This block of uranium is of great historical significance -- it is a remnant of the WWII German Atomic Bomb Project. It was brought to Harvard by Prof. Edwin C. Kemble, Physics Dept. Chairman and also Deputy Science Director of the ALSOS...
In a nuclear reactor or atom bomb, a fissile material such as 235U can capture a neutron. The resulting unstable nucleus fragments into two smaller nuclei, releasing energy and several neutrons (a typical equation is given below). Each of...
The Relativity Train is a realization of the famous Einstein gedanken experiments involving traveling trains carrying clocks and meter sticks. The demonstration is used to show how the preservation of the postulated constancy of physical...
A photon (modeled by a bouncing ping-pong ball) is observed from two reference frames and provides the motivation for time dilation.
The mathematical description of electromagnetic induction as formulated by Maxwell and Faraday requires two different sets of equations to calculate the induced voltage, depending on whether the coil is stationary and the magnet moving or...
Laser and plastic lens with curvature to simulate bending of light by massive object.
Gravitational lensing is caused by the bending of light rays by the gravitational field of an intervening object. The effect is seen with the Sun, but is...
1m diameter rubber sheet acts as curved space for ball bearing masses.
In general relativity, gravity is replaced by a curved space geometry, where the curvature is determined by the presence and distribution of matter. Objects move in...
Curved space segment for open universe geometry.
Whether the Universe continues to expand forever or will collapse back in upon itself depends upon the amount of matter it contains. For a density parameter Ω less than unity the Universe will...
According to present accepted theory the Universe came into existence some 17 billion years ago as a Big Bang and is currently expanding. You can model the expansion of space in two dimensions using a balloon.
We use an 8ft...
You can use a spherical blackboard for many things, including the teaching of geographical coordinates, as a model for a closed Universe, or simply as a mathematical shape.
In the non-Euclidean geometry of the sphere, a circle will have a...
Brass ball doesn't fit through brass ring until ring is heated.
Most solids (see Comments) expand when heated due to increased atomic and lattice vibrations. In this demo, a brass ring expands when heated to let a previously too small a ball...
Pure water cooled to below 273K without freezing; seeded to spontaneously crystallize.
A liquid can be taken to a temperature below its freezing point if it is cooled slowly and there are no nucleation sites for crystallization to begin. In...
