2) If you think you are going to need colored dyes for physics experiments
during the year, now is the time to buy them. They will be very cheap on
Monday, but they are affordable even today. The point is that some of the
food-grade dyes that are available now will not be available at any price
at other times in the year. Ordinary food colorings are always available,
but their range of colors limited.
3) In the last few hours I have made significant improvements to the Liénard-
Wiechert writeup. The physics is the same, but I got smarter about the
numerical methods, leading to prettier pictures. Also I added a spectrum
showing the generation of higher harmonics. http://www.av8n.com/physics/lienard-wiechert.htm
4) Something that somehow got left out of the recent discussion of audio
equipment: headphones. You can get reference-grade headphones for a
tiny fraction of the cost of reference-grade speakers. If you are shopping
for speakers, a rather strict test is to compare them to headphones.
OTOH if you have significant hearing loss, comparing speakers to
headphones won't tell you everything you need to know. It becomes
a necessary but not sufficient test.
In any case, there are eleventeen other reasons why you want a good set of
headphones ... not least because you can do a lot of design-work without
disturbing other folks.