I'm at Wiechert's Earthquake Observatory in Göttingen, Germany.
This is the oldest working seismic station, — earthquake detector — in the world.
But there's also a more unusual bit of scientific equipment here:
a four-ton steel ball that can be raised up 14 metres above the ground
and then dropped,
because it's a lot easier to set up and calibrate an earthquake detector
if you can make the ground shake yourself.
- The equipment we have here started to work in 1903,
and it's still working.
Wiechert was the one who created the first real working seismometer.
These things record on smoked paper.
This is ordinary white paper.
We take the flame of a paraffin burner to get soot onto that paper.
We think we are the only ones in the world who are doing that.
Wiechert had a theory that seismic waves allow you
to look into the inside of our planet.
His assistant, Mintrop, had to prove Wiechert's theory.
He started to calculate, and he found out if he takes a ball of about four tonnes
and drops it, then he is creating a small earthquake,
an earthquake big enough to check the theory of Emil Wiechert.
- The researchers here a century ago could create a tiny artificial earthquake
and then measure it. So what?
Well, earth tremors move through the ground in two ways.
The P-waves, or primary waves, compress the ground back and forth
in the direction that the wave is travelling, squeezing it together.
Travelling slightly slower are the S-waves, the secondary waves,
which shear the ground side-to-side.
And those waves behave differently, in duration, and wavelength, and intensity,
depending on the ground they're travelling through.
So, if you're clever, and Mintrop was clever,
then you could set up seismic detectors all round an area,
create a small artificial earthquake by, say, dropping a four-ton steel ball,
and use the reflections from within the earth
to build up a picture of what was below without having to dig.
- This knowledge spread all over the world.
Mintrop got an invitation to Mexico from an oil-drilling company.
They had an oil field. They asked Mintrop if he could measure the size of that oil field.
He said, "I don't know. We don't have oil fields in Göttingen,"
but he accepted the invitation to Mexico,
and of course he did not take the ball with him,
because in Mexico he was allowed what he wasn't allowed here.
He was allowed to use dynamite.
And he measured the size of this oil field with incredible accuracy.
He had the not-so-nice nickname The Crazy German.
He was running around with bodyguards, hiding his equipment in tents,
because our American friends were very eager to find out how that works,
because that was the licence to print money.
- So, 100 years ago, with a much older release mechanism,
and probably a lot more effort, that steel ball dropped for the first time
onto what was then pretty much flat ground.
Nowadays there's much better equipment
for figuring out what's under the earth's surface but, uh,
it's not quite as dramatic.
- I told you your camera would fall...! - [laughter]
It's still rolling!