They use magnets to accelerate beams of massive particles extremely fast and crash them into each other so they can measure the junk that flys off. By doing that, they can tell what’s inside of the particles.
The reason they’re so stonking huge is that unlike light beams/lasers, the beams in the accelerators are made of the heavy stuff. Beams of lighter particles don’t really make intereating crashes. If you want big wrecks you crash trains, not bicycles.
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