View Full Version : Why do fireworks always look like they're coming down at you?
Especially the globe-shaped ones. I presume that they're spherical and that they burst in all directions. But when I'm sitting on the ground, they always seem to look as if they're bursting downward. Am I the only one to experience this illusion? If not, what is it about the event that seems to lend itself to this impression? Or, maybe my assumption about them is wrong and they really do only burst downward. Doesn't seem likely, though. Any pyrotechnicians out there among the teeming masses? xo, C.
01-18-2006, 01:30 PM
When the explosion occurs it propels hundreds of combustable bits in all directions. These bits have mass before all of the combustable material has been expended, so the effects of gravity would come into play on them. At the epicenter of the explosion all particles are travelling at roughly the same speed. Ultimately though, the particles being shot above the Earth parallel will begin to decellerate as gravity pulls them back down, while the particles shot below the parallel will simply continue to accellerate. This would result in the bottom half looking longer than the top -- or in other words, that it appears to be at least partly exploding downwards.
01-18-2006, 05:24 PM
I too have noticed this Illusion. I am fairly certain it has something to do with the burst being very far away, and consisting of small, bright points of light. I once had the opportunity to help out with a small town shoot, and from the vantage point directly under a shell, they do look fairly spherical.
I don't know. Where we sit for our town's Fourth of July show, we're mighty close to ground zero, and we get that illusion very strongly. I've flown over them, too, but at such a great distance that I can't say for sure if they looked as if they were opening upwards. If memory serves correctly, however, there is that impression. I'm thinking optical illusion here, not so much directly related to the physics of the explosion, gravitational effects on particles of the explosion, etc. More related to human experiences, the effects of brighness and our interpretation of growing brightness as meaning getting closer, and so forth.
01-18-2006, 06:51 PM
If you think about it being a sphere, the ones going towards or away from you are points of light, like a star. The ones travelling perpendicular to your viewpoint are long streaks of light, like a shooting star. Your perception is that there are many more travelling out and down than there are traveling towards and away from you. I can confirm for you that they are coming down at you...I have gotten firework in my eye at a fouth of July show. However, if you watch fireworks from a hilltop at a distance, or across a lake from where they are actually being launched, they appear as if they are a disc perpendicular to the ground. But, if you see the little ones being shot from the river while you are on the Empire State Building, they look pretty spherical since they're coming right at you!
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