This one (http://www.ebaumsworld.com/manillus.html) is pretty cool.

Theres some other neat ones here (http://www.ebaumsworld.com/illusions.shtml) and here (http://www.ebaumsworld.com/magic.shtml).

You know i started to look at it, but I chickened out. I have seen too many of those "freak the shit outta ya" suprise things to trust any pic that needs you to stair at it.
Before I look at it can you say honestly say that nothing is gonna jump out at me? Lol because I have a self diagnosed heart problem.

DOH! I forgot, I was gonna say theres no "scare the living sh!t out of you" stuff on that site (that I've seen). I was afraid of doing that first one myself, but my friend in class did it first and he said it was pretty cool, so I tried it. It is pretty sweet if it works for ya.

http://www.ebaumsworld.com/trigrid.gif

This one's pretty crazy. The only possible explanation is that it's not really a triangle - the two smaller triangles aren't proportional and thus have different hypotenuse slopes (The tangent of the smaller angle in the green triangle is 2/5, whereas the red one's corresponding angle's tangent is 3/8 )

aaaahhhh. after spending about 20min staring at it i think Will is right. although its hard to tell because of the way the grid is set up and how suptle the break is it does apear that the line on the top one bends up slightly between and the red trianle and on the lower one is bends down slightly. but thats still pretty trippy.

The trick with the triangles is that the hypotaneus is bent... in on the top one, and out on the bottom. The illusion is that you can't tell.

did i just see jesus !!??! my life is compleat

I see dead saviors...

i cut up the triangles...and checked all the pieces, they are all completely identical. same slope...same everything

top one is definatly bent, you can tell by looking at the slopes of the triangles above the white box, there is signicantly more space in boxes on the one on top than the one on the bottom

-Brel

Another way you can tell there's something fishy going on with this triangle is to do the math. Just by going by the points involved and not paying attention to the lines, the area of the triangle should be 32.5 units ((5x13)/2)

However, if you add up the individual sections, again just going by points which seem to line up neatly, You get a discrepancy.

For the top triangle. The teal triangle is 5 units. The red is 12 units. The green is 8 and the orange is 7. 12+8+7+5 = 32 units.

For the bottom triangle, you have the same four shapes just going by points (again ignoring the lines). However, you toss in the little white square, and suddenly get a shape that is 33 units big.

32, nor 33 is not, in my book at least, equal to 32.5, so something fishy is going on. The bent Hyp. explains this. The mean of the two triangles is 32.5 however.

The base is the same, and the height is the same in both shapes.

However, if you were to straighten out the Hyp, you would find that the red triangle and the teal triangle are not as symmetrical, nor as 'cute' as the image leads you to believe.

Even easier :
Take the blue one, and count the base length : 5 units.
Take the red one, count from left 5 units, and get a vertical line to make another triangle. You see you don't get the same height with the normal blue (2 units) and the shorter red (2.5 units).

Hypothenus in both cases are bent, one concave(sp) and one convexe(sp too, my english is poor). Surface between them represents (as Zehn explained) the "missing" square.

I'm such a nerd.