I have fond memories of watching fireworks on a golf course in Madison, WI after eating my favorite cupcakes -- the ones with sprinkles and flags. Nothing compares to watching fireworks with friends and family and this may be our first year taking our kids to see them. Below is information to help answer some of your children's questions including How do they work? Why are they so loud? What makes them look different? How do they get up there? and How big are they? plus links for more information...
How do they work?
Fireworks are composed of an outer shell or container, stars (the material that forms the designs we see), a charge (black powder), and a fuse (so the firework doesn't go off until it's at the right altitude). If I were explaining it to my son I would tell him to imagine a container, like his sippy cup, filled with something that looks like grapes in black sand with a long string attached to it called a fuse. When the fuse burns into the shell it ignites the charge, which causes the shell to explode throwing the stars in all directions. The shells can be round or cylindrical and come in sizes from 2" to 36". The larger the shell, the more stars can be put in it and the more expensive it is. A good overview of the history of fireworks and minerals that contribute to the exploding colors see FactMonster's Fireworks Facts. For more information on how they work or fireworks history, see How Stuff Works and Answers.com.
What makes them look different?
As a geologist, I love learning about how minerals color the fireworks. For example, copper gives blue, barium - green, sodium - yellow, calcium - orange, strontium or lithium - red, and aluminum or magnesium - white. There are special formulas for making the colors look bright instead of washed out. For more colors and information about the chemistry of fireworks see About.com - Chemistry of Firework Colors.
Why are they so loud?
There are several types of noises at a fireworks show to add to the light display. The Salute or Maroon is one of the loudest - it's the big bang one and is made up of powdered titanium. The Titanium Report is a loud explosion with white sparks (also titanium) and Battle in the Clouds is a shell that creates several loud noises (multiple salutes) after bursting. The cascades of silver and gold sparkles that hiss and sizzle are aluminum or iron filings. The whistling sound is created by rapid pulses of escaping gas (potassium perchlorate oxidiser and an organic salt eg. sodium salicylate) from a narrow tube. From pyrotechnic glossary, Elite Pyrotechnics site (includes pictures), and The Chemistry of Fireworks.
How do they get up there?
The aerial fireworks at Fourth of July shows are fired into the sky from a mortar, which is basically a small cannon. Determining the height a shell will reach when fired out of a cannon is a classic physics (ballistics) problem (see the reference in How big are they for example equations).
How big are they?
You can estimate the size of the firework display using the following formula from efg's lab (in their example the display is about 380 feet across).
6π x time (second) x angle (degrees)
- 6π can be estimates as 20
- Time = Count the seconds between the light display and sound
- Angle = "Hold your fist out at arm's length and look at your knuckles. You will see a ^-^-^-^ configuration: the gaps between knuckles are approx 3,2,3 degrees.(from efg's lab)"
You might also want to check out Longwood Gardens, they have a history of the DuPonts' interest in fireworks and explanations of their beautiful displays. For safety information see the National Council on Fireworks Safety.
And finally, here are a few places to create virtual fireworks or send ecards.
