Braingle: 'Touch But Can't See' Brain Teaser

Touch But Can't See

Science brain teasers require understanding of the physical or biological world and the laws that govern it.

Puzzle ID:	#4408
Fun:	(2.44)
Difficulty:	(1.88)
Category:	Science
Submitted By:	LungTungBeng
Corrected By:	Palsha

What is solid and not translucent which you can touch with your finger but you can't see it in broad daylight, even through a mirror?

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Comments

AlliePotter Jun 12, 2002	That's very clever =)
WizardMagus Jun 19, 2002	Sight is the reflection of photons off of a surface into your eye. If the mirror reflects light, even if it appears to be something else, you are actually 'seeing' the mirror. :-)
Mogmatt16 Jun 20, 2002	i would have said glass but glass is a liquid
jimmh22 Jun 26, 2002	glass.
kool_lil_girl Jun 27, 2002	naw
scorpio666 Jun 29, 2002	Look at the mirror at a flat angle and you can see the suface.
PiNK Jul 10, 2002	Soooo Easy but good job!! Love, P!NK
CART_JUNKIE Sep 10, 2002	My guess was the back of my head. It can't be seen with "a mirror".
(user deleted) Oct 03, 2002	Sorry about this, but how about "something deep inside your nostril"?
Cattleman7x7 Aug 22, 2003	actually, glass is neither solid nor liquid. it's actually classified as an amorphous solid. but not a solid or a liquid.
jimbo Nov 12, 2003	That's not what I was taught cattleman. Glass is a supercooled liquid. It flows. Look at very old window panes and the glass has flowed downwards due to gravity making the bottom of the panes thicker than the top.
curtiss82 Dec 30, 2003	Cattleman is right, glass is an amorphous solid, (I've taken a whole course on materials, so I know what I am talking about.) A liquid is an incompressible substance that flows due to shear stress. An amorphous solid is just a solid with no crystaline structure. Your are right that glass will flow very slowly due to gravity but it also breaks if too high of a pressure is applied. That is why it is a solid, liquids don't break.
Riddlerman Jul 03, 2005	Forget all this amorphous stuff, lets agree its a good riddle okaY?
JasonD Aug 12, 2008	jimbo, I learned the same thing about glass flowing over time. However, I recently learned that it's not really true as stated. The scientific premise regarding amorphous solids is correct, but for glass the time frame is something like 10^32 years. The historical glass panes have imperfections because of the manufacturing proccess.