## Metadata - Author: [[Neil Shubin]] - Full Title: The Universe Within - Category: #books ## Highlights - The playbook that fossil hunters use to develop new places to look has been pretty much unchanged for the past 150 years. Intellectually, it is as simple as it gets: find places on the planet that have rocks of the right age to answer whatever question interests you, rocks of the type likely to hold fossils, and rocks exposed on the surface. The less you have to dig, the better. ([Location 80](https://readwise.io/to_kindle?action=open&asin=B008LMD8PI&location=80)) - I learned plenty of lessons that first year in Greenland, ones that were to become useful when I began running my own Arctic expeditions eleven years later. By bringing leaky leather boots, a small used tent, and a huge flashlight to the land of mud, ice, and the midnight sun, I made so many bad choices that first year that I remained smiling only by reciting my own motto, “Never do anything for the first time.” ([Location 116](https://readwise.io/to_kindle?action=open&asin=B008LMD8PI&location=116)) - Helium, the second-most abundant atom in the entire universe, has an internal structure that leaves it no room to trade electrons with others. Unable to make these exchanges, it cannot participate in the chemical reactions that define life—metabolism, reproduction, and growth. On the other hand, oxygen and carbon are about twenty times rarer than helium. But unlike helium, these atoms can easily interact with different elements to form the variety of chemical bonds that are essential in living matter. Reactivity is the order of the day for the common atoms of bodies. Loners need not apply. ([Location 217](https://readwise.io/to_kindle?action=open&asin=B008LMD8PI&location=217)) - A slight—and by that we mean about one-billionth of 1 percent—excess of matter over antimatter was enough for matter to take hold in the universe. Because of that tiny imbalance, we are, as the physicist Lawrence Krauss once described, every bit the direct descendants of that one-billionth of 1 percent surplus of matter over antimatter as we are of our own grandparents. ([Location 374](https://readwise.io/to_kindle?action=open&asin=B008LMD8PI&location=374)) - A little over three minutes after the birth of the universe began the stirrings of one of the deepest patterns in the world, captured by the chart that is the source of either awe or angst for young science students—the periodic table. The periodic table catalogs all known elements by the weight of their nuclei. The chart drawn for this moment of time would be a huge relief to our students. There would be only three boxes on it: hydrogen, helium, and lithium. Hydrogen and helium today remain the most common elements in the universe. Hydrogen makes up about 90 percent of all matter, helium about 5 percent. All of the others that compose us and run through the lives of people and stars are but a rounding error. ([Location 379](https://readwise.io/to_kindle?action=open&asin=B008LMD8PI&location=379)) - Supernovae are one engine that powers the movement of atoms from one star system to another. ([Location 460](https://readwise.io/to_kindle?action=open&asin=B008LMD8PI&location=460)) - It took big ideas and big science to see how our little patch of the universe came into being. The Swedish thinker Emanuel Swedenborg was occupied by important questions throughout his life. Born in 1688, he lived most of his eight decades believing he should have one great idea per day. In his early years, he worked as a natural philosopher seeking to intuit the structure of the natural world. He inferred, for example, the presence of nerves and a nervous system. Turning his thoughts to the cosmos, Swedenborg proposed a theory for the origin of the solar system. He envisioned that the sun developed from a cloud of gas and dust that collapsed on itself and condensed. As the sun took shape, the primordial dust remained as a disk of debris that swirled around the young star. Over time, portions of this cloud coalesced to form the planets of the solar system. The idea was to remain dormant until two decades later, in 1755, when the philosopher Immanuel Kant had his go at developing ideas on the origin of the solar system. The theory he ultimately developed was largely similar to Swedenborg’s. ([Location 472](https://readwise.io/to_kindle?action=open&asin=B008LMD8PI&location=472)) - During our time in the womb, we form three different kinds of kidneys, one after the other. The first kidneys are clumps of tissue that line the body and open to the body cavity, much like those seen in jawless fish. The second, like those of bony fish, run the length of the back to a common plumbing system. The adult kidney, which appears at the end of the first trimester, replaces both of these. In our first three months, we track our fishy past. ([Location 600](https://readwise.io/to_kindle?action=open&asin=B008LMD8PI&location=600)) - Life’s connection with water is no accident; the water molecule itself has special properties. With one oxygen and two hydrogen atoms, it looks something like a Mickey Mouse head: small hydrogen atoms form the ears atop a head made by a large oxygen atom. This whole molecule is polarized, with a negative charge at one end, where the oxygen resides, and positive charges at the opposite end, corresponding to the hydrogens. This arrangement makes water the ideal medium in which to dissolve a large variety of substances. Salts, proteins, amino acids—so many compounds can be incorporated into water that it provides the matrix for the chemical reactions on which life depends. ([Location 603](https://readwise.io/to_kindle?action=open&asin=B008LMD8PI&location=603)) - Comparisons of the DNA inside humans, animals, and bacteria speak of a common ancestor of all three that lived over 3 billion years ago. This is roughly the age of the earliest fossil-containing rocks. The broad match of dates from rocks and DNA is all the more remarkable given how the rocks have been heated and heaved over the same billions of years that DNA has mutated, evolved, and been swapped among species. Agreement between these different kinds of natural clocks leads to confidence in our hypotheses. ([Location 840](https://readwise.io/to_kindle?action=open&asin=B008LMD8PI&location=840)) - Go to fossil reefs 400 million years old, and you will find four hundred layers inside the corals—suggesting that each year was actually four hundred days long and contained a whopping thirty-five more days than our current year. What accounts for this discrepancy? Since the duration of a year is fixed by Earth’s rotation about the sun, the days must have been shorter 400 million years ago than they are today. To make the algebra work, each day had to have been twenty-two hours in length. In the eons since those corals were formed, two hours have been added to every day. Like a slowing top, Earth spins slower and slower with each passing moment, making days longer now than in the past. As the planet rotates, the water in the oceans moves about and serves to brake the spin of the planet. That is why today is two milliseconds longer than yesterday. ([Location 862](https://readwise.io/to_kindle?action=open&asin=B008LMD8PI&location=862)) - Virtually every part of us—every organ, tissue, and cell inside—is set to a rhythm of day and night. Kidneys slow down at night. That’s a wonderful trait if you want to minimize trips outside bed—something very useful when inside a sleeping bag in the Arctic. Body temperatures vary over the course of the day, with the coolest ones happening at 3:00 a.m. Liver function is time dependent as well: the human liver works slowest in the morning hours, meaning the cheapest dates would be at breakfast. ([Location 895](https://readwise.io/to_kindle?action=open&asin=B008LMD8PI&location=895)) - In 1967—forty-eight years after his adviser’s gift of the cage—Richter removed one little patch of tissue at the base of the brain. Excision of a fleck of cells not much bigger than a grain of rice obliterated virtually all of the rhythmic behaviors in the rats. The rats’ internal clocks were in a tiny field of cells right behind the eyes, later named Richter’s patch. ([Location 962](https://readwise.io/to_kindle?action=open&asin=B008LMD8PI&location=962)) - Scientists have scoured populations looking for mutants. Careers have been made, and Nobel Prizes won, by cataloging mutants or by finding just the right one with an extra toe, different jaw, or oddball eyes, limbs, or heart. While the rewards can be high, this approach is often like rolling the dice. Some mutations crop up only once in every 100,000 individuals. Unfortunately, the creatures we are most interested in, mammals like us, are the hardest to work with, because they take a longer time to develop than other creatures, they take more resources to rear, and they spend most of the critical phases of their development hidden from the outside world inside the female. ([Location 975](https://readwise.io/to_kindle?action=open&asin=B008LMD8PI&location=975)) - Much of our health depends on clocks: shift workers who sleep during the day and work at night have higher rates of heart disease and some cancers, notably of the breast. Researchers studying mice discovered that the error-correction machinery of the DNA of skin cells functions on a clock: it’s most active in the evening. The DNA that gets copied in the morning is likely to carry the most errors. The UV radiation of the sun causes cancers in the skin when it induces errors in copying DNA. Putting these facts together leads to the conclusion that in mice UV light hitting the skin in the morning is more carcinogenic than evening and afternoon exposure. Humans also have these clocks, but ours are reversed relative to mice: our DNA error-correction apparatus is most active in the morning. This means tanning at the end of the day is more carcinogenic than doing so in the morning. Even our metabolism is affected by the clocks inside our cells: some kinds of obesity can be correlated to a lack of sleep. ([Location 1073](https://readwise.io/to_kindle?action=open&asin=B008LMD8PI&location=1073)) - Darlington was a naturalist of the old school: when he wasn’t teaching courses at Harvard College, he was off in the jungle collecting new species, beetles in particular. Tales of his days in the field are legendary, including the time he was grabbed by a crocodile, pulled to the bottom of a stream, and, as the crocodile began to consume him, kicked himself free. Hiking miles to safety with shredded legs and hands, he wrote to his wife later that night only that he had an “episode with a crocodile.” ([Location 1154](https://readwise.io/to_kindle?action=open&asin=B008LMD8PI&location=1154)) - Let’s say you want to predict what an animal can do—how long it lives, how it moves about—and what it looks like without ever having seen it. A number of factors may be influential: the kinds of foods the creature eats, where it lives, where it sits in the food chain, and so forth. People have explored this issue by cataloging measurable traits that creatures possess and hitting the data with a number of different statistical tools to gauge which measurement accounts for the differences we see. In analysis after analysis, one factor reigns supreme in its predictive power—size. Know a creature’s size, and you can make educated guesses about much of its biology, including its resting heartbeats per minute (smaller animals have higher heart rates), its perception of danger (larger animals have less fear), even its life span (in general, larger means longer). ([Location 1171](https://readwise.io/to_kindle?action=open&asin=B008LMD8PI&location=1171)) - Anton van Leeuwenhoek (1632–1723) spent much of his career as a draper and found himself needing to develop magnifying glasses to assess the quality of his fabrics. Becoming fascinated by the properties of glass, he manufactured new kinds of lenses that magnified objects many times beyond the tools common to his trade at the time. He tweaked the shape of the glass again and again, each time seeing smaller things, ultimately magnifying objects two hundred times. With each new lens he crafted, he was exploring a new world. ([Location 1182](https://readwise.io/to_kindle?action=open&asin=B008LMD8PI&location=1182)) - Our ancestors gained new possibilities when they made the shift from van Leeuwenhoek’s microscopic world to the Galilean one over a billion years ago: they left a world dominated by intermolecular forces and entered one more influenced by gravity. ([Location 1249](https://readwise.io/to_kindle?action=open&asin=B008LMD8PI&location=1249)) - Impressions of disks, ribbons, and fronds in slabs of 600-million-year-old rocks are a pretty unremarkable bunch of fossils. But looks are deceiving. These fossils reflect revolutionaries, a new kind of individual that the world had not yet seen. These are the first creatures with bodies composed of many cells. ([Location 1253](https://readwise.io/to_kindle?action=open&asin=B008LMD8PI&location=1253)) - Small animals can transport oxygen across their bodies by simple diffusion. Once animals get large, they need new mechanisms to move nutrients and wastes about. How do they deal with this? Large animals have specialized systems to circulate blood, carry wastes, and capture and pump oxygen to their far-flung cells. These kinds of specialized organs are game changers in the world of size. Hearts, gills, and lungs are all inventions necessary in large animals. ([Location 1257](https://readwise.io/to_kindle?action=open&asin=B008LMD8PI&location=1257)) - Iron-rich layers begin to appear in rocks about 2 billion years old on every continent. No matter whether on Australia, North America, or Africa, they generally form the same series of precisely layered reddish-brown bands. As anyone who has left wet tools in the garage knows, the color is a clue to the iron’s chemistry. Oxygen in the air turns iron reddish brown as it rusts. ([Location 1283](https://readwise.io/to_kindle?action=open&asin=B008LMD8PI&location=1283)) - When Earth formed over 4.5 billion years ago, the only major source of atmospheric gases was Earth itself. Volcanoes spew all kinds of molecules but precious little oxygen. We’d have an easier time breathing on the top of Mount Everest than on this ancient Earth. The bands of rust in mor recent rocks reveal the change: a global increase of oxygen in the atmosphere. ([Location 1286](https://readwise.io/to_kindle?action=open&asin=B008LMD8PI&location=1286)) - Algae, quietly producing oxygen for hundreds of millions of years, gave breath to life on Earth. ([Location 1298](https://readwise.io/to_kindle?action=open&asin=B008LMD8PI&location=1298)) - Oxygen is an atom that is greedy for electrons because it lacks two of them in its outer shell. The powerhouses of our cells—mitochondria—along with aerobic bacteria make use of this fact in their energy processing. Some metabolic reactions, such as respiration, have elaborate cascades that transfer electrons from one molecule to the next, where, at each electron-transfer step, energy is either stored in new forms or released. The more free oxygen there is about, the more fuel there is for living creatures to use. ([Location 1309](https://readwise.io/to_kindle?action=open&asin=B008LMD8PI&location=1309)) - Oxygen lifted the lid on big: it fueled the push from microscopic creatures living in a world dominated by intermolecular forces to a planet with ever-bigger species with new kinds of bodies. ([Location 1322](https://readwise.io/to_kindle?action=open&asin=B008LMD8PI&location=1322)) - The chemistry that makes oxygen so efficient at generating energy can turn it into a poison. A great receptor for electrons from other atoms, oxygen generates energy while it forms new compounds. Unchecked, these molecules can disrupt cells and damage DNA. A number of theories of disease and aging are based on these properties of oxygen. Every time you take an antioxidant like vitamin C, you are trying to fight the effects of these kinds of oxygen-containing molecules. ([Location 1324](https://readwise.io/to_kindle?action=open&asin=B008LMD8PI&location=1324)) - Ewing did manage to fire Tharp. Lacking an office, she ended her career working out of her Nyack, New York, home. Her view of the tumultuous personal and scientific times was revealed twenty years after Heezen’s death when, during an oral history project at Columbia, she recalled, “I worked in the background for most of my career as a scientist, but I have absolutely no resentments. I thought I was lucky to have a job that was so interesting. Establishing the rift valley and the mid-ocean ridge that went all the way around the world for 40,000 miles—that was something important. You could only do that once. You can’t find anything bigger than that, at least on this planet.” ([Location 1536](https://readwise.io/to_kindle?action=open&asin=B008LMD8PI&location=1536)) - In 1984, over half a century after Wegener’s death, NASA released the first direct measurements of continental drift. About twenty stations around the world were established, each capable of bouncing lasers off satellites equipped with reflectors. A telescope next to the laser on the ground picked up the reflection by the satellite. By measuring the time that laser light took for the round-trip to each station, NASA calculated the distance to the satellite. If the plates move, then the distance to the satellite should change over time. Using this technique, NASA showed that North America and Europe are getting farther apart by 1.5 centimeters per year. Australia is heading for Hawaii at about 7 centimeters per year. The plates on our planet move about as fast as hair grows on our scalps. ([Location 1568](https://readwise.io/to_kindle?action=open&asin=B008LMD8PI&location=1568)) - The rift that began to open over 200 million years ago and split the supercontinent into multiple bits created enormous amounts of new coastline. Each coast is an area where land meets the sea. As every coastal homeowner knows, these areas are subject to erosion. A dramatic increase in erosion can set off a chain reaction. Imagine entirely new coastlines dumping sediment into the sea. With this sediment comes the burial of very special mud that covers the bottom of the ocean shelf. This muck is extremely important, because every day trillions of single-celled creatures die and sink to the bottom; as they decay, they consume oxygen. Left alone, this mass of waste eats enormous amounts of oxygen from the water—and ultimately from the atmosphere—as it rots. But when these layers get buried, oxygen is no longer consumed as quickly, allowing it to build up in the water and the air. This is what the rifts and new coastlines have wrought: increasing levels of oxygen in the air brought about by the burial of oxygen-consuming muds. ([Location 1605](https://readwise.io/to_kindle?action=open&asin=B008LMD8PI&location=1605)) - Not only are we insulated from the outside world as adults; we begin our lives inside a womb surrounded by membranes that protect the embryo and provide it with connections to the mother’s blood supply. Since the fetus receives all of its oxygen from the mother, there needs to be a way that oxygen can be transferred from the mother’s blood. The transfer is facilitated by a steep gradient between the concentration of oxygen in the maternal blood and that of the fetus: under these conditions, oxygen will travel into the fetus. Importantly, the oxygen content of the mother’s blood has to be sufficiently high to enable this transfer in the first place. This constraint means that mammals with a placenta do not easily develop above fifteen thousand feet altitude. Tellingly, the oxygen at these altitudes is equivalent to that in the atmosphere at sea level 200 million years ago, before the Atlantic Ocean formed. ([Location 1622](https://readwise.io/to_kindle?action=open&asin=B008LMD8PI&location=1622)) - One trait—among all those that life has ever had—seems to give us the ability to predict whether a species is likely to live or die at a catastrophe. The best survival tip for a species is to be widely spread around the globe. Species that have individuals spread about, preferably on different continents, fare better than those that are found in only one spot. ([Location 1869](https://readwise.io/to_kindle?action=open&asin=B008LMD8PI&location=1869)) - The connection among parts of Earth depends on how carbon moves through air, rock, water, and bodies. To see this chain of connections, we need to consider living things, rocks, and oceans not as entities in their own right but as stopping places for carbon as it marches along during our planet’s evolution. ([Location 1987](https://readwise.io/to_kindle?action=open&asin=B008LMD8PI&location=1987)) - Carbon in the interior of Earth gets injected back into the atmosphere by volcanoes that eject gases. That is the long-term source of much of the carbon we breathe: while acid rain and the weathering of rocks remove carbon from the air, volcanoes emitting gases return ([Location 1999](https://readwise.io/to_kindle?action=open&asin=B008LMD8PI&location=1999)) - All else being equal, increasing erosion of rocks leads to lower temperatures, decreasing erosion to higher ones. ([Location 2011](https://readwise.io/to_kindle?action=open&asin=B008LMD8PI&location=2011)) - The planet’s temperatures are kept within a narrow range by the movement of carbon molecules through air, rain, rock, and volcano. Hot weather leads to more rock erosion, which leads to more carbon being pulled out of the air and thus colder weather. Then, just as things get colder, the cycle moves the planet’s temperatures in the opposite direction: colder weather leads to less erosion, increasing amounts of carbon in the air, and hotter temperatures. ([Location 2013](https://readwise.io/to_kindle?action=open&asin=B008LMD8PI&location=2013)) - The Tibetan Plateau is a vast barren face of virtually naked rock. It contains over 82 percent of the rock surface area of the planet and reaches over twelve thousand feet high. ([Location 2040](https://readwise.io/to_kindle?action=open&asin=B008LMD8PI&location=2040)) - The rise of the Tibetan Plateau led to the shift from a warm Earth to a cold one; it did so by pulling carbon from the air via erosion of rock. ([Location 2043](https://readwise.io/to_kindle?action=open&asin=B008LMD8PI&location=2043)) - At one time in the past, the entire southern part of the globe was indeed one giant super landmass composed of what are today all the southern continents: Antarctica, Australia, South America, and Africa. The distinctive blue oceans that define our South today weren’t there. Then, with the birth of this volcanic ring surrounding Antarctica, the continents separated and moved away from their southern neighbor. Three things happened at once: Africa, Australia, and South America moved north, Antarctica became isolated at the South Pole, and vast seas opened up separating all the southern continents. ([Location 2072](https://readwise.io/to_kindle?action=open&asin=B008LMD8PI&location=2072)) - Ever since the nineteenth century, primatologists have known about a big split in our primate family tree: all Old World monkeys have full color vision, whereas this trait is lacking in their New World cousins. ([Location 2106](https://readwise.io/to_kindle?action=open&asin=B008LMD8PI&location=2106)) - Howler monkeys, as the name implies, have a distinctive cry. They were described by the great explorer Alexander von Humboldt in the nineteenth century as having “eyes, voice, and gait indicative of melancholy.” Scientists studying their behaviors and visual structures in the 1990s discovered that unlike South American monkeys, all howlers are able to see in the same spectrum of color as we do. There is a huge difference in the diets of howlers and their South American cousins. All other monkeys eat mostly fruit, whereas howlers exist on leaves. ([Location 2108](https://readwise.io/to_kindle?action=open&asin=B008LMD8PI&location=2108)) - To Dominy and his colleagues, a hypothesis emerged: color vision enabled creatures to discriminate among different kinds of leaves and locate the most nutritious ones. This advantage gained new prominence when climates changed and plants responded. More clues to color vision are nestled inside DNA. Mammals that lack color vision have only two proteins to perceive color; we and the Old World apes that perceive colors have three. ([Location 2133](https://readwise.io/to_kindle?action=open&asin=B008LMD8PI&location=2133)) - Libby’s insight was that all living things will have the same amount of carbon 14 in their bodies as the atmosphere in which they live. Living creatures breathe, eat, and drink carbon atoms in their daily lives and thus share the same balance of carbon with the atmosphere. ([Location 2304](https://readwise.io/to_kindle?action=open&asin=B008LMD8PI&location=2304)) - the ratio of heavy and light oxygen atoms in a material was dependent on temperature. To Urey and his team, this success meant that if you could measure the infinitesimal amounts of the different forms of oxygen in any substance—water or bone, for example—you might be able to guess the temperature of the environment in which it formed. ([Location 2316](https://readwise.io/to_kindle?action=open&asin=B008LMD8PI&location=2316)) - With oxygen atoms as the thermometer, carbon atoms as the timekeeper, and the regularity of the layers as a guide, the teams set off to see how climate changed over the ice ages. ([Location 2327](https://readwise.io/to_kindle?action=open&asin=B008LMD8PI&location=2327)) - If you have a graph with lots of different wiggles in it, perhaps that mess is made by several different rhythms superimposed on one another. The mathematical technique, known as Fourier transform analysis, is a way of revealing how a complex pattern can be made by a number of regular and more simple ones. ([Location 2339](https://readwise.io/to_kindle?action=open&asin=B008LMD8PI&location=2339)) - The fine-grained view of climate and ice reveals surprises. Earth’s climate during the past 100,000 years has swung wildly on occasion. The ice ages weren’t just long invariant cold periods: glacial periods have witnessed warm intervals, and warm intervals have seen glacial conditions. The emerging picture is that Earth’s climate depends on the heat balance of the planet—the amount of heat coming in from the sun minus the heat that escapes into space—and the ways that this heat is transferred among the oceans, land, air, and ice. Music is an analogy for what drives climate: a composition can be heard as one entity but be decomposed into rhythms, backbeats, and harmonies of different instruments acting on their own cycles. Orbital motions of the kind revealed by Milankovitch define the main cadence. The movement of heat through ocean currents, winds, and ice floes form other beats. The result of the interacting effects of these components is a system that has a long-term rhythm and short-term riffs. ([Location 2376](https://readwise.io/to_kindle?action=open&asin=B008LMD8PI&location=2376)) - The American philosopher William James often said that religious experience emanates from “feeling at home in the universe.” With bodies composed of particles derived from the birth of stellar bodies and containing organs shaped by the workings of planets, eroding rock, and the action of the seas, it is hard not to see home everywhere. ([Location 2534](https://readwise.io/to_kindle?action=open&asin=B008LMD8PI&location=2534)) - In our past, long-term success came from spreading one’s genes and traits, often in response to changes to the environment. The major source of information passed from one generation to the next was written in DNA. The situation now is not so simple. The American scientist Norman Borlaug and his wife had three children, five grandkids, and six great-grandchildren. We can look at his entire family tree and assess the extent to which his genetic traits have been passed from generation to generation. If we transport to the future, we could assess the success of his biological traits in the gene pool: hair color, ability to curl his tongue, susceptibility to diseases, and so on. But how much will traits like those really matter for our future as a species? In addition to passing on his genes, Borlaug was the widely acclaimed father of the “green revolution,” whose work on corn and wheat increased their pest resistance and yield. He is responsible for bettering or saving the lives of millions of people around the world. His ideas live in the ways others have used them and improved them and in an entire planet changed by his genius. From the people saved by agricultural and medical breakthroughs to the lives changed by great literature, philosophy, and music, the success of our species resides inside the offspring of our minds. ([Location 2598](https://readwise.io/to_kindle?action=open&asin=B008LMD8PI&location=2598)) - Calculating absolute time in rocks and minerals depends on understanding the radioactive decay of atoms. Some atoms have an unstable configuration of electrons, neutrons, and protons, causing them to lose or gain components. As they do this, their atomic weights can change, and they become new forms. The important point is that this transformation happens at rates that are physical constants, known as the half-life. The half-life of an atom is the time required for one-half of a sample to decay, or transform, into its daughters. If you know the amounts of parent atoms, daughter atoms, and the half-life, then you can calculate the time that the atoms have been decaying. A number of atoms are useful to geologists: uranium 238, argon 39, and carbon 14, for example. In general, you try to match atoms for the job: atoms with the slowest decay rates are useful for the oldest rocks, whereas those that decay faster are useful for more recent ones. Uranium 238, with its long half-life, is useful for questions about the most ancient phases of Earth. Carbon 14 has such a rapid decay rate it is useful for more recent events, such as those of human history and culture. ([Location 2735](https://readwise.io/to_kindle?action=open&asin=B008LMD8PI&location=2735))