Photon

Quantum of light and all other forms of electromagnetic radiation.

Core Principles & Analysis

• Einstein proposed light quanta in 1905 to explain the photoelectric effect.
• Travels at exactly 299,792,458 meters per second in vacuum.
• Compton scattering, observed in 1923, confirmed that photons carry momentum.

Specifications & Metrics

• MASS: 0 (massless)
• SPIN: 1
• SYMBOL: γ
• MASS LIMIT: < 1 × 10⁻¹⁸ eV/c²
• PDG ID: S000
• PDG EDITION: PDG 2026
• CHARGE: 0 (neutral)

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