# Time in Powers of Ten

At this website there are already two pages devoted to ways of making the depths of geological time and the size of the universe comprehensible in some intuitive way. The most elaborate one is If a Millimeter Were a Year/Light-Year, in which a unit of visible size, the millimeter, is related to time, as a year, and to space, as a light year. At that scale, a two dimensional map of the universe, whether with a radius of about 13 billion light years, as now thought, or 19.5 billion, as believed in the 1970's, can easily fit on the surface of the earth. However, most of familiar space and time don't even make it, from Los Angeles Valley College, out of California.

The other device, Comparison of Cosmological Distances with Historical, Paleontological, and Geological Time, as of 1993, is logarithmic. Time and distances are foreshortened as the numbers get larger, with the scale based on the logarithm of the distance in light years or time in years.

This page does something similar, just with time, with visible scales for powers of ten in years. I began thinking of this because of an observation, that geological time since the Cambrian, and human history, are both divided into three periods, each taking up about half of the relevant powers of ten in time, and with the divisions of each roughly proportional to the divisions of the other.
Thus, the Phanerozoic ("appearing life") Aeon, the last 600 some millions of years, is divided into the Paleozoic ("ancient life"), Mesozoic ("middle life"), and Cenozoic ("new life") Eras. In the same way, the 5000 years of human history is divided into Ancient, Mediaeval, and Modern History. Modern history is the shortest, slightly more than half a millennium, while the Cenozoic, slightly longer proportionally, takes up 65 million years. The Paleozoic Era and Ancient times both dominate their respective scales.

This gives us a sobering perspective on both of them. But it also raises the question what characterizes the intermediate chunks of time. If a millimeter were a year, then a meter is a thousand years, a kilometer a million years, and 1000 kilometers (621.4 miles) a billion years. But for these powers we don't get a sense of the scale of events, or what is going on at such levels of time.

As it happens, we can expand the representation with scales that again only show just more than half of divisions of a power of ten. Ten to the 9th is billions of years, but we only need 5 billion for the history of the solar system and the Earth. Earth history begins with the Hadaean Aeon, of which by definition nothing remains, since any rocks formed then got remelted. So it is like "Hades" in the sense of being hot. The Archaean is when we get the first rocks, continents, etc. The idea of the Proterozoic is that this is when we begin to get the first forms of life, but now there is apparently evidence of bacterial life, at least, in the Archaean. There also used to be a "Cryptozoic" ("hidden life") division used, in contrast to "Phanerozoic," but this seems to have been dropped.
In our familiar Phanerozoic time, we get an explosion of multicelled organisms. Only about halfway through the Paleozoic does life come out on land. At the end, we are already getting mammal-like reptiles, which briefly (in geological terms) seem dominant. In the first part of the Mesozoic, they are overtaken by the dinosaurs, everyone's favorite ancient animals, which dominate the Earth for the rest of the Mesozoic -- the Jurassic and Cretaceous Periods.
As we move down into tens of millions rather than hundreds of millions of years, we zero in on the Cenozoic. There are now different ways to divide this into Periods, but the traditional division is between the Tertiary and the Quaternary Periods. These names survive from the earliest days of geology. The smaller division, the Epochs, were proposed in terms of percentages of species that survive into the present. About the first half consists of very strange animals, initially birds that are sometimes the top predators over mammals, but then the appearance of large mammals that are the equal of anyone in predation (cats, dogs, bears) or are simply too large to be attacked (elephants, whales). By the Miocene we begin getting apes that suggest the coming direction of primate evolution.
On a scale of single digit millions of years, we are full on the scene of human evolution. The last five millions years, however, still about evenly divides between the last of the Tertiary (the Miocene) and the Quaternary (the Pleistocene and Holocene). This is when familiar mountain ranges, like the Rockies and Himalayas, are forming. At first we get Australopithecines, which begin not very bright or large but run around upright in a quite modern way. By the end of the Miocene, we have some species of the genus Homo. The Pleistocene then poses a grave environmental test, with ice covering a good part of North America, Europe, and Asia, in four great successive glaciations. Homo erectus leaves Africa to travel as far away as East Asia. They use fire and may have developed the first stages of human language. Unfortunately, since they didn't write, we will probably never know how that worked.
At hundreds of thousands of years, we see people with size and intelligence comparable to modern humans. Neanderthals adapt to the cold and ice of Europe and begin to bury their dead. I'm sure that an anthropologist would give an up major body parts to have a few hours to examine and question a live Neanderthal. But time has snatched that away from us.
If truth be told, life at the scale of tens of thousands of years is mysterious enough. Fully modern humans have existed about the last 30 thousands years. They have religion, art, certainly fully functional languages, and God knows what else. We can at least guess what their societies and cultures were like given our knowledge of isolated peoples, like Australian Aborigines and Kalahari Bushmen, who survived with Paleolithic technologies into the 20th century. At this scale, however, we already see the point of the Neolithic revolution, in which gathering plants and hunting animals, the source of Paleolithic and Mesolithic nutrition, are replaced by agriculture. This does not quite get us into history, but it is close. The Neolithic revolution involves greater social organization and durable settlement. States, records (which at first were tokens, such as survived among the Incas), and writing soon follow; and writing opens the window of history.
At last we are back down to the scale of history, about the last 5000 years. History can give us what paleontology and physical anthropology alone could not do, not just the remains of individuals, but their names, what they did, and even, sometimes, what they thought or felt. We can even get that if the individuals are physically gone. History can thus be laid out as a list of names, starting with the Egyptians and Sumerians, down to the present. Ancient history has rather informally been divided into copper, bronze, and iron ages. The Egyptians built the pyramids with copper tools. Bronze, an alloy of copper and tin, was harder and stiffer. Towards the end of the second millennium BC, iron appears on the scene. This actually means steel, since iron itself is still pretty soft. In Tutankhamon's tomb, there is one steel knife, buried with the King himself. It was polished and bright when initially unwrapped. The problem of producing steel in large and conistent quantities would not be solved for three thousand more years.

Intermediate between the 103 diagram and the 102 one is the time-line I prepared to illustrate Roman history. Here a century is exactly half the length of the 102 diagram. This about the last 500 years of Ancient History (the First Empire) along with the whole Middle Ages.

Until Columbus, knowledge of distant regions of the planet was either non-existent or a matter of a few literate travelers bringing imperfect reports, or rumors and legends. The ability to go much of anyplace was gravely limited. And although it had been known for about 1800 years that the Earth was (roughly) a sphere, this was a theoretical discovery, with considerable controversy about the absolute size of the sphere, let alone the real size and arrangement of the continents and oceans. Then Europeans crossed the oceans, all of them (except the Arctic), in little more than three decades. This settled the issue of the size of the Earth, revealed the existence of two continents, then four, that the Eurasian civilizations had no knowledge of, and launched an international culture.

This is all recent enough that some people still don't think it was a good idea, and a lot of hostility gets directed at Columbus personally. Some results were indeed devastating. The diseases of Eurasia decimated (i.e. 1 out of 10), or worse, the human populations of the New World, which had been isolated for 10,000 years or more. The Incas, Aztecs, and Mayans, with brilliant civilizations in their own right, nevertheless technologically had not advanced beyond the Neolithic. They were physically and culturally overwhelmed by small bands of often unofficial freebooters. It didn't take Genghis Khan with an army of 200,000 -- with perhaps fewer long term consequences. However, the avenue across Central Asia that the Mongol domain established, soon brought the Black Death to Europe and the Middle East. This may have been as devastating to populations as smallpox was in the Americas; but it is not clear that it had nearly as much political or cultural an impact. No one in modern politics thinks to accuse the Mongols of genocide -- it was, after all, the Wrath of God -- but European settlement in the American is routinely so characterized, even though the spread of disease is inevitable, as we learn again in 2020.

For the last two centuries, the Industrial Revolution entailed a quantum jump in the quantity and sophistication of economic production. This involved a new scale in the use of energy, with steam power, and then gas, electricity, and petroleum, adding to the force of machines and transportation. Again, some people still wonder if this was a good idea, though now they tend to communicate their ideas by way of computers -- the Information Revolution. In other words, it will be impossible to go back -- the genie is out of the bottle -- without, that is, the kind of destruction happening that we know finished off the dinosaurs, delivered now either by nature (supervolcanoes, supertsunamis, or asteriod impacts) or by the new horrors of modern weapons. In any case, it is also interesting that some people think that they do or should have the power to require the rest of mankind to abandon modernity.