 |
| University of Queensland photo |
Almost
everyone has heard of the scientific experiment called the “pitch drop
experiment” – it’s been ongoing for 83 years. Nothing much happens, and
researchers spend more time watching it than recording its results. But
something rather spectacular happened on 17 April 2014 – it produced a result (Canberra Times, April 23, 2014).
The
world’s longest-running laboratory experiment started in 1927 when Thomas
Parnell, the founding professor of physics at the University of Queensland in
Australia wanted to demonstrate to his students that objects that look solid can
in fact flow like liquid, no matter how slowly it takes.
He
took a lump of pitch – the kind of pitch that is used in shipbuilding, bitumen or
asphalt to make roads and pathways. That’s where the term “pitch-black” comes
from. Some refer to pitch as tar, but pitch is actually more solid than tar. It
is a hard substance that will break when hit with a hammer. Pitch is semi-solid
so it will flow, but extremely slowly. Parnell put some pitch in a glass funnel
to allow it to drip – in its own time with no added heat or chemical additives –
through the funnel aided only by the atomospheric pressure from being squeezed
through the narrow tube.
The
pitch drops have averaged one drop every 8 years. Air-conditioning was
installed in the laboratory at the university in the 1980s and since then the
drops have taken longer to form and fall – now every 13 years or so (but they
are a little larger). The 8th fell on 28 November 2000.
The
current result – the 9th drop – fell last week, on 17 April 2014 –
after almost 13.5 years.
But
the amazing this is that no one had ever seen a drop fall – until last week,
the first time in 83 years.
Thomas
Parnell put his experiment in a cupboard, physicist John Mainstone recovered it
and has been watching the experiment for 50 years. He died after suffering a
stroke in August 2013, aged 78 – only 8 months before the 9th pitch
drop. But in his 50 years of watching he never saw a drop fall – even when he
knew one was about to occur. He missed three drops. He missed the drop in 1977 when
he stayed in the laboratory all weekend, but went home exhausted – and it
dropped the next day. In 1988 it happened in the five minutes when he left the
room to get a cup of tea. In 2000, there was a webcam and Mainstone who was in
England could watch it – but a tropical storm caused a 20-minute power outage
in the laboratory just at the time the 8th drop fell.
After
professor Mainstone’s death eight months ago, the custodianship was in the eye
of professor Andrew White, a quantum physicist, who witnessed the 9th
drop – and the first to ever see one. He admitted it is not a “high-yield”
experiment, but it does have a fascination – and a number of adages that hold
true, such as “a watched pot never boils,” and “good things come to those that
wait” and "patience is always rewarded."
White
indicated that, given the amount of pitch left in the beaker, the experiment
could run for at least another 80 years, with the next drop perhaps marking the
100th year since the experiment began – 2027.
Comments
Post a Comment