congratulations I've just made you
brighter I'm 61.2 M underground with 20
million tons of rock above my head and
I'm under the town of Bendigo in
Australia not far from melbour as part
of my lecture tour and I'm in a gold
mine never been in a gold mine before
and Joel pierce the Mind guide has been
taking us around if you don't see it it
can't be gold telling us about how gold
is min I never knew the mechanics and
he's even given me a piece of gold to
hold not to keep no not to keep that's
the size of the pieces of gold that are
found in the mine they don't find huge
nuggets unfortunately what I want to
tell you about is another recent paper
in a journal this time in the journal
Nature and there is a paper which tries
to explain why it is that you find gold
in some places like here in bendo and
not all over the surface of the Earth
it's really good I've never seen gold
before in its natural state it's really
quite exciting you see
geologists and space scientists
have always wondered because the Earth
began as a really molten bowl of iron
and minerals why the heavy elements
didn't all sink to the Center of the
Earth I've got a small object here just
to help you see this this is a
scarf and you can see if you look at
this
scarf that you have the Light Elements
at the top and all the heavy well
have sunk down to the bottom so as you
imagine the heavy elements would go to
the Center of the Earth which you'd have
to dig down thousands of miles to get to
the gold because gold is a really heavy
element one of the very densest elements
there is and even though we're 61.2 M
down we're still near the Earth's
surface because as you know the Earth is
8,00 miles in diameter so this is just a
tiny bit down so why is there go so near
the
surface and the theory is and what this
paper has been believes they have proved
is that early in the earth history but
once it was already
solid large
objects asteroids and so on slammed into
the Earth's surface when it was already
solid and spread these elements near the
surface and because they did went in
particular places not all over the
Earth's surface then you get some places
where they gold and other elements the
paper itself was about
tongon but you don't get it uniformly
all over the surface so if you're lucky
in life enough to live in a place like
here Bendigo you dig thousands of mines
in the hope of getting lots of
gold but if you dug the same number of
holes in Nottingham where I live all
you'd get is coal not a trace of gold
are are these scientists seriously
suggesting that the s for example the
site here where bendo is had chunks of
gold Landing from outer space no they're
suggesting that you
have an asteroid or something which
contains heavy metals
which slammed into an area probably much
bigger than this and in the melting and
whatever caused by the
Collision that deposits of the heavier
metals were formed around this area I
think that sounds pretty good to me was
that news to you oh well I like the idea
of an asteroid impact caus it certainly
it's more fun but definitely it's
explains why so much gold can be found
in Bendigo but almost none other parts
of the world there's loud then there's
this
because what you've experienced might
not compare to
well one two
3 so here is the paper and because of
the way they do the measurements which
is using Isotopes they've actually
analyzed tungston in the Rocks rather
than gold but they have then gener ized
from tungsten to all the Noble Metals so
the heavy metals like gold platinum
idium and so on so and because it's an
exciting result they have published a
simpler explanation for those who are
not specialist here talking about the
Earth's patchy veneer in the diagram
here they first of all show how
everything concentrates in the Earth's
core and then here you can see things
slamming into the Earth's surface
bringing in later on if you like in the
Earth's history these heavy metals I
think it's perhaps important to say that
if you went into outer space now and
found an asteroid or something like that
it wouldn't contain large lamps of gold
but it would have the gold dist
distributed around it much the same way
as in the area around here so there's no
point going by rocket hoping that you'll
get rich quick because you won't so a
lot of asteroids had to hit for this to
happen well they're not clear whether
it's a lot of small ones or some rather
larger ones but it's the principle
that's being discussed here