We know that life originated on Earth about 3.7 billion years ago . But we still don’t understand exactly how. Is life something rare or frequent?
Australian astrophysicist Brandon Carter once argued that there are restrictions on inferring that abiogenesis took place elsewhere in the universe, not just on Earth. In essence, Carter was arguing that life cannot be said to exist on other planets solely based on the knowledge that abiogenesis occurred on Earth.
How likely is it that life exists on other planets?
Scientists have often wondered if the existence of life on Earth might tell us something about abiogenesis, or the origin of life from inorganic substances, on other planets. Thus, according to Carter, since we already live on a planet where abiogenesis has occurred, we cannot predict the probability of the existence of life on other planets from our observation, since our very existence limits our observation.
Now, a new study published in the International Journal of Astrobiology reviews Carter’s reasoning, stating that if life could happen on Earth, it could also take place elsewhere in the cosmos. Basically, the document is an argument against the opinion of the astrophysicist Carter.
If Carter was saying that we don’t have a known set of Earth-like planets to compare it with, being meticulously conservative, as is often the case in science, the new paper argues that Carter is using faulty logic, pointing out what what philosophers call the problem of old evidence in Bayesian confirmation theory, which refers to what happens when a theory or hypothesis is updated, following the appearance of new evidence: a means of updating theories in the light of new evidence. the new information.
Scientist Daniel Whitmire, now a professor of mathematics at the University of Arkansas, who signs the paper, basically says that Carter does not take into account the long cosmic time scales at stake in the universe, for example, the time it takes for life to emerge on a planet.
“The observation of life on Earth is not neutral, but it does show that abiogenesis on Earth-like planets is relatively easy. I…give an independent timescale argument that quantifies prior probabilities, leading to the inference that the timescale for abiogenesis is less than the timescale of planetary habitability, and thus the The occurrence of abiogenesis on Earth-like planets is not rare ,” says Whitmire.
The appearance of life on planets similar to Earth is much more likely than we thought
Whitmire used what he calls the conception analogy to show that abiogenesis is quite possible on Earth-like planets. “One could argue, like Carter, that I exist regardless of whether my conception was hard or easy, so nothing about whether my conception was hard or easy can be inferred from my existence alone .”
“However, my existence is ancient evidence and should be treated as such. When this is done, the conclusion is that it is much more likely that my conception was easy. In the case of abiogenesis interest, it is the same. The existence of life on Earth is ancient evidence and, as in the conception analogy, the likelihood that abiogenesis is easy is much more likely,” Whitmire continues.
This analysis by Whitmire suggests that an update to Carter’s widely accepted theory may need to be made as new data become available, suggesting that “observation of life on Earth is not neutral, but rather evidence that abiogenesis on planets similar to Earth is relatively easy.
The expert is convinced that we are not alone and we have the ability to find life on other planets.
Referencia: Whitmire, D. (2022). Abiogenesis: The Carter argument reconsidered. International Journal of Astrobiology, 1-6. doi:10.1017/S1473550422000350