Lee
Smolin is an American theoretical physicist who has contributed to
quantum gravity theory. He specifically known for the theory of loop
quantum gravity.
Smolin
is also a faculty member at the Perimeter Institute for Theoretical
Physics, an adjunct professor of physics at the University of
Waterloo and a member of the graduate faculty of the philosophy
department at the University of Toronto.
In
terms of the following piece, Smolin is a very philosophical
theoretical physicist and cosmologist
who
takes philosophical positions on various issues in science. One example of that is his position on the nature of space
and time and the things
(to use
a very broad term) which exist within space and time.
Newton
on Space and Time
Smolin
expresses what he deems to be Isaac
Newton's
“hierarchical picture” of space and time when
he
says
that within that picture
“atoms
with fixed and absolute properties move against a fixed background of
absolute space and time”.
Indeed
Newton's position (which has been called
substantivalism)
has it that space and time are themselves things
(for want of a better word). That is, space and time are things which
exist independently of all the other things "within" them.
Smolin
concludes by saying that this Newtonian picture is “quite dead”.
Smolin
is what philosophers would call an anti-essentialist. That is, Smolin
doesn't believe that there are “intrinsic properties”. Instead,
as he puts it, “all properties are about relations between things”.
Thus,
in the quote above, Smolin used the words “absolute
properties”, by which he meant:
“absolute
entities” = entities with "intrinsic properties"
Thus if entities have intrinsic properties, then those properties will neither change over time nor will they be changed by other
entities or conditions. (Unless the entity concerned simply stops
existing as the entity that it is.) According to Smolin, it's this
ostensibly unchanging nature of intrinsic properties which makes them
“absolute”.
Such
much for absolute entities. What about Newtonian space and relations?
It's
not immediately clear why Newton's position on space would automatically exclude a “relationist”
take on things/atoms.
After all, “atoms with fixed properties” may still partake in
relations even if space is
fixed
and also if the atoms within space have absolute
properties.
Why can't we have absolute properties and things which partake in relations?
Smolin's
alternative picture to this is a “relational” or “dynamical”.
It's a case of spacetime itself - and all properties/things/atoms
within it - being relational or dynamical. In other words, in
Smolin's universe, literally nothing is absolute
or intrinsic.
Leibniz
on Space and Time
Smolin
then cites Gottfried Leibniz as a relationist.
Or, at the very least, he sees Leibniz as being a relationist when it
comes to space and time. So, unlike Newton, Leibniz
“wanted
to understand [space and time] as arising only as aspects of the
relations among things”.
Smolin
sums up the two opposing positions when he says that “this fight”
is
“between
those who want the world to be made out of absolute entities and
those who want it to be made out of relations”.
Smolin
adds that this opposition is a “key theme in the story of the
development of modern physics”.
In
terms of Leibniz again, Leibniz's position (as expressed by Smolin) is that
space and time don't exist – at least not as independent phenomena.
Space and time essentially arise as ways of making sense (as it were)
of the (as Smolin puts it) “relations among things”.
In other words, space and time are the means by which we plot the
relations among - or between - things. That basically means that if
there were no things, then there would be no space and time either.
That is, space and time aren't (to use Smolin's word again)
“absolute”: they're a consequence of things and their
interrelationships.
Nonetheless,
if space and time don't exist, then what are these things
moving about in? It can be supposed, of course, that both space and
time come into being as soon as there are things which have relations
with one another. But how does that work? Even if space and time do
spring into existence as soon as things
spring into existence, then it's still the case that things move
about in space and exist through time.
So
here are two alternative conclusions:
i)
Space and time depend on things and their relations.
ii)
Things and their relations depend on space and time.
The
obvious way out of this opposition is simply to say that there's no
hierarchy involved here: spacetime and things depend on each
other. That is, space and time aren't more important (or fundamental)
than things; and things aren't more important (or fundamental) than
space and time.
What's
called “relational
theory”, however,
is indeed eliminativist about space. This theory has it that if there were
no things, then there would be no space either. Relational theory is
eliminativist about time too in that if there were no events (in
space), then there would be no time.
Smolin's
sums up his non-Newtonian (or Leibnizean) position when he states (in
his Three
Roads to Quantum Gravity)
that it's
“absurd
in general relativity to speak of a universe in which nothing
happens”.
Relationism
or Relation[al]ism?
Smolin explicitly states his relationist
(or Leibnizean) position
in
the following:
“There
is no meaning to space that is independent of the relationships among
real things of the world. ...Space is nothing apart from the things
that exist. ...If we take out all the words we are not left with an
empty sentence, we are left with nothing.”
However,
there may be a problem here with the use (above) of the word
“relationist”. That's because there are in fact two different words
which are often used within this metaphysical context: “relationism”
and “relation[al]ism”. Prima
facie,
they denote two (slightly?) different positions. However,
on analysis, the distinctions between them appear to break down –
at least in certain respects.
On
my own reading, Lee Smolin seems to go one step beyond what's called
“relationism” and delves into the domain of “relation[al]ism”.
What I mean by that it can be said that relationism
simply emphasises the relations between things: it doesn't deny that
things exist. With relationalism (with an added “al”), on the
other hand, “things exist and function only as relational
entities”. That is, if there were no relations, then there would be
no things. Relationism, on the other hand,
simply notes the importance of relations between things; it doesn't
claim that things -
in and of themselves – don't exist.
Nonetheless,
even if these definitions are incorrect (or if I've misnamed Smolin's
own position), it's still the case that there's a difference between
what can be called the eliminativist
and the
non-eliminativist
position
on things.
Thus
relationalism is like ontic structural realism (which will be discussed later) in that the latter eliminates things
from its metaphysical picture (“every
thing
must
go”).
Relationism, on the other hand, simply places relations in an
important position in the metaphysics of
things.
Having
said all that, it's hard not to see the importance of relations even
if one accepts the existence of things as independent entities. (Of
course the metaphysical notion of independence
would also need to be cashed out.) On the other hand, it's also hard
to accept (prima
facie)
the
elimination of things from the metaphysical picture.
Moreover, one can also see the vital importance of relations when it comes to physics. On the other hand, one can't really see how things could be entirely eliminated from physics either. (This may also ultimately depend on how the word 'thing' is defined.)
Moreover, one can also see the vital importance of relations when it comes to physics. On the other hand, one can't really see how things could be entirely eliminated from physics either. (This may also ultimately depend on how the word 'thing' is defined.)
Yet
in (“analytic”/pure) metaphysics one can indeed conceive of
(or imagine) a metaphysical picture in which things don't exist. One
could also imagine a picture in which things don't have any
relations (at least no causal relations) to other things or indeed to anything. These scenarios could
constitute the metaphysical natures of particular possible worlds.
Though, since Smolin is dealing with the actual universe, it's hard
to make sense of such metaphysical eliminativism when it comes to
physics itself.
Nonetheless,
relation[al]ism can also be read as not actually being eliminativist
at all. After all, this metaphysical position may simply have it that
things (or entities) aren't what's called “self-standing”. To put that
another way: what makes things the
things that they are
may be their relations to other...
things.
Or we can even say that particulars (things) are essentially relational.
Alternatively, we can say that all a thing's properties are
relational. That is, it has no “intrinsic properties”.
Thus,
in a weak (or even strong) sense, if all things only have relational
properties (and such properties literally make all these things the
things that they are),
then there is a sense in which things
are indeed eliminated from the metaphysical picture. To put that
simply: if a thing's relations (or relational properties) were
eliminated, then it would no longer be that thing. Indeed it would
no longer exist.
Relations
and Structure
Despite
all the above, it's still hard to make sense of the idea (to use
Smolin's words) that “the world is [only?] made of relations”. What does
that mean?
This
question also relates to the metaphysical position known as
scientific
structuralism
(i.e.,
in
the philosophy of science).
Here too relations
and structures
are deemed to be fundamental. Yet two similar questions can also be
asked here:
i)
How can there be structures without things?
ii)
How can there be structures without space and time?
Relations
and structures may well be of utmost importance in both metaphysics
and physics. Nonetheless, surely there are no relations and
structures without things (or even substances).
So,
again, how can the world be “made out of relations” alone? The
same goes for Smolin's other claim that “all properties are about
relations between things”.
And
what does Smolin mean by the words “all about”? We can easily
accept that relations between things are important. But so too are
things and their properties. So how is it that properties “are
[only] about” the relations between things? In other words, is this
part of an identity statement? Namely:
“properties”
= relations between things
There
are indeed properties which are relational. However, it can be argued
that not all
properties are relational. Indeed isn't it the case that in order for
some properties to be relational, other properties need to be
non-relational?
As
for the elimination of things.
Take this simple sentence: “x
is bigger than y.”
In
order for x
to be bigger than y,
both x
and y
need to exist as things
(or at least as something).
It's true that the property (or universal) IS BIGGER THAN may be seen to have an abstract non-spatiotemporal nature. However,
the original statements was “x
is bigger than y”,
not simply “is bigger than”. That is, we're not simply talking
about the abstract property (or universal) IS BIGGER THAN.
Despite that,
there may indeed be certain relations (or relational properties)
which don't involve concrete
things. (There are relations between numbers, for example.) However, if we
return to Smolin, it's not the case that he's talking about relations
between abstract entities even if
the relations themselves can
be deemed to be abstract.
Ontic
Structural Realism
Smolin
elaborates on his relationist universe firstly by saying that if
“the
only meaningful things in this theory are relationships between real
things”
then
“it
doesn't make sense to talk about space being made up of different
parts, or time being made up of distinct moments, unless the points
and the moments can be distinguished by what's happening there”.
Here
Smolin's position is fairly close to another structuralist
position in the philosophy of science. Namely, the contemporary
philosophical metaphysical position (as usually applied to physics)
of ontic
structural realism.
In the ontic structural realism picture, “it doesn't make sense to
talk about” things with their own determinate (or intrinsic)
properties when these things “can only be distinguished” in terms
of their structures and relations to other things (within spacetime).
In simple terms, the “things” of ontic structural realism can
only be distinguished in
terms of their mathematical structures and relations. There literally isn't
anything else.
In
terms of Smolin's own picture, spacetime itself can only be
distinguished in terms of (in Smolin's own words) “what's happening
there”. That is, what's happening at specific spacetime points. And
what's happening at specific spacetime points is invariably a matter
of dynamical non-intrinsic properties and their mutual relations.
So
just as spacetime works as a means to plot dynamic properties and
things together, so ontic structural realism has it that things
are mere placeholders
used to
plot relations and structures together.
Loop
Quantum Gravity
Lee Smolin
updates his relationism by tying it to the scientific theory of
“loop
quantum
gravity”. Smolin also ties loop quantum gravity theory itself to relativity
and quantum theory. Or as Smolin
himself puts it:
“I
believe that the main lesson of relativity and quantum theory is that
the world is nothing but an evolving network of relationships.”
Thus
Smolin explicitly ties Einstein's general theory of relativity to his
own relationist position. Smolin believes (as stated in his The
Trouble With Physics)
that in the general theory of relativity
“[t]he
geometry of space and time changes and evolves, as does everything
else in nature”.
What's
more, “[w]e no longer have fields moving in a fixed-background
geometry”. Instead,
“[w]e
have a bunch of fields interacting with one another, all dynamical,
all influencing one another, one of which is the geometry of
spacetime”.
Smolin
christens this a “background-independent theory”. He defines this
position as one in which
“[n]either
space nor time has any existence outside the system of evolving
relationships that comprises the universe”.
Indeed
this soup of interrelating fields not only creates spacetime, it also
creates the particles and all the other entities/conditions which
exist at a specific point in time and place in space.
As
just stated, Smolin makes his metaphysical relationism more
concrete by tying it the physicists' notion of a “field”. More
specifically, he ties it to the theory of “electric fields”.
According
to Smolin,
“physicists using general relativity” can't
“speak
of a point, except by naming some features of the field lines that
will uniquely distinguish that point”.
Moreover,
this “network of relationships evolve[s] with time” and is
“constantly changing”.
Specifically in terms of “loops”.
The
loops of loop quantum gravity theory describes the nature (or
structure) of space. That is, loops are
extremely
small (the size of a Planck length) and they make up the “fabric”
of space. Loops are also called “spin networks” (which provides a
“spin foam”). Thus both matter and space (in the loop quantum
gravity picture) are deemed to be “atomic” (this word is used
very loosely in this context).
Another
way of describing this is to say that in loop quantum gravity space
and time are quantized. That is, space and time are made up of the
aforementioned “atoms”. Or, more technically, space and time are
seen to be “granular and discrete” in the same way that the
quantities (e.g., photons, etc.) of electromagnetism (or energy) are
seen to be discrete in quantum theory. This means that space, time
and energy can be quantized precisely because they're discrete (or
atomic).
Smolin
himself says that
“what's
wonderful about the loop picture is that it's entirely a picture in
terms of relations”.
It
is these loops which are relational and dynamic. And, by inference,
loops make up our relational and dynamic spacetime.
In
more detail, in this picture it's the case that
there's
“no
preexisting geometry for space, no fixed reference points; everything
is dynamic and relational”.
What's
more, Smolin claims that
“[t]his
is the way Einstein taught us we have to understand the geometry of
space and time – as something relational and dynamic, not fixed or
given a priori”.
So
whereas Newton believed that space and time are fixed; Smolin rejects
that position by claiming that there's “no preexisting geometry for
space” (or “no fixed reference points”). That means that we
have a spacetime with a geometry that's “relational and dynamic”.
However,
it's almost certainly the case that Einstein would never have
expressed his own position in Smolin's own way. Nonetheless,
Smolin's words may well still be an accurate (or faithful) reworking of
Einstein's essential position on spacetime geometry.
Loop
Quantum Gravity vs. String Theory
Smolin
specifically counterposes loop quantum gravity with
string theory. As Smolin
puts it:
“In
string theory one studies strings moving in a fixed classical
spacetime. ...what we call a background-dependent approach. ...One of
the fundamental discoveries of Einstein is that there is no fixed
background. The very geometry of space and time is a dynamical system
that evolves in time.”
Indeed
Smolin (along with such people as
Carlo
Rovelli,
John
Baez and Abhay Ashtekar)
have rejected string theory precisely because he deems it to have
retained the (Newtonian) notion of “absolute space”. Loop
quantum gravity, on the other hand, upholds “backgroundlessness”.
So
here again Smolin allies himself with Einstein and connects his own
“background independent” theory to his metaphysical relationism.
Let's sum up Smolin's overall relationist position.
Smolin
isn't only talking about things and their relations: he also sees the
geometry of space and time as being relational. Indeed one can says that the geometry of
spacetime is relational/dynamical precisely because things and their
relations are also relational/dynamical.
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