In Brief
Every second we are being bombarded with invisible cosmic rays from space. Now you have a chance at constructing a cloud chamber to visually capture some of those rays.

Peeking at Cosmic Rays

Every second, about 34 cosmic rays from the Sun (and some from distant supernovae) zip through your body. That’s 3 million cosmic rays penetrating you a day.

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Typically we are totally oblivious, unaware of the stunning particle symphony enveloping us.  However, we can make that all change.  You can see cosmic rays with your own eyes! See them clearly for the first time with these easy direction listed below. It will forever change the way you think about your surroundings.

Materials To Conduct the Experiment:

  • Vapor source: any alcohol will work: Methanol, ethanol (denatured or very high proof alcohol), propanol, or isopropyl.
  • Container: Used to trap the vapor.  I have seen the following used effectively: A petri dish, pyrex, tuperware, an aquarium, or even a plastic cup.
  • Absorbent material: This will be soaked with the alcohol: A sponge, paper towel, felt, etc.  It will need to be fixed on the top of the container using tape, clay, pins, or other material (see steps below for more details).
  • Dry ice: used to supersaturate the vapor, allowing for small contrail clouds to form.
  • Black base for container: this allows for contrast to see the contrail clouds (maybe a pan or something similar).
  • Light source: This is used to illuminate the contrails.  The brighter, the better.  Experiment with which angle illuminates the droplets best.
  • Hot water bottle (optional)if your container is large enough, such as an aquarium, you can use a hot water bottle to heat the alcohol, saturating the air.  This increases the amount of vapor in the air, but it also may raise the saturation level.
  • Source of radioactivity (optional): You don’t have to have this, but it’s awesome if you do.  You’ll see quite clearly the alpha and beta particle decays.  Common sources of radioactivity: smoke detectors (Americium-241), propane gas lamps (the fabric gas mantles often contain thorium dioxide), orange Fiestaware (uranium), old glow in the dark clocks/watches/instrument dials (radium), antique 19th century yellow/green vaseline or canary glass, some rocks/stone counter tops, etc.
  • Magnet (optional)These are charged particles we are dealing with.  If you introduce a magnetic field they will be attracted to one pole and repelled by the other, depending on their charge.
  • Sealant (optional): If you want to trap the vapor more effectively you could use clay or vaseline around the edge where the container and the base meet.