Hello and welcome to the series on physics and philosophy from the University of Oxford.
As children, we ask many questions like where the world comes from, what we're made of, and why the sky is blue.
These big questions have fascinated us throughout history, and we have turned to different ways of solving them.
Today, we may ask a physicist or a philosopher for answers.
But once upon a time, they would have been the same person.
What started off as just pure thought has today branched into a number of disciplines which aim to study the world around us in different ways.
However, it seems that to gain a full understanding of the workings of the world, it is important to use these disciplines to complement each other.
I am anchored on everyone and I am speaking to Dr. Christopher Palmer, physics lecturer at Baylor College, Oxford.
Dr. Palmer is the head of Lab for Physics and Philosophy Undergraduates and
also the chairman of the Joint Standing Committee for Physics and Philosophy.
Dr. Palmer The original ideas behind modern particle physics can be traced back to ancient Greek philosophers.
How closely would you say Greek atomism is related to modern physics?
Well, I think that's interesting because in some ways it is.
And in some ways it isn't. If you're thinking about the nature of matter,
you've got a kind of choice between whether you think what's at the root of it or what's
what's the most fundamental thing is something continuous or whether it's something discrete,
and the discrete option is atomism. And to say that it's discrete, you have to say that.
And also fundamental is is to suggest that it's indivisible.
And that's what atoms fundamentally means. It's the thing that can't be cut.
It's what is indivisible. And of course, the name Atom is now got attached to the wrong thing, because the chemical atom is, of course,
very divisible and has been split in several different ways, both chemically and the nucleus by particle physics.
So the indivisible is not the atom, as we now call it.
But nonetheless, particle physics does deal with indivisible the particles, the fundamental particles of nature.
So the idea is continuous, even though the name has got attached to the wrong thing along the way.
So how did these ideas develop? Well, Aristotle backed the continuum idea and that was picked up by the church.
And in the Middle Ages Atomism was associated with heretics on the whole.
So that sort of held back the development of atomic ideas in the in the early part of the Renaissance,
because nobody wanted to go out into the open and say that they supported Atomism.
A lot of people thought that it offered ways of explaining things that couldn't be explained by assuming that the fundamental matter was a continuum.
And and so from Galileo through to Newton, the fundamental atomic hypothesis got fairly well developed in physics,
and many people began to think in those terms,
although there were still people who didn't really believe in atoms for another couple of hundred years after that.
Really? It was Einstein who offered quite a lot of proofs.
Well, not proofs.
Indications of the atomic theory by finding various different ways to calculate the number of molecules in a in a standard quantity of gas,
all of which seem to give the same answer, which was quite indicative of the correctness of the ideas.
But then when subatomic particles were discovered, beginning, of course, with the electron in 1897, these were seen to be constituents of atoms.
And so the thing that can't be can't the original indivisible is not the atom itself, but some piece of the atom.
First the electron, and the electron is still thought of as essentially indivisible and fundamental,
although the other particles that were discovered at an early date like the proton,
are now thought of as composite and containing more fundamental pieces within them.
But I suppose the idea of particle physics that the name itself is suggesting some
kind of fundamental entity which is discrete and in the original Greek sense,
atomic. So today we have fundamental particles such as quarks and leptons, which we believe to be indivisible,
but say that these could be divided further, which we could discover in a few years with more research.
Do you think that by dividing atoms and quarks up infinitely, almost,
we could reach a sort of stage where we do come to the conclusion that matters continues?
Or do you think there is a discrete, fundamental level which we can cut it down to?
I think maybe it's more subtle than that.
And we're coming to see that this original Greek choice between the continuum and the particle doesn't have to be made and that they can coexist.
Because the idea of the fundamental particle is that it's embedded in a sea of interacting
fields which give the space between the particles something of the nature of a continuum.
So what we now call the vacuum is now not seen just to be nothingness,
but actually quite a fertile ground where lots of things are going on and where more things can be made to go on.
But if you if you deposit some energy into it, that the particles themselves are not,
in fact, separated by a nothingness, but something that's much more like a continuum.
So it seems that the dichotomy between the Greek atomism and the Greek ideas of, for example,
ourselves elements which are continuous, a kind of coming together now with modern physics.
I think that's quite a fruitful way of looking at it.
During the scientific revolution when modern physics, as we know it started, physics and philosophy were still very closely linked.
In what ways would you say that the progress in the two disciplines influenced each other?
That's a very big question. Originally in the early part of the Renaissance, physics was a philosophy based discipline,
natural philosophy, and it didn't have a very strong experimental base.
And in fact, there was a lot of debate in right up until the early 17th century as to whether experiments could refute philosophical ideas or
whether they were necessarily too much influenced by specific and local things and didn't give you any insight into universe laws.
And that may be the way to find universal laws was not by looking at specific experiments, but by thinking about things in a philosophical way.
So in that sense, in the early stage,
philosophy was a brake on physics because it prevented people from using the results of experiment to correct ideas.
Once the idea of an experimental program had developed more cogency and people had thought that that was a useful approach to physics,
then there was, I think, quite a long period when physics and philosophy were in touch with each other,
and that probably continued right up until the early part of the 20th century,
when certainly in continental countries and to a lesser extent in Great Britain, a philosophical training was part of the training of a physicist.
But maybe the generation of Einstein and Bull and Heisenberg was perhaps the last generation to have that real philosophical background,
and that the later part of the 20th century saw much less explicit engagement in philosophical ideas from the physicists.
So what would you say was a turning point when experiments started to be taken seriously and when experimental physics really took off on its own,
away from natural philosophy, which relied more on the theoretical side of things.
Well, you could answer that in several different ways. You could go right back to something like boil in the air pump in the 1660s and the debate with
Hobs over whether or not they were making something that was approximating to a vacuum and so on.
And whether or not experimental ideas were capable of being taken as reliable because of the difficulty of many
people witnessing the experiment and what the experiment had actually shown and where the experiment had worked,
and all questions that were much debated in the 1660s and seventies.
Or you could take it much later and say that James Clerk Maxwell, for example, in the mid-19th century,
used philosophical ideas to develop his theories of electricity magnetism,
which became ultimately the Maxwell electrodynamics that we use still today.
Richard Feynman in the 20th century was notably and perhaps famously dismissive of philosophy, although I think,
in fact, he was probably much more sensitive to philosophical implications than he wished to admit.
More recently, eminent physicists in the 20th century, such as Heisenberg and Seneca,
have used philosophical ideas, as you mentioned, to explore the implications of their theories.
What are the philosophical implications of modern scientific theories,
and how important do you think it is for the modern physicist to have an understanding of philosophy?
Well, I think all modern theories have got to a point where the issues that they're dealing with are quite deep and need careful,
structured, philosophical thought.
Quantum mechanics has been at this stage for a long time, and there's been enormous debate about the correct way to think about it.
Which is, of course, still ongoing. But so also is field theory with this search for a unifying theory of gravitation and particle physics.
Because our best theories of gravitation and particle physics seem to start from such
very different starting points that it's very hard to see how to put them together.
And therefore,
in a sense that there is an initial philosophical question of what fundamental elements of the two theories will pass into the new theory,
the choice of of the building blocks of the theory.
And that's really a philosophical question, even if the physicist isn't necessarily recognising to such.
Thank you very much, Dr. Palmer.