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 […]

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. […]

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 […]

A Rubens tube, also known as a standing wave flame tube, or simply flame tube, is a physics apparatus for demonstrating acoustic standing waves in a tube. Invented by German physicist Heinrich Rubens in 1905, it graphically shows the relationship between sound waves and sound pressure, as a primitive oscilloscope. Today, it is used only occasionally, typically as a demonstration in physics education. The middle image shows materials scientist Anna Ploszajski blowing a trumpet into a Rubens […]

Some e-bikes with stepless shifting gear are equipped with a cute analog indicator. From the user manual: Controlling the ratio of the N360 is simply a matter of rotating the shifter grip. The shifter display indicates ratio as a simple graphic; a hill for slower speeds and a flat for faster speeds. Since there are no fixed gears, the exact ratio is determined by your comfort level. This indicator was introduced by the US-based NuVinci company in 2010. In 2018, the company was rebranded to […]

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