The original claim, in plain language
In July 2012, two independent experiments at CERN’s Large Hadron Collider (the world’s largest particle accelerator, in a 27-kilometer ring under the Swiss-French border) announced they’d found a new particle matching the predicted properties of the Higgs boson — a particle first proposed in 1964 by physicist Peter Higgs and others.
Why physicists needed this particle to exist
The Standard Model of particle physics — our best description of the fundamental particles and forces — predicted that particles get their mass by interacting with an invisible field that fills all of space, called the Higgs field. The Higgs boson is a ripple in that field, similar to how a photon is a ripple in the electromagnetic field.
Without the Higgs mechanism, the math of the Standard Model only works if every particle is massless — which clearly isn’t true. Finding the Higgs boson was the last missing piece confirming this explanation for where mass comes from.
How you actually “find” a particle like this
You can’t see a Higgs boson directly — it decays into other particles almost instantly (in about a septillionth of a second). Physicists smashed protons together at nearly the speed of light, billions of times, and combed through the aftermath for a very specific, rare pattern of decay products that only a Higgs boson would produce, showing up as a small “bump” in their data at a specific energy.
Why a high schooler should care
This is a genuine example of the scientific method working at the grandest scale: a specific, mathematical prediction made in 1964, confirmed 48 years later using a machine built by thousands of scientists and engineers from over 100 countries. Peter Higgs and François Englert won the Nobel Prize in Physics in 2013 for the original prediction.