Quark life

Friction, quarks and alternative life forms

‘I had a bit of an arts student moment the other day,’ a musician was explaining to me, ‘and I asked a biochemist friend what would happen if there was no friction. It would be hilarious, we’d all be slipping around all over the place!’ His friend looked back at him sternly and said ‘No, it would be worse than that. Life as we know it would cease to exist.

Turning off ‘friction’ is actually significantly harder than my musician friend might think. Dismissed in the vernacular with a single word, friction is actually a complicated collection of interactions between adjoining surfaces which depend on chemical composition, roughness and applied pressure, not to mention the scale on which you’re operating: to bacteria, the ‘friction’ they experience ‘swimming’ through water is more akin to a human spinning their arms and drilling through concrete.

However, fundamentally, all friction comes down to is electrostatic forces: it’s the way the outer electrons of atoms interact when you press two materials close enough together. So, though friction is complicated, if we want to turn off friction there is at least a simple way: turn electrostatic forces off.

Alas, the biochemist was right: a universe with no electrostatic attraction could not support life as we know it. All human-sized objects are held together by electromagnetism, and without it sticking us together, our meticulous, complex bodies would just drift apart into a gas of guts, and then…nothing.

M81 galaxyM81 galaxy UV, visible and IR composite by NASA

But electromagnetism is not the only glue in the Universe. Objects larger than the human scale are stuck together by gravity: the planets and other assorted rocks and detritus of the Solar System are stuck to the Sun by their mutual gravitational attraction. Indeed, stars are glued into star systems, star clusters and even whole galaxies by gravity, the Universe’s long-range lasso. There are also two other forces: the strong and weak nuclear forces, which stick things on a scale much smaller than ours. The nuclear forces hold the neutrons and protons in atomic nuclei together.

So, could these forces hold together something which we might call alive?

Gravity is not a very strong contender. Its first problem is that it’s not very complex: all it does is attract stuff. A system left under gravity just clumps into an approximate sphere and sits there, lifeless, for all eternity. If your systems starts out in motion (like the Universe did, expanding rapidly from the Big Bang), you can get more interesting and complex shapes (the awe-inspiring beauty of galaxies being a case in point) before everything collapses into a sphere. Even if it is possible to envision, say, a collection of stars tumbling through space slurping up matter and using it to create copies of itself, it would almost certainly be very slow. It takes us a year to go around the Sun, and a structure vaguely approaching the complexity of an interesting life-form, like a galaxy, rotates (or self-replicates?) over hundreds of millions of years. Even our oldest creatures, tortoises and trees, only live for around a hundred years, and they have had a few hundred million years at least to evolve—millions of generations, even for these most long-lived of creatures. This means that the thirteen billion years since the Universe began probably isn’t long enough for any gravitational life-forms to have evolved if their generations are millions of years apart.

A better candidate is the strong nuclear force. These days it is little more than gravity for the tiny scale, pulling nuclei together against the electric repulsion of the positively-charged protons. However, much, much earlier in the history of the Universe, the strong force was probably the dominant cosmic glue, simply because none of the other forces were mighty enough to hold anything together. Moments after the Big Bang, the Universe was hotter than a fireball—billions of billions of billions of degrees—and puny gravity, or electromagnetism, were powerless against particles that hot, with that much energy, leaving the strong force to reign supreme.

The particles were moving very fast, the Universe was much smaller and therefore denser than it is today, and the strong force is very, very strong—all of which means that interactions would be taking place at a speed which leaves both the glacial amble of gravity and even our electrostatic, chemistry-powered evolution firmly in the dust. The trouble is that any evolution didn’t have very long to take place: depending on what exact mechanism you propose for strong nuclear life, it would have had to evolve in one of the momentary epochs in the ridiculously early Universe. For example, if life had come to being in the quark–antiquark period, which existed whilst it was too hot for protons and neutrons to form, it would have had about one ten-thousandth of a second to evolve. Whether anything could have evolved in the plasma is probably beyond sensible speculation with current physics: you’d need a more precise idea of the necessary pre-conditions for an abstract self-replicator to come into being, and a way of modelling the obscenely complex physics of a sea of particles interacting by the strong force (currently modelling a few tens of protons and neutrons in an atomic nucleus is on the fringes of computational possibility—the strong force is a tough one).

Perhaps in that first tiny shard of a fraction of a second at the beginning of the Universe, life came to being in the sizzling soup of quarks, evolution was hurried through its paces by the searing heat, civilisations rose, fell and culminated in a highly advanced, scientifically-literate society which realised that it had barely a few lifetimes remaining before the Universe became too cool to sustain it. Atomic nuclei today are an enduring memorial to their senseless obliteration, ripped apart by the scalding cold shooting through the Universe as it expanded.

As science fact has catalogued and analysed our carbon-, DNA-based life on Earth in ever-more vertigo-inducing detail, science fiction has allowed us to dream of life in ever-less conventional forms. Gedankenexperiments from Fred Hoyle’s sentient Black Cloud of space dust to James Lovelock’s Gaia hypothesis, which contemplated that the Earth itself could be regarded as a living being, question what it means to be ‘alive’, and if and where consciousness arises. Sadly, we have neither observed any of these alternative life forms nor do we have the computational horsepower to attempt to simulate them*.

The idea of strong force, quark-based life in the Universe is nothing more than fantastical speculation; but the silly suggestion of turning off friction led me to the top of a fascinating slippery slope.

* And what it would mean if we did have a computer big enough to simulate life forms raises a whole new set of complicated issues about its biological status, and whether the things being simulated are alive, or whether we are all living in just such a ‘matrix’ ourselves…

Comments

  1. Hmmm, structure in the universe does not arise because objects having velocity as you suggest in the paragraph under the picture of the galaxy as you need to consider the curvature of space-time and the cosmological constant. You imply a ‘closed’ universe based on the knowledge of Newtonian mechanics which insufficient, it is possible to create or rather model an artificial universe in which you would not find the clustering you describe, ie and ‘open’ universe.

    From what I recall of cosmology course, the universe has structure because of rapid exponential expansion (inflation) which ‘scaled’ up quantum fluctuations and created regions in space which were over-dense leading to clustering after the inflation epoch to the galaxies we see today.

    It’s not entirely clear but you seem to suggest that galaxies will somehow eventually collapse to form a sphere of gas, that just doesn’t happen, but I probably misunderstood something…

  2. “However, much, much earlier in the history of the Universe, the strong force was probably the dominant cosmic glue, simply because none of the other forces were mighty enough to hold anything together.”
    Unless, I think, you believe in a GUT, where at those very energies, all the forces are unified, and defining “electromagnetism” or “strong force” as separate entities isn’t very physically meaningful.

  3. Gravity-wise: firstly, I am referring to local, rather than Universe-wide structure, where gravitation rather than the expansion of space–time itself is the dominant interaction. I don’t think that the galaxies will collapse to form a huge black hole, but each individual one, given enough time (and a cosmological constant small enough that galaxies themselves aren’t eventually ripped apart) should..?

    I’m not sure what combination of initial inhomogeneity and velocity give rise to structure which persists over thirteen billion years. A uniform sphere of gas without friction or similar interactions would collapse to a point, but an inhomogeneous one, or one which starts in motion, might either start with or obtain the angular momentum necessary to make a whirling galaxy which doesn’t collapse on Universe-lifetime timescales.

    As for GUTs, I don’t think your criticism is necessarily valid. I avoided mentioning force unification in an attempt to keep things simple, but also because, depending on when you propose that these quarky beings might come into being, force separation could well have already happened. The strong force is thought to have separated out at about 10−36 seconds—rather a ‘long’ time before 10−5 seconds, when the quark–antiquark period to draws to a close. Check out HyperPhysics’s ridiculously early Universe chronology for a good summary.

    That said, the notion of life under any of these circumstances is so speculative that perhaps strange things existed in the really, really early Universe, in the weird sea of unified forces and unknown particles. I don’t know. It’s just a GUT feeling. (Groan.)

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