Fireworks: How Science Ignites the Night
As the clock strikes midnight on New Year’s Eve, the sky erupts in a wondrous display of light and sound. But behind these mesmerizing displays lies a fascinating fusion of chemistry, physics, and engineering. Each firework that lights up the sky is a carefully crafted wonder, designed to ignite our senses in a brilliant explosion of color and sound. From the surface, it’s pure magic, but at its core, it’s all science. Let’s take a closer look at the physics and chemistry behind these magical moments.
The Blueprint of the Boom
At the core of every firework is a shell – a paper sphere packed with powder that produces the polychromatic pops we see in the sky. The shell is launched from a mortar – a tall cylinder that holds the firework before its launch, ensuring it is directed skyward. The shell itself has three main components:
1. The Lift Charge: Located at the base of the shell, this explosive mixture – usually made from potassium nitrate, charcoal, and sulfur – launches the firework out of the mortar and into the sky when ignited.
2. The Stars: These tiny pellets contain chemicals such as metal salts. The elements in the metal salts determine the color, while the placement of the stars determines the pattern. This will be elaborated upon later.
3. The Burst Charge: Located at the center of the shell, this ignites the stars within the firework. It is made of the same explosive mixture as the lift charge.
To set off a firework, its fuse must first be lit. The heat travels along the fuse to the lift charge, igniting it. Once the firework reaches a certain altitude, the timed fuse ignites, activating the burst charge.
The Chemistry of the Colors
The sensational shades that sweep across the sky are caused by certain chemical compounds reacting to the scorching heat of the explosions. These substances, which are contained within the stars, are called metal salts. Metal salts are powdered compounds made from metals combined with non-metallic elements such as chlorine or oxygen.
When the firework ignites, the metal salts absorb large amounts of energy. This causes their electrons to become “excited” and jump to higher energy levels. As they “calm down” and return to their original states, they release energy in the form of light. Different metals emit different wavelengths of light, producing different colors. Each of the vibrant strobes, starbursts, and trails shooting through the sky were once simple spheres of metal.
The Physics of the Patterns
The physics behind fireworks governs not only their dazzling displays but also the powerful sounds they produce. The way the stars are sorted inside the shell shapes the style of the explosion, whether it’s a spherical burst, a star-shaped pattern, or a cascading waterfall of sparks.
The different patterns are achieved by using varying shapes, sizes, and spacing of stars. For example, if the stars are placed in a star shape inside the shell, then the pattern created will be a star as the rocket explodes. Yep, it’s that simple.
Sound, too, is a product of physics. The loud booms heard during a firework display are the result of shock waves produced by the explosion. Similar to a supersonic jet creating a sonic boom, the rapid expansion of gasses exceeds the speed of sound, generating intense pressure waves that we perceive as sound. The tightly confined space within the shell builds up enormous pressure, and when it bursts, these pressure waves are released, producing the characteristic explosive sound.
Overall, the blooming spring of the New Year’s night sky flowers are the simple product of the relationship between chemistry and physics. However, this does not take away from the life they embody. As the fireworks light up the night sky on December 31st, remember that they, too, are cheering you on to make good on your New Year’s resolution.
Sources:
https://penntoday.upenn.edu/news/chemistry-behind-fireworks
https://www.bbc.co.uk/bitesize/guides/z7g26yc/revision/3
https://www.ontariosciencecentre.ca/science-at-home/diy-science-fun/the-science-of-fireworks
https://www.researchgate.net/publication/366733580_The_Physics_Behind_Fireworks
https://www.usgs.gov/faqs/what-minerals-produce-colors-fireworks
