How to explain that loud scary sound the subway makes

This one is by special request from EB who has an inquisitive daughter. A very sweet young girl who like many people of a tender age dislike loud unexpected sounds.

The NYC subways have both electric and pneumatic (compressed air powered) breaks. The loud sound you are hearing could be from the primary pneumatic breaking system releasing the air pressure used to bring the train to a stop. However I suspect since this seems to happen when the train is at rest for a while (and not just a quick stop) that it is actually a spring-applied parking break engaging by releasing the air holding the springs back. I think releasing the air from the parking break also makes more sense because you wouldn't want to release all of the pressure from the main breaks.

Pneumatics are also used to operate the subway doors.

Additional reading:
http://www.nycsubway.org/nyc/nywb/nywb3.html

How to make infrared goggles

This one is from Bill Beaty, a fixture in the Seattle fringe science scene. I wasn't aware that the human eye could see in the infrared range but appearently we can. Your basic instructions to converts some welding goggles to infrared filters using lighting gels can be found here:

http://www.amasci.com/amateur/irgoggl.html

Cost? $20. Walking around is broad daylight looking like a mad scientist? Priceless.

How to tell a raven from a crow

If you find yourself wondering, "was that just a really big crow?" then it probably wasn't. Most crows are around the size of a pigeon while ravens can get to be more of a hawk like size. However there are a couple other key things that will help you tell them apart:

1. What does it sound like? A raven makes a "wrack wrack..." sound, while a crow is more of a raucous laugh of "haw haw haw.."
2. What shape is it's tail? Rounded like a C (for Crow) or pointed like a V (for raVen)?

One last tip: if it looks scruffy in the chest then it's probably a raven.

How to Stencil

I've been making woodcuts off and on for a few years now. I like the balance of design and execution it offers. I ran across this stencil site today and realized that these guys use a lot of the same design and seperation techniques that I use when making multi-block prints. The only real difference is the added consideration of stencil integrity and support of void areas in the stencil. That and the fact that with woodblocks you remove what you don't want inked instead of the image.

Check out the tutorials page: http://www.stencilrevolution.com/tutorials/

This has a lot more appeal to me that silkscreening. It's probably because this too has that same balance of design and execution.