There was a lot of smoke after the fireworks and we decided to see if we could tell how far up it extended by shining our astronomy laser pointer straight up through the smoke.

The smoke overhead wasn't thick enough to prevent us from seeing planes and we were careful to avoid shining the laser near any. There was also a fair amount of traffic from people heading back into town, so we kept the laser pointer close to vertical at all times.

We failed to determine the height of the smoke, but we did make several interesting observations.

1. The smoke particles were apparently more particular than we'd thought. Rather than a smooth haze, we saw the usual thin green line but added on was a sparkle of bright green dots. Guessing, the smoke particles were maybe between 1 and 10cm apart along any given line, although we couldn't agree on how far apart this would mean the smoke particles were on average.
2. If someone shines the laser straight up (using a level to make sure) it will appear to lean towards people and end directly "overhead" no matter where they stand, at least within 10m or so. This would imply that the "end" of the laser beam is rather high–if the sine of the angle between the two definitions of "straight overhead" is small (<5°) and the opposite side is 10m the hypotenuse & opposite side must be hundreds of meters.
3. The "safety" key on our laser DOESN'T DO ANYTHING! We've only tried to turn it on (press the button) when the safety key was in the on position, but we discovered that if you push the button with the so-called safety key in the off position the laser comes on just the same. The "safety" apparently has no effect! This is a very bad design! For now we are keeping the batteries out while not in use.