Throwback Thursday: The Physics Of Fireworks (Synopsis)

“Celebrate the independence of your nation by blowing up a small part of it.” -Summer of 4 ft. 2; The Simpsons

There are few things as closely associated with American independence as our willingness and eagerness to celebrate with fiery explosions. I refer, of course, to the unique spectacle of fireworks, first developed nearly a millennium ago halfway across the world.

Image credit: © Copyright 2005–2015 Capital Concerts, Inc. Image credit: © Copyright 2005–2015 Capital Concerts, Inc.

But these displays don't happen by themselves; there's an intricate art and science required to deliver the shows we all expect. So what's the science behind fireworks?

Image credit: the three basic types of firework; original source unknown. Image credit: the three basic types of firework; original source unknown.

From the shape to the height to the color and even the sound, find out all of it on today's Throwback Thursday, just in time for July 4th!


More like this

“Celebrate the independence of your nation by blowing up a small part of it.” -The Simpsons When gunpowder was first invented more than 1,000 years ago by mixing activated carbon (charcoal), sulfur and potassium nitrate together, its first major application was to the development of fireworks. By…
Note: This post has been updated and improved as of 2014 here, at the new Starts With A Bang blog. What follows, below, is the original version that was first published here. "I love the sounds and the power of pounding water, whether it is the waves or a waterfall." -Mike May The world's oceans…
“If the Universe Is Teeming with Aliens… Where Is Everybody?” -Stephen Webb It's one of the biggest conundrums in the Universe, known as the Fermi Paradox: if the Universe is so conducive to life, and if there are so many opportunities for it within our galaxy alone, why isn't there any evidence (…
"This scenario implies that the giant planet instability is not the source of the Late Heavy Bombardment and that terrestrial planet formation finished with the giant planets in their modern configuration." -Nathan A. Caib & John E. Chambers It's a common but nonetheless spectacular occurrence…

Another bit of physics with fireworks that most of the scientifically minded readers on here probably already know, but those without scientific background may not. It is possible to determine how far away a firework is igniting in much the same way that you can do so with a lightning strike. Wait for one of the bright white flashes, followed by a loud boom. You will see the white flash before hearing the boom. Measure the time (or estimate it) between seeing the flash and hearing the boom. The distance to the firework is approximately 0.2 miles per second of time delay.

Of course, this occurs because sound travels much more slowly than light. We see the flash essentially instantly, but the sound of the boom travels much more slowly. The distance you get from this measurement is the total distance, which includes the height. If you happen to be right under the fireworks display (as I happen to be for our local town's display), you can get an approximate height of the display. I would estimate from past displays it's about a quarter of a second delay, which is pretty consistent with the heights for small displays that Ethan's article quotes - about 300 feet.

It's nice you celebrate the French beating the British in a relatively unimportant side-show war in the late 18th Century.

You'll notice they won't celebrate the war against Canada.

Likewise, Canada don't feel the need to thump their chest and celebrate it either.