Today's shiny new toy...

...is a 5mw green laser pointer, which I got for £3.84 including shipment from Hong Kong - in six days! What's more, it's a very solidly built laser, it runs on 2 AAA batteries and the casing is all metal; when it arrived I was surprised that there weren't batteries in it, it felt heavy enough.

Tried it out a little this afternoon and tonight, and discovered that

(a) cats pay even more attention to the bright green spot monster than they do to the red one - from 40+ feet, taking good care to avoid shining the light in her eyes.

(b) the spot is visible on a building about 200 yards away by day - by night I could clearly see it on a sign about half a mile away.

(c) the beam is faintly visible in cool slightly humid air at night.

What I would have really liked would have been for it to include a diffraction grating that let it project two perfect circles side by side, so that I could play Mysteron...

Really not sure what I'll be doing with this - it's illegal for educational use at school level, so I won't be using it for experiments at work. I do occasionally give talks, but I think it's probably overkill for any venue I'm likely to visit short of a Worldcon.

Never mind, it's a fun toy, and that's enough for now.