Ever since John Adams declared that July 4 "ought to be solemnized with pomp and parade... bonfires and illuminations [fireworks]... from one end of this content to the other, from this time forward forevermore," America's independence day has been celebrated with fireworks.
While many may be familiar with the explosion of a firework, the actual scientific processes that occur every time a firework is lit are much less visible, even though they occur every time one is set off.
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Business Insider reports that the fireworks shows deemed so quintessential to American independence celebrations can be understood as a "a whole lot of chemical reactions happening at once."
What exactly is a firework?
Simply put, fireworks are vessels for the explosives inside of them. The first part of a firework to be lit are the explosives at the bottom of the container, known as a lifting charge. Those explosives provide the firework's initial descent into the sky.
The most colorful of the explosives are small balls known as "stars," which typically comprise all of the visual elements of a firework.
Those explosives are connected to a timed fuse. Once that fuse gets low enough, it sends out a bursting charge, which ignites other explosives that will propel the stars.
All of the gases inside fireworks are to blame for the notoriously loud booms that accompany fireworks shows. As the gases expand, they move faster than the speed of sound.
Once the stars are ignited and released, the fireworks show ensues.
How do fireworks achieve precise patterns and colors?
Chemical reactions take the credit of producing fun and colorful fireworks shows. Each of the star explosives contain an oxidizing agent, a binding agent, fuel and a certain metal that provides color.
Depending on the metal used and the heat of the explosives, colors can cycle through orange, red, yellow and white or remain just one color. Often, many of these metals are mixed to create a desired look. Controlling the temperature of a firework means deciding exactly what colors it will be.
Shapes and patterns in firework displays come down to how the explosives are arranged in the vessel. Placing the star explosives in a certain pattern on the outside of the firework allows for a controlled traveling distance for each one.