DIY Subatomic Particle Detector

  • By Greg Kestin
  • Posted 03.19.15
  • NOVA

Right now, the smallest particles in the universe are shooting, not only in front of you, but also through you. Here’s how to reveal them at home with alcohol, a jar, dry ice, and a sponge.

Running Time: 02:13


DIY Subatomic Particle Detector

March 19, 2015

You and everything around you is made of subatomic particles; they’re the smallest and most fundamental building blocks of matter. They’re everywhere, yet you’ve never seen them. Here’s a way to reveal them at home.

All you need is: a jar, a sponge, rubbing alcohol, a flashlight, a black marker, and some dry ice.

Now we just need a subatomic particle. But on Earth, most subatomic particles, like electrons, are bound inside atoms. Lucky for us, when stars die, they can explode, shooting pieces of atoms across the universe. Some eventually reach Earth’s atmosphere. Here they collide with molecules in our air, bursting into showers of electrons and other subatomic particles, like muons. They’re shooting invisibly—all around you, and through you. Here’s how to actually see them fly by.

First stuff the sponge in the bottom of the jar and pour some alcohol on it.

Then color the inside of the lid black and place it on the jar.

Pour out a pile of dry ice.

Turn the jar upside down on the dry ice.

Wait several minutes for the lid to cool down.

Shine your flashlight over the lid, turn off all other lights, and look closely for a line of small droplets to appear.

Here’s what’s happening. As alcohol gas vapor floats down from the sponge toward the freezing-cold lid, it becomes supersaturated, meaning any disturbance will cause the gas to condense into a cloud of liquid droplets. So, if an electron or muon from a cosmic shower shoots through the vapor, a cloud of droplets forms along its path.

As amazing as it may seem, every line that you see in your jar comes from a subatomic particle. You've revealed the smallest building blocks of the universe, as they shoot past your eyes, all the way from distant star.



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:
“Microscopy” APM Music, Music, SFX


(main image: DIY experiment)
©WGBH Educational Foundation 2015



U.S. Dry Ice Distributor Directory
Outside the U.S.
Some grocery stores also carry dry ice.


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!


  • The setup here is a simple version of a cloud chamber.

  • 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.
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