January 26, 2023 • 47 mins
Daniel and Jorge talk about how the Universe's preference for left-handed particles may have shaped our chemistry.
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Speaker 1 (00:08):
Okay, I realized I've never asked you this. Are you
left or right handed? Usually draw with my right hand,
so I'm sure you've tried to draw with your other hand.
What's that like? It's it's pretty tricky. Yeah, if you're
used to doing things with one hand, it's hard to switch. Well,
what about driving? Have you ever driven on the left
side of the road, you mean, on purpose or against
(00:29):
the law or following the laws of Well, you know
there are some places in the world where they drive
on the other side. I have driven in Australia and England. Yeah,
it's pretty tricky, but after a while you get used
to it. What would you say is better your left
side of the road driving or your left handed drawing. Well,
I've fortunately have not had an accident on either side
of the road, so the data says that I am
(00:52):
equally good. Well, I'm glad you're even handed. That sounds
like a left handed compliment, Daniel, I think that's right.
Hi am poor handed cartoonists and the creator of PhD comics. Hi,
(01:15):
I'm Daniel. I'm a particle physicist and a professor. And
you see Irvine and I have tried to do math
left handed. I mean you write out math with your
left hand. Is that what you mean? Yeah? I try
to write out math with my left hand or sometimes
upside down. Sometimes when I'm teaching math to my kids,
I have to write it so that they can see it,
which requires a little bit of awkward gymnastics. But if
(01:36):
you use your left hand and maybe it's it's it's normal.
If I use my left hand and my handwriting looks
as sloppy as theirs. I know people who would aspire
to be ambidexterous, so they purposely used the mouths even
though they're right handed. They use their mouse but their
left hand so that they're you know, are able to
do both. How would you give my right arm to
be ambidextrous. Well, if you give your right arm, then
(01:56):
you wouldn't be ambidexterous. Sounds like you're caught in a paradox.
Welcome to a podcast Daniel and Jorge Explain the Universe,
a production of I Heart Radio, in which we try
to tickle the right side of your brain and the
left side of your brain. We want to understand the
entire universe, the top half, the bottom half, the left side,
the right side, and everything in between even the backside,
(02:18):
the backside, the front side, the dark side, and the
light side. Every side of the universe deserves to be understood,
and we think it's possible. And on this podcast we
ask those big questions about the nature of reality, the
nature of life, why we are all here, what it
all means, how long we will be here, and whether
we're alone, and we try to explain all of them
to you. And today I want to especially explain things
(02:41):
to Walter Bloom, a long time listener of the pod
from Switzerland, whose girlfriend Victoria wants to wish him a
happy thirty eighth birthday. Happy birthday, Walter, Yeah, it is
a big universe to explain. It is a wide universe,
full of many sides to it, many different ways that
you can look at things, and also many different in
ways that things can be put together. There are almost
(03:03):
an infinite way for a matter to arrange itself. And
one of the joys of physics is figuring out how
the universe works, because then we get to ask why.
When we discover that we are put together out of
time of little particles, we get to wonder, like, why
is the universe arranged out of these time little particles.
Why does it have these patterns? What does that really mean?
The joy physics is really that it's setting us up
(03:23):
to ask philosophy questions. Oh, is that the main goal
of physics just to be a primer, like a trailer
to philosophy, just the opening act for philosophy. Example, what
you're saying businesses are just there to warm up the crowd.
In the end, I think the almost science really is
motivated by philosophy questions. You know, at the heart of
almost every science question we ask, there is a why question,
(03:45):
which is in the end fundamentally philosophical. Yeah, and we
ask these questions not just because it's interesting and fascinating
and we understand more about the universe. But sometimes these
questions and these issues have a big impact on our daily,
everyday lives, even maybe on life itself. Yeah, we notice
these patterns in the universe. The universe seems to organize
(04:05):
itself in this way and not some other way. We
noticed sometimes there are symmetries in the universe, like you
could rotate everything and the laws of physics wouldn't change.
But also sometimes we notice that there are not symmetries
in the universe, that the universe has a strong opinion
about how things should be done, and the opposite way
just does not happen. Time flows forwards and not backwards,
(04:26):
and these are the things that inspire our philosophical musings
to wonder what it would be like for universe or
time flowed backwards, or what it would be like for
universe in the mirror of our universe. Yeah, and so
our universe likes to put things together in a particular way,
and you can trace sometimes that to the very properties
of the smallest particles in the universe, the things that
(04:48):
everything is made out of, and some of these properties
can have a pretty big impact on what gets formed
in the universe and even whether we would be here
or not. It does seem sometimes like at the smallest
level of the universe, US follows really different rules, really
strange quantum rules that don't really affect our lives, Like
how a particle moves through space is totally different from
(05:08):
how a baseball flies through space. But as you say,
sometimes there is a connection. Sometimes we can even find
a portal from the timeliest particle to our everyday lives.
So to be on the podcast, we will be tackling
the question does particle spin affect life on Earth? Are
(05:29):
we trying to put a positive spin here on life
on Earth? I'm trying to put a positive spin on particles.
I'm like, look, particles are relevant. Give me money, is
what you're saying. Well, you know that's the philosophy that's
underlying all of it. And yes, we're trying to make
our science relevant. Do you share any of your funding
with philosophers? Philosophers really need funding? I mean, how much
does paper and pencil cost? Anyway? Isn't that aren't dose
(05:52):
the tools of your research as well? Um? Ten billion
dollar particle colliders. You can build those out of pencil
and paper. You could, You just haven't tried the paper
mache particle collider. Put that on the table next time
we're discussing the future of the field. Can you demonstrate
mathematically that you cannot build a particle collider with paper mache.
Let's show the spitball collider. Yeah, let's see what we
(06:13):
can learn my colliding spitballs at nearly the speed of light. Yeah,
it's possible, right, it is possible. I have to do
some pencil and paper calculations to see what kind of
experiments we could do and what we might learn about
the universe from a paper machee collider. Yeah, i'll fund
out here. Here's five bucks. But this is an interesting question.
We're trying to link life on Earth to something as
(06:35):
small and maybe and seemingly insignificant as the spin fundamental
particle of nature. That's a pretty big leap. It is
a pretty big leap, And you might think it sounds
a little bit desperate, like is Daniel just trying to
be irrelevant to life? But remember that I'm actually doing
this research mostly because I think it's irrelevant honestly, because
it doesn't affect everyday life on Earth, which means you
(06:57):
can't use it to build weapons. Wait, did you just
admit your research is irrelevant to all life on Earth.
It's irrelevant in the sense that it doesn't have immediate
practical applications the way that you admit your research has
no immediate practical applications. Oh, absolutely, yes, learning about particles
has no immediate practical applications. I can't tell you tomorrow
that it's going to improve technology or even next year.
(07:19):
It's basic research in the sense that we might discover
something crazy and new about the universe. Will down the road,
I'm sure will benefit society, but in terms of life
immediate impact and you know tomorrow's weapons systems, No, we
have no relevance. All right, Well, I guess possible deniabilities
is important for some people. But this is an interesting
question to wonder if maybe the spin of particles could
(07:41):
have affected how life on Earth evolved, or even if
life itself evolved at all on this planet. Yeah, it's
a fascinating hypothesis with a little bit of evidence to
back it up. Well, as usually, we were wondering how
many people have thought about this question. I had thought
about maybe the properties of particles having an impact on
life on Earth, so it's usual Daniel went out there
to ask people do you think particle spin can affect
(08:03):
life on Earth? So thank you very much to everybody
who participates in this segment of the podcast. We really
appreciate hearing your thoughts and I think everybody out there
enjoys it as well. If you'd like to share your
thoughts on the topic of the day for future episodes,
please don't be shy right to us. Two questions at
Daniel and Jorge dot com. It's what people have to say.
I betterly know what particle spin is, but I could
(08:27):
surely say that it does not affect life on other
planets from the Solar System. Well, everything is spinning. Particles
are spinning, the earthy spinning, the galaxy and spinning. Realms
are spinning. Everything is spinning. So yeah, the life is spinning.
I'm going to say yes, because it affects the way
(08:50):
matter is made up. But I really don't know what
would happen if particles spin were to be reversed. I
don't know for you would even recognize the effects of that.
It will be interpreted maybe a couple of ways outside
of like the necessity it's spen make physics work, I
would say probably not very much impact life. I don't think.
(09:10):
I don't think like DNA is interacting with particles spin.
All right, Some people said yes, some people said no.
There are strong opinions here. There are positive and negative spins.
On one hand, it does seem hard to imagine that
the behaviors of tiny little particles could affect something like
life on Earth. On the other hand, if you believe reductionism,
if you believe that everything in the universe comes out
(09:32):
of how tiny little bits are dancing around and tooing
and frowing that in principle, everything about life comes down
to how particles work. Well, yeah, I mean I guess
if particles, for example, didn't feel the electromagnetic force, I mean,
the whole universe would be different. Yeah, I'm sitting here
trying to imagine what a universe would be like without electromagnetism.
I mean, it would be a dark universe for sure, right,
(09:52):
there would be no light at all in that universe. Yeah.
Or I guess even m if the particles had a
different mass, it would also change the ole universe, right,
like planets would form differently, galaxies would form differently. Who knows,
And maybe life can or could have would have formed
here on Earth. And yeah, it's a deep mystery why
the parameters of the universe seem to be set up
(10:13):
to allow life. Although you know, that's just sort of
like life that we can imagine. It's possible that if
you tweaked all those parameters, you might have completely different chemistry.
But that might allow for different kinds of biology, different
kinds of life, maybe even different kinds of intelligence. So
while the universe does sort of seem fine tuned for us,
it might be that other fine tunings are good for
(10:34):
other kinds of beings. All right, Well, the question at
hand is does particle spin affect life on Earth? And
so I guess particle spin is something that is the
property of particles. Maybe we can get a little bit
into that first. Particle spin is a really fun and
super weird property of particles, and it's especially fascinating because
(10:54):
the universe seems to have a preference for one kind
of spin over another kind of spin. Fundamentally, we don't
really know what particle spin is. I mean, you might
imagine that it's like a little ball and it's spinning.
The problem is that particles are not little balls, and
they don't really have surfaces, so we don't think that
they are physically spinning. But they do have a property
(11:16):
which is very similar to the kind of things we
call spin, for like the Earth is spinning and the
galaxy is spinning. Particles have properties which have similar mathematical
behaviors to spin of like big objects, and so we
call it spin even though it's not like technically physically spinning, right,
because quantum particles are not like little balls, as you said,
(11:36):
they're like little dots basically, and so they have this
property called spin. And if it's not related to it
actually spinning, why did you call it spin? Or not
you specifically, but you know the physics physicism birth did it?
Why did they call it spin? They call it spin
because even if it isn't actually physically spinning, it is
a form of angular momentum. Right, things in the universe
(11:57):
can spin, and they can have momentum in the same
way that things can have normal momentum. Right, momentum is
just like if you push an object, it keeps going,
or if you don't push it, it doesn't go anywhere.
The same thing holds true for spin. If you spin something,
it will keep spinning, like out in space where there
isn't any air to slow it down. Or if you
don't push an object, it won't spin. Right, It's something
floating in space won't spin unless you push it. That's
(12:20):
angular momentum, and that's conserved in the universe. That's why
if you push something to make it spin, it'll just
keep spinning out there in space until something stops it.
But you can transfer that angular momentum to something else, right,
it can bump into something else and make that spin.
We call particles spin spin because it's a kind of
angular momentum. You can take anglar momentum and convert it
into particle spin and back. So when the universe does
(12:42):
its accounting to make sure that angular momentum is conserved,
particle spin is part of its balance book, you're allowed
to move some angle momentum into that category. So it
really is a kind of angular momentum, even if it's
a weird quantum kind. But you said that, like regular
objects in space and have zero angular momentum or a
little bit or a lot of angular momentum, can particles
(13:05):
have zero or a lot of angular momentum? And also
why not just call it angular momentum? Yes, particles can
have different amounts of spin. Of Photons, for example, can
have spin up or down or zero. Electrons can only
have spin one half or negative one half. They can't
have zero spin. They're different kind of particles. So matter
(13:26):
particles are all either spin up or spin down by
one half, whereas forest particles those can be up or
down or zero. Can the same particle have zero and
then I give it a spin and then it starts
spinning or is it just an inherent property of that
particle that's a really interesting philosophy question. Right, Essentially, you're
saying a photon moving through the universe with zero spin,
(13:47):
if you give it spin, is it's still the same photon. Well,
to give it spin, you have to impart angular momentum
on it, which means an interaction, and so philosophically it
is changed. Right, It's like interacts with some particle, and
you think of that as like being absorbed and re emitted.
So I think philosophically you can think of it it's
like a new particle, or it's at least a new
(14:07):
quantum state. But yes, photons can have zero spin, or
they can have spin one, or they're gonna have spin
minus one m. And the spin it's quantized as well,
Like you have a photon with like three point five spin, No,
you can't, And you can't have photons with like half
a spin or point seven to nine spin. It's absolutely quantized.
So photons have three possible states plus one, zero or
(14:30):
minus one, and electrons have two states plus a half
or minus a half. And that's true for all fer meon's.
All fermons are either plus a half or minus a half.
They have half integer spins. That's why we call them fermons.
They all observe the Firmi exclusion principle, which means they
can't be in the same quantum state as each other. Bosons,
which have integer spin, they can hang out in the
same state, So you can have like a million photons
(14:52):
all in the same state. Now, you said earlier that
spin is up or down, right, that's kind of the
possibility ane's of it. But in a in space there
is no up and there's no down. So what does
it mean for a spin to be up or down
for a particle. Well, in the same way that you
can pick any access to calculate ingle momentum, you can
pick any access to project the spin. So you have
(15:14):
a particle, you pick an access, you say, here's my axis.
I want to know if it's spin is up or
down along this axis, and you can pick any access
you like and call it up or down. Typically, what
we do is we choose the axis of the particle's motion,
and we ask is the particle spin in the direction
of its motion or in the opposite direction of its motion?
But isn't. Then then the problem the motion and not
(15:36):
the spin. Like if I throw a baseball face up
or if I toss a frisbee face up or face down,
it's not that it's a whole different frisbee. It's the
same frisbee. I just threw it upside down. Yeah. And
in the case of particles, you can measure their spin
along any direction, or you can measure it along their motion,
or you can measure it perpendicular to their motion or
in any direction, and you'll always get either plus a
half or minus a half or particles. Okay, So it's
(15:59):
just some sort of like an arbitrary label. You're saying, like,
particles have this thing called spin, and we're gonna there's
kind of two kinds of the spin. There's the upspin
and there's down spin exactly. And the universe seems to
have a preference for particles who spin is pointed away
from the direction of their emotion, like an electron is
flying through space in the positive ex direction. The universe
(16:22):
seems to have a preference for those particles to spin
the opposite direction of their motion, for their spin to
be sort of like back along the negative X axis.
If their motion is in the positive X axis, we
call those particles left handed. If their spin is the
opposite direction of their motion. I guess it's kind of
like a clock. Like a clock can move through space
(16:44):
where it's either the face of the clock is facing
where it's going, or the face of the clock is
facing away from where it's going, or facing back. And
so you're saying that particles tend to be the kind
where the clock face is facing back. Those kind of
particles where the clock is facing backwards with a spin
is the opposite direction of motion. We call them left
handed particles. In our universe, we have left and right
(17:05):
handed versions of most particles, but one of the forces,
the weak nuclear force, which is responsible for like beta decay,
it will only talk to left handed particles. It does
not interact at all with right handed particles. So that's
when we mean when we say the universe seems to
have a preference for left handed particles. The other forces, electromagnetism,
(17:25):
the strong force, they don't care. They're happy to talk
to right or left handed particles, but the weak force
only talks to left handed particles. So it's almost like
the universe um is not ambidexterous, like the universe seems
to prefer or at least favor, left handed particles. Over
right handed particles. Yeah, and it's a slight preference, right,
(17:46):
because remember, the weak force is a feeble force. It
is not a powerful force. Does not control the structure
of our galaxies, it does not control the structure of
your body. It does not control lightning. Right, It's not
a very powerful force. And so it's a subtle effect.
And this was actually overlooked for years and years and years.
Even well after the weak force was discovered, people hadn't
(18:07):
really checked to see if it was symmetric, if it
talked to both kinds of particles. There was this moment
in the middle of last century when people realized, wow,
nobody's ever actually checked this to see if the weak
force was symmetric. And every thought, of course, it's symmetric.
Everything in the universe is symmetric, strong forces, symmetric, electromagnetism
is symmetric. It would be bonkers if the weak force
(18:29):
was not symmetric. But nobody had checked, and so very
quickly a famous scientist at Columbia skipped or Christmas vacation
to do this experiment and discover the shocking result that
the weak force is not just a little bit anti symmetric,
it's completely antisymmetric. It only talks to left handed particles.
It was a huge shock wave that went through the
physics community about fifty years ago. Yeah, I think we
(18:51):
had a whole episode about this experiment that demonstrated the
universe has a little bit of a left handed preference,
and so this preference has pretty big imp cations and
how the universe works and maybe even how life on
Earth developed. So let's get into right and left handedness
of the universe and life on Earth. But first let's
take a quick break. All right, we're asking the question
(19:25):
does particle spin affect life on Earth? And so we
talked about what spin is. It's a property of particles.
Particles can spin up or down. They can be left
handed or right handed. And this handedness is something we
see all throughout, not just the universe, but nature itself. Right,
I mean in Chemis City they talk about hand in
this as well of molecules. Yeah, you can apply this
(19:46):
principle in general to anything. You can ask if something
is left handed or right handed, and basically you're asking
would it look the same in the mirror? Right, if
you flip something in the mirror, would you get something
the same? And You can literally do this experiment in
front of yourself with your hands. Like, take your left hand.
It's not the same as your right hand right. There's
(20:07):
a different orientation of the fingers relative to the thumb.
If you put your left hand in the mirror, then
it looks like your right hand. Right. The mirror flips
your left hand to a right handed sort of shape.
But if you just take your right hand, you can't
like turn around or twist it in any way to
make it look exactly like your left hand. They're different, right.
We call that chirality, the one is left handed and
(20:28):
one is right handed, that they're not the same, right.
I guess if you're doing the mirror experiment, you would
see that maybe some parts in your body are symmetric
and are are not handed right. Like if you take,
for example, your eyeball, if you put it in front
of the mirror, you can't tell which eyeball it is,
where your right one or your left one right, the
one eyeball looks the same in the mirror as in
(20:49):
as it does in you. Or for example, I think
your your nose right, Your nose is also a symmetric
You can't sort of tell which one is the mirror
one which is the real nose. But like your right hand,
you can't tell which one is, assuming a spherical eyeball.
I think that's true, and my nose actually isn't symmetric.
I could tell the difference in the mirror because it
leans one way instead of the other. That can be fixed. Right,
(21:11):
we are in Orange County. I mean basically, everybody's getting
some work done these days. In principle and idealized human nose,
you're right, is symmetric, and yeah, hands are not symmetric. Right,
the real life version of your left hand looks like
a right hand in the mirror. Right, And the same
can be said about molecules, right, Like, you can arrange
a molecule in a way that is symmetric, where it
looks the same in the mirror, or you can arrange
(21:32):
a molecule in a way that does not look the
same in the mirror. An example of a symmetric molecule
is like water. Right, water is H two. Oh, you
have two hydrogens with an oxygen in the middle. If
you flip it, like if you make the left side
the right side and vice versa, it looks the same right,
it's exactly the same in the mirror, but you can
build much more complicated molecules, and chemistry of life specifically
(21:54):
is filled with complex molecules built off of these carbon chains,
and those do have a chirality. They do not look
the same in the mirror. There are left handed versions
and right handed versions basically every kind of molecule. So
if you just say the chemical formula c H four
for example, that tells you what's in it. It doesn't
(22:14):
tell you which orientation is it is. It's the left
handed or the right handed version of that object. Right,
Like c H four you can take one carbon and
four hydrogen and put them in together in one way
or in a way that looks like it's mirror image.
That's what do you mean? Right? Actually, c H four
is an example of a molecular probably is symmetric. You
have the carbon and then the hydrogens are arranged around it.
(22:36):
So I think it does look symmetric in the mirror.
But as they get more complicated, you know, for example,
the meno acids and the building blocks of life, these
are much more complicated structures. They're not all the same
in the mirror. Yeah, Like if you take carbon a
bunch of carbon and a bunch of hydrogen and some
other atoms. There are two different ways you could maybe
put them together. You could put them together in one
way or in a way that looks like it's mirror image,
(22:57):
which is not the same. Molecular just looks the same
in the mirror, and it actually kind of affects how
it interacts with other molecules. Right, Like a right handed
molecules doesn't do the same things as a left handed molecule. Yeah, Interestingly,
you can't just mix them. You can't have a bunch
of left handed molecules and a bunch of right handed
molecules and assume that they will all act the same.
(23:18):
Because chemistry is like these little building blocks. He's like
tiny little machines made out of proteins. They have to
click together and just the right way to like activate
certain sites to cleave off bits of a molecule. It's
actually trying to shake somebody's hand but using the wrong
hand it just doesn't sort of fit together, or trying
to dance where both people are leading. In order for
the chemistry of life to happen, everything has to match.
(23:40):
Means you need like all the pieces to have the
right chirality, so you can't mix and match left and
right handed chemistry of life. That's why I fastpoint people
when I meet them these days. It's just too confusing.
But I was thinking, it's sort of like Tetris, right,
Like in Tetris, you have pieces, and like every piece
in Tetris is made out of four blocks, but depending
on how you put them there is symmetrical or not.
(24:00):
Like if you have a two white two block, that's
a metric and you can slide that in anywhere. But
if you have like an L shaped block, then you
gotta wait for the right left hand or the right
side L block to fit a certain spot in your
touchris pile. And for the chemistry of life to work,
it seems like you need to be either all one
chirality or all the opposite chirality. And that's exactly what
(24:20):
we see when you take organic molecules and you sort
of like distill them from living objects, from plants or whatever,
you see all one chirality. All of life on Earth
uses left handed amino acids and right handed sugars. There's
nothing alive on Earth that uses right handed amino acids
or left handed sugars that form of life just does
(24:41):
not exist, right, But it's it's like, it's possible to
make right handed amino acids, but all life on Earth
seems to use only left handed amino acids. And once
life got started and life starts to make amino acid,
it then only makes left kind, which is the kind
of uses. If you synthesize some organic molecular like to
make one of the amino acids chemically from basic building blocks,
(25:04):
you'll end up with both kinds, left handed and right handed.
But if you pull it out of life, if you
distill it from a living being, you'll only get one chirality, right,
and you're right. We think that life is possible with
the other orientation. We suspect that it is, though of
course we don't have any examples. We think the probably
universe is symmetric and that it would allow for life
(25:25):
to have both chiralities, but we don't actually know. Well,
that's interesting to think about, Like maybe there's a version
of humans out there, maybe the multiverse or maybe in
this universe that uses only right handed amino acids, and
maybe if we met them, I mean, we could shake hands,
but we couldn't. Maybe like have kids together, right, or
even eat their food, because our bodies cannot interact with
(25:47):
that kind of chemistry. I mean, like some of the
artificial sweeteners that are in our foods are really interesting
because they exploit the fact that, despite being a sugar
and they do interact with your tongue in a way
that you can haste them, our bodies can't actually take
them apart to use energy, so we can't metabolize them
even though we can taste them because they have the
(26:08):
wrong chirality. Interesting, Yeah, artificial sweet nurse you're saying, used
the wrong candidness of sugar molecules which activate our taste buds,
but they can't be processing our stomachs, yeah, because those
are different processes, right, Tasting something recognizing the sugar your
tongue doesn't actually break it down and extract the energy,
and so it's like, oh, yeah, that's sugar plus one
(26:30):
for you. But then when he gets into your stomach,
the little machines down there that take things apart and
actually extract the energy and turn it into a TP
they're like, I don't know what to do here. My
locks are not fitting into these keys. So it just passes, right,
through you. Mmm. Interesting, this is something we've known for
a while, right. This was discovered by Louis Pasteur himself
more than a hundred and fifty years ago. He synthesized
(26:51):
a bunch of chemicals and then he also distilled them
from life, and he noticed this difference. He noticed that
the ones that came from life had only one chirality,
and the ones that he synthesized himself had both kinds
of chirality. So it's been an open puzzle for more
than a hundred fifty years of why life has this thing.
They call it bio chirality. But back then, how do
(27:12):
we know that a molecule was right handed or left handed? Right?
We can like X ray it or have super electron microscopes.
The way he discovered it was that these chiralities interact
with light a little bit differently. The light can have
different polarizations, which is related to the spin of those photons,
and that interacts slightly differently with those photons. And so
that's how he detected that the chemicals that he pulled
(27:34):
out of life were different from the chemicals that he
synthesized in the laboratory. And he actually predicted before we
even knew about the weak force or parody violation. He
predicted that there must be some sort of cosmic particle
asymmetry which is generating this fundamental asymmetry in life. So
like a hundred years before we discovered parody violation, he
(27:55):
basically predicted it. Wait one, he was thinking, maybe the
reason of life and Earth is mostly left handed. One
type of molecule is something like something from space. He
was thinking that this asymmetry was revealing a deep asymmetry
in the universe itself. Right, there must be some sort
of cosmic origin to this. So pastor a road. This
(28:17):
is in eighteen forties Hero quote. If the foundations of
life are die symmetric, then because of die symmetric cosmic
forces operating at their origin. This, I think is one
of the links between life on the Earth and the cosmos.
That is the totality of forces in the universe. So
that's Pasteur writing in the eighteen hundreds, before we understood
(28:39):
life the quantum nature of these forces or particle spin
or parody violation at all, he had the sense that
maybe the handedness of life came somehow from the handedness
of the universe. Whoa feels like a little bit of
a stretch there for Li to make that connection. It
might be one of these things where people write a
lot and most of their predictions are wrong, but when
(29:02):
they do hit the jackpot, people later on dig them
out and like, hey, look how forward thinking they are,
you know, the way you can find almost anything you like.
In the writings of mister Damis, I wonder if it's
sort of like saying like, maybe in a way he
would saying I mean, I'm sure no, he was assignist,
but maybe in a way he's saying like, you know,
maybe God is left handed and that's why he made
a human, you know, humans in a particular handed or
(29:24):
like maybe God is right handed, that's why most humans
are right hand Yeah, that's another great example of asymmetry. Right,
why are humans mostly right handed and not left handed?
We know that it can work both ways, obviously, but
why are humans mostly right handed and not mostly left handed?
It seems like sort of an arbitrary choice, and it
makes you wonder, like where does that come from? Is
(29:44):
it just random or is there a fundamental reason at
the heart of the universe that's creating this asymmetry that's
sort of the philosophy question, right, you always want to
know the why, not just the how, right, right, And
we all know we're just here to set things up
for the greater discipline of philosophy. But I think, you know,
if I guess, if half of the humans on Earth
are right handed and half of them were left handed,
(30:05):
it would be pretty awkward all the time trying to
shake hands with people. So maybe the whole reason most
people right hand is just to you know, make things
more social. Yeah, I think that's beyond my pay grade.
All right, Well, that's a big question. Why does life
on Earth prefer one kind of handed molecules and not
the other? I guess one reason is that it could
(30:26):
have been random, right, Like it just you know, picked
the left handed molecules and went with that. Yeah, it
could be basically a coin flip billions of years ago.
It could have gone either direction. But once you pick
one side, it's like symmetry breaking. Then you just gotta
go with it. Like if a bunch of people are
seated at a table and you have like glasses placed
(30:48):
between the plates, is your glass on the left side
or the right side? As soon as one person picks
their glass on the right side, then everybody's going to
use the right handed glass. But they could have picked
the left one and everything would have worked just fine.
So we don't know if it was just like a
random event billions of years ago in the primordial soup
that led us to all have this one handedness, or
(31:09):
maybe there is a reason. Yeah, I wonder like if
there was some competition in the early life billions of
years ago, like maybe a bunch of particles started assembling
with the left handed way and a bunch of particles
started assembling in a right handed way, and for a while,
maybe there was life could potentially early on there could
have been life with both handedness. It's just that one
(31:30):
somehow beat out the other. Yeah, it could be, or
it could be that it's selected for either before life
starts or after. Right, it might be that the processes
that generate these organic molecules naturally prefer to generate them
in a right handed or left handed way, like out
there in space when you have these organic molecules in soups,
are there equal amounts of left and right handed molecules?
(31:53):
Or is there an asymmetry there before life even gets started?
And then you can also ask afterwards, if life gets
started equal leave often left and right handed, is there
some preference for is one more likely to survive? Is
there something about the universe which gives one of them
a boost? Right? I think you're asking, maybe God is
not ambidexterous. Maybe God this my preference for right or
(32:16):
left handed? And could we see that in the laws
of the universe. And so let's get into whether or
not there is a connection between the left handedness of
life and the right handedness of quantum particles. But first
let's take another quick break. All right, we are doing
(32:43):
some of the pre work here for philosophers or warming
the crowd up here with some interesting thinking about the
universe and life on Earth, asking the question can particles
spin or did particles spin affect life on Earth? And
so we've talked about how fundamental quantum particles have a spin,
they have an upper down spin. And we also talked
(33:05):
about how life on Earth has a preference for left
handed molecules over right handed amino acid molecules. And so
the question is are these two things related. Does the
spin of sparticles of fact how molecules form or do
somehow the laws of physics somehow prefer left handed amino acids.
Let's get into that connection. It is a really fun question.
(33:25):
And I was reading this very long and detailed paper
about the connections between particle spin and bio chirality and
actually start out with a bit of a rant, a
complaint about calling life left handed or right handed, because
there's all sorts of ways you can define it. So
they prefer to define the orientation of our chemistry as
live l i v E and the opposite orientation as
(33:46):
evil live backwards e v I L. So this whole
paper talks about normal life versus evil life. And this
is a physics paper or is this a blog post?
This is a science paper published in the Prestigious journal.
And somehow calling life evil or live is better than
calling it the left handed or right handed. I don't know.
(34:07):
It's a philosophy question. So this is all based kind
of on on a paper that tries to make connection
between quantum particle spin and the kind of the corality
or the handedness of life molecules. Is there a connection
danial between these two things. So there is a plausible
mechanism for connecting the preference of the weak force to
produce left handed particles and life selecting for this kind
(34:31):
of chirality. There's a plausible mechanism. It's very very thin,
it's a very very slight preference, and it's not something
we've proven, but it is possible, and it comes down
to particles from space. Right. Cosmic rays are these particles
that hit the Earth at very very high speeds and
they come from like the centers of other galaxies, or
they come from our Sun, and they're just normal particles, protons, electrons, positrons.
(34:57):
Sometimes they hit the top of the atmosphere and they
create big shower of particles. Because a particle hits the
atmosphere is sort of like a meteor hitting the atmosphere.
It heats up and slows down and spreads out its energy,
so you get a big shower of particles on the surface.
And this is something very normal. It's something we've been
experiencing as living beings on the surface of the Earth
for a very very long time. Cosmic rates hit the
(35:18):
atmosphere and create essentially radiation on the surface of the
Earth that interacts with us and interacts with our organic chemistry,
specifically our d n A. Right. We sort of can't
see it on our on our regular skies, but you
can sort of see it in the northern lights, right.
That's kind of what the northern lights are. Particles hitting
the atmosphere. Yeah, Particles hitting the atmosphere and in that
(35:39):
case getting shunted up to the poles by the magnetic fields.
One of the reason that we don't have more radiation
here on the surface of the Earth is our atmosphere.
The second reason is our magnetic field acts sort of
like a shield, but some of it does get through
and gets down to the surface and affects the way
life operates. You know. A crucial element of evolution is mutation. Right.
(35:59):
You don't want just to copy the genes of the parents.
You want to try something new, which requires either making
a mistake when you're transcribing the DNA from the parent
to the child, or having a mistake introduced from for example,
a cosmic ray. A mu on passing through your DNA,
for example, could alter the chemistry of it in the
same way that like radiation can give you cancer by
(36:21):
changing the fundamental operation of your cells, it can also
change your d NA. Yeah, and that's kind of an
essential ingredient in life and evolution, right, Like if you
didn't have mutations, then life would never evolve, It would
never change, like that's how it started. But also like,
you need mutations just to evolve life because the DNA
never changed. If it copied perfectly from one generation to
(36:43):
the other, you would just still have the same organism
you started with. You would never evolve or come up
with better versions of the species. Yeah, in order to
explore the space of all possible organisms effectively, right, you
need a population that has different abilities, and the best
way to do that is to introduce random mutation. That's
essentially what evolution does. So cosmic rays have played an
(37:05):
important part in our evolution. We think it's actually key.
Like if you could build a perfect shield so we
had no radiation on the surface of the Earth, then
the history of life on Earth would be very very different.
It might not have succeeded. Right, Well, you would still
have mutations, did you just wouldn't have them from radiation
coming from space. Right, And we don't really know what
would happen in that scenario, right, life would evolve very differently.
(37:27):
Changes the conditions of life, And so what we do
know is that the conditions we have here on Earth
are the ones that gave birth to us, right to
this kind of life, Right, I guess, I guess if
we had less of a shielding from radiations from space,
we would have had more radiation and maybe too many mutations, right,
in which case we wouldn't have evolved either. Yeah, it's
really interesting question is sort of like bio philosophy, like
(37:49):
what is the best rate of mutation? We just don't
know the answer to that. People theorize and run experiments.
But you know, we have a certain level of radiation
and we think that that's a key part of how
we evolved to be who we are. Right, So, then
how does left the right handedness come into it? Well,
it turns out that these cosmic rays that come from
space are not equally left or right handed. When we
(38:09):
talk about the particle spin, is what happens when a
particle hits the upper atmosphere is it creates the shower
of particles. Typically, these particles called pions, which don't live
very long. They tend to decay, and they decay into muans.
That decay is done by the weak force. The weak
forces the thing that breaks up the pions, It turns
it into a muon and also for example, a new trino,
(38:31):
and because the weak forces in charge of that moment,
it only makes left handed muans because that's all it
knows how to do. It doesn't know how to make
right handed muans. It ignores right handed muans. It pretends
they don't even exist. So, coming from space, were overwhelmed
with left handed muans, which means that the cosmic rays,
all of a sudden, are not symmetric. Right, so the
environment we've involved in is not symmetric because of the
(38:54):
weak force, and those left handed muans tend to interact
with our d NA slightly differently than right handed muans would,
meaning that most of the meals that come down on
Earth are left handed, not right handed exactly. Those muons
are left handed, and that creates a slight preference for
left handed amino acids. We think that left handed muons
(39:15):
have a slightly higher probability of ionizing left handed amino
acids than right handed amino acids. Wait, what, why why
is it that left handed muons interact mostly with left
handed amino acids. It's very subtle effect, but it's again
because of the weak force. The weak force has this
asymmetry and has very small effects on the chemistry of life.
(39:37):
It can, for example, change the electric and magnetic dipole
moments of some of these atoms inside these molecules, so
their shape is like slightly different if they're left handed
or right handed, which means that the muons passing through
them are like more or less likely to interact with
them because they spend like more or less time within
that electric or magnetic atomic fields. It's a very subtle
(39:59):
calculat Wait, are you saying that the left handed muons
showering the Earth, coming down on earth thrower atmosphere are
more likely to interact with a certain type of atom
or a certain type of electron that you can only
see on the left handed molecules. Yeah, that's right. Left
handed muans will interact with right handed or left handed
(40:20):
amino acids, but they are more likely to interact with
left handed amino acids than right handed just by a
little bit. It's not like a complete preference. Why because there,
like a left handed amino acid is different than the
right hand aminu acid, not because of any spin, it's
just how the particles atoms are arranged. So why would
the left handed muan, which is a tiny tiny particle
(40:40):
care about the giant structure of a molecule, because when
the muon is interacting with that atom, it's interacting not
just with the electromagnetic force, but also with the weak force,
because the mulan feels the weak force. And so there
is a difference between the left and right handed amino
acids because of the weak force affects the electric dipole
moment in the mag netic dipole moments of these atoms,
(41:03):
and so that affects how the left or right handed
particles will interact with them. Are you saying that like
a left handed amino acid is made up of different
atoms or different atoms with different spins than the right
handed amino acid. No, it's the same atoms, right, it's
just flipped to be left handed, and so the arrangement
is slightly different, and that gives a different pattern of
(41:23):
the electromagnetic fields. And this is a very small effect, right,
This is really a tiny effect. It's like second order.
This effect is like three parts in twenty thousand. Right,
most of the time these things will be treated exactly
the same, because most of the time is the electromagnetic
interaction that dominates, which is symmetric, but the weak force
sometimes it is a thing that mediates at interaction, and
(41:45):
so it tends to prefer the left handed version of
these amino acids. But again just a tiny fraction of
the time. Oh, it seems to be like a totally
different effect, like a left handed muon. It could have
been that the left handed muon prefers to interact with
the right handed molecule. Right, It's just that it just
so happens that the molecules that left handed meals like
(42:05):
to interact with a little bit more are the ones
we call the left handed amino acids. Yeah, that's right.
Or in this paper they call them the live choice.
And the paper they go through this very complicated calculation
and they come out with this prediction. They say, we
predict that there is a difference and it has to
do with the time the particle spends traversing the electromagnetic
(42:25):
field and how the weak force interacts with it, and
so they predict this very slight effect. Again, really really
tiny effect. But the idea is that maybe over millions
and billions of years, these cosmic rays introduced more ionization
effects in our kind of chirality and not in the
evil the alternative kind of bio chirality which give us
(42:48):
a boost, which let us explore these things faster, create
more mutations and sort of like adapt more rapidly to
changing conditions, And that maybe over billions of years, lad
life to have this chirality instead of the opposite hiality
because we get more mutations from left handed cosmic rays.
I see. I think it's all making sense now because
(43:08):
there are many different kinds of amino acids right like,
I think maybe what this writer is saying is that
there's lots of different kinds of amino acids, but the
ones that are used by life right now, he wants
to call those like A and the one. The versions
that are not used by us, he wants to call
those B and so he wants he's trying to say,
(43:29):
or she's trying to say that left handed muons, can
you can prove that maybe that left handed muans somehow
like to interact more with a kinds of amino acids
than be kind of amino acids. They're saying that he's
saying left and right for the muons and left and
right for the molecules is confusing. Let's just call them
molecules A or B, A being the ones that life
(43:50):
prefers seems to have preferred here on Earth. And then
let's take the left and right hand for the Muans,
where in the article they call A live and be evil.
But yeah, we can go with A versus B. Yeah,
it sounds a little more benign. I mean, if we
do meet like humans from another place and they have
the other handedness of their biochyrality, you're not gonna let
me call them evil humans? No, because how do you
(44:11):
know you're not the evil one? Maybe left handed humans
are better than right hand humans. I think I've just
realized we are the badis, aren't we? That's right? The
enemy is us. We've met the enemy and it is us, Yes, exactly.
So that's the idea. And nobody knows if this effect
is big enough to actually have an impact on life
at all. There's a lot of dot dot dots here.
(44:34):
It's like almost the same as pasteurs saying like maybe
somehow the universe prefers one kind of chirality. This is
the way that the universe does seem to prefer one
side of a symmetric pair, and you can draw some
dots between that and how it might have influenced life.
It's not conclusive to say that this is definitely why
life has this reality, but maybe the the idea here
(44:56):
is that the kinds of I mean, assets that flourished
here on Earth flourished because they're more likely to be
affected by left handed new muans, which is what the
universe prefers to make. And so it's in a way,
the universe kind of preferred to make the a kind
of amino acid or the one the kind that lead
to us, at least here on Earth. You know, in
our Solar system, Earth is the only planet that has
(45:18):
an atmosphere, which creates these muon showers that come all
the way down to the Earth's surface. Muans don't last
very long. They last form micro seconds, but because they're
going so fast, they actually do penetrate down to the
Earth because their clocks are time dilated due to special relativity,
so they tend to die off right around the Earth's surface.
If the Earth's atmosphere was thicker, for example, they would
(45:40):
make it all the way down to the ground. Right,
But that's just our solar system. This preference for left
handed muons is universal, right, It's a basically a lot
of the universe. And so if there are other planets
like ours with an atmosphere, and if maybe the very
existence of life depends on having that kind of atmosphere
in that planet, the condition may also prefer the A
(46:02):
kind of amino acid that we're made out of, because
the universe is prefers left handed muance and so over there,
also the universe will prefer the A kind of amino acid. Yeah,
that's the hypothesis right, not yet proven, but that's the
idea that maybe this is the reason that we have
the A kind of amino acid and not the B kind.
So you're saying we're less likely to meet evil twin
(46:25):
versions of us out there, were more likely to meet
people who are just like us. Yeah, maybe particle spin
will make for happy reunions with aliens. Yes, with non
awkward hand shaps. Maybe we should just fist bump the
aliens when they get here, just in case. Yeah, that
always works. I'm up for that that way, Well, you
don't have to have that awkward question when you meet
an alien. Hey are you right handed or left handed? Uh?
(46:47):
Fist bump? All right. Well, that's an interesting idea that
maybe the universe does have a preference for the kind
of life that we're made out of, and that we
were maybe destined to be the way we are right now,
and maybe Particles six is actually relevant to our life
and your life and all life in the universe. We
hope you enjoyed that. Thanks for joining us, see you
(47:07):
next time. Thanks for listening, and remember that Daniel and
Jorge explained. The Universe is a production of I Heart Radio.
For more podcast for my heart Radio, visit the i
heart Radio app, Apple Podcasts, or wherever you listen to
(47:28):
your favorite shows. Ye
Okay, I realized I've never asked you this. Are you
left or right handed? Usually draw with my right hand,
so I'm sure you've tried to draw with your other hand.
What's that like? It's it's pretty tricky. Yeah, if you're
used to doing things with one hand, it's hard to switch. Well,
what about driving? Have you ever driven on the left
side of the road, you mean, on purpose or against
(00:29):
the law or following the laws of Well, you know
there are some places in the world where they drive
on the other side. I have driven in Australia and England. Yeah,
it's pretty tricky, but after a while you get used
to it. What would you say is better your left
side of the road driving or your left handed drawing. Well,
I've fortunately have not had an accident on either side
of the road, so the data says that I am
(00:52):
equally good. Well, I'm glad you're even handed. That sounds
like a left handed compliment, Daniel, I think that's right.
Hi am poor handed cartoonists and the creator of PhD comics. Hi,
(01:15):
I'm Daniel. I'm a particle physicist and a professor. And
you see Irvine and I have tried to do math
left handed. I mean you write out math with your
left hand. Is that what you mean? Yeah? I try
to write out math with my left hand or sometimes
upside down. Sometimes when I'm teaching math to my kids,
I have to write it so that they can see it,
which requires a little bit of awkward gymnastics. But if
(01:36):
you use your left hand and maybe it's it's it's normal.
If I use my left hand and my handwriting looks
as sloppy as theirs. I know people who would aspire
to be ambidexterous, so they purposely used the mouths even
though they're right handed. They use their mouse but their
left hand so that they're you know, are able to
do both. How would you give my right arm to
be ambidextrous. Well, if you give your right arm, then
(01:56):
you wouldn't be ambidexterous. Sounds like you're caught in a paradox.
Welcome to a podcast Daniel and Jorge Explain the Universe,
a production of I Heart Radio, in which we try
to tickle the right side of your brain and the
left side of your brain. We want to understand the
entire universe, the top half, the bottom half, the left side,
the right side, and everything in between even the backside,
(02:18):
the backside, the front side, the dark side, and the
light side. Every side of the universe deserves to be understood,
and we think it's possible. And on this podcast we
ask those big questions about the nature of reality, the
nature of life, why we are all here, what it
all means, how long we will be here, and whether
we're alone, and we try to explain all of them
to you. And today I want to especially explain things
(02:41):
to Walter Bloom, a long time listener of the pod
from Switzerland, whose girlfriend Victoria wants to wish him a
happy thirty eighth birthday. Happy birthday, Walter, Yeah, it is
a big universe to explain. It is a wide universe,
full of many sides to it, many different ways that
you can look at things, and also many different in
ways that things can be put together. There are almost
(03:03):
an infinite way for a matter to arrange itself. And
one of the joys of physics is figuring out how
the universe works, because then we get to ask why.
When we discover that we are put together out of
time of little particles, we get to wonder, like, why
is the universe arranged out of these time little particles.
Why does it have these patterns? What does that really mean?
The joy physics is really that it's setting us up
(03:23):
to ask philosophy questions. Oh, is that the main goal
of physics just to be a primer, like a trailer
to philosophy, just the opening act for philosophy. Example, what
you're saying businesses are just there to warm up the crowd.
In the end, I think the almost science really is
motivated by philosophy questions. You know, at the heart of
almost every science question we ask, there is a why question,
(03:45):
which is in the end fundamentally philosophical. Yeah, and we
ask these questions not just because it's interesting and fascinating
and we understand more about the universe. But sometimes these
questions and these issues have a big impact on our daily,
everyday lives, even maybe on life itself. Yeah, we notice
these patterns in the universe. The universe seems to organize
(04:05):
itself in this way and not some other way. We
noticed sometimes there are symmetries in the universe, like you
could rotate everything and the laws of physics wouldn't change.
But also sometimes we notice that there are not symmetries
in the universe, that the universe has a strong opinion
about how things should be done, and the opposite way
just does not happen. Time flows forwards and not backwards,
(04:26):
and these are the things that inspire our philosophical musings
to wonder what it would be like for universe or
time flowed backwards, or what it would be like for
universe in the mirror of our universe. Yeah, and so
our universe likes to put things together in a particular way,
and you can trace sometimes that to the very properties
of the smallest particles in the universe, the things that
(04:48):
everything is made out of, and some of these properties
can have a pretty big impact on what gets formed
in the universe and even whether we would be here
or not. It does seem sometimes like at the smallest
level of the universe, US follows really different rules, really
strange quantum rules that don't really affect our lives, Like
how a particle moves through space is totally different from
(05:08):
how a baseball flies through space. But as you say,
sometimes there is a connection. Sometimes we can even find
a portal from the timeliest particle to our everyday lives.
So to be on the podcast, we will be tackling
the question does particle spin affect life on Earth? Are
(05:29):
we trying to put a positive spin here on life
on Earth? I'm trying to put a positive spin on particles.
I'm like, look, particles are relevant. Give me money, is
what you're saying. Well, you know that's the philosophy that's
underlying all of it. And yes, we're trying to make
our science relevant. Do you share any of your funding
with philosophers? Philosophers really need funding? I mean, how much
does paper and pencil cost? Anyway? Isn't that aren't dose
(05:52):
the tools of your research as well? Um? Ten billion
dollar particle colliders. You can build those out of pencil
and paper. You could, You just haven't tried the paper
mache particle collider. Put that on the table next time
we're discussing the future of the field. Can you demonstrate
mathematically that you cannot build a particle collider with paper mache.
Let's show the spitball collider. Yeah, let's see what we
(06:13):
can learn my colliding spitballs at nearly the speed of light. Yeah,
it's possible, right, it is possible. I have to do
some pencil and paper calculations to see what kind of
experiments we could do and what we might learn about
the universe from a paper machee collider. Yeah, i'll fund
out here. Here's five bucks. But this is an interesting question.
We're trying to link life on Earth to something as
(06:35):
small and maybe and seemingly insignificant as the spin fundamental
particle of nature. That's a pretty big leap. It is
a pretty big leap, And you might think it sounds
a little bit desperate, like is Daniel just trying to
be irrelevant to life? But remember that I'm actually doing
this research mostly because I think it's irrelevant honestly, because
it doesn't affect everyday life on Earth, which means you
(06:57):
can't use it to build weapons. Wait, did you just
admit your research is irrelevant to all life on Earth.
It's irrelevant in the sense that it doesn't have immediate
practical applications the way that you admit your research has
no immediate practical applications. Oh, absolutely, yes, learning about particles
has no immediate practical applications. I can't tell you tomorrow
that it's going to improve technology or even next year.
(07:19):
It's basic research in the sense that we might discover
something crazy and new about the universe. Will down the road,
I'm sure will benefit society, but in terms of life
immediate impact and you know tomorrow's weapons systems, No, we
have no relevance. All right, Well, I guess possible deniabilities
is important for some people. But this is an interesting
question to wonder if maybe the spin of particles could
(07:41):
have affected how life on Earth evolved, or even if
life itself evolved at all on this planet. Yeah, it's
a fascinating hypothesis with a little bit of evidence to
back it up. Well, as usually, we were wondering how
many people have thought about this question. I had thought
about maybe the properties of particles having an impact on
life on Earth, so it's usual Daniel went out there
to ask people do you think particle spin can affect
(08:03):
life on Earth? So thank you very much to everybody
who participates in this segment of the podcast. We really
appreciate hearing your thoughts and I think everybody out there
enjoys it as well. If you'd like to share your
thoughts on the topic of the day for future episodes,
please don't be shy right to us. Two questions at
Daniel and Jorge dot com. It's what people have to say.
I betterly know what particle spin is, but I could
(08:27):
surely say that it does not affect life on other
planets from the Solar System. Well, everything is spinning. Particles
are spinning, the earthy spinning, the galaxy and spinning. Realms
are spinning. Everything is spinning. So yeah, the life is spinning.
I'm going to say yes, because it affects the way
(08:50):
matter is made up. But I really don't know what
would happen if particles spin were to be reversed. I
don't know for you would even recognize the effects of that.
It will be interpreted maybe a couple of ways outside
of like the necessity it's spen make physics work, I
would say probably not very much impact life. I don't think.
(09:10):
I don't think like DNA is interacting with particles spin.
All right, Some people said yes, some people said no.
There are strong opinions here. There are positive and negative spins.
On one hand, it does seem hard to imagine that
the behaviors of tiny little particles could affect something like
life on Earth. On the other hand, if you believe reductionism,
if you believe that everything in the universe comes out
(09:32):
of how tiny little bits are dancing around and tooing
and frowing that in principle, everything about life comes down
to how particles work. Well, yeah, I mean I guess
if particles, for example, didn't feel the electromagnetic force, I mean,
the whole universe would be different. Yeah, I'm sitting here
trying to imagine what a universe would be like without electromagnetism.
I mean, it would be a dark universe for sure, right,
(09:52):
there would be no light at all in that universe. Yeah.
Or I guess even m if the particles had a
different mass, it would also change the ole universe, right,
like planets would form differently, galaxies would form differently. Who knows,
And maybe life can or could have would have formed
here on Earth. And yeah, it's a deep mystery why
the parameters of the universe seem to be set up
(10:13):
to allow life. Although you know, that's just sort of
like life that we can imagine. It's possible that if
you tweaked all those parameters, you might have completely different chemistry.
But that might allow for different kinds of biology, different
kinds of life, maybe even different kinds of intelligence. So
while the universe does sort of seem fine tuned for us,
it might be that other fine tunings are good for
(10:34):
other kinds of beings. All right, Well, the question at
hand is does particle spin affect life on Earth? And
so I guess particle spin is something that is the
property of particles. Maybe we can get a little bit
into that first. Particle spin is a really fun and
super weird property of particles, and it's especially fascinating because
(10:54):
the universe seems to have a preference for one kind
of spin over another kind of spin. Fundamentally, we don't
really know what particle spin is. I mean, you might
imagine that it's like a little ball and it's spinning.
The problem is that particles are not little balls, and
they don't really have surfaces, so we don't think that
they are physically spinning. But they do have a property
(11:16):
which is very similar to the kind of things we
call spin, for like the Earth is spinning and the
galaxy is spinning. Particles have properties which have similar mathematical
behaviors to spin of like big objects, and so we
call it spin even though it's not like technically physically spinning, right,
because quantum particles are not like little balls, as you said,
(11:36):
they're like little dots basically, and so they have this
property called spin. And if it's not related to it
actually spinning, why did you call it spin? Or not
you specifically, but you know the physics physicism birth did it?
Why did they call it spin? They call it spin
because even if it isn't actually physically spinning, it is
a form of angular momentum. Right, things in the universe
(11:57):
can spin, and they can have momentum in the same
way that things can have normal momentum. Right, momentum is
just like if you push an object, it keeps going,
or if you don't push it, it doesn't go anywhere.
The same thing holds true for spin. If you spin something,
it will keep spinning, like out in space where there
isn't any air to slow it down. Or if you
don't push an object, it won't spin. Right, It's something
floating in space won't spin unless you push it. That's
(12:20):
angular momentum, and that's conserved in the universe. That's why
if you push something to make it spin, it'll just
keep spinning out there in space until something stops it.
But you can transfer that angular momentum to something else, right,
it can bump into something else and make that spin.
We call particles spin spin because it's a kind of
angular momentum. You can take anglar momentum and convert it
into particle spin and back. So when the universe does
(12:42):
its accounting to make sure that angular momentum is conserved,
particle spin is part of its balance book, you're allowed
to move some angle momentum into that category. So it
really is a kind of angular momentum, even if it's
a weird quantum kind. But you said that, like regular
objects in space and have zero angular momentum or a
little bit or a lot of angular momentum, can particles
(13:05):
have zero or a lot of angular momentum? And also
why not just call it angular momentum? Yes, particles can
have different amounts of spin. Of Photons, for example, can
have spin up or down or zero. Electrons can only
have spin one half or negative one half. They can't
have zero spin. They're different kind of particles. So matter
(13:26):
particles are all either spin up or spin down by
one half, whereas forest particles those can be up or
down or zero. Can the same particle have zero and
then I give it a spin and then it starts
spinning or is it just an inherent property of that
particle that's a really interesting philosophy question. Right, Essentially, you're
saying a photon moving through the universe with zero spin,
(13:47):
if you give it spin, is it's still the same photon. Well,
to give it spin, you have to impart angular momentum
on it, which means an interaction, and so philosophically it
is changed. Right, It's like interacts with some particle, and
you think of that as like being absorbed and re emitted.
So I think philosophically you can think of it it's
like a new particle, or it's at least a new
(14:07):
quantum state. But yes, photons can have zero spin, or
they can have spin one, or they're gonna have spin
minus one m. And the spin it's quantized as well,
Like you have a photon with like three point five spin, No,
you can't, And you can't have photons with like half
a spin or point seven to nine spin. It's absolutely quantized.
So photons have three possible states plus one, zero or
(14:30):
minus one, and electrons have two states plus a half
or minus a half. And that's true for all fer meon's.
All fermons are either plus a half or minus a half.
They have half integer spins. That's why we call them fermons.
They all observe the Firmi exclusion principle, which means they
can't be in the same quantum state as each other. Bosons,
which have integer spin, they can hang out in the
same state, So you can have like a million photons
(14:52):
all in the same state. Now, you said earlier that
spin is up or down, right, that's kind of the
possibility ane's of it. But in a in space there
is no up and there's no down. So what does
it mean for a spin to be up or down
for a particle. Well, in the same way that you
can pick any access to calculate ingle momentum, you can
pick any access to project the spin. So you have
(15:14):
a particle, you pick an access, you say, here's my axis.
I want to know if it's spin is up or
down along this axis, and you can pick any access
you like and call it up or down. Typically, what
we do is we choose the axis of the particle's motion,
and we ask is the particle spin in the direction
of its motion or in the opposite direction of its motion?
But isn't. Then then the problem the motion and not
(15:36):
the spin. Like if I throw a baseball face up
or if I toss a frisbee face up or face down,
it's not that it's a whole different frisbee. It's the
same frisbee. I just threw it upside down. Yeah. And
in the case of particles, you can measure their spin
along any direction, or you can measure it along their motion,
or you can measure it perpendicular to their motion or
in any direction, and you'll always get either plus a
half or minus a half or particles. Okay, So it's
(15:59):
just some sort of like an arbitrary label. You're saying, like,
particles have this thing called spin, and we're gonna there's
kind of two kinds of the spin. There's the upspin
and there's down spin exactly. And the universe seems to
have a preference for particles who spin is pointed away
from the direction of their emotion, like an electron is
flying through space in the positive ex direction. The universe
(16:22):
seems to have a preference for those particles to spin
the opposite direction of their motion, for their spin to
be sort of like back along the negative X axis.
If their motion is in the positive X axis, we
call those particles left handed. If their spin is the
opposite direction of their motion. I guess it's kind of
like a clock. Like a clock can move through space
(16:44):
where it's either the face of the clock is facing
where it's going, or the face of the clock is
facing away from where it's going, or facing back. And
so you're saying that particles tend to be the kind
where the clock face is facing back. Those kind of
particles where the clock is facing backwards with a spin
is the opposite direction of motion. We call them left
handed particles. In our universe, we have left and right
(17:05):
handed versions of most particles, but one of the forces,
the weak nuclear force, which is responsible for like beta decay,
it will only talk to left handed particles. It does
not interact at all with right handed particles. So that's
when we mean when we say the universe seems to
have a preference for left handed particles. The other forces, electromagnetism,
(17:25):
the strong force, they don't care. They're happy to talk
to right or left handed particles, but the weak force
only talks to left handed particles. So it's almost like
the universe um is not ambidexterous, like the universe seems
to prefer or at least favor, left handed particles. Over
right handed particles. Yeah, and it's a slight preference, right,
(17:46):
because remember, the weak force is a feeble force. It
is not a powerful force. Does not control the structure
of our galaxies, it does not control the structure of
your body. It does not control lightning. Right, It's not
a very powerful force. And so it's a subtle effect.
And this was actually overlooked for years and years and years.
Even well after the weak force was discovered, people hadn't
(18:07):
really checked to see if it was symmetric, if it
talked to both kinds of particles. There was this moment
in the middle of last century when people realized, wow,
nobody's ever actually checked this to see if the weak
force was symmetric. And every thought, of course, it's symmetric.
Everything in the universe is symmetric, strong forces, symmetric, electromagnetism
is symmetric. It would be bonkers if the weak force
(18:29):
was not symmetric. But nobody had checked, and so very
quickly a famous scientist at Columbia skipped or Christmas vacation
to do this experiment and discover the shocking result that
the weak force is not just a little bit anti symmetric,
it's completely antisymmetric. It only talks to left handed particles.
It was a huge shock wave that went through the
physics community about fifty years ago. Yeah, I think we
(18:51):
had a whole episode about this experiment that demonstrated the
universe has a little bit of a left handed preference,
and so this preference has pretty big imp cations and
how the universe works and maybe even how life on
Earth developed. So let's get into right and left handedness
of the universe and life on Earth. But first let's
take a quick break. All right, we're asking the question
(19:25):
does particle spin affect life on Earth? And so we
talked about what spin is. It's a property of particles.
Particles can spin up or down. They can be left
handed or right handed. And this handedness is something we
see all throughout, not just the universe, but nature itself. Right,
I mean in Chemis City they talk about hand in
this as well of molecules. Yeah, you can apply this
(19:46):
principle in general to anything. You can ask if something
is left handed or right handed, and basically you're asking
would it look the same in the mirror? Right, if
you flip something in the mirror, would you get something
the same? And You can literally do this experiment in
front of yourself with your hands. Like, take your left hand.
It's not the same as your right hand right. There's
(20:07):
a different orientation of the fingers relative to the thumb.
If you put your left hand in the mirror, then
it looks like your right hand. Right. The mirror flips
your left hand to a right handed sort of shape.
But if you just take your right hand, you can't
like turn around or twist it in any way to
make it look exactly like your left hand. They're different, right.
We call that chirality, the one is left handed and
(20:28):
one is right handed, that they're not the same, right.
I guess if you're doing the mirror experiment, you would
see that maybe some parts in your body are symmetric
and are are not handed right. Like if you take,
for example, your eyeball, if you put it in front
of the mirror, you can't tell which eyeball it is,
where your right one or your left one right, the
one eyeball looks the same in the mirror as in
(20:49):
as it does in you. Or for example, I think
your your nose right, Your nose is also a symmetric
You can't sort of tell which one is the mirror
one which is the real nose. But like your right hand,
you can't tell which one is, assuming a spherical eyeball.
I think that's true, and my nose actually isn't symmetric.
I could tell the difference in the mirror because it
leans one way instead of the other. That can be fixed. Right,
(21:11):
we are in Orange County. I mean basically, everybody's getting
some work done these days. In principle and idealized human nose,
you're right, is symmetric, and yeah, hands are not symmetric. Right,
the real life version of your left hand looks like
a right hand in the mirror. Right, And the same
can be said about molecules, right, Like, you can arrange
a molecule in a way that is symmetric, where it
looks the same in the mirror, or you can arrange
(21:32):
a molecule in a way that does not look the
same in the mirror. An example of a symmetric molecule
is like water. Right, water is H two. Oh, you
have two hydrogens with an oxygen in the middle. If
you flip it, like if you make the left side
the right side and vice versa, it looks the same right,
it's exactly the same in the mirror, but you can
build much more complicated molecules, and chemistry of life specifically
(21:54):
is filled with complex molecules built off of these carbon chains,
and those do have a chirality. They do not look
the same in the mirror. There are left handed versions
and right handed versions basically every kind of molecule. So
if you just say the chemical formula c H four
for example, that tells you what's in it. It doesn't
(22:14):
tell you which orientation is it is. It's the left
handed or the right handed version of that object. Right,
Like c H four you can take one carbon and
four hydrogen and put them in together in one way
or in a way that looks like it's mirror image.
That's what do you mean? Right? Actually, c H four
is an example of a molecular probably is symmetric. You
have the carbon and then the hydrogens are arranged around it.
(22:36):
So I think it does look symmetric in the mirror.
But as they get more complicated, you know, for example,
the meno acids and the building blocks of life, these
are much more complicated structures. They're not all the same
in the mirror. Yeah, Like if you take carbon a
bunch of carbon and a bunch of hydrogen and some
other atoms. There are two different ways you could maybe
put them together. You could put them together in one
way or in a way that looks like it's mirror image,
(22:57):
which is not the same. Molecular just looks the same
in the mirror, and it actually kind of affects how
it interacts with other molecules. Right, Like a right handed
molecules doesn't do the same things as a left handed molecule. Yeah, Interestingly,
you can't just mix them. You can't have a bunch
of left handed molecules and a bunch of right handed
molecules and assume that they will all act the same.
(23:18):
Because chemistry is like these little building blocks. He's like
tiny little machines made out of proteins. They have to
click together and just the right way to like activate
certain sites to cleave off bits of a molecule. It's
actually trying to shake somebody's hand but using the wrong
hand it just doesn't sort of fit together, or trying
to dance where both people are leading. In order for
the chemistry of life to happen, everything has to match.
(23:40):
Means you need like all the pieces to have the
right chirality, so you can't mix and match left and
right handed chemistry of life. That's why I fastpoint people
when I meet them these days. It's just too confusing.
But I was thinking, it's sort of like Tetris, right,
Like in Tetris, you have pieces, and like every piece
in Tetris is made out of four blocks, but depending
on how you put them there is symmetrical or not.
(24:00):
Like if you have a two white two block, that's
a metric and you can slide that in anywhere. But
if you have like an L shaped block, then you
gotta wait for the right left hand or the right
side L block to fit a certain spot in your
touchris pile. And for the chemistry of life to work,
it seems like you need to be either all one
chirality or all the opposite chirality. And that's exactly what
(24:20):
we see when you take organic molecules and you sort
of like distill them from living objects, from plants or whatever,
you see all one chirality. All of life on Earth
uses left handed amino acids and right handed sugars. There's
nothing alive on Earth that uses right handed amino acids
or left handed sugars that form of life just does
(24:41):
not exist, right, But it's it's like, it's possible to
make right handed amino acids, but all life on Earth
seems to use only left handed amino acids. And once
life got started and life starts to make amino acid,
it then only makes left kind, which is the kind
of uses. If you synthesize some organic molecular like to
make one of the amino acids chemically from basic building blocks,
(25:04):
you'll end up with both kinds, left handed and right handed.
But if you pull it out of life, if you
distill it from a living being, you'll only get one chirality, right,
and you're right. We think that life is possible with
the other orientation. We suspect that it is, though of
course we don't have any examples. We think the probably
universe is symmetric and that it would allow for life
(25:25):
to have both chiralities, but we don't actually know. Well,
that's interesting to think about, Like maybe there's a version
of humans out there, maybe the multiverse or maybe in
this universe that uses only right handed amino acids, and
maybe if we met them, I mean, we could shake hands,
but we couldn't. Maybe like have kids together, right, or
even eat their food, because our bodies cannot interact with
(25:47):
that kind of chemistry. I mean, like some of the
artificial sweeteners that are in our foods are really interesting
because they exploit the fact that, despite being a sugar
and they do interact with your tongue in a way
that you can haste them, our bodies can't actually take
them apart to use energy, so we can't metabolize them
even though we can taste them because they have the
(26:08):
wrong chirality. Interesting, Yeah, artificial sweet nurse you're saying, used
the wrong candidness of sugar molecules which activate our taste buds,
but they can't be processing our stomachs, yeah, because those
are different processes, right, Tasting something recognizing the sugar your
tongue doesn't actually break it down and extract the energy,
and so it's like, oh, yeah, that's sugar plus one
(26:30):
for you. But then when he gets into your stomach,
the little machines down there that take things apart and
actually extract the energy and turn it into a TP
they're like, I don't know what to do here. My
locks are not fitting into these keys. So it just passes, right,
through you. Mmm. Interesting, this is something we've known for
a while, right. This was discovered by Louis Pasteur himself
more than a hundred and fifty years ago. He synthesized
(26:51):
a bunch of chemicals and then he also distilled them
from life, and he noticed this difference. He noticed that
the ones that came from life had only one chirality,
and the ones that he synthesized himself had both kinds
of chirality. So it's been an open puzzle for more
than a hundred fifty years of why life has this thing.
They call it bio chirality. But back then, how do
(27:12):
we know that a molecule was right handed or left handed? Right?
We can like X ray it or have super electron microscopes.
The way he discovered it was that these chiralities interact
with light a little bit differently. The light can have
different polarizations, which is related to the spin of those photons,
and that interacts slightly differently with those photons. And so
that's how he detected that the chemicals that he pulled
(27:34):
out of life were different from the chemicals that he
synthesized in the laboratory. And he actually predicted before we
even knew about the weak force or parody violation. He
predicted that there must be some sort of cosmic particle
asymmetry which is generating this fundamental asymmetry in life. So
like a hundred years before we discovered parody violation, he
(27:55):
basically predicted it. Wait one, he was thinking, maybe the
reason of life and Earth is mostly left handed. One
type of molecule is something like something from space. He
was thinking that this asymmetry was revealing a deep asymmetry
in the universe itself. Right, there must be some sort
of cosmic origin to this. So pastor a road. This
(28:17):
is in eighteen forties Hero quote. If the foundations of
life are die symmetric, then because of die symmetric cosmic
forces operating at their origin. This, I think is one
of the links between life on the Earth and the cosmos.
That is the totality of forces in the universe. So
that's Pasteur writing in the eighteen hundreds, before we understood
(28:39):
life the quantum nature of these forces or particle spin
or parody violation at all, he had the sense that
maybe the handedness of life came somehow from the handedness
of the universe. Whoa feels like a little bit of
a stretch there for Li to make that connection. It
might be one of these things where people write a
lot and most of their predictions are wrong, but when
(29:02):
they do hit the jackpot, people later on dig them
out and like, hey, look how forward thinking they are,
you know, the way you can find almost anything you like.
In the writings of mister Damis, I wonder if it's
sort of like saying like, maybe in a way he
would saying I mean, I'm sure no, he was assignist,
but maybe in a way he's saying like, you know,
maybe God is left handed and that's why he made
a human, you know, humans in a particular handed or
(29:24):
like maybe God is right handed, that's why most humans
are right hand Yeah, that's another great example of asymmetry. Right,
why are humans mostly right handed and not left handed?
We know that it can work both ways, obviously, but
why are humans mostly right handed and not mostly left handed?
It seems like sort of an arbitrary choice, and it
makes you wonder, like where does that come from? Is
(29:44):
it just random or is there a fundamental reason at
the heart of the universe that's creating this asymmetry that's
sort of the philosophy question, right, you always want to
know the why, not just the how, right, right, And
we all know we're just here to set things up
for the greater discipline of philosophy. But I think, you know,
if I guess, if half of the humans on Earth
are right handed and half of them were left handed,
(30:05):
it would be pretty awkward all the time trying to
shake hands with people. So maybe the whole reason most
people right hand is just to you know, make things
more social. Yeah, I think that's beyond my pay grade.
All right, Well, that's a big question. Why does life
on Earth prefer one kind of handed molecules and not
the other? I guess one reason is that it could
(30:26):
have been random, right, Like it just you know, picked
the left handed molecules and went with that. Yeah, it
could be basically a coin flip billions of years ago.
It could have gone either direction. But once you pick
one side, it's like symmetry breaking. Then you just gotta
go with it. Like if a bunch of people are
seated at a table and you have like glasses placed
(30:48):
between the plates, is your glass on the left side
or the right side? As soon as one person picks
their glass on the right side, then everybody's going to
use the right handed glass. But they could have picked
the left one and everything would have worked just fine.
So we don't know if it was just like a
random event billions of years ago in the primordial soup
that led us to all have this one handedness, or
(31:09):
maybe there is a reason. Yeah, I wonder like if
there was some competition in the early life billions of
years ago, like maybe a bunch of particles started assembling
with the left handed way and a bunch of particles
started assembling in a right handed way, and for a while,
maybe there was life could potentially early on there could
have been life with both handedness. It's just that one
(31:30):
somehow beat out the other. Yeah, it could be, or
it could be that it's selected for either before life
starts or after. Right, it might be that the processes
that generate these organic molecules naturally prefer to generate them
in a right handed or left handed way, like out
there in space when you have these organic molecules in soups,
are there equal amounts of left and right handed molecules?
(31:53):
Or is there an asymmetry there before life even gets started?
And then you can also ask afterwards, if life gets
started equal leave often left and right handed, is there
some preference for is one more likely to survive? Is
there something about the universe which gives one of them
a boost? Right? I think you're asking, maybe God is
not ambidexterous. Maybe God this my preference for right or
(32:16):
left handed? And could we see that in the laws
of the universe. And so let's get into whether or
not there is a connection between the left handedness of
life and the right handedness of quantum particles. But first
let's take another quick break. All right, we are doing
(32:43):
some of the pre work here for philosophers or warming
the crowd up here with some interesting thinking about the
universe and life on Earth, asking the question can particles
spin or did particles spin affect life on Earth? And
so we've talked about how fundamental quantum particles have a spin,
they have an upper down spin. And we also talked
(33:05):
about how life on Earth has a preference for left
handed molecules over right handed amino acid molecules. And so
the question is are these two things related. Does the
spin of sparticles of fact how molecules form or do
somehow the laws of physics somehow prefer left handed amino acids.
Let's get into that connection. It is a really fun question.
(33:25):
And I was reading this very long and detailed paper
about the connections between particle spin and bio chirality and
actually start out with a bit of a rant, a
complaint about calling life left handed or right handed, because
there's all sorts of ways you can define it. So
they prefer to define the orientation of our chemistry as
live l i v E and the opposite orientation as
(33:46):
evil live backwards e v I L. So this whole
paper talks about normal life versus evil life. And this
is a physics paper or is this a blog post?
This is a science paper published in the Prestigious journal.
And somehow calling life evil or live is better than
calling it the left handed or right handed. I don't know.
(34:07):
It's a philosophy question. So this is all based kind
of on on a paper that tries to make connection
between quantum particle spin and the kind of the corality
or the handedness of life molecules. Is there a connection
danial between these two things. So there is a plausible
mechanism for connecting the preference of the weak force to
produce left handed particles and life selecting for this kind
(34:31):
of chirality. There's a plausible mechanism. It's very very thin,
it's a very very slight preference, and it's not something
we've proven, but it is possible, and it comes down
to particles from space. Right. Cosmic rays are these particles
that hit the Earth at very very high speeds and
they come from like the centers of other galaxies, or
they come from our Sun, and they're just normal particles, protons, electrons, positrons.
(34:57):
Sometimes they hit the top of the atmosphere and they
create big shower of particles. Because a particle hits the
atmosphere is sort of like a meteor hitting the atmosphere.
It heats up and slows down and spreads out its energy,
so you get a big shower of particles on the surface.
And this is something very normal. It's something we've been
experiencing as living beings on the surface of the Earth
for a very very long time. Cosmic rates hit the
(35:18):
atmosphere and create essentially radiation on the surface of the
Earth that interacts with us and interacts with our organic chemistry,
specifically our d n A. Right. We sort of can't
see it on our on our regular skies, but you
can sort of see it in the northern lights, right.
That's kind of what the northern lights are. Particles hitting
the atmosphere. Yeah, Particles hitting the atmosphere and in that
(35:39):
case getting shunted up to the poles by the magnetic fields.
One of the reason that we don't have more radiation
here on the surface of the Earth is our atmosphere.
The second reason is our magnetic field acts sort of
like a shield, but some of it does get through
and gets down to the surface and affects the way
life operates. You know. A crucial element of evolution is mutation. Right.
(35:59):
You don't want just to copy the genes of the parents.
You want to try something new, which requires either making
a mistake when you're transcribing the DNA from the parent
to the child, or having a mistake introduced from for example,
a cosmic ray. A mu on passing through your DNA,
for example, could alter the chemistry of it in the
same way that like radiation can give you cancer by
(36:21):
changing the fundamental operation of your cells, it can also
change your d NA. Yeah, and that's kind of an
essential ingredient in life and evolution, right, Like if you
didn't have mutations, then life would never evolve, It would
never change, like that's how it started. But also like,
you need mutations just to evolve life because the DNA
never changed. If it copied perfectly from one generation to
(36:43):
the other, you would just still have the same organism
you started with. You would never evolve or come up
with better versions of the species. Yeah, in order to
explore the space of all possible organisms effectively, right, you
need a population that has different abilities, and the best
way to do that is to introduce random mutation. That's
essentially what evolution does. So cosmic rays have played an
(37:05):
important part in our evolution. We think it's actually key.
Like if you could build a perfect shield so we
had no radiation on the surface of the Earth, then
the history of life on Earth would be very very different.
It might not have succeeded. Right, Well, you would still
have mutations, did you just wouldn't have them from radiation
coming from space. Right, And we don't really know what
would happen in that scenario, right, life would evolve very differently.
(37:27):
Changes the conditions of life, And so what we do
know is that the conditions we have here on Earth
are the ones that gave birth to us, right to
this kind of life, Right, I guess, I guess if
we had less of a shielding from radiations from space,
we would have had more radiation and maybe too many mutations, right,
in which case we wouldn't have evolved either. Yeah, it's
really interesting question is sort of like bio philosophy, like
(37:49):
what is the best rate of mutation? We just don't
know the answer to that. People theorize and run experiments.
But you know, we have a certain level of radiation
and we think that that's a key part of how
we evolved to be who we are. Right, So, then
how does left the right handedness come into it? Well,
it turns out that these cosmic rays that come from
space are not equally left or right handed. When we
(38:09):
talk about the particle spin, is what happens when a
particle hits the upper atmosphere is it creates the shower
of particles. Typically, these particles called pions, which don't live
very long. They tend to decay, and they decay into muans.
That decay is done by the weak force. The weak
forces the thing that breaks up the pions, It turns
it into a muon and also for example, a new trino,
(38:31):
and because the weak forces in charge of that moment,
it only makes left handed muans because that's all it
knows how to do. It doesn't know how to make
right handed muans. It ignores right handed muans. It pretends
they don't even exist. So, coming from space, were overwhelmed
with left handed muans, which means that the cosmic rays,
all of a sudden, are not symmetric. Right, so the
environment we've involved in is not symmetric because of the
(38:54):
weak force, and those left handed muans tend to interact
with our d NA slightly differently than right handed muans would,
meaning that most of the meals that come down on
Earth are left handed, not right handed exactly. Those muons
are left handed, and that creates a slight preference for
left handed amino acids. We think that left handed muons
(39:15):
have a slightly higher probability of ionizing left handed amino
acids than right handed amino acids. Wait, what, why why
is it that left handed muons interact mostly with left
handed amino acids. It's very subtle effect, but it's again
because of the weak force. The weak force has this
asymmetry and has very small effects on the chemistry of life.
(39:37):
It can, for example, change the electric and magnetic dipole
moments of some of these atoms inside these molecules, so
their shape is like slightly different if they're left handed
or right handed, which means that the muons passing through
them are like more or less likely to interact with
them because they spend like more or less time within
that electric or magnetic atomic fields. It's a very subtle
(39:59):
calculat Wait, are you saying that the left handed muons
showering the Earth, coming down on earth thrower atmosphere are
more likely to interact with a certain type of atom
or a certain type of electron that you can only
see on the left handed molecules. Yeah, that's right. Left
handed muans will interact with right handed or left handed
(40:20):
amino acids, but they are more likely to interact with
left handed amino acids than right handed just by a
little bit. It's not like a complete preference. Why because there,
like a left handed amino acid is different than the
right hand aminu acid, not because of any spin, it's
just how the particles atoms are arranged. So why would
the left handed muan, which is a tiny tiny particle
(40:40):
care about the giant structure of a molecule, because when
the muon is interacting with that atom, it's interacting not
just with the electromagnetic force, but also with the weak force,
because the mulan feels the weak force. And so there
is a difference between the left and right handed amino
acids because of the weak force affects the electric dipole
moment in the mag netic dipole moments of these atoms,
(41:03):
and so that affects how the left or right handed
particles will interact with them. Are you saying that like
a left handed amino acid is made up of different
atoms or different atoms with different spins than the right
handed amino acid. No, it's the same atoms, right, it's
just flipped to be left handed, and so the arrangement
is slightly different, and that gives a different pattern of
(41:23):
the electromagnetic fields. And this is a very small effect, right,
This is really a tiny effect. It's like second order.
This effect is like three parts in twenty thousand. Right,
most of the time these things will be treated exactly
the same, because most of the time is the electromagnetic
interaction that dominates, which is symmetric, but the weak force
sometimes it is a thing that mediates at interaction, and
(41:45):
so it tends to prefer the left handed version of
these amino acids. But again just a tiny fraction of
the time. Oh, it seems to be like a totally
different effect, like a left handed muon. It could have
been that the left handed muon prefers to interact with
the right handed molecule. Right, It's just that it just
so happens that the molecules that left handed meals like
(42:05):
to interact with a little bit more are the ones
we call the left handed amino acids. Yeah, that's right.
Or in this paper they call them the live choice.
And the paper they go through this very complicated calculation
and they come out with this prediction. They say, we
predict that there is a difference and it has to
do with the time the particle spends traversing the electromagnetic
(42:25):
field and how the weak force interacts with it, and
so they predict this very slight effect. Again, really really
tiny effect. But the idea is that maybe over millions
and billions of years, these cosmic rays introduced more ionization
effects in our kind of chirality and not in the
evil the alternative kind of bio chirality which give us
(42:48):
a boost, which let us explore these things faster, create
more mutations and sort of like adapt more rapidly to
changing conditions, And that maybe over billions of years, lad
life to have this chirality instead of the opposite hiality
because we get more mutations from left handed cosmic rays.
I see. I think it's all making sense now because
(43:08):
there are many different kinds of amino acids right like,
I think maybe what this writer is saying is that
there's lots of different kinds of amino acids, but the
ones that are used by life right now, he wants
to call those like A and the one. The versions
that are not used by us, he wants to call
those B and so he wants he's trying to say,
(43:29):
or she's trying to say that left handed muons, can
you can prove that maybe that left handed muans somehow
like to interact more with a kinds of amino acids
than be kind of amino acids. They're saying that he's
saying left and right for the muons and left and
right for the molecules is confusing. Let's just call them
molecules A or B, A being the ones that life
(43:50):
prefers seems to have preferred here on Earth. And then
let's take the left and right hand for the Muans,
where in the article they call A live and be evil.
But yeah, we can go with A versus B. Yeah,
it sounds a little more benign. I mean, if we
do meet like humans from another place and they have
the other handedness of their biochyrality, you're not gonna let
me call them evil humans? No, because how do you
(44:11):
know you're not the evil one? Maybe left handed humans
are better than right hand humans. I think I've just
realized we are the badis, aren't we? That's right? The
enemy is us. We've met the enemy and it is us, Yes, exactly.
So that's the idea. And nobody knows if this effect
is big enough to actually have an impact on life
at all. There's a lot of dot dot dots here.
(44:34):
It's like almost the same as pasteurs saying like maybe
somehow the universe prefers one kind of chirality. This is
the way that the universe does seem to prefer one
side of a symmetric pair, and you can draw some
dots between that and how it might have influenced life.
It's not conclusive to say that this is definitely why
life has this reality, but maybe the the idea here
(44:56):
is that the kinds of I mean, assets that flourished
here on Earth flourished because they're more likely to be
affected by left handed new muans, which is what the
universe prefers to make. And so it's in a way,
the universe kind of preferred to make the a kind
of amino acid or the one the kind that lead
to us, at least here on Earth. You know, in
our Solar system, Earth is the only planet that has
(45:18):
an atmosphere, which creates these muon showers that come all
the way down to the Earth's surface. Muans don't last
very long. They last form micro seconds, but because they're
going so fast, they actually do penetrate down to the
Earth because their clocks are time dilated due to special relativity,
so they tend to die off right around the Earth's surface.
If the Earth's atmosphere was thicker, for example, they would
(45:40):
make it all the way down to the ground. Right,
But that's just our solar system. This preference for left
handed muons is universal, right, It's a basically a lot
of the universe. And so if there are other planets
like ours with an atmosphere, and if maybe the very
existence of life depends on having that kind of atmosphere
in that planet, the condition may also prefer the A
(46:02):
kind of amino acid that we're made out of, because
the universe is prefers left handed muance and so over there,
also the universe will prefer the A kind of amino acid. Yeah,
that's the hypothesis right, not yet proven, but that's the
idea that maybe this is the reason that we have
the A kind of amino acid and not the B kind.
So you're saying we're less likely to meet evil twin
(46:25):
versions of us out there, were more likely to meet
people who are just like us. Yeah, maybe particle spin
will make for happy reunions with aliens. Yes, with non
awkward hand shaps. Maybe we should just fist bump the
aliens when they get here, just in case. Yeah, that
always works. I'm up for that that way, Well, you
don't have to have that awkward question when you meet
an alien. Hey are you right handed or left handed? Uh?
(46:47):
Fist bump? All right. Well, that's an interesting idea that
maybe the universe does have a preference for the kind
of life that we're made out of, and that we
were maybe destined to be the way we are right now,
and maybe Particles six is actually relevant to our life
and your life and all life in the universe. We
hope you enjoyed that. Thanks for joining us, see you
(47:07):
next time. Thanks for listening, and remember that Daniel and
Jorge explained. The Universe is a production of I Heart Radio.
For more podcast for my heart Radio, visit the i
heart Radio app, Apple Podcasts, or wherever you listen to
(47:28):
your favorite shows. Ye
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