Here’s a way you can reveal subatomic particles that are shooting in front of your eyes all the time.
Credits:
Produced, animated, and edited by
Greg Kestin
A special thanks to:
Anna Rothschild
Lauren Aguirre
Ari Daniel
Demonstration and lighting technician:
Allen Crockett
Original Footage
© WGBH Educational Foundation 2015
Media Credits:
Pond5
Videoblocks
“Microscopy” APM Music, Music
Freesound.org, SFX
Where to buy dry ice:
U.S. Dry Ice Distributor Directory: http://www.dryicedirectory.com/usa.htm
Outside U.S.: http://www.dryicedirectory.com/world.htm
Some grocery stores also carry dry ice.
Experiment Instructions:
Materials: Jar & lid, sponge, 91% rubbing alcohol (or greater % purity; not 70%), permanent black marker, flashlight, and dry ice.
• Step 1: Stuff the sponge in the bottom of the jar so it doesn’t fall down when the jar is turned upside-down.
• Step 2: Pour a bit of alcohol on the sponge, but not too much that it will drip or fall when turned upside-down.
• Step 3: Color as much of the inside of the lid black as you can. This is so there is contrast with the droplets, which will appear white as they reflect the flashlight’s light. Thin black paper attached to the lid may also work, but it must be thin enough so the cold lid still cools down the bottom of the jar.
• Step 4: Put the lid on the jar.
• Step 5: Put on well-insulated gloves and pour out a pile of dry ice.
• Step 6: Place the jar upside-down on the dry ice. You may want to surround the edge of the lid with dry ice, so it cools down faster.
• Step 7: Shine your flashlight over the lid (try various angles to get best visibility of droplets).
• Step 8: Turn off all other lights.
• Step 9: Look for lines of droplets. You should be able to see droplets in the vapor falling down to the lid like snow, but a few times a minute (or more frequently) you will see a line of droplets appear and fall down to the lid. When you see a line, it was from a subatomic particle shooting through your jar!
Scientific notes:
• The setup here is a simple version of a cloud chamber: http://youtu.be/Ako0RY6KltY
• Subatomic particles include both elementary particles, such as electrons and muons, as well as nuclei such as protons or alpha particles. “The smallest and most fundamental building blocks of matter” refers to the former.
• The “pieces of atoms” from exploded stars include predominantly protons, alpha particles, and some heavier nuclei.
• The showers of subatomic particles are called “air showers.” While the subatomic particles that eventually reach the earth are mostly muons, electrons, positrons and photons, higher up in the shower protons, neutrons, pions, and kaons are also present.
• “Cosmic rays” are the high energy particles that bombard the earth’s atmosphere, creating “air showers”
• When a charged particle passes through the alcohol vapor, some of it is ionized (becomes electrically charged), and the neighboring vapor is attracted to the ions, forming visible droplets. This is the “disturbance” that muons or electrons create as they pass through the vapor.
