Science fiction has come up with countless ideas for weird forms of life not based on
boring old DNA, or even on matter as we know it.
There’s Stanislaw Lem’s sentient ocean in Solaris, or the neutron star civilization
made of nuclear matter in Robert L Forward’s Dragon’s Egg.
Oh, and here’s an extra crazy one - life composed of cosmic strings and magnetic monopoles,
evolving in the hearts of stars.
Oh, wait a minute - that last one is an actual scientific proposal.
Scientists can sometimes be a little carbon-chauvanistic when we imagine other possible life forms.
Which is understandable - carbon-based chemistry enables the most complex structures that we
know of in this universe.
But could some other mechanism exist that could allow the incredible chemical diversity
needed to power life?
Well, not that we know of.
But that hasn’t stopped some scientists from looking.
One of the most bizarre proposals for life not as we know it doesn’t even use atoms.
It proposes that fundamental kinks and defects in the fabric of the universe - cosmic strings
beaded with magnetic monopoles - may evolve into complex structures, and even life, within
stars.
This idea was just published in Letters High Energy Physics Letters by physicists Luis
Anchordoqui and Eugene Chudnovsky, and today on Space Time Journal Club we’re going to
see how legit this idea actually is.
But first we need to go through some of the basics.
What exactly are cosmic strings and magnetic monopoles?
Both of these are fascinating subjects well overdue for their own episodes, so I’ll
keep in brief here.
Cosmic strings and magnetic monopoles are what we call topological defects.
The best way to describe topological defects is with some examples.
Imagine a fur rug in which you can brush the fur to lie in whatever direction you like.
If the fur is pushed to the left at one end and the right at the other end, then somewhere
in between there must be a transition between the two states.
There’s no way for that transition to be smooth, so you have this line.
You can move the line around by brushing the rug left or right, but you can’t get rid
of it without brushing the entire rug in one direction.
You could also get a topological defect if you tried to brush the rug into a spiral.
The transition between all points would be smooth, with the grain changing angle only
slightly.
But at the eye of the spiral you’d have a non-smooth transition.
And that’s the common feature of a topological defect - a sudden change in the “grain”
of some space that can’t easily be disentangled.
You can have exactly the same thing in magnetic materials, where the direction of the poles
of the little magnetic particles changes across the substance.
Topological defects are also found in crystals.
They form during the phase transition from liquid to solid.
That crystallization can begin in different places in the liquid.
And these lattice regions spread and join until you have a single crystal, but if those
initial regions didn’t all line up in the same way then you have defects where the regions
meet each other.
Quantum fields should also be able to develop topological defects.
These may have been formed soon after the Big Bang when massive phase transitions swept
across the universe.
These transitions were analogous to the phase transitions between states of matter - for
example, water freezing into ice.
But here, the quantum fields themselves changed state due to the rapidly dropping
temperature.
The technical term is “spontaneous symmetry breaking” - the same events that led to
the appearance of the separate forces from an initial unified force.
We’ll be discussing that more in the future, but for now the important thing is that these
phase transitions could have resulted in different types of topological defects, just like when
crystals form.
Let’s go through the possibilities: a 0-dimensional topological defect is a magnetic monopole
- like the north or south pole of a bar magnet that somehow lost its counterpart.
A 1-D topological defect is a cosmic string - an extremely thin filament.
2-D defects are called domain walls - they’re the boundaries between regions of the universe
with different properties - for example, different vacuum energies.
We’re interested in the strings and monopoles for now.
In certain theoretical scenarios, a monopole can be connected to the end of a string - or
two strings, actually.
Such monopoles are called beads.
And you can have a chain of beads - a necklace..
Anchordoqui and Chudnovsky imagine a type of nuclear life, in which these chains form
complex structures that can have a sort of chemistry - possibly even evolving into what
we might call life.
The goal of their study was to figure out under what circumstances this might happen.
The authors lay out three conditions for life that they investigate.
Let’s go through them.
Condition 1) The ability to encode information.
Fair enough - our DNA encodes all the instructions our cells need to build the molecular machinery
of life.
It’s hard to imagine a life form that didn’t have a way to store information.
Condition 2) The ability of information carriers to replicate faster than they disintegrate.
Again, straight forward - any given chain of molecules holds information, but it isn’t
much good if it falls apart before it reproduces itself.
And 3) a source of free energy.
This is something we know is essential for any life, including nuclear life.
Let’s go through each of these conditions in detail.
Can these string-monopole necklaces store information?
Well, in DNA there are 4 different base pairs and the ordering of those base pairs is a
language - it dictates the order of amino acids transcribed into proteins.
With simple magnetic monopoles, the only possible necklace is an alternating series of north
and south poles - or poles and anti-poles.
There’s only one possible configuration, and so there’s no way to store information that
way.
But if you add slightly more exotic physics you can form different types of monopole.
For example, there’s this scenario in this early universe symmetry-breaking stuff where,
after the monopoles form, they split in two - into so-called semi-poles.
There are four types of seminole - two for each of the original monopole type.
Four coding “letters” - sounds a bit like DNA.
Semipoles have an added bonus: whereas monopoles and anti-monopoles will always attract each
other and annihilate if they come together.
With semipoles, it’s possible to form string segments capped by NON-annihilating semipole
pairs that actually repel each other.
In this way, it may be possible to develop complex string structures, analogous to chemistry.
And maybe you can even build something like DNA.
OK, moving on to life condition number 2: can these information carriers replicate faster
than they can disintegrate?
These necklaces are probably not too stable - but that’s OK as long you can replicate them
faster than they fall apart.
And this is where stars come in.
Others have speculated that cosmic strings may get trapped inside stars in the process
of star formation.
Those stellar interiors might then provide the mechanism for necklaces to rapidly change
and even replicate.
Depending on the stellar type and region, the insides of stars can be very turbulent
places.
Flowing plasma and magnetic fields may stretch and break necklaces, which could reconfigure
them over and over until they find a state that is stable in the environment, combined
with developing the ability to replicate faster than they are torn apart.
As for how that replication happens - well the study doesn’t go into detail, except
to say that it might be catalyzed by interactions with atomic nuclei in the star.
Perhaps nuclei somehow help necklaces build a parallel chain of beads, that then peels
off as an identical necklace, similar to how RNA reproduces.
And finally, life condition number 3: do we have a source of free energy?
By free energy, I don’t mean energy that you don’t have to pay for.
I mean energy that is available for use, in a thermodynamic sense.
Energy can only be used to do work if there exists differences in the amount of energy
in different possible states.
If energy is concentrated in certain places we would call that an ordered, low entropy
situation.
Energy likes to spread itself out as evenly as possible, moving towards disordered, high-entropy
states.
It’s possible to use energy as it flows between different states in this process,
like putting a water wheel in a flowing river.
For example, life uses the energy flowing from the high energy-density of the Sun to
the lower energy density of the Earth.
In fact we talked about all of that in our episode on the physics of life.
We saw that these temporary increases in order, represented by life, actually speed up the process of
smoothing out all of the energy.
Little low-entropy blips like life ultimately accelerate the increase in entropy of the
universe.
OK, so inside a star there’s definitely free energy.
Energy flows from the fusion engine in the core to the surface.
It’s conceivable that a lifeform could harness that flow.
Well what would that look like?
Well, it would have to hasten the spreading out of energy.
Energy could be spread more evenly across the electromagnetic spectrum, which would
look like cooling - the star might appear cooler than it should.
Or perhaps the nuclear reactions in the core proceed faster, hastening the dissipation
of the star’s energy through space.
At any rate, the star should behave differently to what our stellar physics models predict.
There are a few stars in our modern surveys that don’t quite act as they should, however
there are many other possible explanations and it might be a little premature to claim
discovery of a new lifeform.
We’re going to have to get a much better understanding of cosmic strings and monopoles
- and, you know, actually verify that they exist in the first place - before we can decide
whether they can interact with the complexity needed to evolve into life.
And the authors of this paper are not pretending that any of this is likely - their point is
more to show that other possible bases for life might exist, beyond the familiar carbon
chemistry.
So are the stars filled with thriving ecosystems of critters built from fractured quantum fields?
Not likely, but not yet impossible.
And who knows what other bizarre life forms may be waiting to be discovered, in distant,
stranger parts of space time.
Hey Everyone. A few announcements before we get to comments
It's that time of year again where PBS DIgital Studios and Space Time want to hear from you
Every year we do an audience survey that helps us know what you like, what you don't
and want other kinds of content you want to see.
The Space Time audience has always done a great job making their voices heard on the survey,
so check out the link in the description and let us know what you think!
Well regardless going to keep making Space Time and keep making it better -
and a big part of what makes that possible is the support we get from some of you on Patreon.
Those few bucks a month really lets us plan much further ahead. For those of you who might be thinking of helping out -
added bonus is that we have this hoppin Patreon discord channel where space and physics geeks from
around the world ponder the nature of reality.
And while I'm talking Patreon, I have to give a gigantic shoutout to James Younger,
who supports us at the Big Bang level.
For those who don't know, James is a higher being composed of cosmic strings and monopoles,
visiting Earth from the core of the Sun to help spread cosmic wisdom.
By, like, supporting physics youtube shows and such. Thanks James, may your semipoles never annihilate.
Hey everyone. Comment responses today are on our episode on the pursuit of beauty in physics.
A very contentious topic these days - and so sparked some passionate debate in the comments.
I’m not going to go too deep into the back and forth right now… but will make my own
stance very clear.
Many of you mentioned Sabine Hossenfelder, whose book Lost in the Math was a big part
of highlighting this issue of excessive dependence on beauty.
She’s of course not the only one to highlight this.
But tor Sabine’s own words read the book and check out our Theories of Everything livestream
from a month ago, also with Lee Smolin and Eric Weinstein.
Look, I don’t want to get to much into where I agree or disagree with these guys here - but
I will say this - it’s useful to highlight when we think science is going astray, and
Sabine and others see a real problem with the excessive weight placed on the importance
of mathematical beauty, by some, perhaps by many, in the theory-of-everything game.
But I also have to add - do not throw the baby out with the bathwater.
Arguably the greatest advances of the 20th century were in part driven by the simple
intuitions of the likes of Einstein and Dirac that physical law should be mathematically
elegant.
So we should try to learn from the past successes of this pursuit of beauty in math, as well
as its failures.
The failures tell us that the narrow-minded pursuit of pure beauty at the expense of everything
else is doomed.
Why?
Because beauty is not a fundamental property of the universe - it is, by definition, a
subjective sense.
Which means it’s a proxy for other more fundamental qualities.
So let’s identify those qualities that our beauty-compass is pointing to.
We can allow our powerful and inexplicable intuition for beauty guide us subtly, while
at the same time remaining healthily skeptical even of our own intuitions.
Regarding the epicycles in Ptolemy’s theory, Ry706 says “adding epicycles upon epicycles
can represent any motion is literally true by Fourier theory”.
Ry706 - that’s exactly what epicycles are, thank you!
For those unfamiliar - Fourier’s theorem tells us that we can represent any continuous,
periodic function can be represented as a sum of sine waves of different frequencies.
But then motion in a circle can be represented by 2 separate sine waves for displacement
in the x-y directions.
So any arbitrarily complex orbital motion can be represented with enough sine wave pairs
in a fourier series - which can also look like a series of epicycles.
That’s why Ptolemy was able to make this Earth-centered model sort of work - with enough
epicycles he could have created a working model centered on the moon, or on the library
of Alexandria, or on his mom.
And this is why Occam’s razor is useful - it kindly requests that we please slice
off as many literal and metaphorical epicycles as possible.
Speaking of beauty, Joey Crowly asks everyone to please give some mad props to the animators
of this show, with the production quality being absolutely off the chain.
Uh, you’re not kidding Jaoey.
Animators Leo, Yago & Pedro and team are the ones who really bring this show alive.
I felt terrible asking for the fur rug animation from today’s episode - and honestly I don’t
know how they managed to do pull it off in a couple of days.
Leo and team - mad props from all of of us fans.
Shirsendu Chatterjee points out that it’s finally time to give the address to the time
traveler’s party that we hosted a year ago.
At the time no one showed up, but that only tells us that time travel is false if we actually
give the address as promised.
Done - here’s the time and address.
We wrote it in neutrinos, just to make sure only sufficiently advanced civilizations can
read it - don’t want any of those lame steampunk time travelers showing up.
See you at the party.
Which we didn’t.
I guess that scientifically proves that time travel is impossible, or that we’re scientifically
conclusively unpopular with the cool time traveler set.
Cue highschool flashbacks.