do you want me to sing an octave
and anybody sing that for
are you nervous about answering these
questions
moderately you never know what you're
going to get from the public
someone has asked can you explain string
theory in a way that i can understand
that's very easy to answer no
no
yes
i'm not sure i understand or believe in
string theory we're used to the idea of
particles and we're used to the idea of
forces
one big goal in science is to unify all
of this under one umbrella the thing
that's proved most difficult to
incorporate has been gravity one
possible way of doing it is through
what's known as string theory because
string theory
is where you replace a particle a point
like object with a small string that's
it okay every time you think of a part
you have a small
string and that string vibrates and the
vibrations the modes on the string the
frequencies if you like of this
vibration correspond to different
particles when you get down to the very
very tiniest scale in the universe so
you're talking in a very sub-atomic sub
elementary particle scales
you need some way of explaining the
properties of matter and one of the ways
of trying to explain the properties of
matter is that it seems to behave a
little like a wave on a string and
usually as a little loop of string so
you've got like a standing wave so it's
a useful way of just thinking about the
properties of matter the beauty of
string theory is that there's a there's
a
a closed looper string that can form and
that closed loop of string can contain
gravity it sort of comes down to a
philosophical question as to whether
that really is fundamentally what's
going on or whether that's just a
convenient mathematical description of
what's going on because you can never
see it it's too small to see
what is the speed of gravity
i think you're
referring geared to the idea of
a gravitational wave gravity
travels at the speed of light a
gravitational wave would have a speed
and people are trying to detect
gravitational waves
it's very important for cosmology my
feeling is that they must travel at the
speed of light anything that's massless
travels at the speed of light and
einstein told us that nothing can travel
faster than the speed of light carrying
information and gravity being massless
it's called the the massless particle if
you like is called the graviton
and that
shoots from one place to the next at the
speed of light so it actually propagates
at a finite uh speed if another huge
planet mystically appeared somewhere
else in the solar system we wouldn't
know about it straight away you wouldn't
you'd have to wait for the light travel
time so you'd see the planet appear at
the same time that you would start
feeling its gravitational influence as
well
what is magnetism how does magnetism
work magnetism arises from electrical
current so it's very closely associated
with electricity and electrical currents
normally arise from
electrons electrons are
small fundamental particles that carry
charge on the atomic level you have
atoms with electrons whizzing around in
circles and whenever you have a charge
going around in a circle or in a closed
orbit and coming back to the same place
that will create a magnetic field around
it the magnetic properties of say a
piece of iron it can be a permanent
magnet this is probably not a permanent
magnet but it can be a permanent magnet
that's due to the fact that in a lump of
iron uh
there are more electrons where they're
which with their spin pointing upwards
they're spinning in this direction than
there are with a spin pointing downwards
spinning in the opposite direction if
you get them all lined up in the same
direction so all these little whirling
electrons are going around the same way
and pointing in the same direction then
you'll get a magnetic field out a bit of
iron well in a in a piece of wood or or
in us or or in water of course the
electron spins in that case the the
bonds between the atoms that form up the
molecules or the material in that case
all the spins are sort of paired off
one is anti-parallel with each other
like this but in iron you can have if
you make a small piece of iron the right
way you can make it a permanent magnet
so you can get up to about half a tesla
or a bit more than that with bits of
clever metal that everything's lined up
if you want something of about
nine seven tesla
ten times larger you're much better off
taking a superconducting
cylinder so you have a bit of metal
which is superconducting you set a
permanent current going around it the
other way to produce a magnet of course
is a solenoid magnet where you get a
copper wire or superconnecting wire you
wind it in the coil and then you flow
electrons through it you pass a current
through it and that can also generate a
magnetic field so that's then generating
a field by passing a current through a
superconductor or a piece of copper wire
and that's how you create a big magnet
but you wouldn't want to do that at home
what would happen if a car was traveling
at the speed of light and then turned on
its headlights yeah that's a good one it
was the same question more or less that
einstein asked when he said i'm
traveling on a moon beam or a sunbeam
and what would i see how would the world
exist if i could travel at the speed of
light well first of all like you can't
get a car to travel at the speed of
light because you need to take uh all of
the energy in the universe and some more
to get it up to the speed of light so
then the next question is okay so
supposing the car was going very very
close to the speed of light and turned
its headlights on and then there's this
weird property that at least from the
driver in the car's point of view he
would see the light from his headlights
streaming away from him at the speed of
light
and the strange thing about special
relativity is that somebody who was just
standing next to the car as it went
whizzing past would also see the light
heading out at the speed of light and
this is very different from our everyday
kind of experience of throwing things
you know if you throw something from
moving train then the ball that you
throw is travelling at the sum of the
speed you threw it plus the speed of the
train light doesn't work that way light
always travels at the speed of light it
is completely crazy and you know it
that's
you know there's a very fine line
between crazy and genius and einstein
was a genius because it's a crazy idea
that turns out to be true why do things
like the galaxy and the solar system lie
in a flat plain conservation of angular
momentum
ah so
in fact the first person who figured out
the answer to this somewhat irritatingly
wasn't actually a physicist or an
astronomer at all uh it was a
philosopher guy called emanuel kent
who's most famous for crazy bits of
political political philosophy but
actually in his spare time kind of
messed around with natural sciences as
well and he wrote a book which explained
this as galaxies form they form from a
big cloud of gas and as that glass
starts to collapse under gravity it
starts to spin and it's the same thing
with the solar system just on a much
smaller scale and it collapsed under
gravity and in the middle of it the sun
formed and then the rest of it kind of
collapsed down and because it was
spinning it ended up not collapsing in
that direction but collapsing in that
direction so you ended up forming a thin
disc of the gas
and then that gas and other junk turned
into the planets and so the planets kind
of remembered that an original disk of
material from which it formed
and the neat thing is just as kind of a
throwaway line in this book is a natural
history of the heavens that he wrote he
just said and presumably things like the
milky way are the same thing on an
enormously larger scale that presumably
they formed from some big blob of gas
that collapsed
and the stars formed out of that gas and
ended up just orbiting around in this
nice orderly fashion well it doesn't
have to be spinning much that's the neat
thing if it's just spinning you know so
presumably there was some big bubble gas
and another big bob of gas near it and
they flew past each other and they just
kind of twisted each other a little bit
and set themselves spinning very
slightly and then just as you know the
when the skater pulls their arms in and
they end up spinning faster and faster
so as this thing as it collapsed down it
conserved its angular momentum which
meant as it collapsed it ended up
spinning faster and faster and faster
until it was kind of just this
rotationally supported disc is there a
common misunderstanding about physics or
astronomy that annoys you there is
something that gets me i'm getting a
little bit serious now brady there's
things that annoy me personally and
there's things that just annoy me at a
professional level the one that annoys
me personally is when people refer to me
as an astrologer oh the thing that
drives me mad is when i get mistaken for
being an astrologer and then you know
they asked me to do their styles for
them that's not what we astronomers do
astrology is one of my bug bears and it
drives me mad that so much energy
is put into
talking about and um referring to what
star signs someone is it's ridiculous
you would say that because you're a
pisces
i'm a tauren actually i think we're
meant to be all geeks
and that irritates me there's a general
feeling that the kind of areas that i
work in and my colleagues here work in
the blue skies the particle physics the
astronomy has no application so we
should just effectively stop funding it
i mean
we should stop supporting certain eso
and we should pile all our money into
practical aspects as they the the end
engineers
role academy of engineers recently put
out statements basically saying we
should stop funding and and that really
bugs me because these are these are
academics who know about
the benefits of of science and of
physics in particular
but what's wrong with knowing stuff
what's wrong with
actually spending your time studying and
then leaving a normal life elsewhere and
being really interested and passionate
about stuff i love physics because i
want to know how the world works who
knows what benefits will come out of
cern who knows what benefits will come
out of
the the techniques that are used in
astronomy they could have revolutionary
effects the internet the fact that ev
all these viewers can can watch these
videos is because of particle physics
it's because of what went on at cern
and that wasn't foreseen 20 20 odd years
ago and yet there's this
there's this mindset which we we we must
cut things immediately especially those
that don't have obvious immediate
benefits and that bugs me because some
of the people that are saying that i
think should know better
the the media image of us is probably
sheldon off the big bang theory and
there are people in physics i mean dirac
was a bit like sheldon
who are so literal literal-minded that
they can't interrelate with other people
at all but you've talked to all my
colleagues we're not really like that at
all there's a very strange
misunderstanding which is to do with the
phases of the moon which is so basic and
fundamental that it's a bit worrying
that so many people don't get it in that
a lot of people think that the reason
why there's a dark side of the moon and
a light side of the moon is because the
earth gets in the way and so blocks out
some of the sun's light and that's
that's a thing called an eclipse and it
does happen from time to time but it's
not the main thing that goes on the
thing that most frustrates me about not
so much physics but the
[Music]
physics and science in culture and
physics and science and society is the
abuse of physics terms so particularly
energy and energy fields and negative
energy and positive energy and how this
is coupled into mysticism that's the
thing that
really gets my goat the main reason why
half the moon is dark and half of it is
light is just because just like the
earth there's a day side and a night
side and sometimes we can see just the
day side of the moon which is when you
see a full moon sometimes you just see
the dark side the night side of the moon
and that's when you see a new moon and
sometimes it's in between the two and
you see a bit of dayside and a bit of
nightside so that's probably the
misunderstanding that worries me the
most and there's a lot of pseudo-science
where things are dressed up and products
are dressed up with pseudo-scientific
sciency terms uh my biggest annoyance is
this email that continues to get
forwarded every year that says the mar
that mars will look as bright and as big
as the full moon in the sky it'll happen
uh in mid-august or something and every
year it gets forwarded and every year
people believe it and it's totally wrong
totally false won't ever happen
you