Have you ever seen glass flow? Have you ever touched a hard liquid?
In our everyday experience, glass is a hard material that behaves like a solid, but what if over a long enough time scale we observed such a material flowing like a liquid? Staff in the School of Physics and Astronomy have captured images of bitumen, a substance with a similar molecular structure to glass, behaving simultaneously as a solid and a liquid.
Elongated stationary “drips” of bitumen form at the end of different sized nozzles. The drips make small mounds as they build up in the conical flasks below.
The bitumen appears stationary on time scales of minutes, days and weeks - characteristic of a solid glass. However, time-lapse videos show that over several months, the bitumen flows like a liquid. These videos were captured over approximately 24 days and are made up of around 600 photographs, each taken once per hour.
What is happening?
Although our everyday experience tells us that a solid glass is very different from a flowing liquid, this experiment shows that the difference is only quantitative, but not qualitative. This applies even when a material flows over a period of time exceeding the age of our Universe, as is the case for familiar silica glass and other "apparent" solids1.
Click on the picture above to see the video
Physical laws in other areas such as relativistic and quantum physics can appear counter-intuitive. This experiment challenges our intuition too, and illustrates the limits of our human understanding in situations that are outside of our everyday experience, such as exceedingly long time scales.
This installation was designed and created with the help of Prof David Dunstan, Dr Anthony Phillips, Dr Kostya Trachenko and Mr Dima Bolmatov from the Centre for Condensed Matter Physics as well as Dr Ben Still, Dr Alex Owen, Mr Predrag Micakowic, Dr Terry Arter, Mr Geoff Simpson and Prof. Bill Spence, all of the School of Physics and Astronomy Queen Mary, University of London.
This experiment was featured in a BBC News article, Tedium, tragedy and tar: The slowest drops in science about pitch drop experiments across the world.
1. Physical Review B 83, 014201, 2011