A water clock (or clepsydra) is an instrument where time is measured by regulating a flow of liquid. The oldest water clocks simply consisted of a pierced bowl placed in a larger pot filled with water (see left image, Persian artefact from 400 BC). These existed back in the 16th century BC. The passage of time was observed by counting how many times the bowl overflowed and its content had to be poured back in the larger pot. This was used for example in Persia to ensure fair irrigation […]

A seismoscope is a qualitative indicator of seismic activity -- as opposed to seismographs which show quantitative data, typically through line graphs. The oldest known seismoscope is Chinese and dates backs from 132. It was a large bronze device that dropped a ball into a bronze container (one of the eight frogs on the image above) every time an earthquake was detected, thus producing a loud sound. The direction of the earthquake could then be examined by looking at the container in which the […]

Although today computer graphics is often used for doing flow visualization, a range of physical methods exist that can visualize flows in-place. Leonardo da Vinci was presumably one of the first to use these methods: Leonardo da Vinci (1452-1519) also developed techniques for observing the wind (by generating smoke in a tube and adding it to the wind at suitable points). Most important of all, he made actual experiments under controlled conditions. For this purpose, he used, among other […]

A Galileo thermometer consists of a set of floaters immersed in a clear liquid (typically ethanol) inside a sealed glass tube. Today a floater is typically a glass sphere containing a colored liquid and to which is attached a metallic temperature tag. The composition of a floater is irrelevant, its overall density just needs to be calibrated to a certain value and remain stable. Floaters being made of glass and metal, their volume - and therefore density - is largely unaffected by temperature. […]

The mercury thermometer was invented by Dutch physicist Daniel Gabriel Fahrenheit in 1714. It consists of a narrow glass tube with a bulb at the bottom, containing mercury. The volume of mercury changes with temperature; mercury is driven out of the bulb and up the tube as the temperature rises. Sources: Wikipedia article on Mercury-in-glass thermometer Image Credit: Donar Reiskoffer, Wikimedia Commons

In 1787, German physicist and musician Ernst Chladni published a technique to visualize the modes of vibration of a rigid surface. Chladni's technique [...] consisted of drawing a bow over a piece of metal whose surface was lightly covered with sand. The plate was bowed until it reached resonance, when the vibration causes the sand to move and concentrate along the nodal lines where the surface is still, outlining the nodal lines. The patterns formed by these lines are what are now called […]

In 1850, British doctor and inventor George Merryweather built a barometer that uses live medicinal leeches to predict storms: The twelve leeches are kept in small bottles inside the device; when they become agitated by an approaching storm they attempt to climb out of the bottles and trigger a small hammer which strikes a bell. The likelihood of a storm is indicated by the number of times the bell is struck. The device, which Merryweather called the "tempest prognosticator", was shown at the […]

Kundt's tube is an apparatus invented in 1866 by German physicist August Kundt for measuring the speed of sound. It mostly consists of a transparent tube of adjustable length with powder in it. Sound is produced at one end of the tube, and the tube's length is adjusted until the sound becomes louder, indicating the tube is at resonance and the sound forms a standing wave. The powder then accumulates at the nodes of the standing wave, where is no vibration. The wavelength of the sound can be […]

This device was the location indicator for Russian spacecrafts from the world's first manned spaceflight by Yuri Gagarin, 12 April 1961, until 2002. It contains a mechanical computer and a physical globe which rotated to always display the point on earth exactly underneath the spacecraft, or, alternatively, the point where the spacecraft would land if the re-entry rockets where fired at that exact moment. The numbered bullets on the globe in the third picture indicate radio communication […]

This ShockWatch tilt indicator can be attached to packages which must remain upright during transportation. If the packet is tilted to either side, the little balls move into the next chamber. The recipient can then later check the degree of tilting the packet experienced during transportation. The upper row indicates tilting to the left, the lower to the right. The ball in the round indicator moves in to the outer torus when the packet is turned over 180°. Source: ShockWatch, TiltWatch Plus […]

This simple prop or analog interface by designer Chang Hee Lee is part of an art project titled "Three Studies of Synaesthesia", and studies how weight and scale could be associated with each other. The liquid between the two glass sheets immediately expands its surface according to the pressure it receives on the glass surface. The heavier the weight or pressure, the more the surface expands. Sources: via Chang Hee Lee website