November 4, 2021 • 49 mins
Daniel talks to Carlo Rovelli about a fascinating alternative way of thinking about the nature of reality. And aliens.
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Speaker 1 (00:01):
Hey, it' Jorhan Daniel here, and we want to tell
you about our new book. It's called Frequently Asked Questions
about the Universe because you have questions about the universe,
and so we decided to write a book all about them.
We talk about your questions, we give some answers, we
make a bunch of silly jokes as usual, and we
tackle all kinds of questions, including what happens if I
fall into a black hole? Or is there another version
(00:22):
of you out there that's right? Like usual, we tackle
the deepest, darkest, biggest, craziest questions about this incredible cosmos.
If you want to support the podcast, please get the
book and get a copy not just for yourself, but
you know, for your nieces and nephews, cousins, friends, parents, dogs, hamsters,
and for the aliens. So get your copy of Frequently
Asked Questions about the Universe is available for pre order now,
(00:46):
coming out November two. You can find more details at
the book's website, Universe f a Q dot com. Thanks
for your support, and if you have a hamster that
can read, please let us know. We'd love to have
them on the podcast. We all know that quantum mechanics
(01:10):
can't be quite right. I'm not talking about the counter intuitive,
probabilistic aspects of it that it forced us to accept
that the world we live in is fundamentally weirder than
we have ever imagined. Probabilities and correlations and uncertainty is no.
Those bits are probably right, But there's a problem at
(01:30):
the heart of quantum mechanics, one that has baffled physicists
and philosophers for nearly a hundred years, and that may
take another hundred years to solve. But some recent ideas
maybe showing us a path forward, even if it's a
stranger path. Then we imagine, Hi, I'm Daniel. I'm a
(02:05):
particle physicist and a professor at u C Irvine, and
I'm still confused by quantum mechanics. Confused but not frustrated,
You might say, I'm deliciously confused. What could be more
delightful than grappling with the deep mysteries of the nature
of reality, seeing the truth written down in cold black
and white and mathematical equations, and struggling to gain an
(02:27):
intuition to incorporate those alien concepts into our human brains.
After all, that is the deepest goal of physics, and
that's the goal of our podcast. Daniel and Jorgey explain
the university production of My Heart Radio, in which we
tackled the biggest and hardest and nastiest and funnest of
questions of the universe, the ones that make your brains twist,
(02:50):
the ones that slip away from you just as you
thought you had figured them out, the ones that might
elude humanity for centuries or forever. We don't show away
from any questions on the podcast, but we seek to
approach them and explain our knowledge and our ignorance to you.
My friend and co host Jorge is on a break,
but I have a special treat for you. We are
(03:12):
very lucky to have as a guest one of my
favorite physicists, one of my favorite writers, and one of
my favorite writers about physics, truly a poet of science communication.
Today we'll be talking to Carlo Rovelli about some of
the problems at the heart of quantum mechanics and explaining
a lesser known but absolutely fascinating alternative version of quantum mechanics.
(03:35):
So today on the podcast, we'll be answering the question
what is relational quantum mechanics? So it's my great pleasure
today to introduce Professor Carlo Rovelli. He's a professor of
physics in Marseille, and he cut his teeth and made
his name for himself developing theories of quantum gravity, mostly
(03:56):
loop quantum gravity. If I understand correctly, he also became
a household name. Is the author of the book Seven
Brief Lessons on Physics, which sold more than a million
copies and was translated into forty one languages. I've read
it and enjoyed it immensely and heartily recommended to you. Today,
Professor Rivelli is here to talk to us about his
new book, Hell Go Land and a fascinating alternative take
on the measurement problem in quantum mechanics. Professor Velli, welcome
(04:19):
to the podcast, and thank you for joining us. Thank
you question that it's a pleasure in the honor of
being here, wonderful. Well. I always love talking about quantum
mechanics and puzzling over it with other people. I feel
like every time I talk about quantum mechanics with somebody else,
I think of a new question I've never thought of before,
or a new angle on it, or a new mystery
frankly like a new corner of my mind that I
(04:41):
haven't ever really examined, and I get confused, and so
it's always fun to figure things outside of on the fly.
So today we wanted to talk about your new book
and Hell Go Land, And the book essentially lays out
for lay audience this idea of relational quantum mechanics, sort
of a new interpretation on quantum mechanics. And the first
question for you I have is if you could describe
(05:01):
for us what is the problem that relational quantum mechanics solves, Like,
why do we need another quantum mechanics interpretation? What is it?
At the heart of relational quantum mechanics is trying to
do One of the difficulties the problem of quantum mechanics
is to say exactly what the problem is. So quass mechanics,
on the one hand, it's extraordinary successful, is used in
(05:25):
a lot of our technology, is used a lot of
our understanding of the world world. We explain with quantum
mechanics the basics of chemistry, basic apastrophysics, all sorts of stuff,
and it works. It works fantastically. On the other hand,
there is a persisting, mysterious aspect about this theory. It's
a theory that it's a it's sort of formulity differently
(05:48):
than previous basic physical theories. This difference puzzles everybody, and
this is where the problems can in because the scientists
disagree about how to think abou quantum mechanics. If you
if you want to, if you go to a physicist
conference and you want to really start a furious discussion,
(06:08):
just like drop the question at the banquets, say oh,
by the way, what do you think going to mechanics,
And ten minutes later everyone's screaming against everybody. But is
this a conference of philosophers or physicists in your mind? No,
No physicist physicist physicism, including the one to say there's
no problem at all, what are you talking about? And
that they say, of course there's a problem. You know,
(06:29):
where is the problem? I mean, how how can we
characterize the problem? Well? Sort of all physical theories from
saying Newton or maybe even before from the card or
even from Aristotle all the way to Maxwell and Twinstein,
special activity, general activity, electro dynamics. The theories describes the
systems and just the sens the system with some variables.
(06:52):
I don't know a pendulum. It's a physical object and
the variable is the angle with the vertical and tell
you how this variable ease and evolves. Given something that
you know at the beginning and you know where it is,
you know the velocity, and then you have you have
any questions that tell you how the variable changes continuously
in time. So of course this allows assume ex predictions
(07:13):
because we can measure the position. The velocity doesn't close
our eyes with two seconds, open again and the new position.
New velocity can be predicted by the theory because they
tell us exactly how it moves in time. So that's
how Newton physics works, or Maxwell theory works of ice.
Since theory works well probamical, it does not work this way.
(07:34):
That's the point. It works in a completely different manner.
It does not tell us what happens at the pendulum
while he's moving. It only tells us the prediction without
saying what is in between. And if you try to reconstruct,
what is this in between? So the data that you
know and the prediction that you make, all devils go loose,
(07:58):
namely every stray. Things happen, and people disagree about what
happened in between in between, you mean that moment when
you close your eyes and you're trying to use physics
to predict the future exactly. So typically think about quantum
mechanics in this way. I mean, you make a measurement,
that's the language which is used. They'll certainly makes a measurement,
and you make a prediction of what's going to happen
(08:20):
at the next measurement sometime later, and the prediction is binger.
It works. I mean, it tell us exactly what we see,
but if you ask what happened in between, it's confusing.
And the reason it's confusing one way of presenting it,
one of the many ways of presenting it is the following.
If you have a particle, an electron, or a little
mole for that, or an atom remocal, and you throw
(08:42):
it in some way, then going to mechanics tell you
where it's going to be, or at least probility distribution
of what's going to be. Because the prediction about the
mechanics and probabilistics are not not exactly that's one of
the corrector is still going to mechanics, but it's telling
me the sort of probility going to be here that
you're probably going to be here, to be going to
be here. Then in between, what happens to the mathematics
(09:04):
is the particle opens up in a wave. It's it's everywhere,
and with this way you compute the different probabilities, so
the particles at the same time many positions in the mathematics.
So some people say, okay, so the particle isn't many,
it's a wave, it's all over. But then when you
look at the particle is not a way. It's in
(09:25):
a single position. So other people say, no, come on,
I mean, we look at the particle is always a particle.
When we look where it is, it is always in
one point. But when you compute how it goes from
from here to here, it's not in one point. And
if you assume that it is in one point, you're
led to make some kind of mistakes and things like that.
So it's capable of making predictions, concrete predictions, or be
(09:49):
can compared to measurements. But to make those predictions you
need this intermediate step, which seems sort of nonsensical and
conflicts with our sense of like what is real in
the universe around exactly. So, but the real problem, it's
the thing people are debating with is what does it
mean that the theory describe what we measure. That's why
(10:11):
it's called the measurement problem. In a sense, it's like
when we measure something special happened, But we are not special, right,
We are just you know, piece of the universe like
any others. So the standard formulation of quantum mechanics, the
one reading textbooks, it's only in terms of the observer
and the measurement, which is fine as long as you
(10:31):
don't ask, what about the physics of the observer? What
about the observer itself isn't to observe itself a quantum system,
so it should be described the quantum mechanics as well,
so it should also open up on it like a wave.
But that's it, and that's where people start disagree. And
some physicists thinkly, yes, we do. We do our waves
(10:51):
the multiple copies of Daniel and me and Carolo and
some versions of us, some some some answers are given,
is some other versions of different. It is given because
we're a wave of different configurations of ourselves. Other people think, no,
come on, that's not a good way of thinking about reality.
And that's where the the disagreement start. So the disagreement
(11:12):
is realized in the number of so called interpretations of
quanto methadnics ways to make sense about this funny story
about the observer and the measurement and on the market
that there are many but maybe three or four or
four or five which are dominant, and many variants of
these which is pretty different from one another, and give
a profoundly different picture of reality. And that's the beauty
(11:34):
of the story. It's not just a technical thing about
using the theory. In fact, it's not the technical thing
about using Everybody agrees on using the theory, but everybody
disagrees on if you want on what happens between the measurements,
that's what way you're putting it. So I think it's
really fascinating that it's so important to us to understand
what happens when we're not looking. Right. Clearly, physics takes
(11:55):
it very important to predict what happens when we look,
because it's very practical. We need to know how trans
star's working, whether our airplanes will fly. But when we're
not making measurements, where we're not looking, when we're not
watching the universe, we still want to know what is real,
what is going on? We want to have like a
model in our minds of how the universe works. Are
we still doing physics in that case there's that philosophy
(12:15):
or do you think they're you know, forever intertwined. I
think they're forever intertwined, and I think they should be
forever intertwined, because it's precisely by asking those kinds of
questions that in the past physics has made the big jumps. Um,
let me make an example of maybe two. What example
is is the Earth the center of the universe. This
(12:38):
was a huge debate at the time of between Copernicus
and Newton. It's it's it's a center of debate, and
nobody could say that this was not a scientific debate,
because that's the debate that started that allowed Newton to
do new to mechanics and allowed Galileo to understand the
Gali little relativity, and this debate on on which Kepler BILLT.
(13:00):
Kepler was a strenuous defender of the idea that there
is not the center the universe. The universe is not
the center. Going around the said, but if you think
for a moment, is this Earth as the central universe?
A scientific question in the sense of something we can
test them, of course not. There's no way of testing.
There's no there's no operational meaning, there's no measurement that
(13:23):
I can make that can distinguish if there Earth is
the central universe. So it is not because you know,
I mean it can stay somewhere and see moving. But
what does it mean if I am moving, I see
I I see the center moving. So it's really a
non empirical question. And yet it's a profound way scientific question.
(13:44):
Why because it gives a different way depending if you
answer one way or the other. If you start by
thinking there Earth is the center, everything goes around that all.
If you start by allowing there is to be one
of the things moves, so you go to a completely
different way for conceptualizing reality, and one which worked very well.
The other was bad. It was not the good one.
(14:04):
So I think this is one of the aspect of
science which I think is often misunderstood. They would say,
sciences is not just about you know, close your eye,
make make a model, make mathematics, make a measurement, make
a prediction, and that's it. Science is about understanding reality,
meaning building up a conceptual structure, the way you're thinking reality,
(14:27):
how to put things in cases. One way of putting
things in cases is in one case there's the Earth
and in the other the celestial bodies, the sound, the wound,
the planets, the stars, and then you throw that away.
That's that's that. That's not the right characterizasue. The right
way is there are stars, the planets, and then there
are satellites. Do something different and that's works really different,
(14:50):
and boom, we understand the universe better. So I think
there are questions which are not directly empirical but are scientific,
and I think the interpetitional quantum mechanics turn out something
like that, Namely, one way you're thinking about the story
will turn out to be useful on the long run.
(15:20):
So then let's dig into the details of the different interpretations,
just to recap for our listeners, what exactly is the
problem that we're trying to solve here. The way I
think about it sometimes is that we have these particles,
and our mathematical model of them is that they are probabilistic.
They can have the probability to be doing one thing
or another thing. But of course that's not what we
measure when we measure something, it does either one thing
(15:41):
or the other. And the question is, how do you
go from being probabilistic to being sort of classical. And
you know, it seems arbitrary to say I'm making a
measurement now or I'm not making a measurement, And you
can ask questions like, well, when it interacts with other particles,
why isn't that a measurement? Or if I'm making a
measurement and I'm using a stick, and you know the
tip of that stick is made of quantum mechanical particles,
(16:03):
So why doesn't it just interact with my stick the
way it interacts with other quantum mechanical particles and maintain
it's probabilistic nature. And you know, people think about like
do you have to have a conscious observer involved? But
there's all sorts of fun things that you can dig
into there. And had a fun conversation with the author
of What is Real, which people can also dig into
if they're interested in more details on what the measurement
problem is. And the classical approach to people take this
(16:26):
Copenhagen interpretation seems sort of arbitrary. It says that you know,
the wave function moves by the shorting air equation, and
it's smooth and continuous, and then boom, all of a sudden,
when there's a measurement, everything collapses. But it doesn't tell
you what a measurement is, right, And so there's this
deep question still the heart of the most common interpretation.
And let's listener as the podcast can also check out
(16:47):
our episodes on the Many World's interpretation. But today I
want to talk about your idea or this concept of
relational quantum mechanics. So how does relational quantum mechanics deal
with the measurement problem in a way that's different from
this our try obviously unworkable approach of the Copenhagen interpretation.
Yea very good and I think this is a nice
way of putting the question. Let's take a let's take
(17:10):
a concrete case. Was simplest the quantum mechanical experiment and
measurement that we can make. We can take an atom,
radioactive atom, right, just a piece of a block of
radius radius uranium. They waited there and you put around
it some detectors of radiation, you know, the guide detector,
the click when when a radiation arrives to wait for
(17:32):
a while and after a while, one of these clicks
flink okay, and then you say, okay, the atom has
emitted a radiation and it has been detected by these detectives.
This is the fact. Now, how do we describe this
in the equations? What we do when we do want
to mechanics, we pretend that this radiation is some particles
that are inside trapped inside the atoms, and they have
(17:56):
a wave that describe them is a wave the way
functions describes them and never automatics. These waves leaks out
from the atom or from the nucleus of the atom
slowly and continuously, and it's all over so and slowly.
The imagine that this this wave continuously leaking out. So
there's this continuously wave that around spherical and go out.
(18:20):
So each one of the detectors is touched by these waves.
Goes on. Then at some point the measurement happened. As
you say, something happens. We go from this quantum wave
to a classical factor, which is one single detector that happened,
and this is a measurement. Now, different interpretation try to
fill up the story in different way. Let me just
(18:42):
compare to one or two interpretation. What is the many
world interpretation that you mentioned, and the other is the
Copenagen interpretation that dimension the many world, in a sense
is the most radical idea of taking away very seriously,
the Copenaga interpetition is the one we study at school,
the one the teacher tell you tell you how to use.
So the many one interpretation says that there's this wave
(19:04):
that come out and you see only one detector clicking.
But why do you see one the technical clicking, Because
in reality, you yourself are a wave. Okay, So you,
yourself are a superposition of different you like the particle
and different positions in a superposition different positions. So it's
not true that there is one detector that clicks. All
(19:26):
the detectors clicks, but you yourself interacting with these detectors
split up in one you that sees this the technical clicking.
One UITs is that the tector clicking. One U that
is that the technical clipping, and so on. Okay, So
now you would imagine that the wave contains copies of you,
(19:46):
and the reason you've seen one and not the others
is only because you happen to be one copy of
you and not the other copies of the other. Now
does this work. Yes, it works. Is it plausible, Well,
it sounds very implausible, extremely implosed. Well, the problem is
everything you do with pant the mechanics sounds implausible. So
many people say, Okay, we have to accept this, that
in reality we live in immense waves, that the copies
(20:09):
and copies of ourselves, and that's the many world interpetation.
Can I ask you a question actually about that many
world interpretation? There is something about that that's never set
right with me. But maybe it's very naive and and
that's this you say that there are many, many copies
of me, And so it breaks the problem of why
is this one detector clicked by saying it's not just
that one detector clicked, all of them have clicked, just
(20:29):
in other versions of the universe. But that doesn't make
all the versions of the universe equal or on the
same footing. Because I'm in this one, you know, this
is the one that I feel is the truth that
I'm making the measurement in. And that's different from the
other ones because I'm not in those other ones. And
maybe there are other means in the other ones. And
let's say that they're you know who I actually am.
(20:51):
But this is the one that I'm experiencing, and so
it still feels to me like it has a special place.
Is that a naive concern or is that something that
you think many worlds can address. It is a concern
because about many words plays exactly on the fact that
there is a contingency in who you are, which is
hard to making, not either informals or in words, and
(21:15):
it is left a little bit vague into that. So
it is a concern that some philosophers have raised about
about many worlds. All right, Well, as long as philosophers
agree with me, then i'm solid. Okay, Yeah, but you know,
you can always find a philosopher that has a low
(21:35):
bar apparently. All right, so that's the many worlds interpretation.
Let's go to the cobanagen which is what you said
at school, okay, The communities says, well, there are special
things which observers, okay, which are classical, namely a big,
big compared to to the quantum phenomena. It's when you
don't see quantum phenomena because they're too subtle for you.
(21:58):
They are not visible to you there because you're too
heavy to see quant phenomena. To isolate things, you go
to small things, so they are classical ob genia many
all the ones around us, and there is a classical
So forget quantum mechanics. About this. When a quantum system
interacts with the classical world, bingo, that's a measurement. And
this works in practice very well. That's what we do
(22:22):
in the laboratory. But in theory it obviously does not
work because what is a classical system? But we I
am many electrons and protons, and each one of them
it's a quantum particle, so each one has a wave,
so I have a big wave. I am a quantum
system in a sense copenagen it's a works with an
(22:43):
approximation saying, well, imagine that your theory is wrong for
big things, forget about it, and still use it for
small fixed And you know that's why it appeals to
everybody who does not want to ask questions. And you can,
but if you don't ask sans, you don't get answers.
I mean, on those sides of scientists about asking questions,
(23:04):
A lot of scientists who say, as well, I don't
want to care about that. There were more in the past,
in the sixties and the seventies, in the eighties, I
would say the majority of physicists would have said, oh,
come on, just use the theory. It works very well.
Nowadays there are less and less people who do that,
so I would say the large majority of people agree
that there is something to say better here. So let's
(23:26):
come to relationship quantum mechanics. What does the relational quantum
mechanics says about that? It says that all systems are quantum,
and that's the first assumption. Let's see that we're, as
far as we know, quantum mechanics the best ecup, but
we haven't about the world. So after to disconfirm all
systems have led to So that's already in contradiction with
(23:47):
Copenhagen interpretation that says like I am classical and you
are classical. It says everything is made of quantum. Even
classical objects are just like massive quantum objects. This is
just what quantum objects look like when they're really big, exactly.
So therefore there is nothing which is an observer, but
by itself, nothing that separates an observer in the sense
of quantum mechanics from a piece of stone. Of course,
(24:11):
you know, there the people who have eyes, the machines,
there are things that store information, but that's irrelevant here.
The point is in a relational quantum mechanics. That's the
suggestion of relational quantum mechanics that the measurement happens in
some sense every time two systems interact. But the actual
(24:34):
element of reality which is realized in the interaction, so
that when the detector clicks or the particle is here
is here because they see here, the particle hits another particle,
and therefore it has a specific position that has to
be soked, not as a property of the particle by itself,
but as a proper relational property of the particle and
(24:57):
the system it is interacting with in relation to the
thing during the measurement, exactly innovation to the same door
and literally which could be anything. We can be another
party in a sense. So therefore, the central idea of
religion wanto mechanics is, let's be radical in the following sense.
We describe the world in terms of systems, particle, electron,
(25:17):
et cetera. And these have the properties variables that describe them,
But these variables don't describe how the system is, it interacts,
how the system interact with something else. Okay, so for example,
we have a particle and it's flying along and it
has a certain way function for things that might do,
and Copenhagen interpretation says it stays probabilistic until something classical
(25:39):
interact with it. Relation or quantum mechanics says it can
collapse when it interacts with anything, but that collapse is
different for depending on who is interacting with it. So
if it interacts with this particle might collapse in this way.
If it interacts with somebody else, that might collapse in
another way. In that sense, it's also sort of like
a branching of what reality is real, because what is
(26:00):
real now depends on who is doing the measurement. Is
that right? That's exactly correct. So the so called collapse
of the way function is by itself, something which is
relative to the system against which the particles is interacting,
which doesn't need to be a macroscopical object, doesn't need
to be anything special. It's anything but this. The subtlety
(26:23):
is the following. I suppose the particle interact with my machine,
my detector, okay, and I am I am a distance
and the two are not interacting with me. So with
respect to me, there is no collapse happening. So the
way the particle and the machine are gonna manifest themselves
(26:44):
to me later on if they interact with me is
still computed with quantum mechanics. So if I want to
compute what happens with respect to me, I still use
the way function of the particle and the way function
of the machine, because the machine is quite mechanical, I think.
So for example, I'm here talking to you, so I'm
measuring you. I'm collapsing your way function. But our listeners
(27:06):
have not yet heard this podcast, so from their point
of view, you and I are still in some uncollapsed
quantum state, and only when they hear this does it
collapse into an actual stream of words. So for us
it is collapsed, but for them it's not yet collapsed exactly.
So I believe that this is coherent. This can be
made clearing by going into details. It offers a possible
(27:27):
solution of the puzzle quantum theory. This is a relation
with dempetition. It does require it has a cost. There's
a conceptual cost, because as you said, reality is a
little bit more subjective. No subjective relative. I'll come back
to the difference subject in relative. So it weakens realism
(27:47):
in a sense, but it's still a realistic interpetation. So
I think that this cost is more worthwhile paying for
being fruitful for the future of physics than imagining that
there are many copies of myself, or than not asking
the question when you come to the subtle team. In
(28:07):
your example, you talked about you and me and the
listeners all people. Okay, that's fine, but the key intuition
of relationship about the mechanics that this has nothing to
do with people. That's the key point. And that's a
big difference with respect also with coping again in a sense, right,
this is nothing to do with subjectivity. That's it to
(28:29):
do the subject. But factly you and I are are
subject of perceptions as need to do. You would also
work if you and I were dogs or bananas or particles, right, exactly,
the same mathematics work, exactly as I'm the same story
would work. And to make an example of this, because
I think that you know, relative to observer observable are
(28:51):
often misinterpreted as subjective while it's just relational. For instance,
there's a very well known example of relational notion in
physics which students struggle at the beginning when they encounter
it the first time, because it's very contin intuitive if
you think at the beginning, which is velocity. When we
study Galian theory a Newton theory, we learn that velocity
(29:17):
is not absolute, velocity is relative. So what is the
velocity of the moon. Well, depend there's the velocity of
the moon we respect to this Earth, the velocity of
the moon we respect to the Sun. The velocity moon
we respect to the center of the galaxy, the loscy
moon respect to the cosmic microwave background average. Which one
(29:38):
is the true one? Well, no, it's a velocity. It's
a notion that pertains the two objects, the moon and
something else. It's always velocity of the moon with respects
something else. We sort of know that, right, because when
we say don't move, we know that don't move is
relativitally to something. For instance, if you're in a train
(29:59):
and your little daughter is jumping around and you say
don't move, you don't mean that you little daughters to
jump out of the train and don't cove with respect
to the earth. Right, you mean don't move respect to
the train. And she understand correctly right that she should
soon move respect the train and she's just still moving
very fast because the train is running. So we understand
(30:20):
that velocities are it's it's a relational notion. But this
is nothing to do with subjectivity, right because if I
say that the moon has a velocity respect to the sound,
I'm not saying that the Sun is a subject that
sees the moon and perceives something. Is nothing to do
with that, nothing to do with mind subjectivity, Just physics,
pure physics. There is a quantity to velocity which doesn't
(30:44):
depend on one thing. It depends on two things, the
Moon and the Sun. And it's velocity the relative velocity
of the two, say how they move respect one of that.
So that's a big philosophical step, right, You've sort of
taken away from the moon the fact that it can
have a property called velocity. Say, you can't have a
property called velocity. Only a pair of things can have
this property. A single object cannot. And the sort of
(31:06):
the mental game i'd like to place to imagine, like
a particle in an empty universe, can it have a velocity? Well,
it has no meaning to have a velocity if you
are the only thing in the universe, right, And so
I want to also ask you about this concept of cost.
You're talking about the cost of a theory, and so
here is that the cost you mean that you're like
now changing philosophically what it means to be real that
(31:26):
no longer can you include in your sort of you know,
category or your index of what it means to be
that you have a certain velocity that you've like taken
that away from objects. Yes, this is the course, and
I think you said it very cleanly. It's a deep
philosophical point when we realize that velocity is not a
property of an object you need another object, is a
(31:48):
property of two objects. A quantum mechanics in a sense.
The phone suggestion that we in this em better quantum
mechanics if we just interpreted all properties, all variable in
this way, not just velocity. Okay, any variablity, even think
about a system only makes sense if you if you
(32:11):
have another system. You're saying it's this is a variable
with suspect to this other system. And what you mean
is that there was an interaction to these two systems
and that variable was realized in this interaction. Namely, describe
the way one system affected the other one. And can't
you use even the same language. Because now we talked
about velocity. We say velocity of the moon as measured
by an observer on the Sun, or as measured by
(32:33):
observer on the Earth. Now you can say the location
of this particle or the color of this particle as
measured by this observer versus as measured by that observer exactly.
(32:56):
Now you went strongly in saying, does this mean that
reality itself it's relative to um? I hesitate. Namely, the
same reaction could have been raised against the Galileo and
Newton when they started using velocity. In this sense, I
(33:18):
think that the reality of the motion of the moon
and velocity of the moon and the Sun and things,
in spite of what we have understood about relativity velocity
is still very solid. Still we still have a realistic
interpretation of motion, and so I would like to think
about relational quantum mechanics as a realistic picture. So reality
(33:41):
is there, it's I mean, things are there, and then
there's nothing to do with us. Of course, we are
just a part of nature. Is not that nature is
a part of our mind. That's my naturalism if you want.
But the way reality is is subtle. According to quantum
mechanics can be described. Reality can be described by systems
that have a properties relative to other systems. So then
(34:05):
can you have something which exists by itself like imagine,
you know, the sort of simple example I mentioned earlier.
For velocity, a single particle an empty universe can't have
a velocity. Now you said that everything is relation on
the way velocity is. Does that mean a single particle
in an empty universe does not exist or cannot have
any properties because it would need something else in order
(34:27):
to measure it. Can a single particle universe exists? No,
if quantum mechanics max is the correct description of the units.
And in fact that can be said in a beside
the way. There's a philosopher which is Madorato who is
elaborated much on that, saying, if we take relationhp quantum
mechanics correctly, we cannot talk about the quantum state of
the universe. We cannot state of the quantum state of everything.
(34:50):
We cannot even talk about the description of the universe
because the scripture universe needs to be if you use
this way of thinking, a point of mechanics scripture relatively
to something else. So in the moment in which you're
saying the description units, so you're assuming there is something
outside that is looking at the universe. Well you can,
but then in your reality there is something else in
(35:10):
addition to what you just called the universe a moment ago.
For instance, the famous way functional units, what is it
is a mathematical object that allows you to predict what
you would measure if you are outside the universe to
interact with it. But then it's not the universe anymore
because there is something else outside the universe interacting with it.
(35:31):
So there's the way functional use is meaningless. It's always
the way function of something. I was hoping to use
that example to lead you down the garden path to
admit that means the universe can't exist, but you just
went straight there and said, if this is true, then
we don't have a meaningful concept of what the universe is.
I mean, isn't that a problem? I mean, if we
(35:53):
want a theory of reality that tells us what is happening,
doesn't it need to also allow us to think about
what reality is. I think that it's a deeper point
one of the things we have understood more and more
in modern physics, but also another realm of modern culture
is that we're always part of the story. So we
(36:13):
see reality from we think, not from outside in completely
different parts of our culture. First this this was famously
an immense issue and toropology, right, you want to describe
a society. When the Europeans went around the world to
try to describe societies objectively, um, non European societies, maybe
I don't know some people in their matson and then
(36:36):
they re allies that they were not doing nothing objectively.
They were just comparing their own culture with the culture
of these people. In some of they were interacting with
these people and not being outside a cultural scheme, but
doing something and olmously interesting, not something that lacked value,
but that was not a stepping out from what is
(37:00):
being described. And I think physics to some extent has
encountered the same set of problems. Namely, we described the
universe from within. We are part of the universe. What
physics tell us is if I encounter this, I know
what I can expect, and I know what a what
(37:21):
I can expect, what kind of things aide around me.
But the idea that physics give a list of all
or everything existing with the state, it's a first of all,
totally unplausible by itself, right, I mean, how many stars
there are in the universe, and how many atoms in
each one of these stars? So it's just totally outside
(37:42):
or a capacity. But even in principle, what does it mean.
I mean, physics is all in the form if this,
then that, right, If I found this pendulum in this way,
then it's going to move that like that. It's model,
as the philosopher says. So it's always a story of
out given some initial conditions, this is what I expect
(38:03):
to happen, given some data, this is what comes later,
and then it tells what kind of atoms are around,
the forces are around. But we shouldn't expect from physics
the total novel of the universe. That's what everything is
in the universe. That's at all the state of the universe.
Why it's not that's far outside our capacities, And probably
(38:26):
I would say it's meaningless because of what we said before,
because that would be an issue that God might have
if he or she exists seeing from the units from
the outside, not of all our business. And I think
this makes exactly the point that you were talking about earlier,
that we want to know the answers these the philosophical questions,
because they tell us which questions then makes sense to
(38:49):
ask which questions have answers, and which questions are even
relevant to think about. I think that's some of the
most important reason why physicists need to think about philosophy.
And I know that you talked about the mechanics a lot,
and you're quite an expert on this, So I want
to try to ask you a question that maybe nobody
has asked you before, put you on the spot, and
and that's this. Have you thought about what it might
be like to talk about physics or quantum mechanics with aliens?
(39:14):
Imagine that we have meet extraterrestrial physicists, right, and we
go and we we say with to them whole you
must know the secrets of the universe because you figured
out how to travel here from distant stars. Do you
think there's any possibility that we would be asking the
same questions or that their answers to our questions would
make any sense to us. Do you think that the
way that we look at the universe is sort of
(39:35):
the way Europeans, you know, looked at other cultures. Do
you think that's deeply imbued with our human bias, or
do you think that we are probing something universal which
should be part of sort of like some galactic physics project.
Great question. A bit of both, but more of the
first and the second. That's my answer. There is a
precise sense in which what we discover in science is
(39:55):
it's just two in universal mean. I don't think this
can be denied, and people who denied it, I think
have a toak way of denying it, and don and
physics in some sense, it's true. It works described reality.
It's I mean, the fact that everything is made by
atoms and there are ninety and so kind of different atoms.
That's a fact. It's like when you you know, when
(40:18):
you go down the street and you see that you
know your three friends are in the cafe. That's a fact.
It's true. And I believe that science is a higher
level of understanding. Fact is the way humankind organizes an
understanding of reality better and better. But from this, to
have the idea that there is a unique, clearly path
(40:43):
to the perfect description of reality and we are on need,
or even that we're close to the end of it,
that seems to me unbelievably full of self pretension, and
I see no sign that we're close to that. And
we have a sort of experiment of that because we
know what asked centurists, scientists thought, and we do know
(41:07):
that some of the things that we know would be
meaningless for them, It would not answer their questions in
really going in a different direction, which does not mean
that they are better than us. We are better than
them because we know what they are in some objective sense,
and the objective sense is that if both one came alive,
(41:27):
and if I could have enough time also want to
me sitting here, I believe that I could slowly arrive
to convince him that there are a lot of interesting
things he doesn't know. So I think it's the same
with some aliens. If some millions would come, I wouldn't
be surprised if they have a completely different story. And
it might be possible that we just don't understand one
another because the story is two different. It might be
(41:48):
different because they have a different way of perceiving reality. Right,
we view reality on the basis of what useful to
our They're being an evolution, not on the basis of,
you know, some contient rationalism or simply even if they
had the same senses, because culture of them was going
in other directions. But I believe there is communication, right,
(42:08):
Cultures communicate, So maybe with this aliens we could learn
to communicate. And we were very surprised of learning completely
different perspectives. If they are more advanced than us in
some sense, or maybe they will be surprised to learn
something from us, or maybe both. So in other ways,
I don't think there is a path to tools, and
(42:28):
they would know everything we know any more. Maybe they
would never think about quantum mechanics and we teach them
quanto mechanics. That was fantastic. You're right, it's a relationship.
But will send you to meet the aliens and how
they don't eat you. There is a greater novel, The
Dark Clouds The Black Cloud, in which there is this
it's a huge cloud that come towards the sermon and
(42:51):
somebody realizes that it's actually intelligent something down there, and
it's uh, and somebody realized that it is going to
be a disaster for the Earth is going to exactly
edge of the sound. And somehow so the scientists arrived
to communicate and so gently convinced this cloud to leave
us alone. But then there is one scientist so too.
(43:12):
I don't remember. That's the Wait a minute, I want
to learn everything you know, So the cloud answer, well,
it's tandrous. I mean your little brain. But they really
wanted to so they can say, okay, if you really want, so,
I think it's two of them. They sit around the screen, okay,
and the screens start flickering, and they just look at
(43:32):
this at the beginning. At the beginning, they don't understand,
but then they start understanding, and then finally they start learning,
and then they're lost because then they're considered fool and
they're putting all the psychotic hospital and the body knows what.
That's the danger of talking physics with aliens is you
can see reality, so clearly the humans can no longer
(43:53):
relate to you. So let me bring it back to
one last question about relational quantum mechanics. What you're proposing
here is really a ratheric of departure on a way
of seeing the universe, imagining that objects don't contain on
their own properties, but that these things are just dependent
on pairs, essentially things that are measuring other things. So
my question to you is that how could we know
(44:14):
if this is true. Is there some experiment we can do?
They could tell us, look, Copenhagen fails here and we
need relation or quantum mechanics, or we can dispense with
the many worlds, like is this something which can only
ever be a philosophical conversation among physicists motivating our questions
about reality, or is this something we can actually one
day put to the test. I don't see any way
(44:35):
it could put to the test. There's some interpretation quantum
mechanics that assume that quantum mechanics actually wrong, and so
they can be tested because you can do an experiment
to see where the quantum mechanic is wrong right, And
they're very interesting. And so far many of these tests
have been done and quant mechanics always going to be right,
and all alternative from the moment have been all eliminated.
(44:57):
But the various interpretation like many world or de bullyable,
the pilot wave interpretation, hidden variables or relationship quantum mechanics,
which I think are the main one. So cubans maybe
in one sense, they are not distinguishable in an empirical way,
as as far as I know, nobody has come out
with experimented distinguished them, and in a sense studying them,
(45:18):
there's no experiment making a difference, So how would we know, Well,
I think exactly the same way, which we finally all
agree that the Earth is not the center of the universe,
even if there is no experiment that tells us that
the Earth is or is not the center of the universe,
because there's no way to measure just what the center
(45:38):
the center units, namely, the progress of science will work
better with one conceptual scheme than the other. I do
quanta gravity my main the reason I got into the
issue of integrational quantum mechanics, and the mechanic goes back
to the nineties. In fact, my first papers on that
in the late nineties, and then other people can and
(46:00):
have developed it and in recent years have been a
much stronger increasing interest in it. And it's not isolated
because there are the people who are very similar ideas,
So which why is really part of a little group
of interpretation just similar in some sense, maybe with different emphasis,
different tone. I'm thinking of writings by Zeilinger, by Chancellor Bruckner,
(46:27):
by Richard Haley and another. There are a number of
ways of going in the same direction, so in my
own work and trying to put up a quantic see
of gravity, I found that this way of thinking, it's
much more helpful when you don't have space, you don't
have time to locate things, you don't have the observer.
This relational way works well. And one reason it works well,
(46:49):
it works through well well with general activity, where location
is relations. Nothing has a position to be somewhere. It's
only meaningful if you're some well respect to something else.
And now the things start staying together well, because to
be next to something is possibility of interacting with something,
so you can exchange information with something. That's what we're
(47:10):
talking about in physics, this being next to one another
and exchanging something, rather than having, you know, it becomevast
there and placing things and saying that's that's what reality is.
So I hope that the discussion about indevidual quadema is
going ahead. It's not blocked, it's not the same as
thirty years ago. And I think that with the new ideas,
(47:31):
with the new things being discussed, at some point it
will become more and more clear that one way of
viewing things it's productive. It works. It doesn't require us
to assume things which are absurd, but it does require
us to assume things which are necessary to make in
sense of reality. Wonderful. Well, that's a fascinating insight into
(47:53):
how we might make steps forward. And I agree with
you that it makes sense to unify quantum mechanics with
relativity if quantum mechanics itself becomes sort of relativistic, not
in the sense of things moving at very high speeds,
but in the sense that the objects and the quantities
we measure themselves are relational or relative to other objects.
(48:13):
So that makes a lot of sense. Well, thanks very
much for this fascinating conversation, really stimulating, you know, about
quantum mechanics and physics and relativity and of course aliens
and philosophy. I want to thank you very much, and
I want to point our listeners to your book Health
Go Land, which has just come out recently, and it's
fascinating read on these ideas and how they were developed,
and people who are interested in digging more deep into
(48:35):
them might encourage you to check them out. So Carlo,
thanks you very much for joining us on the program today.
Thank you. Emaually, that's what's great. Thank you. Thanks for
listening and remember that Daniel and Jorge explained. The Universe
is a production of I Heart Radio or more podcast
(48:57):
for my heart Radio, visit the I Heart a new Apple,
Apple Podcasts, or wherever you listen to your favorite shows.
H
Hey, it' Jorhan Daniel here, and we want to tell
you about our new book. It's called Frequently Asked Questions
about the Universe because you have questions about the universe,
and so we decided to write a book all about them.
We talk about your questions, we give some answers, we
make a bunch of silly jokes as usual, and we
tackle all kinds of questions, including what happens if I
fall into a black hole? Or is there another version
(00:22):
of you out there that's right? Like usual, we tackle
the deepest, darkest, biggest, craziest questions about this incredible cosmos.
If you want to support the podcast, please get the
book and get a copy not just for yourself, but
you know, for your nieces and nephews, cousins, friends, parents, dogs, hamsters,
and for the aliens. So get your copy of Frequently
Asked Questions about the Universe is available for pre order now,
(00:46):
coming out November two. You can find more details at
the book's website, Universe f a Q dot com. Thanks
for your support, and if you have a hamster that
can read, please let us know. We'd love to have
them on the podcast. We all know that quantum mechanics
(01:10):
can't be quite right. I'm not talking about the counter intuitive,
probabilistic aspects of it that it forced us to accept
that the world we live in is fundamentally weirder than
we have ever imagined. Probabilities and correlations and uncertainty is no.
Those bits are probably right, But there's a problem at
(01:30):
the heart of quantum mechanics, one that has baffled physicists
and philosophers for nearly a hundred years, and that may
take another hundred years to solve. But some recent ideas
maybe showing us a path forward, even if it's a
stranger path. Then we imagine, Hi, I'm Daniel. I'm a
(02:05):
particle physicist and a professor at u C Irvine, and
I'm still confused by quantum mechanics. Confused but not frustrated,
You might say, I'm deliciously confused. What could be more
delightful than grappling with the deep mysteries of the nature
of reality, seeing the truth written down in cold black
and white and mathematical equations, and struggling to gain an
(02:27):
intuition to incorporate those alien concepts into our human brains.
After all, that is the deepest goal of physics, and
that's the goal of our podcast. Daniel and Jorgey explain
the university production of My Heart Radio, in which we
tackled the biggest and hardest and nastiest and funnest of
questions of the universe, the ones that make your brains twist,
(02:50):
the ones that slip away from you just as you
thought you had figured them out, the ones that might
elude humanity for centuries or forever. We don't show away
from any questions on the podcast, but we seek to
approach them and explain our knowledge and our ignorance to you.
My friend and co host Jorge is on a break,
but I have a special treat for you. We are
(03:12):
very lucky to have as a guest one of my
favorite physicists, one of my favorite writers, and one of
my favorite writers about physics, truly a poet of science communication.
Today we'll be talking to Carlo Rovelli about some of
the problems at the heart of quantum mechanics and explaining
a lesser known but absolutely fascinating alternative version of quantum mechanics.
(03:35):
So today on the podcast, we'll be answering the question
what is relational quantum mechanics? So it's my great pleasure
today to introduce Professor Carlo Rovelli. He's a professor of
physics in Marseille, and he cut his teeth and made
his name for himself developing theories of quantum gravity, mostly
(03:56):
loop quantum gravity. If I understand correctly, he also became
a household name. Is the author of the book Seven
Brief Lessons on Physics, which sold more than a million
copies and was translated into forty one languages. I've read
it and enjoyed it immensely and heartily recommended to you. Today,
Professor Rivelli is here to talk to us about his
new book, Hell Go Land and a fascinating alternative take
on the measurement problem in quantum mechanics. Professor Velli, welcome
(04:19):
to the podcast, and thank you for joining us. Thank
you question that it's a pleasure in the honor of
being here, wonderful. Well. I always love talking about quantum
mechanics and puzzling over it with other people. I feel
like every time I talk about quantum mechanics with somebody else,
I think of a new question I've never thought of before,
or a new angle on it, or a new mystery
frankly like a new corner of my mind that I
(04:41):
haven't ever really examined, and I get confused, and so
it's always fun to figure things outside of on the fly.
So today we wanted to talk about your new book
and Hell Go Land, And the book essentially lays out
for lay audience this idea of relational quantum mechanics, sort
of a new interpretation on quantum mechanics. And the first
question for you I have is if you could describe
(05:01):
for us what is the problem that relational quantum mechanics solves, Like,
why do we need another quantum mechanics interpretation? What is it?
At the heart of relational quantum mechanics is trying to
do One of the difficulties the problem of quantum mechanics
is to say exactly what the problem is. So quass mechanics,
on the one hand, it's extraordinary successful, is used in
(05:25):
a lot of our technology, is used a lot of
our understanding of the world world. We explain with quantum
mechanics the basics of chemistry, basic apastrophysics, all sorts of stuff,
and it works. It works fantastically. On the other hand,
there is a persisting, mysterious aspect about this theory. It's
a theory that it's a it's sort of formulity differently
(05:48):
than previous basic physical theories. This difference puzzles everybody, and
this is where the problems can in because the scientists
disagree about how to think abou quantum mechanics. If you
if you want to, if you go to a physicist
conference and you want to really start a furious discussion,
(06:08):
just like drop the question at the banquets, say oh,
by the way, what do you think going to mechanics,
And ten minutes later everyone's screaming against everybody. But is
this a conference of philosophers or physicists in your mind? No,
No physicist physicist physicism, including the one to say there's
no problem at all, what are you talking about? And
that they say, of course there's a problem. You know,
(06:29):
where is the problem? I mean, how how can we
characterize the problem? Well? Sort of all physical theories from
saying Newton or maybe even before from the card or
even from Aristotle all the way to Maxwell and Twinstein,
special activity, general activity, electro dynamics. The theories describes the
systems and just the sens the system with some variables.
(06:52):
I don't know a pendulum. It's a physical object and
the variable is the angle with the vertical and tell
you how this variable ease and evolves. Given something that
you know at the beginning and you know where it is,
you know the velocity, and then you have you have
any questions that tell you how the variable changes continuously
in time. So of course this allows assume ex predictions
(07:13):
because we can measure the position. The velocity doesn't close
our eyes with two seconds, open again and the new position.
New velocity can be predicted by the theory because they
tell us exactly how it moves in time. So that's
how Newton physics works, or Maxwell theory works of ice.
Since theory works well probamical, it does not work this way.
(07:34):
That's the point. It works in a completely different manner.
It does not tell us what happens at the pendulum
while he's moving. It only tells us the prediction without
saying what is in between. And if you try to reconstruct,
what is this in between? So the data that you
know and the prediction that you make, all devils go loose,
(07:58):
namely every stray. Things happen, and people disagree about what
happened in between in between, you mean that moment when
you close your eyes and you're trying to use physics
to predict the future exactly. So typically think about quantum
mechanics in this way. I mean, you make a measurement,
that's the language which is used. They'll certainly makes a measurement,
and you make a prediction of what's going to happen
(08:20):
at the next measurement sometime later, and the prediction is binger.
It works. I mean, it tell us exactly what we see,
but if you ask what happened in between, it's confusing.
And the reason it's confusing one way of presenting it,
one of the many ways of presenting it is the following.
If you have a particle, an electron, or a little
mole for that, or an atom remocal, and you throw
(08:42):
it in some way, then going to mechanics tell you
where it's going to be, or at least probility distribution
of what's going to be. Because the prediction about the
mechanics and probabilistics are not not exactly that's one of
the corrector is still going to mechanics, but it's telling
me the sort of probility going to be here that
you're probably going to be here, to be going to
be here. Then in between, what happens to the mathematics
(09:04):
is the particle opens up in a wave. It's it's everywhere,
and with this way you compute the different probabilities, so
the particles at the same time many positions in the mathematics.
So some people say, okay, so the particle isn't many,
it's a wave, it's all over. But then when you
look at the particle is not a way. It's in
(09:25):
a single position. So other people say, no, come on,
I mean, we look at the particle is always a particle.
When we look where it is, it is always in
one point. But when you compute how it goes from
from here to here, it's not in one point. And
if you assume that it is in one point, you're
led to make some kind of mistakes and things like that.
So it's capable of making predictions, concrete predictions, or be
(09:49):
can compared to measurements. But to make those predictions you
need this intermediate step, which seems sort of nonsensical and
conflicts with our sense of like what is real in
the universe around exactly. So, but the real problem, it's
the thing people are debating with is what does it
mean that the theory describe what we measure. That's why
(10:11):
it's called the measurement problem. In a sense, it's like
when we measure something special happened, But we are not special, right,
We are just you know, piece of the universe like
any others. So the standard formulation of quantum mechanics, the
one reading textbooks, it's only in terms of the observer
and the measurement, which is fine as long as you
(10:31):
don't ask, what about the physics of the observer? What
about the observer itself isn't to observe itself a quantum system,
so it should be described the quantum mechanics as well,
so it should also open up on it like a wave.
But that's it, and that's where people start disagree. And
some physicists thinkly, yes, we do. We do our waves
(10:51):
the multiple copies of Daniel and me and Carolo and
some versions of us, some some some answers are given,
is some other versions of different. It is given because
we're a wave of different configurations of ourselves. Other people think, no,
come on, that's not a good way of thinking about reality.
And that's where the the disagreement start. So the disagreement
(11:12):
is realized in the number of so called interpretations of
quanto methadnics ways to make sense about this funny story
about the observer and the measurement and on the market
that there are many but maybe three or four or
four or five which are dominant, and many variants of
these which is pretty different from one another, and give
a profoundly different picture of reality. And that's the beauty
(11:34):
of the story. It's not just a technical thing about
using the theory. In fact, it's not the technical thing
about using Everybody agrees on using the theory, but everybody
disagrees on if you want on what happens between the measurements,
that's what way you're putting it. So I think it's
really fascinating that it's so important to us to understand
what happens when we're not looking. Right. Clearly, physics takes
(11:55):
it very important to predict what happens when we look,
because it's very practical. We need to know how trans
star's working, whether our airplanes will fly. But when we're
not making measurements, where we're not looking, when we're not
watching the universe, we still want to know what is real,
what is going on? We want to have like a
model in our minds of how the universe works. Are
we still doing physics in that case there's that philosophy
(12:15):
or do you think they're you know, forever intertwined. I
think they're forever intertwined, and I think they should be
forever intertwined, because it's precisely by asking those kinds of
questions that in the past physics has made the big jumps. Um,
let me make an example of maybe two. What example
is is the Earth the center of the universe. This
(12:38):
was a huge debate at the time of between Copernicus
and Newton. It's it's it's a center of debate, and
nobody could say that this was not a scientific debate,
because that's the debate that started that allowed Newton to
do new to mechanics and allowed Galileo to understand the
Gali little relativity, and this debate on on which Kepler BILLT.
(13:00):
Kepler was a strenuous defender of the idea that there
is not the center the universe. The universe is not
the center. Going around the said, but if you think
for a moment, is this Earth as the central universe?
A scientific question in the sense of something we can
test them, of course not. There's no way of testing.
There's no there's no operational meaning, there's no measurement that
(13:23):
I can make that can distinguish if there Earth is
the central universe. So it is not because you know,
I mean it can stay somewhere and see moving. But
what does it mean if I am moving, I see
I I see the center moving. So it's really a
non empirical question. And yet it's a profound way scientific question.
(13:44):
Why because it gives a different way depending if you
answer one way or the other. If you start by
thinking there Earth is the center, everything goes around that all.
If you start by allowing there is to be one
of the things moves, so you go to a completely
different way for conceptualizing reality, and one which worked very well.
The other was bad. It was not the good one.
(14:04):
So I think this is one of the aspect of
science which I think is often misunderstood. They would say,
sciences is not just about you know, close your eye,
make make a model, make mathematics, make a measurement, make
a prediction, and that's it. Science is about understanding reality,
meaning building up a conceptual structure, the way you're thinking reality,
(14:27):
how to put things in cases. One way of putting
things in cases is in one case there's the Earth
and in the other the celestial bodies, the sound, the wound,
the planets, the stars, and then you throw that away.
That's that's that. That's not the right characterizasue. The right
way is there are stars, the planets, and then there
are satellites. Do something different and that's works really different,
(14:50):
and boom, we understand the universe better. So I think
there are questions which are not directly empirical but are scientific,
and I think the interpetitional quantum mechanics turn out something
like that, Namely, one way you're thinking about the story
will turn out to be useful on the long run.
(15:20):
So then let's dig into the details of the different interpretations,
just to recap for our listeners, what exactly is the
problem that we're trying to solve here. The way I
think about it sometimes is that we have these particles,
and our mathematical model of them is that they are probabilistic.
They can have the probability to be doing one thing
or another thing. But of course that's not what we
measure when we measure something, it does either one thing
(15:41):
or the other. And the question is, how do you
go from being probabilistic to being sort of classical. And
you know, it seems arbitrary to say I'm making a
measurement now or I'm not making a measurement, And you
can ask questions like, well, when it interacts with other particles,
why isn't that a measurement? Or if I'm making a
measurement and I'm using a stick, and you know the
tip of that stick is made of quantum mechanical particles,
(16:03):
So why doesn't it just interact with my stick the
way it interacts with other quantum mechanical particles and maintain
it's probabilistic nature. And you know, people think about like
do you have to have a conscious observer involved? But
there's all sorts of fun things that you can dig
into there. And had a fun conversation with the author
of What is Real, which people can also dig into
if they're interested in more details on what the measurement
problem is. And the classical approach to people take this
(16:26):
Copenhagen interpretation seems sort of arbitrary. It says that you know,
the wave function moves by the shorting air equation, and
it's smooth and continuous, and then boom, all of a sudden,
when there's a measurement, everything collapses. But it doesn't tell
you what a measurement is, right, And so there's this
deep question still the heart of the most common interpretation.
And let's listener as the podcast can also check out
(16:47):
our episodes on the Many World's interpretation. But today I
want to talk about your idea or this concept of
relational quantum mechanics. So how does relational quantum mechanics deal
with the measurement problem in a way that's different from
this our try obviously unworkable approach of the Copenhagen interpretation.
Yea very good and I think this is a nice
way of putting the question. Let's take a let's take
(17:10):
a concrete case. Was simplest the quantum mechanical experiment and
measurement that we can make. We can take an atom,
radioactive atom, right, just a piece of a block of
radius radius uranium. They waited there and you put around
it some detectors of radiation, you know, the guide detector,
the click when when a radiation arrives to wait for
(17:32):
a while and after a while, one of these clicks
flink okay, and then you say, okay, the atom has
emitted a radiation and it has been detected by these detectives.
This is the fact. Now, how do we describe this
in the equations? What we do when we do want
to mechanics, we pretend that this radiation is some particles
that are inside trapped inside the atoms, and they have
(17:56):
a wave that describe them is a wave the way
functions describes them and never automatics. These waves leaks out
from the atom or from the nucleus of the atom
slowly and continuously, and it's all over so and slowly.
The imagine that this this wave continuously leaking out. So
there's this continuously wave that around spherical and go out.
(18:20):
So each one of the detectors is touched by these waves.
Goes on. Then at some point the measurement happened. As
you say, something happens. We go from this quantum wave
to a classical factor, which is one single detector that happened,
and this is a measurement. Now, different interpretation try to
fill up the story in different way. Let me just
(18:42):
compare to one or two interpretation. What is the many
world interpretation that you mentioned, and the other is the
Copenagen interpretation that dimension the many world, in a sense
is the most radical idea of taking away very seriously,
the Copenaga interpetition is the one we study at school,
the one the teacher tell you tell you how to use.
So the many one interpretation says that there's this wave
(19:04):
that come out and you see only one detector clicking.
But why do you see one the technical clicking, Because
in reality, you yourself are a wave. Okay, So you,
yourself are a superposition of different you like the particle
and different positions in a superposition different positions. So it's
not true that there is one detector that clicks. All
(19:26):
the detectors clicks, but you yourself interacting with these detectors
split up in one you that sees this the technical clicking.
One UITs is that the tector clicking. One U that
is that the technical clipping, and so on. Okay, So
now you would imagine that the wave contains copies of you,
(19:46):
and the reason you've seen one and not the others
is only because you happen to be one copy of
you and not the other copies of the other. Now
does this work. Yes, it works. Is it plausible, Well,
it sounds very implausible, extremely implosed. Well, the problem is
everything you do with pant the mechanics sounds implausible. So
many people say, Okay, we have to accept this, that
in reality we live in immense waves, that the copies
(20:09):
and copies of ourselves, and that's the many world interpetation.
Can I ask you a question actually about that many
world interpretation? There is something about that that's never set
right with me. But maybe it's very naive and and
that's this you say that there are many, many copies
of me, And so it breaks the problem of why
is this one detector clicked by saying it's not just
that one detector clicked, all of them have clicked, just
(20:29):
in other versions of the universe. But that doesn't make
all the versions of the universe equal or on the
same footing. Because I'm in this one, you know, this
is the one that I feel is the truth that
I'm making the measurement in. And that's different from the
other ones because I'm not in those other ones. And
maybe there are other means in the other ones. And
let's say that they're you know who I actually am.
(20:51):
But this is the one that I'm experiencing, and so
it still feels to me like it has a special place.
Is that a naive concern or is that something that
you think many worlds can address. It is a concern
because about many words plays exactly on the fact that
there is a contingency in who you are, which is
hard to making, not either informals or in words, and
(21:15):
it is left a little bit vague into that. So
it is a concern that some philosophers have raised about
about many worlds. All right, Well, as long as philosophers
agree with me, then i'm solid. Okay, Yeah, but you know,
you can always find a philosopher that has a low
(21:35):
bar apparently. All right, so that's the many worlds interpretation.
Let's go to the cobanagen which is what you said
at school, okay, The communities says, well, there are special
things which observers, okay, which are classical, namely a big,
big compared to to the quantum phenomena. It's when you
don't see quantum phenomena because they're too subtle for you.
(21:58):
They are not visible to you there because you're too
heavy to see quant phenomena. To isolate things, you go
to small things, so they are classical ob genia many
all the ones around us, and there is a classical
So forget quantum mechanics. About this. When a quantum system
interacts with the classical world, bingo, that's a measurement. And
this works in practice very well. That's what we do
(22:22):
in the laboratory. But in theory it obviously does not
work because what is a classical system? But we I
am many electrons and protons, and each one of them
it's a quantum particle, so each one has a wave,
so I have a big wave. I am a quantum
system in a sense copenagen it's a works with an
(22:43):
approximation saying, well, imagine that your theory is wrong for
big things, forget about it, and still use it for
small fixed And you know that's why it appeals to
everybody who does not want to ask questions. And you can,
but if you don't ask sans, you don't get answers.
I mean, on those sides of scientists about asking questions,
(23:04):
A lot of scientists who say, as well, I don't
want to care about that. There were more in the past,
in the sixties and the seventies, in the eighties, I
would say the majority of physicists would have said, oh,
come on, just use the theory. It works very well.
Nowadays there are less and less people who do that,
so I would say the large majority of people agree
that there is something to say better here. So let's
(23:26):
come to relationship quantum mechanics. What does the relational quantum
mechanics says about that? It says that all systems are quantum,
and that's the first assumption. Let's see that we're, as
far as we know, quantum mechanics the best ecup, but
we haven't about the world. So after to disconfirm all
systems have led to So that's already in contradiction with
(23:47):
Copenhagen interpretation that says like I am classical and you
are classical. It says everything is made of quantum. Even
classical objects are just like massive quantum objects. This is
just what quantum objects look like when they're really big, exactly.
So therefore there is nothing which is an observer, but
by itself, nothing that separates an observer in the sense
of quantum mechanics from a piece of stone. Of course,
(24:11):
you know, there the people who have eyes, the machines,
there are things that store information, but that's irrelevant here.
The point is in a relational quantum mechanics. That's the
suggestion of relational quantum mechanics that the measurement happens in
some sense every time two systems interact. But the actual
(24:34):
element of reality which is realized in the interaction, so
that when the detector clicks or the particle is here
is here because they see here, the particle hits another particle,
and therefore it has a specific position that has to
be soked, not as a property of the particle by itself,
but as a proper relational property of the particle and
(24:57):
the system it is interacting with in relation to the
thing during the measurement, exactly innovation to the same door
and literally which could be anything. We can be another
party in a sense. So therefore, the central idea of
religion wanto mechanics is, let's be radical in the following sense.
We describe the world in terms of systems, particle, electron,
(25:17):
et cetera. And these have the properties variables that describe them,
But these variables don't describe how the system is, it interacts,
how the system interact with something else. Okay, so for example,
we have a particle and it's flying along and it
has a certain way function for things that might do,
and Copenhagen interpretation says it stays probabilistic until something classical
(25:39):
interact with it. Relation or quantum mechanics says it can
collapse when it interacts with anything, but that collapse is
different for depending on who is interacting with it. So
if it interacts with this particle might collapse in this way.
If it interacts with somebody else, that might collapse in
another way. In that sense, it's also sort of like
a branching of what reality is real, because what is
(26:00):
real now depends on who is doing the measurement. Is
that right? That's exactly correct. So the so called collapse
of the way function is by itself, something which is
relative to the system against which the particles is interacting,
which doesn't need to be a macroscopical object, doesn't need
to be anything special. It's anything but this. The subtlety
(26:23):
is the following. I suppose the particle interact with my machine,
my detector, okay, and I am I am a distance
and the two are not interacting with me. So with
respect to me, there is no collapse happening. So the
way the particle and the machine are gonna manifest themselves
(26:44):
to me later on if they interact with me is
still computed with quantum mechanics. So if I want to
compute what happens with respect to me, I still use
the way function of the particle and the way function
of the machine, because the machine is quite mechanical, I think.
So for example, I'm here talking to you, so I'm
measuring you. I'm collapsing your way function. But our listeners
(27:06):
have not yet heard this podcast, so from their point
of view, you and I are still in some uncollapsed
quantum state, and only when they hear this does it
collapse into an actual stream of words. So for us
it is collapsed, but for them it's not yet collapsed exactly.
So I believe that this is coherent. This can be
made clearing by going into details. It offers a possible
(27:27):
solution of the puzzle quantum theory. This is a relation
with dempetition. It does require it has a cost. There's
a conceptual cost, because as you said, reality is a
little bit more subjective. No subjective relative. I'll come back
to the difference subject in relative. So it weakens realism
(27:47):
in a sense, but it's still a realistic interpetation. So
I think that this cost is more worthwhile paying for
being fruitful for the future of physics than imagining that
there are many copies of myself, or than not asking
the question when you come to the subtle team. In
(28:07):
your example, you talked about you and me and the
listeners all people. Okay, that's fine, but the key intuition
of relationship about the mechanics that this has nothing to
do with people. That's the key point. And that's a
big difference with respect also with coping again in a sense, right,
this is nothing to do with subjectivity. That's it to
(28:29):
do the subject. But factly you and I are are
subject of perceptions as need to do. You would also
work if you and I were dogs or bananas or particles, right, exactly,
the same mathematics work, exactly as I'm the same story
would work. And to make an example of this, because
I think that you know, relative to observer observable are
(28:51):
often misinterpreted as subjective while it's just relational. For instance,
there's a very well known example of relational notion in
physics which students struggle at the beginning when they encounter
it the first time, because it's very contin intuitive if
you think at the beginning, which is velocity. When we
study Galian theory a Newton theory, we learn that velocity
(29:17):
is not absolute, velocity is relative. So what is the
velocity of the moon. Well, depend there's the velocity of
the moon we respect to this Earth, the velocity of
the moon we respect to the Sun. The velocity moon
we respect to the center of the galaxy, the loscy
moon respect to the cosmic microwave background average. Which one
(29:38):
is the true one? Well, no, it's a velocity. It's
a notion that pertains the two objects, the moon and
something else. It's always velocity of the moon with respects
something else. We sort of know that, right, because when
we say don't move, we know that don't move is
relativitally to something. For instance, if you're in a train
(29:59):
and your little daughter is jumping around and you say
don't move, you don't mean that you little daughters to
jump out of the train and don't cove with respect
to the earth. Right, you mean don't move respect to
the train. And she understand correctly right that she should
soon move respect the train and she's just still moving
very fast because the train is running. So we understand
(30:20):
that velocities are it's it's a relational notion. But this
is nothing to do with subjectivity, right because if I
say that the moon has a velocity respect to the sound,
I'm not saying that the Sun is a subject that
sees the moon and perceives something. Is nothing to do
with that, nothing to do with mind subjectivity, Just physics,
pure physics. There is a quantity to velocity which doesn't
(30:44):
depend on one thing. It depends on two things, the
Moon and the Sun. And it's velocity the relative velocity
of the two, say how they move respect one of that.
So that's a big philosophical step, right, You've sort of
taken away from the moon the fact that it can
have a property called velocity. Say, you can't have a
property called velocity. Only a pair of things can have
this property. A single object cannot. And the sort of
(31:06):
the mental game i'd like to place to imagine, like
a particle in an empty universe, can it have a velocity? Well,
it has no meaning to have a velocity if you
are the only thing in the universe, right, And so
I want to also ask you about this concept of cost.
You're talking about the cost of a theory, and so
here is that the cost you mean that you're like
now changing philosophically what it means to be real that
(31:26):
no longer can you include in your sort of you know,
category or your index of what it means to be
that you have a certain velocity that you've like taken
that away from objects. Yes, this is the course, and
I think you said it very cleanly. It's a deep
philosophical point when we realize that velocity is not a
property of an object you need another object, is a
(31:48):
property of two objects. A quantum mechanics in a sense.
The phone suggestion that we in this em better quantum
mechanics if we just interpreted all properties, all variable in
this way, not just velocity. Okay, any variablity, even think
about a system only makes sense if you if you
(32:11):
have another system. You're saying it's this is a variable
with suspect to this other system. And what you mean
is that there was an interaction to these two systems
and that variable was realized in this interaction. Namely, describe
the way one system affected the other one. And can't
you use even the same language. Because now we talked
about velocity. We say velocity of the moon as measured
by an observer on the Sun, or as measured by
(32:33):
observer on the Earth. Now you can say the location
of this particle or the color of this particle as
measured by this observer versus as measured by that observer exactly.
(32:56):
Now you went strongly in saying, does this mean that
reality itself it's relative to um? I hesitate. Namely, the
same reaction could have been raised against the Galileo and
Newton when they started using velocity. In this sense, I
(33:18):
think that the reality of the motion of the moon
and velocity of the moon and the Sun and things,
in spite of what we have understood about relativity velocity
is still very solid. Still we still have a realistic
interpretation of motion, and so I would like to think
about relational quantum mechanics as a realistic picture. So reality
(33:41):
is there, it's I mean, things are there, and then
there's nothing to do with us. Of course, we are
just a part of nature. Is not that nature is
a part of our mind. That's my naturalism if you want.
But the way reality is is subtle. According to quantum
mechanics can be described. Reality can be described by systems
that have a properties relative to other systems. So then
(34:05):
can you have something which exists by itself like imagine,
you know, the sort of simple example I mentioned earlier.
For velocity, a single particle an empty universe can't have
a velocity. Now you said that everything is relation on
the way velocity is. Does that mean a single particle
in an empty universe does not exist or cannot have
any properties because it would need something else in order
(34:27):
to measure it. Can a single particle universe exists? No,
if quantum mechanics max is the correct description of the units.
And in fact that can be said in a beside
the way. There's a philosopher which is Madorato who is
elaborated much on that, saying, if we take relationhp quantum
mechanics correctly, we cannot talk about the quantum state of
the universe. We cannot state of the quantum state of everything.
(34:50):
We cannot even talk about the description of the universe
because the scripture universe needs to be if you use
this way of thinking, a point of mechanics scripture relatively
to something else. So in the moment in which you're
saying the description units, so you're assuming there is something
outside that is looking at the universe. Well you can,
but then in your reality there is something else in
(35:10):
addition to what you just called the universe a moment ago.
For instance, the famous way functional units, what is it
is a mathematical object that allows you to predict what
you would measure if you are outside the universe to
interact with it. But then it's not the universe anymore
because there is something else outside the universe interacting with it.
(35:31):
So there's the way functional use is meaningless. It's always
the way function of something. I was hoping to use
that example to lead you down the garden path to
admit that means the universe can't exist, but you just
went straight there and said, if this is true, then
we don't have a meaningful concept of what the universe is.
I mean, isn't that a problem? I mean, if we
(35:53):
want a theory of reality that tells us what is happening,
doesn't it need to also allow us to think about
what reality is. I think that it's a deeper point
one of the things we have understood more and more
in modern physics, but also another realm of modern culture
is that we're always part of the story. So we
(36:13):
see reality from we think, not from outside in completely
different parts of our culture. First this this was famously
an immense issue and toropology, right, you want to describe
a society. When the Europeans went around the world to
try to describe societies objectively, um, non European societies, maybe
I don't know some people in their matson and then
(36:36):
they re allies that they were not doing nothing objectively.
They were just comparing their own culture with the culture
of these people. In some of they were interacting with
these people and not being outside a cultural scheme, but
doing something and olmously interesting, not something that lacked value,
but that was not a stepping out from what is
(37:00):
being described. And I think physics to some extent has
encountered the same set of problems. Namely, we described the
universe from within. We are part of the universe. What
physics tell us is if I encounter this, I know
what I can expect, and I know what a what
(37:21):
I can expect, what kind of things aide around me.
But the idea that physics give a list of all
or everything existing with the state, it's a first of all,
totally unplausible by itself, right, I mean, how many stars
there are in the universe, and how many atoms in
each one of these stars? So it's just totally outside
(37:42):
or a capacity. But even in principle, what does it mean.
I mean, physics is all in the form if this,
then that, right, If I found this pendulum in this way,
then it's going to move that like that. It's model,
as the philosopher says. So it's always a story of
out given some initial conditions, this is what I expect
(38:03):
to happen, given some data, this is what comes later,
and then it tells what kind of atoms are around,
the forces are around. But we shouldn't expect from physics
the total novel of the universe. That's what everything is
in the universe. That's at all the state of the universe.
Why it's not that's far outside our capacities, And probably
(38:26):
I would say it's meaningless because of what we said before,
because that would be an issue that God might have
if he or she exists seeing from the units from
the outside, not of all our business. And I think
this makes exactly the point that you were talking about earlier,
that we want to know the answers these the philosophical questions,
because they tell us which questions then makes sense to
(38:49):
ask which questions have answers, and which questions are even
relevant to think about. I think that's some of the
most important reason why physicists need to think about philosophy.
And I know that you talked about the mechanics a lot,
and you're quite an expert on this, So I want
to try to ask you a question that maybe nobody
has asked you before, put you on the spot, and
and that's this. Have you thought about what it might
be like to talk about physics or quantum mechanics with aliens?
(39:14):
Imagine that we have meet extraterrestrial physicists, right, and we
go and we we say with to them whole you
must know the secrets of the universe because you figured
out how to travel here from distant stars. Do you
think there's any possibility that we would be asking the
same questions or that their answers to our questions would
make any sense to us. Do you think that the
way that we look at the universe is sort of
(39:35):
the way Europeans, you know, looked at other cultures. Do
you think that's deeply imbued with our human bias, or
do you think that we are probing something universal which
should be part of sort of like some galactic physics project.
Great question. A bit of both, but more of the
first and the second. That's my answer. There is a
precise sense in which what we discover in science is
(39:55):
it's just two in universal mean. I don't think this
can be denied, and people who denied it, I think
have a toak way of denying it, and don and
physics in some sense, it's true. It works described reality.
It's I mean, the fact that everything is made by
atoms and there are ninety and so kind of different atoms.
That's a fact. It's like when you you know, when
(40:18):
you go down the street and you see that you
know your three friends are in the cafe. That's a fact.
It's true. And I believe that science is a higher
level of understanding. Fact is the way humankind organizes an
understanding of reality better and better. But from this, to
have the idea that there is a unique, clearly path
(40:43):
to the perfect description of reality and we are on need,
or even that we're close to the end of it,
that seems to me unbelievably full of self pretension, and
I see no sign that we're close to that. And
we have a sort of experiment of that because we
know what asked centurists, scientists thought, and we do know
(41:07):
that some of the things that we know would be
meaningless for them, It would not answer their questions in
really going in a different direction, which does not mean
that they are better than us. We are better than
them because we know what they are in some objective sense,
and the objective sense is that if both one came alive,
(41:27):
and if I could have enough time also want to
me sitting here, I believe that I could slowly arrive
to convince him that there are a lot of interesting
things he doesn't know. So I think it's the same
with some aliens. If some millions would come, I wouldn't
be surprised if they have a completely different story. And
it might be possible that we just don't understand one
another because the story is two different. It might be
(41:48):
different because they have a different way of perceiving reality. Right,
we view reality on the basis of what useful to
our They're being an evolution, not on the basis of,
you know, some contient rationalism or simply even if they
had the same senses, because culture of them was going
in other directions. But I believe there is communication, right,
(42:08):
Cultures communicate, So maybe with this aliens we could learn
to communicate. And we were very surprised of learning completely
different perspectives. If they are more advanced than us in
some sense, or maybe they will be surprised to learn
something from us, or maybe both. So in other ways,
I don't think there is a path to tools, and
(42:28):
they would know everything we know any more. Maybe they
would never think about quantum mechanics and we teach them
quanto mechanics. That was fantastic. You're right, it's a relationship.
But will send you to meet the aliens and how
they don't eat you. There is a greater novel, The
Dark Clouds The Black Cloud, in which there is this
it's a huge cloud that come towards the sermon and
(42:51):
somebody realizes that it's actually intelligent something down there, and
it's uh, and somebody realized that it is going to
be a disaster for the Earth is going to exactly
edge of the sound. And somehow so the scientists arrived
to communicate and so gently convinced this cloud to leave
us alone. But then there is one scientist so too.
(43:12):
I don't remember. That's the Wait a minute, I want
to learn everything you know, So the cloud answer, well,
it's tandrous. I mean your little brain. But they really
wanted to so they can say, okay, if you really want, so,
I think it's two of them. They sit around the screen, okay,
and the screens start flickering, and they just look at
(43:32):
this at the beginning. At the beginning, they don't understand,
but then they start understanding, and then finally they start learning,
and then they're lost because then they're considered fool and
they're putting all the psychotic hospital and the body knows what.
That's the danger of talking physics with aliens is you
can see reality, so clearly the humans can no longer
(43:53):
relate to you. So let me bring it back to
one last question about relational quantum mechanics. What you're proposing
here is really a ratheric of departure on a way
of seeing the universe, imagining that objects don't contain on
their own properties, but that these things are just dependent
on pairs, essentially things that are measuring other things. So
my question to you is that how could we know
(44:14):
if this is true. Is there some experiment we can do?
They could tell us, look, Copenhagen fails here and we
need relation or quantum mechanics, or we can dispense with
the many worlds, like is this something which can only
ever be a philosophical conversation among physicists motivating our questions
about reality, or is this something we can actually one
day put to the test. I don't see any way
(44:35):
it could put to the test. There's some interpretation quantum
mechanics that assume that quantum mechanics actually wrong, and so
they can be tested because you can do an experiment
to see where the quantum mechanic is wrong right, And
they're very interesting. And so far many of these tests
have been done and quant mechanics always going to be right,
and all alternative from the moment have been all eliminated.
(44:57):
But the various interpretation like many world or de bullyable,
the pilot wave interpretation, hidden variables or relationship quantum mechanics,
which I think are the main one. So cubans maybe
in one sense, they are not distinguishable in an empirical way,
as as far as I know, nobody has come out
with experimented distinguished them, and in a sense studying them,
(45:18):
there's no experiment making a difference, So how would we know, Well,
I think exactly the same way, which we finally all
agree that the Earth is not the center of the universe,
even if there is no experiment that tells us that
the Earth is or is not the center of the universe,
because there's no way to measure just what the center
(45:38):
the center units, namely, the progress of science will work
better with one conceptual scheme than the other. I do
quanta gravity my main the reason I got into the
issue of integrational quantum mechanics, and the mechanic goes back
to the nineties. In fact, my first papers on that
in the late nineties, and then other people can and
(46:00):
have developed it and in recent years have been a
much stronger increasing interest in it. And it's not isolated
because there are the people who are very similar ideas,
So which why is really part of a little group
of interpretation just similar in some sense, maybe with different emphasis,
different tone. I'm thinking of writings by Zeilinger, by Chancellor Bruckner,
(46:27):
by Richard Haley and another. There are a number of
ways of going in the same direction, so in my
own work and trying to put up a quantic see
of gravity, I found that this way of thinking, it's
much more helpful when you don't have space, you don't
have time to locate things, you don't have the observer.
This relational way works well. And one reason it works well,
(46:49):
it works through well well with general activity, where location
is relations. Nothing has a position to be somewhere. It's
only meaningful if you're some well respect to something else.
And now the things start staying together well, because to
be next to something is possibility of interacting with something,
so you can exchange information with something. That's what we're
(47:10):
talking about in physics, this being next to one another
and exchanging something, rather than having, you know, it becomevast
there and placing things and saying that's that's what reality is.
So I hope that the discussion about indevidual quadema is
going ahead. It's not blocked, it's not the same as
thirty years ago. And I think that with the new ideas,
(47:31):
with the new things being discussed, at some point it
will become more and more clear that one way of
viewing things it's productive. It works. It doesn't require us
to assume things which are absurd, but it does require
us to assume things which are necessary to make in
sense of reality. Wonderful. Well, that's a fascinating insight into
(47:53):
how we might make steps forward. And I agree with
you that it makes sense to unify quantum mechanics with
relativity if quantum mechanics itself becomes sort of relativistic, not
in the sense of things moving at very high speeds,
but in the sense that the objects and the quantities
we measure themselves are relational or relative to other objects.
(48:13):
So that makes a lot of sense. Well, thanks very
much for this fascinating conversation, really stimulating, you know, about
quantum mechanics and physics and relativity and of course aliens
and philosophy. I want to thank you very much, and
I want to point our listeners to your book Health
Go Land, which has just come out recently, and it's
fascinating read on these ideas and how they were developed,
and people who are interested in digging more deep into
(48:35):
them might encourage you to check them out. So Carlo,
thanks you very much for joining us on the program today.
Thank you. Emaually, that's what's great. Thank you. Thanks for
listening and remember that Daniel and Jorge explained. The Universe
is a production of I Heart Radio or more podcast
(48:57):
for my heart Radio, visit the I Heart a new Apple,
Apple Podcasts, or wherever you listen to your favorite shows.
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