hello it's scott manley here and brian
may has been having an interesting week
probably becoming the first person to
appear at a pro nasa press conference
and on stage at the golden globes in the
same week even if technically it wasn't
the same year but regardless obviously
Brian's a bit of a hero of mine because
uh well you know he does actually have a
PhD in astronomy unlike many other rock
stars who have honorary degrees for
their fantastic contributions to popular
culture that Brian actually did the work
back when he was with Queen in the early
days in fact Queen was one of the most
educated bands in history I believe you
know Freddie Mercury had a degree in Art
and Design John Deakin electronics and
Roger Taylor studied biology Brian May
and not only got his degree in astronomy
in physics but then went on to do a PhD
and then 30 years later in 2007 he went
back to complete his PhD because you
know while he had done a lot of academic
work in the early 70s he kind of get
distracted by this whole rock band thing
and disappeared and you for that reason
I'm kind of interested in his career but
yeah many people wonder well what was he
actually studying what was his thesis in
and this is what I want to cover here
Brian's thesis is titled a survey of
radial velocities in the zodiacal dust
cloud and well what he's talking about
with the zodiacal dust cloud is a cloud
of dust that appears to follow the
zodiac in the sky and that is the series
of constellations that lies along the
ecliptic that is that line the Earth's
orbit moves through so this has been
known for thousands of years probably
there are maintence likely mansions in
pre very very old documents of of this
light it was known back then as a
zodiacal light it was first really
studied by Cassini the sadaqa light is
is something if you're in the dark place
say close to the equator after the
sunset after the glow of sunset
disappears there remains a light that
extends up into the sky
rather like a steep pyramid and you know
this is a diffuse light that can
actually be brighter than the Milky Way
similar link when there the Sun rises
long before the Sun rises this starts to
become evident later it was also noticed
there's another patch of bright light
which is exactly opposite the earth and
this is called the Gagan shine now of
course there was much debate as to what
this was but there it was finally
discovered when somebody took a spectra
offered that the spectra exactly matched
that of the Sun therefore this was light
protecting off of solid objects rather
than light that was saved being
scattered by gas or a plasma which would
have had its spectra changed
significantly so the reason there was
dust cloud and of course by the time
Brian me gets around to looking at this
this is a of course in the late 60s
early 70s it's understood that there is
a set of dust near the earth it's still
not sure whether this dust is close to
the earth it's a ring around the earth
there's still weather it's perhaps air
has more structure than that they're not
even sure where the dust comes from so
the you know the dust could come from
comets it could come from asteroid
colliding with each other it could come
from interplanetary or even interstellar
sources and Brian's idea is to look at
the spectra of this and look
specifically at the velocities of the
particles to get an idea of what the
origin of this stuff might be and
whether it's a is living near the earth
or is scattered throughout the entire
solar system
so yeah Brian was hoping to constrain
these models by measuring the radial
velocities of the particles and the way
he wanted to measure the radial
velocities was using spectroscopy so the
idea being is that the the radial
velocity is the distance towards are
away from the observer and if you they
are emitting light then the radial
velocity will Doppler shift the light so
if he could could identify certain
features in the spectra say absorption
or emission lines then these would be
shifted red shifted or blue
depending upon whether they were moving
towards the observer are away from the
observer now it isn't simply a case of
pointing at a grain of dust and getting
its spectra because of course they're
you're getting a whole mix of different
dust as as you shine through or you look
through it and depending upon your model
you will get different chunks of the
dust cloud moving in different speeds so
your model has to account for not just a
shift in the line but a shift in the
shape of the line a spread of the
spectral lines so to measure these
spectra he had a device called a
fabry-perot interferometer so an
interferometer is something that
interferes light and the idea is that
when you have two different waves
interacting if the peaks of the waves
line up then the light will get brighter
if the peaks line up with the troughs
then they will cancel each other out so
fabry-perot interferometer takes the
light and it bounces it back and forth
between two glass plates and as the
lights bounce back and forth they travel
slightly different distances and some of
the light then comes out the other end
and if every reflection is exactly the
same number of wavelengths then you will
get a strong signal so you're able to
sample a very very small part of the
spectrum by adjusting the amount of
distance the light travels but actually
for this particular one it didn't adjust
the distance of the plates what instead
they did was they change the refractive
index of this space of the material in
between the plates and they did this by
adding in nitrogen and changing the
pressure they could go all the way up to
six atmospheres of nitrogen and that
would give a different refractive index
and therefore the light would travel a
slightly different amount of wavelengths
so he could scan this across and I
believe the array range that was
available was something like 10
angstroms an angstrom is one tenth of a
nanometer that's 10 to the minus 10
meters so it's convenient and it's a
commonly used measurement a big part of
his work was specifically improving this
device your removing of redundant
optical
surfaces redesigning the beamsplitter
and actually constructing a whole new
case for it also the entire control
timing and sampling electrics
those were all new ones that he built
and designed himself I mean I guess
those guitar making skills were kind of
useful when you're building high
precision instruments of a different
variety and where you can look at his
thesis and find out the exact details of
what he did but once they had the
instrument they wanted to of course use
it places so they took it to an
observing site in the Italian Alps and
were pretty much stay made by snow and
bad weather they were unable to get
anything useful and ended up you're
digging the device out of six feet of
snow so they could actually take it to a
new location
they got an offer to set up an observing
site and in tenerife and this obvious
there was a whole lot better they built
a hut there that was specifically
designed for it this included a space
for the instrument a space for them to
like hang out and have cups of tea while
the work was being done and a device
called a colio stat now Colio stat is
essentially in mirror are a series of
mirrors with the mirror can be adjusted
so that it will track a specific part of
the sky so they would you know track a
one degree patch of the sky and then
collect light on it and they would then
sample the spectra at different
wavelengths so I believe what they did
was they would pressurize the
interferometer up to six atmospheres and
then they would slowly bleed out that
the nitrogen until they reached you know
ambient atmospheric pressure and that
way they would cover the entire spectrum
each patch of sky for each sample point
would take about 50 seconds so that we
take several minutes to sample the the
sky and of course they're looking at a
fairly large patch of the sky so they
would have to move this thing around and
you sample all the way out to get as
much data as they as possible during
this they found a few interesting things
initially they found emission lines for
magnesium in there's a dye called light
which was not something that had been
expected and they'd they published a
paper on this but
for the radial velocity measurements
that they were looking at they were
using a wavelength of five thousand one
hundred and eighty three point six
angstroms which is a magnesium
absorption line interestingly by the way
many sources say that Brian was doing
his PhD on infrared astronomy because he
was working with the infrared astronomy
department they were very interested in
you know dust clouds and things like
that but the wavelength he was actually
working in is well inside the visible
spectra so anyway he spent a couple of
campaigns collecting a bunch of data and
then had to analyze it and you when you
get a lot of her data what do you do you
analyze on a computer and back then
Imperial College had a pretty badass
computer called the Atlas which was
actually badass for the nineteen sixties
and was starting to show its age so it
was a time sharing system where you
would write your code and submit oh and
punch cards and they would then maybe
come back and you know find out that had
actually crashed and didn't do anything
useful but yeah you know you can
actually see the code that was written
inside the appendices it's nice to see
it on the old green lined fan fold paper
there it's not so nice reading Fortran
because hey I was forced to do that at
some point but I much prefer C these
days but yeah he found after copious
analysis line fitting and models that
the radial velocities of the satellite
were consistent with a flat dust cloud
orbiting the Sun in the same direction
as the earth that meant that it wasn't a
there wasn't anything going retrograde
so therefore this probably wasn't being
fed by commas because comets coming in a
long period orbits will come in and
retrograde orbits just as often as they
come in on pro-grade orbits so it most
likely came from a source like the
asteroid belt and there was also some
evidence of a background interstellar
component which here he remarks point
saying that he really wished he'd
followed up on that because it wasn't
till much later that this was actually
identified and space probes like Ulysses
which observed that once it got far
enough out that the
impact started coming from another
direction and therefore implied that
there was interstellar dust coming in
and flowing through the solar system and
that smallest piece of science from the
Ulysses spacecraft obviously wasn't the
only stuff that was done on solar system
dust but you're considering that he
stopped working on his illness in 1974
when Queen took off and more or less
didn't touch it until abut 2004 30 years
later there was a surprisingly small
amount of additional work done in there
and that was perhaps fortuitous because
of fear that the field had changed
significantly might not have been able
to take his 1974 work and just your
repackage it for modern audiences I mean
there is some stuff that happened in the
satellite it most notably IRAs infrared
Observatory astronomical we have
satellite it it discovered that there
was structure in the disk
there were several overlapping discs
with different inclinations and many of
these actually lined up with well-known
asteroid families asteroid families are
where you've got a collection of
asteroids which cluster around very
similar orbits similar inclinations and
things like that and they're the result
of collisions that break up large
objects and create a cascade of smaller
objects in roughly similar orbits that
presumably produces a lot of dust but
it's also would imagine that since
you've got a lot of objects in very
similar orbits that they are gonna keep
on bumping each other and produce a
steady supply of dust because this dust
is not really really that long-lived the
dust actually will follow regular orbits
and will be affected by all the various
planets and the gravitational forces and
resonances but they're also it's also
strongly affected by the light of the
Sun now the light of the Sun is mostly
pushing it outwards and you can imagine
for a very very very tiny dust grains
that the radiation pressure just pushes
it straight off into interstellar space
but there's a secondary effect which
affects all dust grains and it's
probably more important because it
affects everything
pointing robertson drag now pointing
robertson drag is when you've got the
object the dust particle moving around
the Sun the light is going straight out
to the particle right it's the particles
moving in a circle but when it hits the
particle well the particles moving this
way a bit and in the reference frame of
this particle it actually looks like the
light is coming slightly head-on to it
and that very slight head-on light that
pushes it backwards and slows it down so
dust in the inner solar system is just
being slowly braked by the solar
radiation and will eventually spiral
down into the Sun dust can have
lifetimes of you know ten thousand to a
million years depending upon its size so
the dust that we see near the earth has
to be being continuously refreshed and
it's coming from the asteroid belt so
Brian's final remarks in his thesis show
artist's impressions of how the
understanding missus die called dust has
changed over time and then he adds on at
the end that he was in fact the artist
it's another thesis that would change
the course of science I mean most
doctoral theses aren't the crowning work
of someone's academic career but it was
a solid bit of science and he did drive
the whole thing from modifying the
hardware doing the observing processing
the results and then fitting it into the
models and that shows that this is more
than just an honorary degree that you
know people get from colleges for being
culturally relevant and you know Brian
May isn't the only musician to have
completed a doctorate just off the top
of my head there's Dan Smith who's known
under the stage name of Manitoba or
caribou he does a lot of like electronic
music that I really like and he had he's
got a doctorate in mathematics also from
Imperial College London there's a Greg
gaff and founder of Bad Religion he has
a PhD in zoology and more recently we've
got Dexter Holland from Ed who's the
founder of The Offspring you know best
known for pretty fly for a white guy
he's less well known for his doctorate
in more like
or biology but ultimately brine me is my
biggest Hugh mean I've been a fan of
Queen far as long as I can remember in
fact I think one of the earliest
memories I have is seeing Bohemian
Rhapsody video being played on a TV and
obviously I was really young at the time
and didn't understand the meaning behind
all those lyrics and truthfully to this
day I don't understand the meaning
behind all of those lyrics but yeah I
did get into astronomy and I studied
your objects and the inner solar system
small minor planets and guess what
that's pretty much what Bryan was
looking at as well and I - well yeah I
had I quit my you know thesis never
submitted it because I had a great
opportunity to come out to California to
work in Silicon Valley and you know do
all the stuff that I've done and and so
what Bryan shows me is that well maybe
there is a chance that I could kind of
go back at this and take all these all
this experience that I've got this new
understanding of how to study and solve
problems and apply it to the the work
and the ideas I originally had and
finally submit this body of work and get
that dog for it
yeah Who am I kidding I'm never gonna
have time for that stuff I'm Scott
Manley fly safe
[Music]
you