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Convection Currents

Learn more about this exhibit here: 
Convection Currents Exhibit 

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Convection Currents @exploratorium : intricate and delicate structures called schlieren emerge in convective heat flow as hot, less dense water rises off of an electric heating element. A spot light shines through a thin glass walled tank of water with the L-shaped heating element immersed. The convective flow casts a shadow because the index of refraction of water is temperature dependent, with n decreasing at higher temperatures. Buoyancy, turbulence, heat transfer, physical optics- so much physics behind these mesmerizing patterns! ? With special thanks to the Exploratorium! 

Kraken Automata

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Kraken Automata: “Here be Monsters” is the title of this mechanized sculpture by Wanda Sowry- part of the Curious Contraptions exhibit at @exploratorium. Turn a crank and the scene comes to life using simple mechanisms (such as cams, gears, and levers) to translate rotational motion to linear and oscillatory motions. ? With special thanks to the Exploratorium!


Kinetic Rubin Vase

More ambiguous foreground-background illusions at the Exploratorium: 
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Kinetic Rubin Vase @exploratorium: spin this ceramic version of the Rubin Vase illusion and the white background transforms to two people talking. Entitled "Talking Face to Vase" this kinetic art is a permanent installation at the Exploratorium museum in San Fransisco that features the physics and psychophysics of vision and perception. The vase demonstrates the figure-ground distinction made by the brain- is it a vase, or two faces in profile? ? With special thanks to the Exploratorium. 

Icy Bodies

Another amazing creation by artist Shawn Lani-- Icy Bodies has been installed at 13 science museums around the world: 
See the Shawn Lani Studios website for more details- and make sure to see the exhibit in person! 

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Icy Bodies @exploratorium: exquisitely beautiful and dynamic interactions between small chunks of dry ice and a shallow layer of water play out in this exhibit created by artist Shawn Lani at the Exploratorium in San Francisco. Frozen carbon dioxide (dry ice) is denser than water, but the small pieces do not sink- instead each piece, at −78.5 °C, becomes encapsulated in a shell of ice that then floats. As the dry ice sublimates from a solid directly into a gas, jets stream from holes and fractures in the ice shells propelling and spinning the bits upon the water's surface. Droplets condense out of the air forming a cloudy mist in the vicinity of the cold gas jets which is lighted from the side to dramatic effect. ? With special thanks to the Exploratorium!

In-Feed Google


In-Feed Google 2

In-Feed Google 4

In-Feed Google 5


Avalanche

Make a similar device using CD cases: Step by step instructions in this Exploratorium Science Snack: Avalanche 

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Avalanche @exploratorium : Spontaneous stratification from pouring granular mixtures. Typically pouring stuff together results in further mixing, yet here the result is an ordered sorting into layers. The larger rounded dark grains separate from the smaller sharp-edged white grains forming the layers you see here. The darker grains alone would stack into a steeper pile (larger angle of repose) than the white which would form a less steep pile. An amazing physics discovery of the 1990s showcased here by Ken Brecher and Erik Thogerson.? With special thanks to the Exploratorium! 

String Hyperboloid

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This exhibit reminds me of an amazing geometric sculpture where I used to work: Tractricious by Robert Wilson, founding director of Fermi National Accelerator Lab 

Click this link for inexpensive hyperboloids you can own! 

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String Hyperboloid @exploratorium : 26 strings held straight by hanging weights can be rotated as a set to produce a hyperboliod- the quadric surface related to the revolution of hyperbola around its axis of symmetry. Note that although this 3D shape is curved, an a infinite set of straight lines (like those of the strings) lie on its surface. Turning the top disk of this exhibit raises the weights on each string so that when it is released the potential energy will transfer back and forth to kinetic energy of rotation until the energy is damped out due to friction. ? With thanks to the Exploratorium!

Thermochromic Pencils

Visit the exploratorium: see some of my favorite exhbits here

Get similar pencils here: Thermochromic Pencils

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Themochromic Pencils: some amazing pencils I found in the @exploratorium gift shop last week that exhibit reversible color change. The warm air from a hair dryer can quickly shift the color of these pencils, and then as they cool back to room temperature the original color slowly fades back in. The color change can also be achieved by body heat from the hand (swipe for demo). The color change seen here most likely employs leuco dyes, thermochromic chemicals that have two reversible forms, one colorless when warmed above a threshold temperature.


Hidden Mechanism of Fluorescent Bulbs

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Hidden Mechanism of Fluorescent Bulbs @exploratorium: only half of this bulb is covered with the typical internal white phosphor coating- revealing the electron emitting cathode and eerie blue glow of an excited mercury vapor at low pressure. Energetic electrons flow from one end of the tube to the other, exciting the mercury atoms to emit their characteristic emission spectra, mostly just a bright blue line (436 nm) and green line (546 nm) as seen here with a diffraction grating. Importantly there are also two strong invisible UV emission lines, which are absorbed by the glass in the non-coated section, but are used to make the bulb appear white by stimulating various blends of phosphors, which then emit a wide spectrum of wavelengths/colors- revealed here by an identical diffraction grating. A rare look at the complex physics and engineering of this common light source. ? With thanks to the Exploratorium! 

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Sand Shaker

See more photos and video of this amazing exhibit at the artist's online gallery: Sand Shaker by Charles Sowers 

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Sand Shaker @exploratorium: a thin layer of white sand is subjected to vibrations on top of a circular plate in this exhibit created by artist Charles Sowers at the Exploratorium in San Francisco. When granular substances like sand are rapidly shaken, they often take on the properties of fluids through a process called vibrofluidization. Strange non-Newtonian fluid behavior is seen in this sand when the frequency of vibration is adjusted to 16Hz (shown here in 240fps slow motion)- amazing complexity arising from simple and regular motion! ? With special thanks to the Exploratorium! 

Dancing Drops

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Dancing Drops @exploratorium: an exhibit employing the Coandă effect on water droplets -an air stream attaches and wraps around the drops temporarily trapping them. As the air changes direction to flow around a drop, momentum is imparted to it pushing the drop against gravity. Constrained mostly by surface tension, under these conditions the water drops also have irregular and changing shapes leading to erratic motions in the uneven airstream.? With special thanks to the Exploratorium! 


Catenary Arch

Catenary Curves at the Exploratorium. 
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Paul Hewitt wonderfully describes the physics of the catenary. 

Catenary Arch @exploratorium : when an arch is built in the shape of this special mathematical curve (even with slippery blocks) the compression forces between each block are always parallel to the curve- the stack is stable with no tendency to buckle. The catenary is the exact shape of a chain hanging by its ends, also known as the hyperbolic cosine. Famously used in architecture, from the buttresses of Notre Dame to the Gateway Arch. ?With special thanks to the Exploratorium!