Life might have been possible just seconds after the Big Bang

A composite image of the Bullet Cluster, a much-studied pair of galaxy clusters that have collided head on. One has passed through the other, like a bullet traveling through an apple, and is thought to show clear signs of dark matter (blue) separated from hot gases (pink).
A composite image of the Bullet Cluster, a much-studied pair of galaxy clusters that have collided head on. One has passed through the other, like a bullet traveling through an apple, and is thought to show clear signs of dark matter (blue) separated from hot gases (pink). (Image credit: X-ray: NASA/ CXC/ CfA/ M.Markevitch, Optical and lensing map: NASA/STScI, Magellan/ U.Arizona/ D.Clowe, Lensing map: ESO/WFI)

Life has found a home on Earth for around 4 billion years. That's a significant fraction of the universe's 13.77 billion-year history. Presumably, if life arose here, it could have appeared anywhere. And for sufficiently broad definitions of life, it might even be possible for life to have appeared mere seconds after the Big Bang.

To explore the origins of life, first we have to define it. There are over 200 published definitions of the term, which shows just how difficult this concept is to grapple with. For example, are viruses alive? They replicate but need a host to do so. What about prions, the pathogenic protein structures? Debates continue to swirl over the line between life and nonlife. But for our purposes, we can use an extremely broad, but very useful definition: Life is everything that's subject to Darwinian evolution.

This definition is handy because we'll be exploring the origins of life itself, which, by definition, will blur the boundaries between life and nonlife. At one point, deep in the past, Earth was not alive. Then it was. This means that there was a transition period that will naturally stretch the limits of any definition you can muster. Plus, as we dig deeper into the past and explore other potential options for life, we want to keep our definition broad, especially as we explore the more extreme and exotic corners of the universe.

Related: Life may have evolved before Earth finished forming

With this definition in hand, life on Earth arose at least 3.7 billion years ago. By then, microscopic organisms had already become sophisticated enough to leave behind traces of their activities that persist to the present day. Those organisms were a lot like modern ones: They used DNA to store information, RNA to transcribe that information into proteins, and the proteins to interact with the environment and make copies of the DNA. This three-way combo allows those batches of chemicals to experience Darwinian evolution.

But those microbes didn't just fall out of the sky; they evolved from something. And if life is anything that evolves, then there had to be a simpler version of life appearing even earlier in Earth's past. Some theories speculate that the first self-replicating molecules, and hence the simplest possible form of life on Earth, could have arisen as soon as the oceans cooled, well over 4 billion years ago.

And Earth may not have been alone — Mars and Venus had similar conditions at that time, so if life happened here, it may have happened there, too.

The first life among the stars 

But the sun was not the first star to ignite into fusion; it is a product of a long line of previous generations of stars. Life as we know it requires a few key elements: hydrogen, oxygen, carbon, nitrogen and phosphorus. With the exception of hydrogen, which appeared in the first few minutes after the Big Bang, all of these elements are created in the hearts of stars during their life cycles. So, as long as you have at least one or two generations of stars living and dying, and thereby spreading their elements out into the wider galaxy, you can have Earth-like life appearing in the universe.

This pushes the clock back on the possible first appearance of life to well over 13 billion years ago. This era in the history of the universe is known as the cosmic dawn, when the first stars formed. Astronomers aren't exactly sure when this transformative epoch took place, but it was somewhere within a few hundred million years after the Big Bang. As soon as those stars appeared, they could have started creating the necessary elements for life.

So, life as we know it — built on chains of carbon, using oxygen to transport energy, and submersed in a bath of liquid water — may be much, much older than Earth. Even other hypothesized forms of life based on exotic biochemistries require a similar mixture of elements. For example, some alien life may use silicon instead of carbon as a basic building block or use methane instead of water as a solvent. No matter what, those elements have to come from somewhere, and that somewhere is in the cores of stars. Without stars, you can't have chemical-based life.

The first life in the universe 

But perhaps it's possible to have life without chemistry. It's hard to imagine what these creatures might be like. But if we take our broad definition — that life is anything subject to evolution — then we don't need chemicals to make it happen. Sure, chemistry is a convenient way to store information, extract energy and interact with the environment, but there are other hypothetical pathways.

For example, 95% of the energy contents of the universe are unknown to physics, literally sitting outside the known elements. Scientists aren't sure what these mysterious components of the universe, known as dark matter and dark energy, are made of. 

Perhaps there are additional forces of nature that work only on dark matter and dark energy. Maybe there are multiple "species" of dark matter — an entire "dark matter periodic table." Who knows what interactions and what dark chemistry play out in the vast expanses between the stars? Hypothetical "dark life" may have appeared in the extremely early universe, well before the emergence of the first stars, powered and mediated by forces we do not yet understand.

The possibilities can get even weirder. Some physicists have hypothesized that in the earliest moments of the Big Bang, the forces of nature were so extreme and so exotic that they could have supported the growth of complex structures. For example, these structures could have been cosmic strings, which are folds in space-time, anchored by magnetic monopoles. With sufficient complexity, these structures could have stored information. There would have been plenty of energy to go around, and those structures could have self-replicated, enabling Darwinian evolution. 

Any creatures existing in those conditions would have lived and died in the blink of an eye, their entire history lasting less than a second — but to them, it would have been a lifetime.

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Paul Sutter Contributor

Paul M. Sutter is an astrophysicist at SUNY Stony Brook and the Flatiron Institute in New York City. Paul received his PhD in Physics from the University of Illinois at Urbana-Champaign in 2011, and spent three years at the Paris Institute of Astrophysics, followed by a research fellowship in Trieste, Italy, His research focuses on many diverse topics, from the emptiest regions of the universe to the earliest moments of the Big Bang to the hunt for the first stars. As an "Agent to the Stars," Paul has passionately engaged the public in science outreach for several years. He is the host of the popular "Ask a Spaceman!" podcast, author of "Your Place in the Universe" and "How to Die in Space" and he frequently appears on TV — including on The Weather Channel, for which he serves as Official Space Specialist.

  • Questioner
    I actually like their opening up the definition of life.
    One can define life as kinetic energies, events, actions and distinguish persistent forms that arise in that as life forms.
    On Earth we generally only define life only as (active?) organized biochemical systems exclusively in celled enclosures that self replicate.
    The almost incomprehensible intricate biochemical mechanisms that keep the active systems operating in a regulated manner are stunning.
    They operate in a manner that seems quasi-independent of primary physics.
    Viruses are categorized as nonlife which would be definition dependent.
    We probably make the binary distinction between life and nonlife as kind of a defense mechanism to help preserve our dynamic systems and the self identity that supports its 'independent' ongoing operation(s).
    Egos and psychology are a function of our sustained living states/systems so i wouldn't cavilarly dismiss them.
    It probably dovetails with our immune systems.
    Possibly cultural/societal immune systems as well as our biological ones.
  • rod
    "Life has found a home on Earth for around 4 billion years. That's a significant fraction of the universe's 13.77 billion-year history. Presumably, if life arose here, it could have appeared anywhere. And for sufficiently broad definitions of life, it might even be possible for life to have appeared mere seconds after the Big Bang."

    Very interesting concept. Life emerging just seconds after the postulated BB event. The CMBR does not become light until about 380,000 years after the BB event, thus that universe back to some seconds after BB, very different temperature apparently for life to appear. Charles Darwin in 1871 stated about the warm little pond.

    "My dear Hooker I return the pamphlets, which I have been very glad to read.— It will be a curious discovery if Mr. Lowne’s observation that boiling does not kill certain moulds is proved true; but then how on earth is the absence of all living things in Pasteur’s experiment to be accounted for?—2 I am always delighted to see a word in favour of Pangenesis, which some day, I believe, will have a resurrection3 Mr Dyers paper strikes me as a very able Spencerian production.—4 It is often said that all the conditions for the first production of a living organism are now present, which could ever have been present.— But if (& oh what a big if) we could conceive in some warm little pond with all sorts of ammonia & phosphoric salts,—light, heat, electricity &c present, that a protein compound was chemically formed, ready to undergo still more complex changes, at the present day such matter wd be instantly devoured, or absorbed, which would not have been the case before living creatures were formed.— Henrietta makes hardly any progress, & God knows when she will be well.—5 I enjoyed much the visit of you four Gentlemen, ie after the Saturday night, when I thought I was quite done for.—6 Yours affecy | C. Darwin" ref - little pond#hit.rank2
    URL is, To J. D. Hooker 1 February , Darwin Correspondence Project, “Letter no. 7471,” accessed on 15 August 2023.

    The appearance of life in this article from non-living matter by goes well beyond the warm little pond thinking of Charles Darwin in 1871,
  • Damon A
    I come to for science. Saying that life arose a few hundred million years after the first star ignited is reasonable scientific speculation. We all know that the building blocks of life are forged in the hearts of stars, and the first supermassive stars probably had lifespans measured in the few millions of years. After which they scattered those elements to be picked up by the next generation of stars. So possible? Sure. Personally I think the third generation had a better chance, and certainly more metallicity for life to develop technical civilizations.

    But the last part of the article is drivel. Nothing more than theocratic speculation, really. Non-chemical life? LOL! I feel like that's better suited for the script of a sci-fi channel movie.

    "They've come to get us. They want our.... chemicals!"
  • MelvinA
    Extremely broad definition of life? Yes. Useful? Not really. It's my personal belief that life is a bit more finicky. The universe is just too old for it not to have happened somewhere, somewhen though. The Fermi paradox has a simple answer. The galaxy is simply too vast, to say nothing about the larger universe. The distances are nearly inconceivable to the human mind. It's all a simulation anyway lol.
  • billslugg
    At the extreme densities within one second of the Big Bang, would not the immense gravitational field slow time down to a near stop?
  • Atlan0001
    billslugg said:
    At the extreme densities within one second of the Big Bang, would not the immense gravitational field slow time down to a near stop?
    The densest density in physics is a hole, self-inflicting. A Menger Sponge infinitely holing in its contraction of volume (to discreet quanta) infinitizing in its asymptotic flat surface area expansion.

    The total energy of the universe always and forever equals zero.
  • finiter
    The definition of life should be based on independent action. So the minimum requirement is the ability to store energy, use that energy later and replicate itself using that energy. Living things are heat engines and so life is possible only when the average temperature of the universe is less than the surface temperature of Earth. So 4 billion years, l think, is the best estimate.
  • Unclear Engineer
    billslugg said:
    At the extreme densities within one second of the Big Bang, would not the immense gravitational field slow time down to a near stop?
    I have asked that question several times before, and the theorists are ridiculously quiet about it. Sometimes there is some mumbling about the density being uniform, so there is no "slow" and no "fast" in the early universe.

    It seems that the simplifying assumptions used to get solutions to Einstein's field equations would be incompatible with spontaneous development of structures. And, out to the CMBR, it seems that theorists have been happy with the idea that things were uniform down to quantum fluctuation levels.

    So, is life supposed to be derived from quantum fluctuations?

    I have proposed an experiment to actually try to measure whether time dilation is a matter of being in proximity of mass, or if it requires a differential in mass distribution. Basically, we have the math and measurements to show that time dilation is covariant with escape velocity from a mass when measured outside of that mass. But, what happens to time dilation when it is measured as a function of depth inside the mass? Does it still follow the escape velocity, which continues to increase with depth? Or does it follow the local gravitational acceleration, which decreases with depth and reaches zero at the "center of gravity" of that mass.

    I have seen people spout theory to answer that question, but that is just a head in the sand response. It seems to me that it would be a fundamental test worth conducting. Unfortunately, it is probably not so simple to do, given the changes in environment that can affect instrumentation as a function of depth in the Earth. But, I think it would be within our current technological capabilities. It just would not be cheap.
  • billslugg
    We have had this discussion before. Gravitational time dilation is a function of the gravitational field strength, not whatever weight a scale would show. This number is at a maximum at the center of the Earth. You would be floating but your clock would run slow to an outside observer.
  • Unclear Engineer
    Yes, we had this discussion before, and you provided your answer based on your interpretation of theory. That interpretation of theory would also predict, as you previously posted, that clocks in the early universe should run extremely slowly. But, theorists don't seem to want to discuss that.

    Which calls into question the "seconds after the "Big Bang" stories we always see. What is a second under those conditions? Does "inflation" really need to exceed the speed of light for the universe to evolve as theorized? For that matter, what is the "speed of light" that "all observers agree on" when the whole universe is less than a (current) atom wide. so a "meter" is certainly not what we now perceive as a meter, either.

    The whole theory seems inconsistent at that point, with respect to the sizes and times assumed, especially the "horizon" issues related to cause/effect and "smoothness".

    The real problem seems to be that the theorists jump between a concept of an in-the-universe frame of reference and a concept of an outside-the-universe-with-constant-time-and-physical-dimensions frame of reference without explaining any differences.

    As I said before, the test I proposed would directly address that theoretical position. It would be a useful test for the "show me" folks like myself who want some basis for realism in the theoretical discussions which seem to be only based on opinions.