Half a croissant, on a plate, with a sign in front of it saying '50c'
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see-through ruler

Metal see-through ruler
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Problem... When you are using a cutting board, scapel and ruler, the ruler is usually metal. So you can't see your work underneath the ruler - yes? You may start to use a plastic one so you can see your work. But then you start to cut into the ruler, and before you know it, have jagged edges on your once perfect work. So the solution... someone invent a heavy durable metal ruler that you can see through. Nope, i don't know how either, but someone might.
tallbird79, Aug 07 2001

Dresden: See-through tile for tanks. http://www.spiegel....%2c183008%2c00.html
(In German.) [jutta, Feb 26 2002]


       I thought this was going to be about an invisible Tony Blair.   

       Would a diamond ruler do the trick, or would it distort the light too much?
-alx, Aug 07 2001

       Haven't you guys seen Star Trek IV? Our answer is transperant aluminum!
zhinz, Aug 07 2001

       [PeterSealy] Don't tell that to Mr. Scott (from Star Trek). He once placed a sizable order for transparent aluminum...
phoenix, Aug 07 2001

       The only sensible alternative has to be...   

       ...to use a rubber scalpel. Surely.
st3f, Aug 07 2001

       What's wrong with glass?
beauxeault, Aug 07 2001

       ...speaking of which, here's something cool you can do with the plastic ones: Hold the ruler at a near-vertical angle, grasping the lower end in your left hand. Press on the upper face of the ruler with your left thumb to hold the ruler firmly against the edge of your desk top. Bend the top of the ruler toward the desk with your right thumb and let it go so that it vibrates, making the sound waugsqueke describes. Notice that as you move the contact point of the ruler with the desk up and down the ruler, the pitch of the sound changes. Not so remarkable, right?   

       Here's the cool part. Get a musical instrument nearby and find the point on the ruler at which the pitch corresponds to an identifiable note from the instrument. Note the inch or centimeter mark at this point. Now find the point on the ruler that corresponds to a second note. From this you can determine the distance in 16ths inch or in mm for each note in the scale. You only need to find two notes because on the ruler the scale is linear, so all the other notes can be interpolated or extrapolated. The beauty of using a *clear* plastic ruler for this is that you can draw out a piano keyboard on paper with the keys spaced according to the ruler's "note distance" and can tape this keyboard to the underside of the ruler.   

       Now your ruler can be played like a real musical instrument.
beauxeault, Aug 08 2001, last modified Aug 09 2001

       ...only without sounding like one.
angel, Aug 09 2001

       Er... hold on a mo, Beaux - you hold the lower end in your left hand and press on the top with your left thumb while the ruler is vertical? You must have very large hands or a very small ruler.
Lemon, Aug 09 2001

       Yeah, [Lemon], that took me a while too. I think he means that the ruler is vertical, with its (normally) upper face towards you. You press the (normally) lower face onto the front edge of your desk with your thumb so that most of the ruler is above the desk. Twang, adjust, repeat.
angel, Aug 09 2001

       That's right, angel. Sorry for the confusion. I modified the description a bit to improve the clarity, but it's still a bit confusing.
beauxeault, Aug 09 2001

       A far easier solution than getting scientists to invest time and great expense inventing invisible metal. Just buy those X-Ray spex advertised in the back of all good childrens comics. So simple, it's brilliant.
DaveSt, Aug 24 2001

       'You only need to find two notes because on the ruler the scale is linear'   

       er.... surely the pitch doesn't vary linearly with the length of ruler though. I'd have thought that the frequency is inversely proportional to the square root of the lenght, and the percieved pitch varies as the log of that - ie reducing the length to one quarter of the current length will increase the note by one octave.
pjc51, Aug 25 2001

       Because glass is expensive the best clear thing is plastice. But metal is good because it can't be cut through. Answer.... A standard plastic ruler with a thin metal cutting edge. The cutting edge could have the lenght markers on it and the numbers on the plastic. Result... A see through ruler that doesn't get sliced to pieces.
bob2001, Sep 18 2001


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