what is everything made of
know this for instance
atoms
and atoms are made of electrons and a central nucleus
the nucleus is made up of neutrons and
protons neutrons and protons are made up of quarks
so everything is ultimately electrons and quarks, tiny tiny point light particles
and being point-like
means that they have no inner structure so we don't have to worry about what
parts they might be made of quarks and electrons are the end of the line which is good
but are they really point like
do they have no volume at all
one of the most fascinating fields of study at the present time is the theory that the
fundamental constituents of nature are not point-like particles
but
strings
tiny if I breaking strings called super strings
a bit like this
and depending on how the string vibrates you get different particles
so
this might be an electron
that might be a quark
and this might be a bundle of light energy called a photon
each different particle is a different mode of vibration of the same sort of string
now with a string only certain modes of vibration are allowed
that's the characteristic note for a string of that length under that particular tension
and that's the characteristic note you get if you change the tension
so we'd expect the same behavior to be true of a super string
only certain modes of vibration are allowed
and these different modes
will have different energies
and because energy and mass are related
Einstein's theory of relativity e equals mc-squared
e d energy equals M the mass because of that these different allowed energies
will correspond to different unload masses
in other words only certain masses are allowed
which is exactly what it is with quarks and electrons
so this begins to look intriguing
see'em are we thought in terms of just point
light particles no only to talk about is how those point light particles move through space
and when you got the idea of them being strings we have another handle on it
now the fundamental particles differ in mass
but they also differ in other ways
you know some have electric charge others don't so the question arises as
to whether we can account for the additional properties by invoking yet
further variations in way in the way the super string vibrates
see this string can only vibrate in two directions that way and that way okay we could imagine
the ends not being fixed and that will give you vibrations in that dray which
would add variety or a bit like this
with a slinky spring you can none you've got sideways vibrations but you've also
got longitudinal vibrations and that gives us vibrations in in three spatial dimensions.
It turns out that if we could have vibrations of this
in nine spatial dimensions we could account for all the properties of all the fundamental particles
which would be correct
except of course you're sitting there thinking tough
there aren't nine spatial dimensions there's just three that and
the time dimension for just three spatial dimensions
or are there
take that pointer over there the other day I noticed there was a chalk mark on
it I meant to clean it off
how can i specify where the mark is on the pointer
well how far was it from the end oh I noticed it was 18 inches
oh that's going and take a look
9:18
no mark
a way in saying it was 18 inches from the ends we
haven't specified precisely where the mark is
all that tells us is that it's somewhere around the circumference of the cross section
that's 18 inches from the end
if I twist it round there we are
so in order to specify the position of
the mark precisely we need not only the distance from the end but also its
distance around this extra curled up dimension
and this is an idea
incorporated into string theory
where are these six other spatial dimensions we need
their curled up
here are the the three familiar extended dimensions where x1 x2 and x3
and what I try to do here for that point there is to show you two
extra curled up dimensions we've got x4 there and we've got x5 there and that's
as far as I can go as far as the drawing is concerned and no we can't in fact for
mental image of it in fact there should be six curled up dimensions there and
not not just a true of that particular point in space but of every other point
in the normal conventional three-dimensional space
six extra curled up dimensions at every point as well as the three extended ones
so the promises
of string theory is that one day you will be able to account for all the properties of
all the fundamental particles in terms
of the particles being super strings vibrating in nine spatial dimensions and
one dimension of time
it's no wonder so many theoretical physicists are
enthusiastically engaged in this folk
but the worrying thing is that despite
so many people working on this problem for the past 30 40 years they have yet
to come up with a single prediction that could be verified
you see it's all very well to talk about string theory but there are many variants of string theory
you know the geometry or of the curled up dimensions
I showed a sphere over there like this okay remove we had X 4
and X 5
but it might not be like this
it might be more like this
X 4
and X 5
or some other twisted topology
then there's a variant of string theory that's based on ten spatial dimensions
not nine
but only that but the dimensions are so
small it's thought we shall never be able to devise a way of seeing them
same goes for the super strings themselves they are tiny
forget about the Large Hadron Collider at CERN no 27 kilometers in circumference
that's absolutely no good at all for seeing strings
the strings are believed to be so small it would take an accelerator that's
more the size of a galaxy
in order to be able to observe them directly and to check that they really are strings
finite size strings and not 0.9
so what does that mean
are we destined never to know whether this attractive
idea is true or not
these are but two of the major questions facing fundamental science today
what we've been looking at in this series has not meant to be an
exhaustive list of outstanding questions facing science today
other scientists would doubtless have right to see mention of of other topics as well
but one one things does seem certain to me
one day all of this kind of science
fundamental science that the discovery of new laws of nature
all of it one day must come to an end
not when we've discovered everything
but when we have discovered
whatever is open to us to understand
when we have finally come up against the boundary of the knowable
in all directions
when will that be
who knows a hundred years from now
thousand years
indeed I don't see how we all
almost strictly speaking our descendants
how they were even know when science has
come to an end rather than thinking that it's
just going through a particularly boring bad patch
perhaps when thediscover that the science
textbooks haven't needed updating for the past millennium
which is itself
quite a thought
but only are there things we should never understand
we shall never even be sure what it is we shall never understand
not likely I'm I never did learn a musical instrument nor not be on
chopsticks on me on the piano I could never remember which notes came next I
have a very bad memory that's why I took up physics you don't have to have a good
memory for physics you just learn a few things and then you work everything else
from that logically sort of thing
Yeah, Okay
Okay everybody, moving on...
is a rap puzzle by have we finished
yeah I think so, yep
so you don't need the Pops anymore
No