In message <[email protected]>, Rob Seaman writes:
>I'm giving a colloquium in a couple of weeks and would welcome >suggestions for neat timekeeping gizmos (borrowed or bought) to >spark interest. String out two naked wires across a table, preferably so they hang 10-20 cm above the surface. In one end you connect them to a small 3v light bulb or LED, in the other connect them to two batteries and a switch. Show them the light blinking. Having a clockwork or a little motor flipping the switch on and off every few seconds is a good stunt, otherwise have a volunteer do the flipping on your command. Tell them about the speed of light, tell them that the sun might have taken a day off and we'll only know in 8 minutes time. Next pull out your HP5370B, tell them what it does, show them how to read the display, demonstrate it with two switches which you press in rapid order. Attach two scope-probes, measure the speed of light along a foot of the wire. Move the probes so they are two feet apart. Etc. The reason this is such a dramatic demonstration, is that people hear about speed of light only in context of imense distances: plants, spaceships or fibre-optics around the globe. Seeing speed of light measured right in front of you, is something few people forget easily. Depending on the skill of the audience, you can do A-B/B-A probe-swap and take the average, and explain that its necessary to compensate for the difference in the probes. Alternatively, use the SET REF to get a zero. -- Poul-Henning Kamp | UNIX since Zilog Zeus 3.20 [email protected] | TCP/IP since RFC 956 FreeBSD committer | BSD since 4.3-tahoe Never attribute to malice what can adequately be explained by incompetence. _______________________________________________ LEAPSECS mailing list [email protected] http://six.pairlist.net/mailman/listinfo/leapsecs
