Earth Could Be Unique Among 700 Quintillion Planets in The Universe, Study Finds

So much of humanity's astronomical study is focused on finding something like us out there, whether it's looking for environments that potentially support life, ranking planets in terms of their potential habitability, or comparing faraway worlds to our own.

But what if the odds are stacked against us ever discovering another planet that is even substantially similar to Earth? That's the idea behind a recent study by an international team of academics, who used a computer model to feed what we know about exoplanets outside our Solar System.

Their calculations, which were designed to replicate how galaxies and planets evolved over 13.8 billion years, result in a "cosmic inventory" of terrestrial planets, with Earth appearing to be unique.

"It's kind of mind-boggling that we're actually at a stage where we can start doing this," Carnegie Observatories' Andrew Benson told Shannon Hall of Scientific American.

Nonetheless, the researchers admit that their projections on the spatial and temporal distribution of terrestrial planets in both the local and distant Universes are prone to a variety of inaccuracies. Especially given how little we know about exoplanets, with only roughly 2,000 discovered out of a total of 700 quintillion.

"There are undoubtedly a lot of uncertainties in a calculation like this," Benson remarked. "Our understanding of all of these parts is incomplete."

But what makes Earth so unique? The researchers don't know, but their calculations show that our world is an outlier in comparison to the great majority of other planets in the Milky Way and beyond, which they claim are older, larger, and considerably less likely to host life.

There's no way to be certain given the incredibly small data set used - even 2,000 exoplanets is a tiny sample to base projections on, given the massive number of potential worlds out there in the Universe - but the researchers describe Earth's formation and position as an unlikely incident of chance.

"[W]e would have to acknowledge that we got here through an unusual lottery draw," the scientists wrote in their research, which will be published in The Astronomical Journal. "However, perhaps there is more to the lottery than we previously realised?"

Further findings concerning the composition and position of further exoplanets could refine the predictions based on these large and highly speculative calculations. As the researchers concede, until then, their findings should be interpreted with caution.

"Whenever you find something that stands out," Erik Zackrisson of Uppsala University, one of the team members, told Scientific American, "it suggests that either we are the outcome of an extremely odd lottery draw or we don't understand how the lottery works."