Kind: captions
Language: en
the following is a conversation with
Lisa Randal a theoretical physicist and
cosmologist at Harvard her work involves
improving our understanding of particle
physics super symmetry biogenesis
cosmological inflation and dark matter
this is Al Lex Freedman podcast to
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in the description and now dear friends
here's Lisa
randelle one of the things you work on
and right about is dark matter we can't
see it but there there's a lot of it in
the
universe uh you also end one of your
books with a Beetles song quote got to
be good-looking cuz he's so hard to
see what is dark matter how should we
think about it given that we can't see
it how should we visualize it in our
Mind's Eye I think one of the really
important things that physics teaches
you is just our limitations but also our
abilities so the fact that we can deduce
the existence of something that we don't
directly see is really attribute to
people that we can do that but it's also
something that tells you you can't
overly rely on your direct senses if you
just relied on just what you see
directly you would miss so much of
what's happening in the world and we can
generalize this but we're just for now
to focus on dark matter it's something
we know is there and it's not just one
way we know it's there in my book dark
matter and the dinosaurs I talk about
the many different ways you know this
eight or nine that we we deduce not just
the existence of dark matter but how
much how much is there and they all
agree now how do we know it's there
because of its
gravitational force and individually a
particle doesn't have such a big
gravitational force in fact gravity is
an extremely weak force compared to
other forces we know about in nature but
there's a lot of Dark Matter out there
it carries a lot of energy five times
the amount of energy as the matter we
know that's in atoms Etc so
you can ask how should we think about it
well it's just another form of matter
that doesn't interact with light or at
least as far as we know so it interacts
gravitationally it clumps it forms
galaxies but it doesn't interact with
light which means we just don't see it
and most of our detection before
gravitational wave detectors we only saw
things because of their interactions
with light in some sense so in theory it
it behaves just like any other matter
just it just doesn't interact with light
so when we say it interacts just like
any other form of matter we have to be
careful um because gravitationally it
interacts like other forms of matter but
it doesn't experience electromagnetism
which is why it has a different
distribution so in our galaxy it's
roughly
spherical unless it has its own
interactions that's another story but we
we know that it's roughly spherical um
whereas ordinary matter can radiate and
clumps into a dis and that's why we see
the Milky Way desk so on large scales in
some sense yes all the matter is similar
in some sense in fact dark matter is in
some sense more important because it can
collapse more readily than ordinary
matter because ordinary
matter has has radiative forces which
makes it hard to collapse on small
scales so actually it's dark matter that
sort of drives um Galaxy formation and
then ordinary matter kind of comes along
with it um and there's also just more of
it and because there's more of it it can
start collapsing sooner that is to say
the energy density in Dark Matter
dominates over radiation earlier than
you would if you just had ordinary
matter so it's part of the story of the
origin of a Galaxy part of the story of
the end of the Galaxy and part of the
story of all the various interactions
through exactly I mean in my book I make
kind of sort of jokes about you know
it's like when we think about a building
we think about the architect we think
about you know the high level but we
forget about all the workers that did
all the grunt work and in fact Dark
Matter was really important in the
formation of our universe and we forget
that sometimes that's a a metaphor on
top of a metaphor
okay the the the unheard voices that do
the actual work okay exactly no but it
is a metaphor but it also captures
something because the fact is we don't
directly see it so we forget it it's
there or we don't understand it's there
or we think it's not the fact that we
don't see it makes it no less legitimate
it just means that we have challenges in
order to find out exactly what it is
yeah but the things we cannot see that
nevertheless have uh gravitational
interaction with the things we can't see
is at the uh
Layman level is just mind-blowing you
know it is and it isn't because I think
what it's teaching us is that we're
human the universe is what it is and
we're trying to interact with that
universe and discover what it is we've
discovered amazing things in fact I
would say it's more surprising that the
mount the matter that we know about is
constitutes as big a fraction of the
universe as it does I mean we're limited
we're human and the fact that we see 5%
of the energy density of the Universe um
you know about one six of the energy
density in matter that's kind of
remarkable I mean why should that be
there could be anything out anything
could be out there yet the universe that
we see is the significant fraction yeah
but a lot of our intuition I think
operates using visualizations in the
mind that's absolutely true and it's
certainly writing books I realized also
how many of our words are based on how
we see the world um and that's true and
that's actually one of the Fantastic
things about physics is that it teaches
you how to go beyond your immediate
intuition to develop intuitions that
apply at different distances different
scales different ways of thinking about
things yeah how do you anthropomorphize
dark matter how do I just did I think I
made it the grun work workers oh yeah
that's good yeah you did that's why he
get paid the big bucks with a and write
the great books okay so um you also
write in that book
about uh dark matter matter having to do
something with the extinction events the
extinction of the
dinosaurs um which is kind of a
fascinating presentation of how
everything is connected so I guess the
dist disturbances
from the dark matter they create
gravitational disturbances in the OR
Cloud at the edge of our solar system
and then that increases the rate of
asteroids hitting Earth so I want to be
really clear this was a speculative
Theory I love it though I mean and I
liked it too and um and we still don't
know for sure but we can what we liked
about it so let me take a step back so
we usually assume that dark matter is
what we being physicists that just one
thing it's just basically non
interacting in on aside from gravity or
very weakly interacting matter um but
again we have to get outside this
mindset of just humans and ask what else
could be there and so what we suggested
is that there's a fraction of dark
matter not all the dark matter but some
of the Dark Matter maybe it has
interactions of its own just the same
way in in our universe we have lots of
different types of matter we have nuclei
we have electrons we have mu we have
forces um we have lots of it's it's not
a simple model the standard model but
but it does have some basic ingredients
so maybe Dark Matter also has some
interesting um structure to it so maybe
there's some small fraction and the
interesting thing is that if some of the
Dark Matter does radiate and you know I
like to call it dark light because it's
light that we don't see but Dark Matter
would see it could radiate that and then
it could perhaps collapse into a disc
the same way ordinary matter collapsed
into the Milky Way disc so it's not all
the dark matter it's a fraction but it
could conceivably be a very thin disc of
Dark Matter thin dense disc of dark
matter and so then the question is do
these exist and people have done studies
now to think about whether they can find
them I mean it's an interesting Target
it's something you can measure by
measuring the positions and velocities
of stars you can find out what the
structure of the of the Milky Way is um
but the fun proposal was that the solar
system orbits around the Galaxy and as
it does so it goes a little bit up and
down kind of like horses on a Carousel
and the suggestion was every time it
goes through you have an enhanced
probability that you would dislodge
something from the edge of the solar
system and something called the or Cloud
so the idea was that at those times
you're more likely to have these
cataclysmic events such as the amazing
one that actually caused the last
Extinction that we know of for sure it
wasn't so amazing for the dinosaurs or
for two-thirds of the species on the
planet yeah but it gets amazing for
humans who wouldn't be what really is
amazing I mean I I do I mean I talk
about this in dark matter in the
dinosaurs I it's just an amazing
scientific story because it really is
one of the real stories that combine
together different fields of science
geologists at the time or you know
people thought that things happened
slowly and this would be a cataclysmic
event and also I have to say you know if
you if you think about it it sounds like
a story like a 5-year-old would make up
maybe the dinosaurs were killed by some
big rock that came and hit the Earth but
then there really was a scientific story
behind it and that's also why I like the
dark disc because there's a scientific
story behind it so as farfetched as it
might sound you can actually go and look
for the experimental consequences or the
observational consequences to test
whether it's true I wish you could know
like high resolution details of where
that asteroid came from like where in
the OR Cloud why it happened is it in
fact because of dark matter it's like
the full tracing back to the origin of
the universe CU it humans seem to be
somewhat special but just it seems like
so many fascinating events at all scales
at all scales of physics had to happen
for so I'm really really glad you
mentioned that because actually that was
one of the main points of my book dark
matter in the dinosaurs one of the
reasons I wrote it was because I really
think we are abusing the planet we're
changing the planet way too quickly and
just like anything else when you alter
things it's good to think about the
history of what it took to get here and
and as you point out it took many
operations on many different scales you
know we had to have the formation of of
structure the formation of galaxies the
formation of the solar system the
formation of our planet the formation of
humans I mean there's so many steps that
go into this and humans in some part
were the result of the fact that this
big object hit the earth made the
dinosaurs go extinct and mammals
developed I mean it is an incredible
story
and yes something else might come of it
but it won't be us if we mess with it
too much but it is an a grand scale
Earth is a pretty resilient
system uh C can you just clarify just
fascinating uh the shape of things so
the shape of the Milky Ways of the
observable stuff is mostly
flat and then you said Dark Matter tends
to be spherical but a subset of might be
a flat disc so you want to hear about
the shape of things yes yes please so
structure formed early on and now our
structure that we live in is so we know
about the Milky Way galaxy so the Milky
Way galaxy has the dis you can see in a
dry dark place that's where stars and
light is but you can also measure in
some ways the dark matter and we believe
that dark matter is more or less
spherically
distributed um and like we said there's
a lot of it not necessarily in the dis
but just because it's a sphere there's a
lot of it sitting there and the reason
it doesn't collapse as far as we know is
that it doesn't really it can't radiate
the same way so because it can radiate
ordinary matter collapses and it's
actually because of conservation of
angular momentum it be it stays a dis
and it doesn't just collapse to the
center so our suggestion was that maybe
there are some components of dark matter
that also radiate like I said that's far
from proven people have looked for a
disc they see some evidence of some
discs of certain densities but I see
these are all questions that are worth
asking basically if we can figure it out
from existing measurements why not try
Okay so there's not all Dark Matters
made the same this well that's a
possibility we actually don't know what
dark matter is in the first place we
don't know what most of it is we don't
know what a fraction is I mean it's hard
to measure why is it hard to measure for
exactly the reason you said earlier we
don't see it so we want to think of
possibilities for what it can be if
especially if those give rise to some of
observational consequences I mean it's
it's a tough game because it's not
something that's just there for the
taking you have to think about what it
could be and how you might find it and
the way you detect it is gravitational
effects on things we can see that would
be the way you detect the type of Dark
Matter I've been talking about people
have suggestions for other forms of dark
matter they could be particles called
axons they could be other types of
particles and then there are different
ways of detecting it I mean the most
popular candidate for Dark Matter
probably until pretty recently because
they haven't found it is something
called wimps weekly interacting mass of
particles um particles that have mass
about the same as the Hig boson Mass um
and it turns out then you would get
about the right density of dark matter
but then people really like that of
course because it is connected to the
standard model the particles that we
know about and if it's connected to that
we have a better chance of actually
seeing it fortunately or unfortunately
it's also a better chance that you can
rule it out because you can look for it
and so far no one has found it we're
still looking for it is that one of the
hopes of the large hyron collider that
was originally one of the hopes of the
large hyron collider I'd say at this
point it would be very unlikely given
what they've already accomplished um but
there are these um underground detectors
Xenon detectors that look for Dark
Matter coming in and they
they are going to try to achieve a much
stronger bound than exists today just uh
take that tangent Looking Back Now
what's the biggest to you
Insight uh to humanity that the LHC has
been able to provide it's interesting
it's both um a major victory um the Hig
bosone was proposed 50 years ago and it
was discovered the higs mechanism seemed
to be the only way to explain Elementary
particle masses and it was right so on
the one hand it was a major victory on
the other hand I've been in physics long
enough to know it was also a cautionary
Tale in some sense because um at the
time I started out in physics we had
some proposed something in the United
States called the superconducting super
collider a lot of physicists I'll say
particularly in Europe but I'd say a lot
of physicists were Sayang when that the
large hyron collider would have the
energy reach necessary to discover what
underlies the standard M we don't want
to just discover the we want to know
what the next step is and I think here
um people were more cautious about that
they wanted to have a more comprehensive
search that could get to higher energies
more events so that we could you know we
could really more definitively rule it
out but in that case many people thought
they knew what would be there it would
happen to be a theory called super
symmetry so a lot of physicists thought
it would be super symmetry I mean it's
one of the many factors I think that
went into the fact that the large hron
glider became the only machine in town
and um the super conducting super
collider would have just been a much if
it really had achieved what it was
supposed to would have been a much more
robust test of of the space so so I'd
say for Humanity it's both a tribute to
the ability of Discovery and the ability
of really believing in things so that
you have the confidence to go look for
them but it's also a cautionary tale
that you don't want to you know assume
things before they've been actually
found so you want to do things in you
know you you want to believe in your
theories but you also want to question
them at the same time in ways that
you're more likely to discover the truth
but it's also an illustration of grand
engineering efforts that Humanity can
take on and maybe a lesson that you
could go even
bigger um I I'm really glad you said
that though too because that that's
absolutely true I mean it's it really is
an impressive it's it's impressive in so
many ways it's impressive
technologically is impressive at
engineering level it's also impressive
that so many countries work together um
to to do this it wasn't just one country
and how it was it was also impressive in
that it was a long-term project that
people committed to and made it happen
so it is a demonstration that when
people set their minds to things and
they commit to it that they can do
something amazing but also in the United
States uh maybe a lesson that
bureaucracy can slow things down to
bureaucracy and and politics politics
and economics many many things can make
them faster and make them slower so
science is the way to make progress
politics is the way to slow that
progress down and here we are well I
don't want to overstate that because
without Politics the you know the L
wouldn't happen either so um but you
need broccoli
um but sometimes I do think I mean
you're not asking this question but
sometimes I do think when I you know
think about some of these conflicts you
you know sometimes it's just good to
have a project that people work on
together and there were some efforts to
do that with in science too to have
Palestinians and Israelis work together
project called Sesame um I think it's
not a bad idea when you can do that um
when you can get you
know sort of for forget the politics and
just focus on some particular project
sometimes that can work some kind of
forcing function some kind of deadline
that gets people to sit in room together
and you're working on a thing but as
part of that you realize the common
Humanity that you all have the same
concerns the same hopes the same fears
the same that you all human and that's
an accidental side effect of working
together on a thing I that's absolutely
true and it's one of the reasons CERN
was formed actually it was post World
War II and lot of European physicists
had actually left Europe and they wanted
to see Europeans work together and and
sort of rebuild and and it worked I mean
they they did and it's true and I often
think that that you know one of the
major problems is we just don't meet
enough people so that everyone think
seems like when they seem like the other
it's more easy to forget their Humanity
so I think it it is important to have
these
connections given the
complexity all cosmological scales
involved here that led to the extension
of the dinosaurs when you look out at
the future of Earth do you worry about
future Extinction events I I do think
that we might be in the middle of an
Extinction right now if you define it by
the number of species that are getting
killed off and it's subtle but you know
it's a complex system the way things
respond to events is sometimes things
evolve sometimes animals just move to
another place and the way we've
developed the Earth it's very hard for
species just to move somewhere else and
we're seeing that with people now too I
mean I know people people are worried
just about AI taking over and that's a
totally different story we just don't
think about the future very much we
think about what we're doing now and we
certainly don't think enough about all
the animals that we're destroying all
the things that are precursors to humans
that we sort of rely on it's interesting
to to think whether the the the things
that threaten us is the stuff we see
that's happening gradually or the stuff
we don't really see that's going to
happen all of a sudden I sometimes like
think about what is what should we be
more worried about cuz it seems like
like with the asteroids or nuclear war
it could be stuff that just happens one
day you know when I say one day meaning
over a span of a few days or a few
months but on a you know not on a scale
of decades and
centuries because we sometimes mostly
talk about stuff that's happening
gradually but we can be really
surprised it's actually really
interesting and that was actually one of
the reasons it took a while to determine
what it was that had caused the last
extinction because people did think at
the time many people thought that things
were more gradual and the idea of
Extinction was a very was actually a
novel concept at some point you know I
mean these aren't predictable events
necessarily they're only predictable on
a grand scale um but sometimes sometimes
they are and and I think people were
pretty aware that nuclear um weapons
were dangerous I'm not sure people are
as aware now as they were you know say
20 or 30 years ago and that certainly
worries me um I have to say I was not as
worried about AI as other people but now
I understand and it's not I mean it's
more that as soon as you create things
that we lose control over it's scary and
the other thing that we're learning from
the events today is that is that it
takes a few bad actors it takes everyone
to sort of make things work well well it
takes not that many things to make
things go wrong it's it's the issue with
disease you know we can find out what
causes a disease but to make things
better is not necessarily that simple
sometimes it is but for things to be
healthy a lot of things have to work for
things to go wrong only one thing has to
go wrong and so it's amazing that we do
it and the same is true for democracy
for democracy to work a lot of people
have to believe in it a few bad actors
can destroy things sometimes so a lot of
the things that we really rely on are
delicate equilibrium situ some of you
know and there is some robustness in the
systems we try to build in robustness
but a few extreme events can sometimes
alter things and um I think that's what
people are scared of today in many ways
they're scared of it for democracy
they're scared of it for peace they're
scared of it for AI I think they're not
as scared as they should be about
nuclear weapons to be honest um I think
that's a more serious danger Than People
realize um I think people are a little
bit more scared about pandemics than
they were before um but I still say
they're not super scared about it so
you're right there are these major
events that can happen and we are
setting things up so that they might
happen and we should be thinking about
them the question is who should be
thinking about them how should we be
thinking about them how do you make
things happen on a global scale because
that's really what we need it certainly
shouldn't be a source of division it
should be a source of grand
collaboration probably wouldn't that be
nice yeah I just wonder what it would be
like a to be a dinosaur it must have
been beautiful to like look at the
asteroid just enter the atmosphere until
like everything just man would I that
would be one of the things I would
travel back in time to you know that's
also one of the things that I think you
probably could do with virtual reality I
don't think you have to be there and get
extinct just experience it I think
there's something you know it's an event
you're just watching you're not doing
anything you're just looking at it so
maybe you could just recreate it I
actually heard that there a there's a
nuclear weapon explosion experience in
virtual reality that's good to remind
you about like what it would feel like I
have to say you know so I got I got an
award from the Museum of nuclear history
and technology in the southwest and I
went to visit the museum which turned
out to be mostly a museum of nuclear
weapons and the scary thing is that they
look really cool you know it's true that
you have that yes this is scary but you
also have this this is cool feeling and
I think we have to get around that
because you I kind of think that yes you
can be in that but I'm not sure that's
going to make people scared has it have
they actually asked afterwards are you
more or less scared yeah that's a good
uh it's a really good point I mean
that's a good summary of just Humanity
in general
we attracted to creating cool stuff even
though it's can be dangerous and
actually that was the really interesting
thing about visiting that museum
actually I it was very nice cuz I had a
tour from people who had been working
there in the cold war and actually one
or two people from the Manhattan Project
it was a very cool tour and you just
realize just how just the thing itself
gets you so excited I think that's
something that sometimes these movies
Miss just the thing itself you're not
thinking about the the overall
consequences and it was kind of like in
some ways it was like the early Silicon
Valley you know people were just
thinking like what if we did this what
if we did that and you know not keeping
track of like what the peripheral
consequences are and you definitely see
that happening with AI now I mean I
think that was the moral of the battle
that just happened that you know it's
just Full Speed Ahead which gives me a
really great transition to another quote
in your book so you you write about it
the experience of facing the sublime in
physics and you quote uh Ryan
AR quote for beauty is nothing but the
beginning of Terror which we are still
just able to endure and we're so OD
because it's serenely disdains to
annihilate us it's pretty intense it I
think applies to nuclear weapons but it
also I mean at a more mundane perhaps
level I think it applies you know it's
really interesting one of the things I
found when I wrote these books is you
know some people love certainty you know
scientists kind of many Revel in
uncertainty it's not that you want to be
uncertain you want to solve it but
you're at this Edge where it's really
frustrating because you don't really
want to not know the answer but of
course if you knew the answer that would
be it would be done so you're always at
this Edge where there's you're trying to
sort things out and there is something
scary you don't know what is you don't
know if there's going to be a solution
you don't know if you're going to find
it so it's not something that can
destroy the Earth it's just something
that you do on your individual level but
then of course there are much bigger
things like like the ones you're talking
about where they could actually be
dangerous the stuff I do I just want to
be clear I'm doing theoretical physics
not very dangerous um but sometimes
things end up having bigger consequences
than you think yeah
but dangerous in a very pragmatic sense
but isn't it still in part terrifying
when you think of a just the size of
things like the size of dark matter like
the the the power of this thing in terms
of
uh is is potential gravitational effects
just this Co cosmological objects of a
black hole at the center of our galaxy
so this might be where why I'm a
physicist or why I differ from other
people because I'm not such a big fan of
humanity in some ways some ways I am but
the idea that we were everything would
be really boring to me I love the idea
that there's so much more out there that
there's a bigger universe and there's
lots to discover and that we're not all
there is wouldn't it be disappointing if
we were all there is yeah and the the
full diversity of other stuff it's
pretty interesting you know we have no
idea how much there is you know we we
know what we what we can observe so far
so the idea that there's other stuff out
there that we yet have to figure out
it's exciting well let me ask you out
there
question okay so if you think of like
humans on Earth life on Earth as this
pocket of complexity that
emerged you know and there's a bunch of
conditions that came to be and there's
uh darwinian Evolution and however life
originated do you think it's possible
there's some pockets of complexity of
that sort inside dark matter we can't
see well so that's
possible um I chemistry and biology
evolving in different ways and that's
one of the reasons we suggest I mean
it's not the reason but it would be true
if there were the type of interactions
we suggest I mean it would need more
complex ones and we don't know um I will
say that the conditions that give rise
to life and complexity they're complex
they're unlikely um so it's not like
there's great odds that would happen but
there's no reason to know that it
doesn't happen it's worth investigating
are there other forces that exist in the
dark matter sector that's exactly so the
Dark Matter sector doesn't have all the
forces of the the standard model of
physics right as far as we know it
doesn't have
it might have it at some low level but
it could have its own forces just like
the dark matter might not experience our
light maybe it has its light that we
don't experience so there could be other
kinds of forces I mean there could be
other kinds of forces even within our
sector that are too weak for us to have
discovered so far or that exist at
different scales than we know about I
mean we detect what interacts strongly
enough with our detectors to detect so
it's worth asking and and that's one of
the reasons we build big colliders to
see are there other forces other
particles that exist say at higher
energies at shorter distance scales than
we've explored so far so it's not just
in the dark matter sector Even in our
sector there could be a whole bunch of
stuff we don't yet
know so maybe let's zoom out look at the
standard model of pH of particle physics
how does Dark Matter fit into first of
all what is it can you explain what the
standard model is so the standard model
of particle physics is basically tells
us about Nature's most basic elements
and their interactions and so it's the
substructure as far as we understand it
so if you look at atoms we know they
have nuclei and electrons nuclei have
protons and neutrons in them protons and
neutrons have particles called quirks
that are held together by something
called the strong force they interact
through the strong force Force the
strong nuclear force there something
called the weak nuclear force and
electromagnetism so basically all those
particles and their interactions
describe many many things we understand
that's the standard model we now know
about the higs boson which is associated
with how Elementary particles get their
Mass so that pce of the puzzle has also
been
completed we also know that there are
kind of a weird array of masses of
Elementary particles there's not just
the up and down but there are heavier
versions of the up and down cork charm
and strange top and bottom there's not
just the electron there's a muon and a
tow there are particles called neutrinos
which are under intense study now which
are partnered with the leptons through
the weak interactions so we really do
know these basic
elements and we know the forces we know
I mean when we're doing particle physics
experiments we can usually even ignore
gravity except in exceptional cases that
we can talk about so those are the basic
elements and their interactions Dark
Matter stands outside that it's not
interacting through those forces so when
we look at the world around us we don't
usually see the effects of dark matter
it's because there's so much of it that
we do and it doesn't have those forces
that we know about but the standard
model has worked spectacularly well it's
been tested to a high degree of
precision people are still testing it
and one of the things we do as
physicists is we actually want it to
break down at some level we're looking
for
the Precision measurement or the energy
or whatever it will take where those
where the standard model is no longer
working like not that it's not working
approximately but we're looking for the
deviations and those deviations are
critical because they can tell us what
underlies the standard model which is
what we really want to see next where
can you find the the places where the
standard model breaks down like uh what
are the what are the places you can see
those tiny little deviations so we don't
know yet but we know the kinds of things
you wouldn't want to look for so one
obvious place to look is at higher
energy um we're looking at the large
hron collider but we'd love to go beyond
that higher energies means shorter
distances and it means things that we
just couldn't produce before I mean eals
mc^2 so if you have a heavy particle and
you don't have enough energy to make it
you'll never see it so that's one place
the other place is precision
measurements if you you know the
standard model has been tested
exquisitly so if been if it's been
tested 1% you want to look at a tenth of
a percent MH and there are some
processes that we know shouldn't even
happen at all in the standard model or
happen at very suppressed level and
those are other things that we look for
so all of those things could indicate
there's something beyond what we know
about which of course would be very
exciting when you just step back and
look at the standard model the quirks
and all the different particles and
trinos
and isn't it wild how this like little
system came came to being creates is
underpin depends everything we see
absolutely and that's why we'd like to
understand it better we want to know is
it part of some bigger sector um why are
these particles why do they have the
masses they do yeah um why is the hibos
on so light compared to the mass it
could have had which we might have even
expected based on the principles of
special relativity in quantum mechanics
so that's a really big question why are
they what they are and and they
originate there's like some mechanism
that created the whole thing that's one
of the things we're trying to study why
why is it what it is I mean even just
like the mechanism that creates stuff
like the way a human being is Created
from a single cell it's like embryo
Genesis like the whole thing like bu you
build up this
thing all of it this whole thing comes
to be from just like a don't forget it
is interacting with the environment sure
okay right right right it's not it's
right it's important well that's a
really good question is how much of it
is the environment is it just just the
environment acting on a set of
constraints
and uh like how much of it is just the
information in the DNA or the
information how much is it in the
initial conditions of the universe or uh
versus the the some other thing acting
on it these are Big questions these are
Big questions in pretty much every field
um you know we for the universe we do
consider it you know it's everything
there is by definition but people now
think about it is it one of many
universes um and of course it's a
misnomer but could there be other places
where there are self-contained
gravitational systems that we don't even
interact with so but those are really
important questions and the only way
we're going to answer them is you know
we go back as far as we can we try to
think theoretically and we try to think
about observational consequences it's
all we can do one interesting way to
explore the standard models to look at
your uh fun nuanced disagreement with
with Carlo
relli when you talked about him writing
in his book electrons don't always exist
they exist when they interact they
materialize in a place when they collide
with something else and you wrote that
well I'll just read the whole thing cuz
it's it's kind of interesting stocks may
not achieve a precise value until they
are traded but that doesn't mean we
can't approximate their worth until they
change hands similarly electrons might
not have definite properties but they do
exist it's true that the electron
doesn't exist as a classical object with
definite position until the position is
measured but something was there which
physicists use a wave function to
describe it's a fascinating Nuance
disagreement so do electrons always
exist or not does it does a tree fall in
the forest if nobody's there to see it
so I like to think of the universe is
being out there whether or not I mean it
would be really weird if the only time
things came into existence was when I
saw them or I measured them there's a
lot of weird I mean I could believe that
the Middle East doesn't exist because
I'm not there now I mean that would be
kind of ridiculous I think we would all
agree on that so I think there's only so
much that we can attribute to our own
powers of seeing so and the whole system
doesn't come into being because I'm
measuring it and so what is weird and
this isn't even a disagreement about the
standard model this is agreement about
how you interpret quantum mechanics I
mean I would say that those wave
functions are real I mean one of the
things that forget that particle physics
does that Quantum field Theory says is
that electrons can be created and
destroyed it's it's not that every
electron has to be in the universe I
mean there can be I mean that's what
happens at collider is particles get
created and destroyed um but that
doesn't mean that if I electron in an
atom it's not there it's certainly there
and we know about it its charge is there
so physics is a kind of way to see the
world so what at the bottom what's the
bottom Turtle like what do you have a
sense that there's a bottom reality that
we're trying to approximate with physics
I think we always have in our head maybe
that we'd like to find that but I have
to I mean I might not seem so but I
think I'm kind of more humble than a lot
of physicists I'm not sure that we're
ever going to get to that bottom level
but I do think we're going to keep
penetrating different layers and get
further I just wonder how far away we
are you know we all wonder that um it's
not even like what's even the measure of
how far away we are I mean one way you
can measure it is just by our everyday
lives in terms of our everyday lives
we've measured everything in terms of
what underlies it there's a lot more to
see and so part of it has to do with how
far we think we can go I mean it might
be that the nature of reality changes so
much that even these terms are different
maybe we measure you know this the
notion of distance itself might break
down at some point but also to push back
on the we've measured everything maybe
there's stuff we haven't even considered
as measurable for example Consciousness
or did
there's there might be stuff just like
you said forces unseen undetected so
it's an interesting thing so one and
this is often a confusion that happens
so there's sort of the fundamental stuff
underlying it and then there's sort of
the higher levels what you know what
we'll call like an effective Theory at
some level you know so we're not always
working I mean when I throw a ball I
don't tell you where every atom is I
tell you there's a ball and so there
might be different layers of reality
that are built on ter terms of the
matter that we know about in terms of
the stuff we know about that and when I
say we've measured everything I I say
that with a grain of salt I mean I
measure everything St so so there's lots
of phenomena that we don't understand
that we but often there are complex
phenomena that will be given in terms of
the fundamental ingredients that we know
about but that is an interesting
question because yes there's phenomena
that are at the higher level of
abstractions that emerge but maybe like
with consciousness there is far out
people that you know think that
Consciousness is um panus right that
it's there's going to be almost like a
fundamental force of physics that's
Consciousness that prates all matter
right usually when you have a crazy
sorry okay when you have a far out
theory yes the thing you do is you test
all the possibilities within the
constructs that exist yeah so you don't
just jump to the most far out
possibility I mean you can do that but
then to see if it's true you either have
to find evidence of it or you have to
show that it's not possible without
that uh and we're very far from that I
think one of the criticisms of your
theory on the dinosaurs was that it
requires if I remember correctly for
dark matter to be weirder than it
already is and then I think you had a
clever response to that can you can you
remind I'm not sure I remember what I
said then but I mean we have no idea how
weird dark batter is I mean it's based
on everyone thinking they know what dark
matter is I mean so weirder than it
already is I mean it's not already
anything thing we don't know what it is
so there's no normalization
here so dark matter do we know that if
Dark Matter varies in density it
certainly does in the universe just like
I mean so for example there's more dark
matter in galaxies than there is between
galaxies so it it it clumps I mean it's
so it's it's matter so it's distributed
like matter it is matter it does Clump
but the the uh the full details of how
it clumps and the complexity of the
clumping it's understood
pretty well people do simulations there
I mean where where people are are always
looking for things including us as
particle physics it's sort of at small
scales are the deviations on small
scales so that indicating other
interactions or other processes or
interactions with Barons that is to say
normal matter that we don't understand
but on large scales we have a pretty
good understanding of Dark Matter
distribution you were part of a recent
debate on quote cons science uncover
reality let me ask you this question
then uh what do you think is the limits
of
science I'm smart enough to know I have
no idea and also it's not even clear
what science means right because there's
the science that we do which is partical
physics we try to find fundamental
things and figure out what their effects
are there science like biology where you
know it's at a higher level the kind of
questions you ask are different the kind
of measurements are different um the
kind of science that's going to happen
in the sort of more numerical age I mean
or even AI or like what does it mean to
answer a question does it mean that we
can predict it does it mean we can
reproduce it so I think we're coming up
against sort of the definition of what
we mean by science as human beings so in
terms of the science that we can do I I
don't think we'll know it until we get
there um you know we're trying to solve
hard problems and you know we've made
progress I mean if you think of how much
science has advanced in the last century
or century and a half it's incredible I
mean you know we didn't even know the
universe was expanding at the beginning
of the 20th century we didn't know about
quantum mechanics at the beginning of
the century we didn't know about special
relativity that's a lot in a relatively
short time on depending on how you think
of time um so I think it would be
premature to say we know the limitations
and at various points throughout that
history we thought we solved everything
or declared or at least various people
various people exactly yeah declared
that we've solved everything uh so this
also a good place to maybe could you
describe the difference between top down
and bottom up approaches to theoretical
physics that you talked about in the
book so you could try to jump in and say
I have a theory that I think is so
perfect um that I can predict everything
from it or at least predict some salian
features from it that's top down that
would be top down bottom up is more like
you know like the questions we just ask
why your masses what they are we measure
things we want to put them together mhm
and usually a good approach is to
combine the two if you ask a very
specific question but combine it with
the methods of knowing that there could
be a fundamental Theory underlying it
sometimes you make progress I mean some
you know the community tends to get
segmented or fragmented into people who
do one or the other but there are
definitely times I mean some of my best
collaborations have with with people who
were more top down than I am so that we
come up with interesting ideas that we
wouldn't have thought of if either one
of us was working individually would you
say the truly big leaps happen top down
like Einstein Einstein was not a top
down person in the beginning he was um
special relativity was very much him
thinking about you know they were
thought experiments but he was very much
you know the original theory about
relativity is something like on the
nature of electromagnetism he was trying
to understand how Maxwell's laws could
make sense when they were you know seem
to have different symmetries than what
we had thought they were so he was very
much about bottom up person and in fact
he resisted top down for a long time
then when he tried to do the theory of
general relativity or the general theory
of relativity whichever you want to call
it um incorporating gravity into the
system where you need some feedback then
he was helped by a mathematician who had
developed some differential geometry and
helped him figure out how to write down
that and after that he thought top down
was the way to go but he actually didn't
make that much progress um but certainly
so I think it's you know naive to think
it was just one or the other in fact a
lot of people who made real progress
were rooted in actual measurements well
speaking of mathematicians uh what to
use a difference because you've had a
bit of foot in both uh between physics
and Mathematics in the way it helps us
understand the world well there's to be
frank there's a lot more overlap in
physics and math I think than has been I
mean well maybe not more but there's
certainly a lot but I think again the
kinds of questions you're asking are
usually different um mathematicians like
the structure at itself physicists are
trying to concentrate on to some extent
on the consequences for the world um but
there is a lot of overlap the string
theory is an example there's certain
theories where there's a a certain kind
of mathematical Beauty to it there's
also you know there's also some really
cool ideas that you get in particle
physics where you can describe what's
going on and connect it to other ideas
that's also really beautiful um you know
I think I think basically insights can
be beautiful um you know they might seem
simple but sometime and sometimes they
genuinely are and sometimes they're
built on a whole system that you have to
understand before I mean if you actually
saw Einstein's equations written out in
components you wouldn't think it's so
beautiful you write it in a compact way
it looks nice uh what do you think about
the successes and the failures of string
theory to what degree do you think it's
succeeded to what degree is it not
succeeded yet or has failed I think to
talk about any science in terms of
success and failure often misses the
point because there's not some absolute
thing and I think I do think that
strength theorists were a bit overly
ambitious not overly ambitious but a
little bit overly arrogant in the
beginning thinking they could solve many
problems that they weren't going to
solve that's not to say the methods and
um advances in strength Theory don't
exist and um but they certainly weren't
able to immediately solve all the
problems they thought they could solve
but it has given us tools it has given
us some insights um but it becomes
almost a sociological question of like
how much it should be one or the other I
do think that you can get caught up in
the problems themselves and and
sometimes you can get caught up in the
methods and just sort of do other
examples so the real physics insights
often come from people who are thinking
about physics as well as as math because
you mention AI is there
hope that AI might be able to help
find some interesting insights I mean
another question another way to ask this
question is how special are humans that
were able to discover novel insights
about the
world that's a great question um and it
depends what kind of insights and we're
going to find that out I mean you know
it's because it's hard to think about
something that doesn't quite exist yet I
mean I could just think about something
take a step back you know it's a little
bit like trying to understand three four
dimensions you go back to three
dimension you know so go to something
you can imagine so you can sort of say a
lot of the things in a very different
level about the internet you can say you
know has the internet helped do things
and that you know it definitely took on
a life of its own in some sense but it's
also something that we're able to tame
you know I know that I myself wouldn't
have been able to write books if the
internet didn't exist because I wouldn't
have had the time to go to the library
and look everything up and um it helped
me enormously and in some sense AI could
be that in a very nice World it could be
a tool that helps us go a step further
or than we would and a lot more
efficiently and it's already done that
to some extent or it could be like the
parts of the internet that we can't
control that are ruining politics or
whatever so and there's certainly a lot
of indications that can do that then
there are even bigger things that you
know people speculate about about AI
being able to do its own things but in
terms of actually figuring things out um
you know we're in the early
stages yeah there's several directions
here one is like on the theorem prover
side so wolf from alpha where everything
is much more precise and when you have
large language model type of
stuff one of the limitations of those is
it seems to com