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Sand Pendulum

Frank Oppenheimer, founder of the Exploratorium Museum, demonstrates the sand pendulum display in these images from the 1970s. 
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Sand Pendulum @exploratorium: a swinging pendulum maps out a beautiful sine curve on to a conveyor belt. The belt moves at constant speed such that the sand creates a graph of the pendulum’s position as a function of time. Note how regular the period of oscillation is for any pendulum- the spacing between the turns remains constant even though the size of swing gets smaller as friction dissipates the energy. That is to say: a pendulum’s frequency is independent of its amplitude, the physics of why clocks can use pendulums to keep time. ?With special thanks to the Exploratorium! 

Oil Drop Cascade

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Oil Drop Cascade @exploratorium : interplay of surface tension and gravity bend oil drops into strange shapes as they move through a grid of obstacles in this kinetic art toy. Like other oil drop timer toys, the colored oil will not mix with the clear kerosene liquid. Available at the Exploratorium gift shop. ? With special thanks to the Exploratorium!

Fresnel Mirror Array

"All Eyes om Me" Exhibit 
The physics and design of this exhibit is very similar to what is depicted in this image: 
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Fresnel Mirror Array @exploratorium : 360 mirrors arranged to reflect to a single focal point in this exhibit entitled “All Eyes on Me”. A mirror version of the Fresnel lens, where each concentric ring of mirrors is slanted toward the center, with the lager rings slanted more, such that the full assembly acts like a parabolic mirror.?With special thanks to the Exploratorium! 

Zeeman Effect on Mercury Green Emission Line

Wikipedia has a nice introduction to the Zeeman Effect 

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Zeeman Effect on Mercury Green Emission Line @exploratorium: directly explore the Quantum Mechanics of electron spin with this amazing interactive exhibit. Excited Mercury gas emits a bright green line at 546nm (seen here as concentric circles using a Fabry-Perot interferometer) due to electrons transitioning between the quantized energy levels. We learn in chemistry that electrons come two to a shell with opposing spins (Pauli Exclusion). Indeed when the excited Mercury tube is placed in between magnets the green line splits, demonstrating that the electrons now have slightly different energies corresponding to the spin orientations interacting with the magnetic field. Advanced level quantum phenomena in a museum exhibit! ?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! 

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!

Monochromatic Room

The light source in this exhibit produces a frequency at 589nm 
Wikipedia has a nice description of the physics and applications of Sodium Vapor Lamps 
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Monochromatic Room @exploratorium: a photo of colorful San Francisco is illuminated by a very narrow frequency band of light, with a wavelength of 589nm- the characteristic spectrum of sodium vapor lamps at low pressure. Seeing color is both about the source of illumination and how an object interacts with light. Here a white LED flashlight can momentarily “paint” the scene with color. Sodium vapor lights are a type of gas-discharge lamp that uses sodium metal vapor in an excited state with two dominant spectral lines at 589.0 and 589.6nm, producing the bright yellow light in this exhibit. ? 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!

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! 

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. 

Circling Wave Umbrella

Kinetic Art by artist in residence Ned Kahn 

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Circling Wave Umbrella @exploratorium: kinetic art that produces mesmerizing wave structure in a disk of fabric. Follow the white dot on the bottom of the fabric to see the actual rotation rate of the disk. The stretchy vinyl coated spandex is set to spin at about 60 RPM which sets up a dynamical interplay between the inertia of the fabric and air resistance, producing four waves that travel at about 20 RPM. Thus the waves rotate at about 1/3 the speed of the cloth. Similar rotational waves travel around the arms of galaxies! Created by Ned Kahn, long time artist in residence at the Exploratorium.?With special thanks to the Exploratorium! 

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!