Fusion Simulation

Part of the Einstein exhibition.


A fusion reaction occurs when two lighter atomic nuclei fuse together to form a heavier nucleus. The most simple fusion reaction occurs when a single proton, the most basic positive electric charge, is fused to a second proton. This is the first step in the fusion process that makes energy in the heart of our Sun. The entire three-step process is called the proton-proton chain and the results are a Helium atom and energy in the form of light. This simple demonstration is an illustration of what protons would experience during fusion.

Materials needed:

  • Two strong magnets (magnetic wands work well) with sides that repel each other. It should be difficult, but not impossible, to get these repelling poles to touch each other.
  • Self-stick Velcro


  1. Take the two separate magnets and find the sides that repel each other.
  2. Stick one strip of looped Velcro to one of these repelling sides and the other strip of hooked Velcro to the other magnet.
  3. Now try to squeeze the magnets close enough to each other for the Velcro to engage and stick together to hold the magnets together.

What is happening?
Protons are positive electric charges and repel each other strongly due to the electromagnetic force. However, there is a force even stronger than the electromagnetic force - the strong nuclear force. This "strong force" only works when the protons are really close to each other, and since they normally repel each other, something has to squeeze them together before they can get close enough for the strong nuclear force to take over and bind them.

In this model the magnets repel each other like protons do. The Velcro acts like the strong nuclear force. You need to apply a force in order to squeeze the magnets together until the Velcro touches and joins them. You have now "fused" together two lighter magnets to make a heavier one! Copyright © 2002 American Museum of Natural History. All rights reserved.