken, releasing a poison that kills the cat. The atom has an equal chance of decaying or not decaying. It’s an ingenious way of linking an outcome in the classical world, our world, to a quantum-level event. The Copenhagen interpretation of quantum mechanics suggests a crazy thing: before the box is opened, before observation occurs, the atom exists in superposition—an undetermined state of both decaying and not decaying. Which means, in turn, that the cat is both alive and dead. And only when the box is opened, and an observation made, does the wave function collapse into one of two states. In other words, we only see one of the possible outcomes. For instance, a dead cat. And that becomes our reality. But then things get really weird. Is there another world, just as real as the one we know, where we opened the box and found a purring, living cat instead? The Many-Worlds interpretation of quantum mechanics says yes. That when we open the box, there’s a branch. One universe where we discover a dead cat. One where we discover a live one. And it’s the act of our observing the cat that kills it—or lets it live. And then it gets mind-fuckingly weird. Because those kinds of observations happen all the time.

Take for instance a phenomenon called frustrated spontaneous emission. It sounds like an embarrassing sexual complaint that psychotherapy might help with. In fact, it involves the decay of radioactive particles, which ordinarily takes place at a predictably random rate. The exception, however, is when radioactive material is placed in an environment that cannot absorb the photons that are emitted by decay. In that case, decay ceases—the atoms become “frustrated.” How do these atoms “know” to stop decaying until conditions are suitable? According to Wharton, the unpredictable decay of radioactive particles may be determined in part by whatever receives their emitted photons in the future.20 Decay may not really be random at all, in other words. Another quantum mystery that arguably becomes less mysterious in a retrocausal world is the quantum Zeno effect. Usually, the results of measurements are unpredictable—again according to the famous uncertainty believed to govern the quantum kingdom—but there is a loophole. Persistent, rapid probing of reality by repeating the same measurement over and over produces repetition of the same “answer” from the physical world, almost as if it is “stopping time” in some sense (hence the name of the effect, which refers to Zeno’s paradoxes like an arrow that must first get halfway to its target, and then halfway from there, and so on, and thus is never able to reach the target at all).21 If the measurement itself is somehow influencing a particle retrocausally, then repeating the same measurement in the same conditions may effectively be influencing the measured particles the same way in their past, thereby producing the consistent behavior. Retrocausation may also be at the basis of a long-known but, again, hitherto unsatisfyingly explained quirk of light’s behavior: Fermat’s principle of least time. Light always takes the fastest possible path to its destination, which means taking the shortest available path through different media like water or glass. It is the rule that accounts for the refraction of light through lenses, and the reason why an object underwater appears displaced from its true location.22 It is yet another example of a creature in the quantum bestiary that makes little sense unless photons somehow “know” where they are going in order to take the most efficient possible route to get there. If the photon’s angle of deflection when entering a refractive medium is somehow determined by its destination, Fermat’s principle would make much more sense. (We will return to Fermat’s principle later in this book; it plays an important role in Ted Chiang’s short story, “Story of Your Life,” the basis for the wonderful precognition movie Arrival.) And retrocausation could also offer new ways of looking at the double-slit experiment and its myriad variants.

In August 2008, physicists Jere Jenkins and Ephraim Fischbach, of Purdue University, burst on the scene with an incredible claim. Decay constants are not so constant! Through detailed analysis, they found that the decay rate of radioactive manganese-54 (54Mn) fluctuates in correlation with solar flares (Jenkins and Fischbach 2008). And that was not all. It was also found that the decay rates of radioactive silicon-32 (32Si) and radioactive radium-226 (226Ra) vary over time and that the variations correlate with the changing distance between the Earth and the Sun (Jenkins et al. 2008). When the Earth is closest to the Sun (in January), the decay rate increases; when the Earth is farthest from the Sun (in July), the decay rate decreases. These are incredible, absolutely astounding results with profound ramifications.

Exponential functions appear in many real-world situations: population growth, technological growth, product value over time, compounded interest, radioactive decay, statistical analysis, ...

The USA government states that the New Mexico Trinity nuclear bomb site is still highly radioactive and 'harmless'. It is interesting to note in the era of Electromagnetic Hypersensitivity (EHS) that it is USA government policy that radio frequency (RF) and electricity are also 'harmless'.

Misconception #3. Some physicists claim that length contraction and time dilation are not real and that the physical explanations of Fitzgerald, Larmor and Lorentz are not to be taken seriously. This is not true. As N. David Mermin points out in his popular book on relativity "It's About Time": Moving clocks really do run slowly and moving sticks really do shrink, if the concept of a clock or the length of a stick has any meaning at all...It is necessary for clocks and sticks really so to behave if the while subject is to fit coherently together, and not collapse into a mass of self-contradiction. - N.D. Mermin NASA routinely observes time dilation in orbiting satellites and corrections are applied to keep atomic clocks on the GPS satellites in sync with clocks on earth. Time dilation has also been seen in particle accelerators. At the CERN accelerator radioactive particles traveling at 99.9% the speed of light are observed to decay 30 times more slowly than they do at rest.

The discovery of the neutron was a crucial step in understanding nuclei, including radioactive ones. For example, beta decays are the transformation within a nucleus of a nucleon of one type, either a proton or a neutron, to the other. You may wonder how a proton can decay to a neutron if the neutron is heavier than the proton; conservation of energy would seem to make this impossible. However, while a proton not bound in a nucleus cannot transform to a neutron, it is possible in some circumstances for a proton within a nucleus to do so. This is because the proton can use the additional energy from the force that binds nucleons in the nucleus. Beta decay occurs if it results in the total energy of the final atom, taking into account the energy due to binding, being lower that that of the initial atom. The same applies to a neutron bound in a nucleus, whereas a free neutron can always decay to a proton.

Imagine a cat, a vial of poison, and a radioactive source in a sealed box. If an internal sensor registers radioactivity, like an atom decaying, the vial is broken, releasing a poison that kills the cat. The atom has an equal chance of decaying or not decaying. It's an ingenious way of linking an outcome in the classical world, our world, to a quantum-level event. The Copenhagen interpretation of quantum mechanics suggests a crazy thing: before the box is opened, before observation occurs, the atom exists in superposition—an undetermined state of both decaying and not decaying. Which means, in turn, that the cat is both alive and dead. And only when the box is opened, and an observation made, does the wave function collapse into one of two states. In other words, we only see one of the possible outcomes. For instance, a dead cat. And that becomes our reality. But then things get really weird. Is there another world, just as real as the one we know, where we opened the box and found a purring, living cat instead? The Many-Worlds interpretation of quantum mechanics says yes. That when we open the box, there’s a branch. One universe where we discover a dead cat. One where we discover a live one. And it’s the act of our observing the cat that kills it—or lets it live. And then it gets mind-fuckingly weird. Because those kinds of observations happen all the time. So if the world really splits whenever something is observed, that means there’s an unimaginably massive, infinite number of universes—a multiverse—where everything that can happen will happen.

When an organism dies, its radiocarbon clock starts ticking down with a half-life of 5,730 years (meaning it takes that long for half of the radioactive carbon in the organism to decay). If you are starting to feel an inner glow, don’t worry – only one in a trillion carbon atoms is radioactive, so you’re safe.

Another example of how quantum physics brings the subject back into science is Henry Stapp’s interpretation of the quantum Zeno effect, a phenomenon in physics where repeated observations of a radioactive particle can prevent it from decaying in the usual, predicted manner. Stapp extends this to argue that the deliberate application of mental effort or intention holds in place our brain’s “template for action,” which then produces the brain states that subsequently generate experiential feedback.20 As a result, Stapp contends that we live in “a universe in which we human beings, by means of our value-based intentional efforts, can make a difference first in our own behaviors, then in the social matrix in which we are imbedded, and eventually in the entire physical reality that sustains our streams of conscious experiences.”21 This theory presents a new understanding of ourselves and our place in nature, and raises important sociological and philosophical issues that, according to Stapp, “extend far beyond the narrowly construed boundaries of science.”22

Heat escapes from small planets more easily than from large planets, because small planets have a greater ratio of surface area (through which heat escapes) to volume (which stores heat and generates it by radioactive decay). A small planet would require a much greater amount of radioactive heat generation, per kilogram of rock, to maintain vigorous lava-producing volcanism. This is basically for the same reason that a mouse needs to consume many more calories per gram of body weight than a human. A typical mouse, weighing 40 grams, consumes 10 kilocalories (sometimes called simply ‘calories’ in everyday usage) per day. Scaled up to the mass of a human, that would amount to 25,000 kilocalories a day—equivalent to 7kg of dry spaghetti.

The discovery of slow-neutron radioactivity meant that Fermi’s group had to work its way through the elements again looking for different and enhanced half-lives—which is to say, different isotopes and decay products.

Some types of transmutation happen spontaneously on Earth, in the decay of radioactive elements. This was first demonstrated in 1901, by the physicists Frederick Soddy and Ernest Rutherford,

Be that as it may, the problem of human squeamishness at having an A-bomb explode overhead could be addressed. Simply explaining to soldiers that a nuclear detonation at 10,000 feet was not the same as having it go off at 1,000 feet was true but insufficient. To the soldiers it was a matter of degree. At the high altitude there would be no ground disturbance. No radioactive dust kicked up into a mushroom cloud, no neutron activation of the ground, and negligible fallout. It was all a function of range. The fission neutrons could not travel that far in air before they decayed into hydrogen gas, and the gamma ray pulse would be short-lived and dissipated in a spherical wave-front with a diameter of four miles when it hit the ground.

Some illustrations of the fine-tuning of our universe deal with the so-called four fundamental forces physicists talk about, and with which most laymen are unacquainted. These four forces are 1.) gravity, 2.) the electromagnetic force, 3.) the weak nuclear force, and 4.) the strong nuclear force. Most of us know what gravity is and does. The strong nuclear force holds the nucleus (meaning the protons and neutrons) of an atom together. The weak force deals with radioactive decay and neutrino reactions, among other things, and the electromagnetic force essentially holds atoms and molecules together.

By 1870 there were competing formulae, and luminous paints were selling briskly. Most used strontium carbonate or strontium thiosulphate. It had been found, probably accidentally, that strontium compounds would seem to store sunlight and would then give it back after the sun went down. We now know this phenomenon as a “forbidden energy-state transition” in a singlet ground-state electron orbital. The strontium, like everything else, absorbs and then returns a light photon that hits it, but in this case the return is delayed. The strontium atom, excited to a higher energy state by the absorption of light, “decays,” as if it were radioactive, reflecting the light back with a half-life of about 25 minutes. After four hours of glowing, the strontium compound needs to be re-charged with light.

Their marriage decayed with the exponential determinism of a radioactive isotope and still he sought her out, and accepted her conditions.

you take two radioactive atoms, absolutely identical in every conceivable way, they will decay randomly. The first might decay immediately, while the second doesn’t do the same for an hour or more. Why the difference? After all, they’re identical. Scientists have never found any way to explain it, or predict when this decay will occur.

Erlang himself, working for the Copenhagen Telephone Company in the early twentieth century, used it to model how much time could be expected to pass between successive calls on a phone network. Since then, the Erlang distribution has also been used by urban planners and architects to model car and pedestrian traffic, and by networking engineers designing infrastructure for the Internet. There are a number of domains in the natural world, too, where events are completely independent from one another and the intervals between them thus fall on an Erlang curve. Radioactive decay is one example, which means that the Erlang distribution perfectly models when to expect the next ticks of a Geiger counter. It also turns out to do a pretty good job of describing certain human endeavors—such as the amount of time politicians stay in the House of Representatives.

Archaeologists who want to establish the date of a particular site have a number of techniques they can use. If they find organic material, say the bones of an animal, they can use radiocarbon dating. If they find the remains of wooden structures, a post or lintel say, they can use dendrochronology, or tree-ring dating. If they find a firepit they can use archaeomagnetic dating. Radiocarbon dating works because, when alive, an organism takes in carbon from the air or through the food chain; carbon contains small amounts of the radioactive isotope carbon-14, which decays into nonradioactive standard carbon at a constant rate; when the organism dies it ceases to ingest carbon, so the proportion of carbon-14 in its remains steadily decays. Measuring the relative amount of carbon-14 content therefore establishes a fairly accurate date for the specimen. Dendrochronology works because tree rings vary in width season by season according to the rainfall received, and so trees that grow in a given climatic region and historical period show similar ring-width patterns. Comparing the ring pattern to a known and dated local ring pattern establishes exactly the years in which the wood in the structure was growing. Archaeomagnetic dating works because the earth's magnetic field changes direction over time gradually in a known way. Clays or other materials in a firepit, when fired and cooled, retain a weak magnetism that aligns with the earth's field, and this establishes a rough date for the firepit's last use. There are still other techniques: potassium-argon dating, thermoluminescence dating, hydration dating, fission-track dating. But what I want the reader to notice is that each of these relies on some particular set of natural effects. That a technology relies on some effect is general. A technology is always based on some phenomenon or truism of nature that can be exploited and used to a purpose. I say "always" for the simple reason that a technology that exploited nothing could achieve nothing. This is the third of the three principles I am putting forward, and it is just as important to my argument as the other two, combination and recursiveness. This principle says that if you examine any technology you find always at its center some effect that it uses. Oil refining is based on the phenomenon that different components or fractions of vaporized crude oil condense at different temperatures. A lowly hammer depends on the phenomenon of transmission of momentum (in this case from a moving object-the hammer-to a stationary one-the nail). Often the effect is obvious. But sometimes it is hard to see, particularly when we are very familiar with the technology. What phenomenon does a truck use? A truck does not seem to be based on any particular law of nature. Nevertheless it does use a phenomenon-or, I should say, two. A truck is in essence a platform that is self-powered and can be moved easily. Central to its self-powering is the phenomenon that certain chemical substances (diesel fuel, say) yield energy when burned; and central to its ease of motion is the "phenomenon" that objects that roll do so with extremely low friction compared with ones that slide (which is used of course in the wheels and bearings). This last "phenomenon" is hardly a law of nature; it is merely a usable-and humble-natural effect. Still it is a powerful one and is exploited everywhere wheels or rolling parts are used.

That simple process—macroscopic objects become entangled with the environment, which we cannot keep track of—is decoherence, and it comes with universe-altering consequences. Decoherence causes the wave function to split, or branch, into multiple worlds. Any observer branches into multiple copies along with the rest of the universe. After branching, each copy of the original observer finds themselves in a world with some particular measurement outcome. To them, the wave function seems to have collapsed. We know better; the collapse is only apparent, due to decoherence splitting the wave function. We don’t know how often branching happens, or even whether that’s a sensible question to ask. It depends on whether there are a finite or infinite number of degrees of freedom in the universe, which is currently an unanswered question in fundamental physics. But we do know that there’s a lot of branching going on; it happens every time a quantum system in a superposition becomes entangled with the environment. In a typical human body, about 5,000 atoms undergo radioactive decay every second. If every decay branches the wave function in two, that’s 25000 new branches every second. It’s a lot.