Several experiments provide evidence that particles have mass and not just energy. Here are a few notable examples:
Cavendish Experiment: In 1797-1798, Henry Cavendish conducted an experiment to measure the gravitational constant, G. By suspending a pair of small lead spheres on a delicate torsion balance, he observed the tiny gravitational attraction between the spheres. The experiment demonstrated that mass is a property of matter and that objects with mass can exert gravitational forces on each other.
Mass Spectrometry: Mass spectrometry is a technique used to measure the masses of atoms and molecules. By subjecting particles to electric and magnetic fields, scientists can separate them based on their mass-to-charge ratio. This experimental method allows for precise measurements of the masses of individual particles, confirming that they have mass.
Particle Colliders: Particle colliders, such as the Large Hadron Collider (LHC), accelerate particles to extremely high energies and collide them together. By studying the resulting particle interactions and decay processes, scientists can infer the masses of the particles involved. The discovery of the Higgs boson at the LHC in 2012 provided experimental confirmation of the existence of a particle associated with the mechanism that gives mass to other particles.
Cosmic Ray Experiments: Cosmic rays are high-energy particles from space that constantly bombard the Earth's atmosphere. When these cosmic rays interact with the atmosphere, they produce extensive air showers composed of various particles. By studying the properties and interactions of these particles within the air shower, scientists can determine their masses and energies.
These experiments, along with many others conducted in various fields of physics, provide strong evidence that particles possess mass and that mass is a fundamental property of matter.