The EARTH'S CORE NOW HOTTER THAN THE SUN.

Using a delicious combination of
particle accelerators, X-rays, high-
intensity lasers, diamonds, and iron
atoms, scientists have worked out
that the inner core of the Earth is
actually 6,000 degrees Celsius —
some 1,000 degrees hotter than the
previous scientific estimate. This
means the core of our Earth is
actually hotter than the surface of
the Sun.

This new data could
generate repercussions in the fields
of geophysics, seismology,
geodynamics, and other Earth-
oriented scientific disciplines.
From the outside in, the Earth
consists of the crust (which are all
standing on), the upper mantle
(solid), the mantle (mostly solid),
the outer core (molten iron-nickel),
and the inner core (solid iron-
nickel). The outer core is molten
due to very high temperatures, but
the increased pressure at the center
of the Earth means that the inner
core remains solid. The distance to
the center of the Earth is 6,371
kilometers (3,958 mi), the crust is
35 kilometers (21 mi) thick, the
mantle is 2855km (1774 mi) thick —
and get this: the deepest we have
ever drilled is the Kola Superdeep
Borehole, which is just 12km deep.
In truth, we have almost no direct
knowledge of anything beneath the
crust — all of our data is inferred
from the seismic waves of
earthquakes bouncing off the
various layers, and from various bits
of the Earth’s interior that bubble up
to the surface, such as volcanic
magma.
While we would love to dig down to
the core and take some exact
measurements, it simply isn’t
possible with our current drilling
technology — and probably never
will be. The Kola Superdeep
Borehole had to stop at 12
kilometers because the temperature
had already reached 180 Celsius
(356F), and was expected to reach
300C at the target depth of 15km —
at which point, the drill bit would
cease to work. There are no drilling
technologies that would even come
close to surviving in the mantle,
which ranges from 500C to 4000C
(plus, there’s no oil beyond the
crust, so there’s no need to develop
such technology…)

To work out the temperature of the
inner core, then, the French
researchers have essentially done
their best to recreate the ultra-high
temperature and pressure of the
core… in their very-well-equipped
laboratory. The hardest bit is
recreating the intense pressure of
the inner core, which is estimated
to be 330 gigapascals (GPa) — more
than three million times normal
atmospheric pressure. To do this,
they use a diamond anvil cell —
essentially a diamond-tipped vice
(pictured below) — to crush a tiny
sample of iron with 200 gigapascals.
The iron is then heated with a laser,
and then subjected to X-ray
diffraction analysis to see how the
iron shifts from solid to liquid under
these extreme conditions.

Finally,
the scientists extrapolate their data
from 200 GPa to 330 GPa, giving a
final estimate of 6230 ± 500 Kelvin
(5957 ± 500C, 10755 ± 932F) at the
inner core boundary. The
temperature at the actual core of
the inner core — the center of the
Earth — is probably even hotter.
Why is a revised temperature of the
Earth’s core important? Well, the
simple answer is that the Earth’s
magnetic field is generated by the
core, and a lot of what happens here
on the surface of the Earth is
affected by the magnetic field — for
one, it prevents our atmosphere
from being blown away by the solar
wind. Finding out that the Earth’s
inner core is actually 1000 degrees
hotter than expected won’t have
any immediate repercussions, but
that’s just how science goes. The
updated temperature will be fed
into the computer models of
seismologists and geophysicists, and
who knows: Maybe it will eventually
lead to some kind of planetary
science breakthrough.

In general, the better we understand the world
around us, the better our lives will
be.