• Visit
    • Buy Tickets
    • Calendar
    • After Dark Thursdays
    • Exhibits
    • Artworks on View
    • Getting Here
    • Event Rentals
  • Education
    • Professional Development Programs
    • Tools for Teaching and Learning
    • Learning About Learning
    • Community Programs
    • Educator Newsletter
  • Explore
    • Browse by Subject
    • Activities
    • Video
    • Exhibits
    • Apps
    • Blogs
    • Websites
  • About Us
    • Our Story
    • Partnerships
    • Global Collaborations
    • Explore Our Reach
    • Arts at the Exploratorium
    • Contact Us
  • Join + Support
    • Donate today!
    • Membership
    • Join our donor community
    • Engage your business
    • Attend a fundraiser
    • Explore our reach
    • Thank you to our supporters
    • Host your event
    • Volunteer
  • Store

Exhibits

  • A–Z
  • Subjects
  • Locations
  • Random
  • Visit
    • Buy Tickets
    • Frequently Asked Questions
    • Calendar
      • Today
      • This Week
      • After Dark Thursday Nights
      • Arts
      • Conferences
      • Cinema Arts
      • Free and Community Events
      • Fundraising Events
      • Kids + Families
      • Live Webcasts
      • Members
      • Ongoing + Series
      • Special Hours and Open Mondays
      • Private Event Closures
    • Hours
    • Getting Here
    • Museum Map
    • Reduced Rates & Community Day
    • Accessibility
    • Tips for Visiting with Kids
    • How to Exploratorium
    • Exhibits
    • Tactile Dome
    • Artworks on View
    • Cinema Arts
    • Kanbar Forum
    • Black Box
    • Museum Galleries
      • Bernard and Barbro Osher Gallery 1: Human Phenomena
        • Exhibition: Science of Sharing
          • Educator Activities
        • Tactile Dome
          • 1971 Press Release
        • Black Box
        • Curator Statement
      • Gallery 2: Tinkering
        • Curator Statement
      • Bechtel Gallery 3: Seeing and Listening
        • Curator Statement
      • Gallery 4: Living Systems
        • Curator Statement
      • Gallery 5: Outdoor Exhibits
        • Curator Statement
      • Fisher Bay Observatory Gallery 6: Observing Landscapes
        • Wired Pier Environmental Field Station
        • Curator Statement
      • PlayLists
        • All PlayLists
        • A Different Light
        • “We” or “Just Me”?
        • See Yourself in Cells
        • Greatest Hits: Gallery 2
        • Greatest Hits: Gallery 3
        • Greatest Hits: Gallery 4
        • Museum Map
    • Restaurant & Café
    • School Field Trips
      • Getting Here
        • Bus Routes for Field Trips and Other Groups
      • Prices and Discounts
      • Planning Guide
      • Reservations
        • Field Trip Request Form
      • Resources
    • Groups / Tour Operators
      • Group Visit Request Form
    • Event Rentals
      • COVID-Compliant Options
      • Full Facility & Gallery Bundles
      • Fisher Bay Observatory Gallery & Terrace
      • East Gallery
      • Bechtel Central Gallery
      • Osher West Gallery
      • Kanbar Forum
      • Weddings
      • Proms and School Events
      • Daytime Meeting & Event Options
      • Happy Hour on the Water
      • Rentals FAQ
      • Event Planning Resources
      • Rental Request Form
      • Download Brochure (pdf)
    • Exploratorium Store
    • Contact Us
    • Español
    • 繁體中文
    • 简体中文
    • 한국어
    • Français
    • Deutsch
    • Português
    • 日本語
  • Education
    • Professional Development Programs
      • Teacher Institute
        • About the Teacher Institute
        • Summer Institute for Teachers
        • Teacher Induction Program
        • Leadership Program
        • Teacher Institute Research
        • CA NGSS STEM Conferences
          • NGSS STEM Conference 2020
        • Science Snacks
          • Browse by Subject
          • Special Collections
          • Science Snacks A-Z
          • NGSS Planning Tools
          • Frequently Asked Questions
        • Digital Teaching Boxes
        • Meet the Teacher Institute Staff
        • Resources for Supporting Science Teachers
      • Institute for Inquiry
        • What Is Inquiry?
        • Inquiry-based Science and English Language Development
          • Educators Guide
            • Conceptual Overview
              • Science Talk
              • Science Writing
            • Classroom Video Gallery
              • Magnet Investigation
              • Snail Investigation
            • Teacher Professional Development
            • Project Studies
            • Acknowledgments
          • Conference: Exploring Science and English Language Development
            • Interviews with Participants
            • Plenary Sessions
            • Synthesis, Documentation, and Resources
        • Workshops
          • Participant Portal
          • Fundamentals of Inquiry
            • Summary Schedule
          • BaySci Science Champions Academy
          • Facilitators Guides
          • Commissioned Workshops
        • Resource Library
        • Meet the IFI Staff
      • Resources for California Educators
      • K-12 Science Leader Network
      • Resources for Supporting Science Teachers
      • Field Trip Explainer Program
    • Tools for Teaching and Learning
      • Learning Toolbox
      • Science Snacks
      • Digital Teaching Boxes
      • Science Activities
      • Tinkering Projects
      • Videos
      • Exhibits
      • Publications
      • Apps
      • Educator Newsletter
      • Exploratorium Websites
    • Educator Newsletter
    • Advancing Ideas about Learning
      • Visitor Research and Evaluation
        • What we do
        • Reports & Publications
        • Projects
        • Who we are
      • Center for Informal Learning in Schools
    • Community Programs
      • High School Explainer Program
      • Xtech
      • Community Educational Engagement
      • California Tinkering Afterschool Network
        • About
        • Partners
        • Resources
        • News & Updates
        • Further Reading
  • Explore
    • Browse by Subject
      • Arts
      • Astronomy & Space Sciences
        • Planetary Science
        • Space Exploration
      • Biology
        • Anatomy & Physiology
        • Ecology
        • Evolution
        • Genetics
        • Molecular & Cellular Biology
        • Neuroscience
      • Chemistry
        • Combining Matter
        • Food & Cooking
        • Materials & Matter
        • States of Matter
      • Data
        • Data Collection & Analysis
        • Modeling & Simulations
        • Visualization
      • Earth Science
        • Atmosphere
        • Geology
        • Oceans & Water
      • Engineering & Technology
        • Design & Tinkering
        • Real-World Problems & Solutions
      • Environmental Science
        • Global Systems & Cycles
        • Human Impacts
      • History
      • Mathematics
      • Nature of Science
        • Measurement
        • Science as a Process
        • Size & Scale
        • Time
      • Perception
        • Light, Color & Seeing
        • Listening & Hearing
        • Optical Illusions
        • Scent, Smell & Taste
        • Tactile & Touch
      • Physics
        • Electricity & Magnetism
        • Energy
        • Heat & Temperature
        • Light
        • Mechanics
        • Quantum
        • Sound
        • Waves
      • Social Science
        • Culture
        • Language
        • Psychology
        • Sociology
    • Browse by Content Type
      • Activities
      • Blogs
      • Exhibits
      • Video
      • Websites
      • Apps
        • Total Solar Eclipse
  • About Us
    • Contact Info
    • Our Story
    • Our History
      • 50 Years 1969–2019
    • Fact Sheet
    • Impact Report
    • Awards
    • Arts at the Exploratorium
      • Artworks on View
      • Artist-in-Residence Program
      • Cinema Arts
        • History and Collection
        • Cinema Artists-in-Residence
        • Resources and Collaborating Organizations
        • Kanbar Forum
      • Center for Art & Inquiry
        • Begin Here
          • Lessons
            • Bob Miller/Light Walk
            • Ruth Asawa/Milk Carton Sculpture
          • Workshops
      • Resonance
        • About the Series
        • See & Hear
        • Past Seasons
      • Over the Water
      • Black Box
      • Upcoming Events
      • Temporary Exhibitions
      • Arts Program Staff
      • Arts Committee and Advisers
    • Newsletter
    • Educator Newsletter
    • Press Office
    • Senior Leadership
    • Board of Trustees
    • Board of Trustees Alumni
    • Staff Scientists
    • Staff Artists
    • Partnerships
      • Building Global Connections
        • Global Collaborations
          • Projects
          • Approach
          • People
          • Impact
      • Partnering with Science Agencies
        • NASA
        • NOAA
      • Partnering with Educational Institutions
      • Osher Fellows
    • Exhibit Making
    • Institute for Inquiry
    • Teacher Institute
    • Online Engagement
    • Explainer Programs
    • Studio for Public Spaces
    • Job Opportunities
    • Become a Volunteer
    • Follow & Share
    • FY20 Audit Report
    • 990 FY19 Tax Return
    • Use Policy
      • Privacy Policy
      • Intellectual Property Policy
  • Join + Support
    • Donate today!
    • Membership
      • Membership FAQ
      • Member Benefits
      • After Dark Membership
      • Member Events
      • May Is for Members
    • Join our donor community
    • Engage your business
      • Corporate Membership
      • Luminary Partnerships
    • Attend a fundraiser
      • Wonder Funday
      • Science of Cocktails
      • Party at the Piers
        • Event Leadership and Host Committee
    • Explore our reach
    • Thank you to our supporters
    • Volunteer
      • Benefits
      • How to Apply
      • Application for Corporate Groups
      • Application for Internships
      • Application for Professional Societies
      • Application for School Groups & Clubs
      • Our Contract
      • Application for Individuals
      • Opportunities
  • Press Office
    • Press Releases
    • News Coverage
    • Events Calendar
    • Fact Sheet
    • Photographs
    • Press Video
    • Press Kits
    • Press Visits
    • Exploratorium Logos
    • Recent Awards
    • Praise for the Exploratorium
    • Join Our Press List
  • Store
 

Learn with us online while the Exploratorium is temporarily closed. You can help us reopen—donate today.

Exploratorium
Exploratorium
  • Visit
    • Buy Tickets
    • Calendar
    • After Dark Thursdays
    • Exhibits
    • Artworks on View
    • Getting Here
    • Event Rentals
  • Education
    • Professional Development Programs
    • Tools for Teaching and Learning
    • Learning About Learning
    • Community Programs
    • Educator Newsletter
  • Explore
    • Browse by Subject
    • Activities
    • Video
    • Exhibits
    • Apps
    • Blogs
    • Websites
  • About Us
    • Our Story
    • Partnerships
    • Global Collaborations
    • Explore Our Reach
    • Arts at the Exploratorium
    • Contact Us
  • Join + Support
    • Donate today!
    • Membership
    • Join our donor community
    • Engage your business
    • Attend a fundraiser
    • Explore our reach
    • Thank you to our supporters
    • Host your event
    • Volunteer
  • Store

Exhibits

  • A–Z
  • Subjects
  • Locations
  • Random
  • Visitors interact with the Cloud Chamber exhibit.
  • A closeup of the Cloud Chamber exhibit.
  • See evidence of invisible cosmic rays with Cloud Chamber.

  • Visitors interact with the Cloud Chamber exhibit.
  • A closeup of the Cloud Chamber exhibit.
  • Cloud Chamber

Cloud Chamber

Wispy lines show the path of tiny, high-energy particles generated by cosmic rays.

Look down into the chamber and you’ll see an ongoing cascade of thin white trails appearing and disappearing. These are cosmic ray tracks, created by high-energy subatomic particles from space.


Where:   Bechtel Gallery 3: Seeing & Listening
Exhibit Developer:   Donation from NASA Ames, 1969

What’s going on?

Invented in 1911, cloud chambers like this one were among the first devices used to study high-energy particles called cosmic rays, believed to come from exploding stars called supernovas.

As cosmic rays travel through the air, they collide with air molecules and break them up into charged fragments called ions. Meanwhile, inside the cloud chamber, a tray of alcohol is heated to form alcohol vapor. The alcohol vapor in the cloud chamber condenses around the trail of ions created by a cosmic ray, a trail you see as a visible streak of tiny droplets.

Most of the tracks you see—roughly 4 out of 5—are made by unstable elementary particles called muons. Muons have a negative charge like electrons, but they are 207 times heavier. The rest of the tracks are electrons; these tracks are shorter and curlier than muon tracks. Occasional heavier tracks are made by protons or by natural radioactivity in the air or in the exhibit itself.

Today, cloud chambers have been replaced by tracking chambers and scintillators, which track particle paths by producing an electric signal, rather than a visible trail.

 

Going further

When cosmic rays from outer space reach the Earth’s atmosphere, they crash into air molecules and knock free many more particles. These particles go on to crash into more air molecules and create even more particles. Thus a single particle from outer space—called a primary—can create a shower of particles from the Earth’s atmosphere—called secondaries. Primaries (which are actually protons) rarely reach the Earth’s surface; almost all of the tracks in this exhibit are from secondaries (muons and electrons).

Cosmic Rays Artist’s rendering of showers of particles produced by cosmic rays. (click image to enlarge)

Frank Oppenheimer Before he founded the Exploratorium, Frank Oppenheimer used cloud chambers while working as a physicist at the University of Minnesota. In this 1948 photo, Frank and his colleagues loaded various sensors—including a small cloud chamber—into a sphere to be lofted 100,000 feet into the atmosphere by balloon, to document the interactions of cosmic rays. Photo courtesy of Lawrence Berkeley Lab, University of California, Berkeley. (click image to enlarge)

 
Phenomena: Atoms and Particles, Condensation, Evaporation, Ionization, Scattering, Techniques to Make the Invisible Visible
Keywords: cosmic rays

More to explore

Science activity that models radioactive decay
Radioactive-Decay Model

Substitute coins for radiation.

Science activity that demonstrates how clouds form
Fog Chamber

Create clouds in a bottle by rapidly expanding the air.

The Heart of the Matter: Inside CERN
The Heart of the Matter: Inside CERN

Visit the European Organization for Nuclear Research, known as CERN, which studies what the universe is made of and how the universe works.


IMLS acknowledgment

This web project was made possible in part by the Institute of Museum and Library Services [MA-30-16-0175-16].

Exploratorium
Visit
Join
Give

Pier 15
(Embarcadero at Green Street)
San Francisco, CA 94111
(415) 528-4444

Contact Us

  • Plan Your Visit
  • Buy Tickets
  • Hours
  • Getting Here
  • Calendar
  • Tactile Dome
  • Store
  • About Us
  • Become a Member
  • Donate
  • Event Rentals
  • Jobs
  • Volunteer
  • Press Office

Get at-home activities and learning tools delivered straight to your inbox

© 2020 Exploratorium | Terms of Service | Privacy Policy | Your California Privacy Rights |