Documentary Description
In March 2002, the scientific world was rocked by some astonishing
news: a distinguished US government scientist claimed he had made
nuclear fusion out of sound waves in his laboratory.
Rusi Taleyarkhan’s breakthrough was such important news because
nuclear fusion is one of the most difficult scientific processes, and
also one of the most coveted. It could solve all of our energy problems
for ever. In principle, sufficient fuel exists on earth to provide
clean, pollution-free energy for billions of people for millions of
years.
To make it happen, individual atoms must be slammed into each other
with enough energy to make them fuse together, something that requires
temperatures found only in the core of stars like our Sun – over 10
million Kelvin. The idea that these temperatures had been reached in a
small scale laboratory using only soundwaves took many scientists by
surprise. To them, fusion projects were huge multibillion-pound,
intergovernmental schemes with the far off goal of producing energy in
several decades time.
Taleyarkhan’s fusion breakthrough was based on a little-understood
process called sonoluminescence. It’s a process that magically
transforms sound waves into flashes of light, focusing the sound energy
into a tiny flickering hot spot inside a bubble. It’s been called the
star in a jar.
The star in a jar effortlessly reaches temperatures of tens of
thousands of degrees, hotter than the surface of the sun. Many
scientists had wondered if the core of the bubble was even hotter –
maybe even as hot as the core of the sun. If so, fusion would happen
there. But until Taleyarkhan, no one had been able to either prove it
or disprove it.
The breakthrough and the paper in Science attracted great
scepticism. When fusion takes place, particles called neutrons are
given off. These are considered by scientists to be the key signature
of nuclear fusion – but measuring neutrons on a small, laboratory scale
had proven notoriously difficult in the past – and had even killed off
an infamous fusion claim in 1989.
Many scientists didn’t believe that Rusi Taleyarkhan’ neutron
detection was absolutely right. So to get to the bottom of the issue,
the experiment was re-run by Mike Saltmarsh and Dan Shapiro, colleagues
at the Oak Ridge National Laboratory. They couldn’t find any evidence
of fusion. But the controversy escalated as Taleyarkhan’s team stood
their ground and then, two years later, brought out a new paper showing
even more fusion and more neutrons. This paper was thoroughly reviewed
and published in another respected journal.
But the the controversy wouldn’t die down. Nuclear fusion from
soundwaves would be a huge scientific breakthrough – and to be
convinced of it, many scientists wanted to see better evidence,
evidence that was absolutely incontrovertible. They wanted to look very
precisely at the timing of the neutrons to see just how closely they
were related to the flashes of light.
If they occurred at the exact same time, they would finally be
convinced that fusion was taking place. But they wanted timing with
incredible accuracy, that of a nanosecond, or a billionth of a second.
This was one measurement that, though possible, still hadn’t been
carried out by Taleyarkhan and his team.
So Horizon decided to try to sort out the issue once and for all.
And we commissioned an independent team of leading scientists to
conduct the experiment. Working from the instructions set out in
Taleyarkhan’s paper, we assembled the same key scientific conditions to
create nuclear fusion from sonoluminescence. To see if we could find
fusion, we measured the neutrons and the flashes of light
simultaneously with nanosecond accuracy, something that had never been
done before.
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