Do you want me to explain why?
Open two browser windows…
Look at the cards at the top, compare them to the bottom.
None are identical.
It’s a cool trick though, first time I saw it I was like WTF?! So I had to figure it out and ruin it for everyone.
wow, it really is that simple. i figured we’d collectively figure it out together after i posted it and some other ppl fell for it, but you were totally on top of that one. some of them will still fall for it b4 they read our posts, though.
yup, that’s pretty much what you did alright.
hehe, this trik is very easy to figure out on paper. I once saw it on TV for the first time (so i couldnt go back and see what whas going on) and tought too WTF. But then somebody sent me powerpoint version and this trick was figured out in the matter of seconds 
I have another question to you guys, explain this
That’s nuts. I have absolutely no idea.
The best guess I have is that the border of diagram #2 is covering slightly more area, as in millimeters or nanometers, which would compensate for the missing square.
That’s all I’ve got.
it does look like that, since it doesn’t pass through the gridlines at the same place along the top line
you got me though
surely the top picture is just the only way all the peices fit to make a triangle - anyother arrangement will leave a space or an odd shape?
the fact that all the shapes are the same size in both pictures is irrelevant - it is the way in which they are arranged which matters?
how can you say that? if all the pieces are the same size and the big triangel is the same size, then where is that empty square coming from?
Daemon and Organic IO pretty much guessed the answer though
if you look at the space in each square taken up by the red and green triangles then you notice that each one is different - but my point still stands - why bother with the complicated stuff when you can just rearrange the triangle?
maths has never been my strong point…
are you a girl? 
usually they have this kind of logic (Yeah, i know Johann will bash me for my sexist comments lol )
let me explain this really simple thing once again. On the first picture you have this triangle that is made up from smaller pieces, Now you take those smaller pieces and rearrange them. What you get is another triangel that takes up THE SAME AREA as first. Those smaller pieces that where rearrenged are THE SAME SIZE, so how is it possible to have one extra sqare? The answer is of course its NOT POSSIBLE, Those triangles arent really triangles but quadrangles, the top side has slight breakingpoint with slight angle.
nsound was actually correct.
I rebuild the puzzle in Inkscape as vector objects. I can assure you these are really triangles and all the shapes are actually the same size on both sketches.
If you don’t believe me, take the image and rearrange the shapes yourself.
Or if you have now idea how to use inkscape, print the image out, use scissors and try to rearrange it this way. Also you might want to try overlapping the objects, they are indeed the same size.
Anyway here is the SVG: http://sva.ee/triangles.svg
EDIT:
Ah, yes I read the Weird Energy description incorrectly. The WHOLE shape is indeed not a triangle, but very-triangle-looking quadrangle. As both triangles aspect ratios are different (4/2 and 8/3) so the angles are also different. So the first image arches a bit inside while second a bit outside. Here is a demo of the intersection:
