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The novelist Gabriel Garcia Marquez struck an optimistic note about aging: “The essence of a human being is resistant to the passage of time,” he once wrote. On the other hand, Chuck Palahniuk, author of Fight Club, was a bit less sentimental: “It happens fast for some people and slow for some, accidents or gravity, but we all end up mutilated.” Fashion designer Diane Von Furstenberg likened aging to becoming a myth.

In common understanding, there may be as many types of aging as there are years of age. Is it different in science? To unravel this complexity—or perhaps add to it—Nautilus spoke to scientists and scholars from a wide range of disciplines about their own perspectives on aging.

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Caleb Scharf Astrobiologist, director of the Columbia Astrobiology Center at Columbia University

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The first thought that comes to my mind is “planet age.” We have this prejudice that young planets might give rise to life, and old planets cannot, even though we have no idea if those assumptions are actually correct. The young Earth must have had some set of conditions—be they chemical, thermal, kinetic—that at least allowed life to start, and perhaps even compelled it to get going as more and more complex molecular structures formed and took on functional roles. But we don’t know if that always has to be the case. We also assume that older planets have less geophysical activity as they cool off, and may face drastically changing surface climates as their host star ages and dumps more and more energy onto the planet. Those things could be detrimental to life…or not.

For astrobiology, aging could be part of an even bigger question. The universe is 13.8 billion years old, and we’re here. Is our being here related to that specific age—give or take a few billion years? In the far future the universe may not be a very life-sustaining place, and it probably wasn’t during its very early years. It could be that the optimal time for life is indeed right now.

Hope Jahren Geochemist and geobiologist at the University of Hawaii, and author of Lab Girl

When I think of aging in geochemistry, I think of radiometric dating, which is a method used to determine the age of a rock. This method takes advantage of radioactive isotopes, that is, of atoms that spontaneously change from one configuration of subatomic particles to another by loss of the particles within—or radioactive decay. You may be familiar with the fact that Uranium decays spontaneously to Lead. The rate of radioactive decay inherent within each decay process is very, very faithful and unchanging—in fact, it is the most faithful and unchanging rate of process known. For this reason, if I can measure the ratio of Uranium to Lead in a rock, I can tell it’s age—meaning that I can tell how long it has been actively decaying. This is how geochemists assign “ages” to rocks.

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The interesting thing about this is that as a technique, the geochemistry is changing. For instance, in 2010, geochemists developed a machine that can detect an unprecedentedly small amount of lead. So a rock that we used to think had an Uranium/Lead value of 9.0/3.0 now has a value of 9.0009/3.0003. In other words, in 2010 we learned that the rock is actually younger than we thought it was in 2000. In this way, the age of the rock has itself aged.

This is why the Geologic Time Scale (the schematic that tells geologists when the different epochs were) keeps needing to be revised slightly: Note the slight differences between the 1983, 1999, 2009 and 2012 versions. Even our ages age.

Kenneth Poss Biologist, director of the Regeneration Next Initiative at Duke University

The link between the regenerative potential of tissue and age is what fascinates me. Mammals at the fetal, and even neonatal, stages have a high capacity to regenerate after injury, a feature that dissipates during development to adolescent and adult stages. In their first week of life, mice can even show a strong regenerative response to a heart attack, whereas they repair such injuries by scarring after this point. What is the basis for this change in regenerative capacity?

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Similarly, as animals, including humans, age, the efficacies of tissue renewal and regeneration in response to injury decline. This affects our muscle, blood, and the generation of new neurons in our brain, among other tissues. Thus, I along with many scientists consider aging to be a cumulative effect of an overall decline in the regenerative potential of our tissues. The exciting thing is that by studying how and why regeneration happens, and what the rejuvenating factors in young animals that promote regeneration (or restrict it in older animals) are, we may be able to identify manipulations that improve the quality of living as we age.

Charles A. Ver Straeten Geologist, curator of the New York State Museum & Geological Survey

I’m a sedimentary geologist. While living a human life, measured in decades, I study the detritus of shells and broken-down old rocks (mud, sand and gravel), all remade into rocks hundreds of millions of years ago. Daily my mind crosses back and forth across these very different senses of time—and very different senses of aging. A large part of my research has been reading the history of mountain building along the margin of eastern North America—a history recorded in the layers of Devonian-age sedimentary rocks, deposited 419 to 359 million years ago. Today’s Appalachian Mountains are the ancient remnants of a much more angular, jagged and taller range, a range uplifted by multiple continent-continent collisions 450 to 300 million years ago.

Once uplifted to heights, however, all mountain ranges begin to wear down and erode. Over time, layers of sand, gravel and mud pile up in adjacent lowlands, and turn to rock. West of the Appalachians, sedimentary rocks record the aging of the mountain belt. That history can in part be understood through changes in the type of sedimentary rock, and changes in the minerals grains in those rocks. Conglomerate layers of white quartz pebbles, 410 million years old, change upward to 385 million year-old conglomerates of white quartz and metamorphosed sandstone pebbles. And so it goes, on and on, the rock layers preserving the history of the aging Appalachians over time.

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Today, as much as 450 million years later, the Appalachians are still eroding. Still wearing down to their ultimate leveling, as a flat plain. Still aging.

Jerry McManus Earth Scientist, Professor of Earth and Planetary Sciences at Columbia University

I’m interested in how aging applies to the deep ocean, and how water moves from the surface to the abyss and then spreads at depth from the Atlantic to the Pacific. In this context, aging refers to a parcel of seawater’s last contact with the atmosphere. Things like carbon-14 and other isotopic tracers serve as clocks for this aging, and tell us that the water in the deep Pacific is more than a thousand years “old” today, and that the “age” of various parts of the ocean were different in the past.

Sarah Elwood Geographer, Professor in the Department of Geography at the University of Washington

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How does a map age? Briefly put, much differently than it did in the past. In a world of paper, an aging map was delicate, perhaps a bit tattered, then perhaps shut away for preservation or museum-viewing or special occasions. In a world of digital maps, interactive maps, web maps, and crowd-sourced maps, an aging map is dynamic, always changing, reflecting simultaneously its past, present, future. Aging means growing, changing, becoming, in a way that feels vibrant and creative.

Charles Briggs Sociocultural anthropologist, Professor in the Department of Anthropology at the University of California, Berkeley

Think about how contemporary folklore forms age. Say something happens that’s catastrophic—like 9/11, or something smaller within a social community. All of a sudden something emerges about it—rumor, or gossip. At first, it might contain a whole lot of real details. If it starts to circulate or catches on, a process where some of these details drop out, other details will amplify and take on their own narrative lives. As the narrative circulates, it gets richer and more coherent, and more parts emerge as it travels around. Not that these details are false—but they do shift around, and the story gets more tellable. These days, it’s about how many likes it gets.

Then, guess what? The story usually dies. Most rumors and gossip, at this point, lose the close intimate relationship to the event and, pretty soon the event’s been redefined by the narrative. The aging of folklore helps form it.

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Susie Neilson is an editorial fellow at Nautilus. Follow her on Twitter @schmeilson.

The lead photograph is courtesy of craigfinlay via Flickr.

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