The ATLAS Experiment will be opening its doors to the world on 14 and 15 September 2019 for the CERN Open Days. This weekend-long event will be an exciting opportunity for members of the public to explore the world’s largest particle-physics laboratory – host to the most powerful particle accelerator ever built, the Large Hadron Collider (LHC) – and take part in over 100 activities around the CERN campus.

Visitors will have the chance to speak to ATLAS physicists, explore detector workshops and might even be able to visit the experiment underground. Our ATLAS underground visits will take you 93 metres below ground to see one of the largest and most complex scientific instruments ever constructed: the ATLAS detector. This incredible feat of large-scale precision design and engineering is roughly the size of an apartment building, but infinitely more complex.

But if you don’t take a trip underground, you will still have a chance to see the ATLAS detector… or, at least part of it! The ATLAS detector workshop will also be open to the public, giving you the chance to get up close to our new 10-metre-tall, wheel-shaped detectors. These detectors will soon be installed underground in the ATLAS experiment as part of a major upgrade. Unlike visits underground, the ATLAS detector workshop also has no age limitations – so the whole family can enjoy!

In addition to these major visit points, there will be several ATLAS activity stalls set up around the Globe of Science and Innovation. There, you’ll have a chance to:

• Sit down for a cup of coffee at our science café and chat with an ATLAS "barista" (physicist). Have a question about the Universe? Do you wonder what matter and forces are made of, or how the smallest particles interact with each other? Our baristas will have an answer!
• Take a bite of a proton cookie. Learn about protons and how they are used in the LHC, all while decorating your very own proton cookie.
• Play along with ATLAS physicists in our Higgs corner, and learn all about the challenges and excitement behind the study of this unique particle.
• Take home a photo of yourself as an ATLAS scientist in front of our new selfie wall.
• Build your own particle detector – using Lego bricks. Whether you are 4 or 94 years old (or somewhere in between), we look forward to seeing your design, construction and naming skills in action. Exciting prizes will be given out for the best designs.
• Learn about the extraordinary computing and software required to study the billions of particle collisions detected by ATLAS. Also discover how you can become one of the citizen scientists helping the experiment.
• Take a guided visit of the ATLAS Experiment control room.

Additional activity stalls will be set up near the ATLAS detector workshop:

• Learn about energy conservation in particle collisions in the universal language of… water balloons! Expect these collisions to make a real splash.
• Listen and watch the Colliderscope create the ATLAS Experiment using real waveforms displayed on an oscilloscope.

Over 250 ATLAS members will be volunteering during the CERN Open Days. They will be on hand to share their passion for physics, answer your questions and ensure your visit is as memorable as possible.