Brownian Motion of Latex Spheres

“Under the microscope one, to some extent, immediately sees a part of thermal energy in the form of mechanical energy of the moving particles.” —A. Einstein 1915

What it Shows

Tiny latex spheres in water, viewed under a microscope, undergo a kind of random jiggling motion called Brownian motion—named after the botanist Robert Brown, who observed this kind of motion in 1827 when looking at tiny pollen grains. The spheres are all 1.054 micron in diameter. Each particle can be seen...

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Three-Legged Table

Triangular table supported by platform scales.

What it shows:

This is a two-dimensional version of the Loaded Beam demonstration.

How it works:

An equilateral triangular-shaped table is supported at each corner by a platform scale (same type as in "Loaded Beam"). One of our large (14.5 kg = 32 lb) weights is placed on the table. The scale readings vary with the position of the weight. The procedure to be followed in this demonstration...

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Shive Wave Machine

Rods attached to metal spine; transverse wave generator shows the reflection of waves free, fixed, terminated and transition boundaries.

What it shows

Mechanical demonstration of transverse standing or traveling waves using the Shive wave machine.

How it works

The Shive wave machine consists of a series of horizontal metal rods 1.25 cm apart coupled by a torsion wire. A pulse can be sent down the machine by displacing the end rods (when doing this by hand, pull down on more than one rod as the connections are delicate and do break). The far...

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Hair Raising

What it shows:

A Van de Graaff generator will apply a charge to its dome and anything else in contact with the dome. Should that object be a person, they obtain a net surplus of charge (be it positive or negative). It is especially noticeable with hair, as each individual strand is repelled from every other and from the scalp.


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Spectrum Piano

The visible part of the electromagnetic spectrum is represented by less than an octave of the keys; UV, IR, and microwaves are also indicated.

What it shows:

The keys of a piano are used to represent the electromagnetic spectrum, illustrating the narrow range of frequencies that constitute the portion visible to human sight.

How it works:

An old piano 1 with its center octave of keys (C4=261.6Hz to C5=523.3Hz) colored for the visible spectrum (the seven colors spread to...

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Tether-ball Catastrophe

What it shows:

An accelerated electric charge radiates energy. So according to classical physics, an electron in orbit about an atomic nucleus should emit electromagnetic radiation by virtue of its orbital motion. As it radiates energy, the radius of its orbit decreases. The electron should spiral into the nucleus amidst a burst of radiation in about 10-16 seconds.


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Cloud in a Bottle

A 5-gallon bottle containing air and water vapor is slightly pressurized; a sudden release of the pressure cools the vapor, forming a cloud.

The bottle is a heavy Pyrex carboy with tooled mouth. A one-holed rubber stopper fits the mouth and is air-tight. A meter of Tygon tubing is fitted to a short tube in the rubber stopper.

The bottle is kept stopped and wet, and should work off the shelf. If the bottle is dry, spray about 10 ml of distillled water inside.

To demonstrate cloud formation, fit the stopper to the bottle and apply pressure with the lungs. Blow into the...

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Jupiter's Satellites

Static model of satellite orbits.

What it shows:

Static 3-D model showing the orbital paths of Jupiter's satellites.

How it works:

The model marks the orbital paths of the Jovian satellites to a scale of 1.5cm = 106 km. This scale allows the orbit of the outermost satellite Sinope to fit within a 1m × 1m plywood base. The orbits of the outer 8 satellites are marked using loops of 2mm × 1mm spring steel supported to their correct heights by 5mm Plexiglas rods (Pasiphae rising to the greatest height of 42cm). The...

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