Quantum Fireworks: Ten Facts About The Quantum Mechanics Behind Tonight’s Ohhhs and Ahhhs

To paraphrase Richard Feynman, fireworks are quantum, dammit.

Big Think’s Ethen Siegel offers a super-interesting article that breaks down the science of fireworks — and, in particular the quantum science of fireworks.

Here are a few facts Siegel reveals about the quantum mechanical principles that are behind the booms central to Independence Day celebrations.

Quantum Transitions: The vibrant colors in fireworks are produced by quantum transitions that occur at the atomic level. When atoms are heated, their electrons get excited to higher energy levels. As these electrons return to their ground state, they emit light of specific colors.

Color Emission: Different elements emit different colors due to their unique quantum mechanical properties. For example, sodium emits yellow light, while copper emits blue or green light. This is because of the specific energy levels of electrons in these elements.

Atomic Excitation: The heat from the explosion of fireworks excites the electrons in the metal salts. These excited electrons then fall back to their original energy levels, emitting photons of light that we see as different colors.

Photons and Emission Lines: The light emitted by fireworks is due to photons released during the transition of electrons between energy levels. Each element has characteristic emission lines, which are specific wavelengths of light that correspond to these transitions.

Gunpowder Reaction: The combustion of gunpowder, which propels fireworks into the sky, involves the rearrangement of atoms and the breaking and forming of chemical bonds. This process is driven by the principles of quantum mechanics.

Heat and Light Production: The initial explosion provides the necessary heat to ignite the fuse and the burst charge. This heat causes the metal salts to emit light, a process governed by quantum mechanics.

Stars in Fireworks: The “stars” inside fireworks, which are small pellets containing metal salts, are responsible for the colors. When these stars are heated during the explosion, they emit light due to quantum transitions of their constituent atoms.

Energy Levels and Colors: The specific colors seen in fireworks are determined by the differences in energy levels of electrons in the atoms of the metal salts. Larger energy differences result in the emission of higher-energy (shorter wavelength) light, such as blue or violet, while smaller differences produce lower-energy (longer wavelength) light, such as red or yellow.

Excitation by Heat: The intense heat generated by the explosion of the burst charge excites the atoms in the stars, causing the electrons to jump to higher energy levels. As they return to lower energy levels, they release energy in the form of light.

Combustion without External Oxygen: Fireworks can combust even in the absence of external oxygen because the gunpowder contains its own oxidizer (potassium nitrate). This ensures that the necessary heat and light are produced regardless of the external environment, a process explained by the principles of quantum mechanics.

For a more detailed look at the quantum science of fireworks, check out the story in Big Think.