Reptilian menaces known as Silurians evolved on Earth before humankind -- at the "Doctor Who" rendition of this world. This is a significant question, and serious scientists are speculating about what traces these possible predecessors may have left behind.
When it comes to the search for advanced extraterrestrial civilizations that may exist across the cosmos, an individual has to reckon with the understanding that the world is about 13.8 billion years old. In contrast, complicated life has existed on the planet's surface for just about 400 million years, and people have developed industrial civilizations in just the past 300 years. This increases the possibility that industrial civilizations might have existed long before human ones ever existed -- not only around other stars, but on Earth itself.
" I don't feel an industrial culture existed on Earth before our own -- I do not believe there was a dinosaur culture or a giant tree sloth culture," said Adam Frank, an astrophysicist at the University of Rochester and a co-author of a new study on the subject. "However, the question of what you would look like if it did [exist] is crucial. How do you know there has not been one?
Artifacts of other industrial civilizations will probably not be found on a planet's surface after about 4 million years, wrote Frank and research co-author Gavin Schmidt, manager of NASA's Goddard Institute for Space Studies. As an example, they noticed that urban areas currently consume less than one percent of Earth's surface and that complicated products, even from ancient human engineering, are very seldom found. A machine as complicated as the Antikythera mechanism -- utilized by the ancient Greeks, it's regarded as the world's first computer -- remained unidentified when elaborate clocks were being developed in Renaissance Europe.
An individual may also find it tough to unearth fossils of any beings that might have dwelt in industrial civilizations, the scientists added. The fraction of life which gets fossilized is always extremely small: Of of the many dinosaurs that ever lived, by way of example, just a couple thousand almost complete fossil specimens are discovered. Given that the earliest known fossils of Homo sapiens are only about 300,000 years old, there isn't any certainty that our species may even appear in the fossil record in the long term, they added.
The scientists focused on taking a look at the signs of culture that people might create during the Anthropocene, the geological age of now, characterized by humans' influence on Earth.
"After a few million years, any physical reminder of your culture could be gone, so you need to search for sedimentary anomalies, things such as different chemical balances that just seem wacky," Frank said.
1 sign of industrial civilization might need to do with isotopes of elements like carbon.
As an example, people living in industrial civilizations have burnt an extraordinary quantity of fossil fuels, releasing over 500 billion tons of carbon from coal, oil and natural gas to the atmosphere. When fossil fuels get burnt, they alter the proportion of carbon-12 into carbon-13 normally found in the atmosphere, lands and sea -- a result that could later be discovered in sediments as hints of an industrial culture.
Additionally, industrial civilizations have found ways to "fix" nitrogen -- which is, to break the effective chemical bonds that hold nitrogen atoms together in pairs from the air, using the resulting single nitrogen molecules to make biologically useful molecules.
The Anthropocene is also triggering a mass extinction of a huge array of species that's most likely observable in the fossil record. Human industrial action can also prove to be observable in the geological record in the kind of long-lived synthetic molecules out of plastics and other products, or radioactive fallout from atomic weapons.
1 crazy idea the Silurian hypothesis raises is the conclusion of a single civilization could sow the seeds for another. Industrial civilizations may activate dead zones in oceans, causing the burial of organic material (in the corpses of organisms from the zones) that could down the line, become fossil fuels which could encourage a new industrial culture.
Overall, considering the impact that a prior civilization has on Earth "could help us consider what effects one might see on other planets, or about what's occurring now on Earth," Frank said.