How do we know that humanity established the first intelligent civilization on Earth?

Imagine that millions of years ago, dinosaurs drove cars in cities between mile-high buildings. Ridiculous idea, right? In a compelling thought experiment, the scientists wonder how we would really know if there were such advanced civilizations that left no trace of their impact on the planet?

Imagine that tens of millions of years ago there were dinosaurs driving cars in cities with mile high buildings. Ridiculous idea, right? But how can we be sure it didn't happen?

Over tens of millions of years, all direct evidence of civilization - its artifacts and remains - turns to dust. If so, how do we really know that there weren't previous industrial civilizations on Earth that rose and fell long before humans appeared?

This is a thought experiment that Adam Frank, professor of physics and astronomy at the University of Rochester, and Gavin Schmidt, director of NASA's Goddard Institute for Space Research, published in the journal Astrobiology.

"Gavin and I did not discover any evidence of a previous industrial civilization," explains Frank. But by looking at the deep past in the right way, a new set of questions about civilizations and their impact on Earth emerges. What geological footprints do cultures leave? Can industrial civilization be identified in the geological record once the civilization disappears from the face of its host planet? These questions make us think about the future and the past in a much different way, including how any planetary civilization can rise and fall."

Frank and Schmidt define a civilization according to the extent of its use of energy and called their experiment the "hypothesis of the celery period". Humans have ushered the Earth into a new geological era, which many researchers call the Anthropocene, the period in which human activity greatly affects the climate and the environment. In the Anthropocene, fossil fuels will become markers for future geologists because they will be left behind on Earth. By examining the ecological footprint of the Anthropocene, Schmidt and Frank examine what kinds of clues future scientists might identify and thus prove the existence of human civilization. In doing so, they also interpret evidence for what might be left behind if industrial civilizations like ours had existed millions of years ago.

Humans began burning fossil fuels more than 300 years ago, marking the beginning of industrialization. The researchers point out that the emission of fossil fuels into the air has already changed the carbon cycle in a way that is documented in the ratio between the isotopes. Other ways in which humans may leave behind a geological footprint include:

• Global warming - as a result of the release of carbon dioxide and disturbances to the nitrogen cycle from fertilizers.
• Agriculture - through increased erosion of the soil and deposition of materials such as fertilizers into the soil.
• Plastics, synthetic pollutants, and even steroids - will be detectable after millions and maybe even billions of years.
• Nuclear war - if such a war occurs it will leave behind unusual radioactive isotopes.

"As an industrial civilization, we drive changes in the isotopic ratio because we burn carbon," says Frank. "But burning fossil fuels can actually define us as a civilization, what mark would be left if there was a culture that did this tens of millions of years ago?"
The questions raised by Frank and Schmidt are part of a broader effort to tackle climate change from an astrobiological perspective, and a new way of thinking about life and civilizations across the universe. Looking at the rise and fall of civilizations in terms of their effects on the planet can also influence how researchers approach future studies of other planets.

"We know that early Mars and possibly Venus were more suitable for life than they are now, and we may one day be able to drill there through geological sediments," says Schmidt. "It helps us think about what we should be looking for."

Schmidt points out an irony: If a civilization is able to find a more sustainable way to generate energy without harming its host star, it will leave behind less evidence that it was there.

"You want to have a beautiful, great civilization that does wonderful things, but doesn't push the planet to become a dangerous place for the civilization itself," says Frank. "We need to find a way to produce and use energy that does not endanger us." However, Earth will be just fine, Frank explains. The more important question is, will humans survive?"

Can we create a version of civilization that doesn't push the planet into dangerous territory for us as a species?

"The point is not to 'save the planet,'" says Frank. "No matter what we do to the planet, we are only creating niches for the next cycle of evolution, but if we continue on this path of using fossil fuels and ignore the climate change it leads to, we humans will not be able to be part of the ongoing evolution of the planet."

הThe Silurian hypothesis - a tribute to Doctor Who
Adam Frank and Gavin Schmidt called their study the "Silurian hypothesis" after the breed of "silurus", the bipedal dinosaurs that were introduced inA 1970 episode of the science fiction series Dr. Who. According to the series, the Silurians evolved on Earth during the eponymous era, a geological era that began 443 million years ago and ended 416 million years ago. To avoid disasters, these lizards went into hibernation for millions of years, and were awakened by a nuclear test in a mine in Wells.
"When we wrote the article," Schmidt said, "I tried to find examples of non-human civilization on Earth in science fiction literature, but I couldn't find anything from before the XNUMXs. Although it is highly unlikely that any civilizations existed during the Celery period, because land plants and land animals had not yet established themselves, the name seems to fit our idea following the first example that humans thought of, even if it was in fiction."

for the scientific article

For the announcement of the researchers on the University of Rochester website

More of the topic in Hayadan:

• Astrobiology: Could there be life in space?
• We felt like we were on a real space mission - video coverage of the end of the first D-MARS mission in the Ramon crater
• Questions for the future of humanity: Can the human race avoid extinction?
• are we alone Redefining the uniqueness of our planet