strophysicists say questions about the sustainability of civilisation on our high-tech planet may soon be answered scientifically as a result of new data about the Earth and other planets in its galaxy.
Two American scientists have just sought to find a way of answering the ultimate global warming question: how long can any species last once it has discovered how to exploit fossil fuels and change the conditions under which it first evolved?
In doing so, they have sidestepped the great challenge of astrobiology. This is that all thinking about life in the universe is handicapped by a simple problem: because there is only one so-far identified instance of life in the universe, it is impossible to arrive at a generalisation.
But Adam Frank, assistant professor of astrophysics at the University of Rochester in New York, and Woodruff Sullivan, professor of astronomy at the University of Washington in Seattle, propose a way round the problem.
They report in The Anthropocene journal that since they were interested in the potential lifetimes of human, humanoid or other intelligent species with energy intensive technology (SWEIT), they could start by using a famous equation to estimate the number of such species that exist now or have already gone extinct.
The Drake Equation is the intellectual basis of the search for extraterrestrial civilisation. It calculates the number of possible planetary systems in all the known galaxies, the proportion of these that might be hospitable to life, and the proportion of habitable planets that might be fit for the emergence of a technically-advanced or SWEIT civilisation.
They reason that, even if the chances of a high-technology species are just one in a thousand trillion, that means that a thousand such SWEIT civilisations exist or have existed in our local region of the universe.
Prof Frank says: “That’s enough to start thinking about statistics − like what is the average lifetime of a species that starts harvesting energy efficiently and uses it to develop high technology?”
“We have no idea how long a technological civilisation like our own can last”
But another part of the puzzle is also uncertain. “We have no idea how long a technological civilisation like our own can last,” Frank says. “Is it 200 years, 500 years or 50,000 years? Answering this question is at the root of all our concerns about the sustainability of human society.
“Are we the first and the only technologically-intensive civilisation in the entire history of the universe? If not, shouldn’t we stand to learn something from the past successes and failures of these other species?”
The two authors considered the ways in which human action could threaten human civilisation, including: the partial or complete collapse of 95% of all fish stocks in the last 50 years; the diminishing supplies of fresh water; the loss of rainforest habitat; the acidification of the oceans; and, of course, the change to the climate system. All are a consequence of the use of energy-intensive technology.
They also contemplated the relatively new science of sustainability: how long can such action continue? They note that 20,000 scientific papers that address sustainability have appeared in the last 40 years, and the numbers of these articles has doubled every eight years.
Then they looked at what little could be known from astrobiology − the study of life beyond the solar system. None has been found, but in the last two decades a huge number of extrasolar planets have been identified. The local solar system has been explored in detail, and the Earth’s own history is now well studied.
So astronomers could now be in a position to make judgments about the potential conditions for life on the “exoplanets” identified so far. For the purpose of estimating an average lifetime for an extraterrestrial species, it wouldn’t much matter what form the life took, it would affect entropy, the thermodynamic balance of order and disorder.
“If they use energy to produce work, they’re generating entropy,” says Prof Frank. “There’s no way round that, whether they’re human-looking Star Trek creatures with antennae on their foreheads or they’re nothing more than single-cell organisms with collective mega-intelligence.
“And that entropy will almost certainly have strong feedback effects on their planet’s habitability, as we’re beginning to see here on Earth.”
With this in mind, the report’s authors started to consider the sustainability lessons of Earth’s own history − marked by five mass extinction events in the past 500 million years – and a set of recent human-driven changes so marked that some geologists have labelled the present era the Anthropocene. Their conclusions are less than optimistic.
“Although such rapid changes are not a new phenomenon, the present instance is the first (we know of) where the primary agent of causation is knowingly watching it all happen and pondering options for its own future,” they conclude.
“One point is clear: both astrobiology and sustainability science tell us that the Earth will be fine in the long run. The prospects are, however, less clear for Homo sapiens.”
− Climate News Network
About the Author
Tim Radford is a freelance journalist. He worked for The Guardian for 32 years, becoming (among other things) letters editor, arts editor, literary editor and science editor. He won the Association of British Science Writers award for science writer of the year four times. He served on the UK committee for the International Decade for Natural Disaster Reduction. He has lectured about science and the media in dozens of British and foreign cities.
Book by this Author:
Science that Changed the World: The untold story of the other 1960s revolution
by Tim Radford.