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Home SCIENCE What was it like when life first became possible? | by Ethan Siegel | Starts With A Bang! | Jan, 2024

What was it like when life first became possible? | by Ethan Siegel | Starts With A Bang! | Jan, 2024

by California Digital News

This conceptual image shows meteoroids delivering all five of the nucleobases found in life processes to ancient Earth. All the nucleobases used in life processes, A, C, G, T, and U, have now been found in meteorites, along with more than 80 species of amino acids as well: far more than the 22 that are known to be used in life processes here on Earth. Similar processes no doubt happened in stellar systems all throughout most galaxies over the course of cosmic history. (Credit: NASA Goddard/CI Lab/Dan Gallagher)

Earth wasn’t created until more than 9 billion years after the Big Bang. In some lucky places, life could have arisen almost right away.

The cosmic story that unfolded following the Big Bang is ubiquitous no matter where you are. The formation of atomic nuclei, atoms, stars, galaxies, planets, complex molecules, and eventually life is a part of the shared history of everyone and everything in the Universe. Even though all of these things likely arise at somewhat different times at different locations in the Universe, largely dependent on the initial conditions such as temperature and density, once enough time goes by, they’re found literally everywhere. At least once, here on Earth, life began at some point in the Universe. At the absolute latest, it appeared only a few hundred million years after our planet was first formed.

That puts life as we know it arising, at the absolute latest, nearly 10 billion years after the Big Bang. When the Big Bang first occurred, life was impossible. In fact, the Universe couldn’t have formed life from the very first moments; both the conditions and the ingredients were all wrong. But that doesn’t mean it took all those billions and billions of years of cosmic evolution to make life possible. Based on when the raw ingredients that we believe are necessary for the most primitive forms of life to arise from non-life, it’s reasonable to think that “first life” might have come around back when the Universe was just a few percent of its current age. Here’s the best scientifically-motivated story for how life might have first arisen in our Universe.

The existence of complex, carbon-based molecules in star forming regions is interesting, but isn’t anthropically demanded. Here, glycolaldehydes, an example of simple sugars, are illustrated in a location corresponding to where they were detected in an interstellar gas cloud: offset from the region presently forming new stars the fastest. Interstellar molecules are common, with many of them being complex and long-chained. (Credit: ALMA (ESO/NAOJ/NRAO)/L. Calçada (ESO) & NASA/JPL-Caltech/WISE Team)

At the earliest moments of the hot Big Bang, the raw ingredients for life could in no way stably exist. Particles, antiparticles, and radiation all zipped around at relativistic speeds, blasting apart any bound structures that might have formed by chance. As the Universe aged, though, it also expanded and cooled, reducing the kinetic energy of everything in it. Over time, antimatter annihilated away, stable atomic nuclei formed, and electrons finally bound to…

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