| Quarks are the building blocks of protons, neutrons, and more-exotic entities, whereas gluons are massless particles that glue together quarks. |
| In 1931, he predicted the existence of the massless neutrino to explain away mathematical problems with beta decay. |
| A mathematical string can vibrate in many patterns, which represent a different type of particle, and among these are certain patterns that represent massless particles. |
| This longitudinal electromagnetic energy flux is massless as it is due to distortion, not dilatation, of the spacetime continuum. |
| Even though photons are massless, they still have an equivalent mass because they have energy. |
| In the inside of one there are fly-wheels, in the inside of the other a massless spring. |
