Impossible Arch Puzzle
I found this image in my optical illusions folder today, and wondered why I never got the time to publish it. Look at the picture on your left. What do you see? There must be something strange going on here. No way that the arch shown here has the proper top. Or can it? I’ve also included a solution inside this post. You’ll have to click the expandable box to see it. I wouldn’t want to ruin your solving experience before you’re ready to see the answer. Anyway, by looking at the solution everything becomes clear. Why has our brain presumed the column is aligned differently than it actually is? I really can’t tell, but hope some of you will try and explain this through comments.
Yesterday I tipped you about new Facebook vanity URLs. Have you had the time to check them? Hope you managed to grab something short and unique to represent you, like I did. But it seems not many of you actually read what I post. Probably you check only the illusions, which is also fine. But I’m REALLY curious what names were taken by our audience. Would be very nice to see more and more of you using your facebook logins to post comments. Not only does this automatically shows your image next to your comment, but additionally you have an option to share your comment so it appears in your Facebook feed. This way you can help us reach more people (your friends will see that you left a comment on our site, if you approve it). What is your opinion on this?
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wow. it actually works! (i hope i’m the first to write a comment ^^)
it must be something at the top where the column is in front of the peak of the arch…i guess…o.O
Cool illusion! I hadn’t expected that solution, I really thought it was impossible, thanks for sharing!
-xxx- Hanna
i think that the column posted is off-centered. this gives the impression the the archways are angled the wrong way. think about it….if i’m wrong let me know —zodhiateswutspoppin@gmail.com
It think this illusions works because our brain prefers symmetry. So our brain assumes that the column is in the middle of the arch when in fact it is slightly to the right of the arch.
the arch is extremely possible.
its just improbable for someone
to do it. kind of an odd choice
to classify this as an illusion.
Wow, it sure doesn’t look right but it is.
I agree with Zwaan, our brains do like symmetry. Cool illusion.
Witchcraft is what that is…
Great illusion.
THANKS!
It’s quite simple, the arches are shaped as paraboles. But the brain probably extends the arches in the same direction as the end. Also, because the column is off-centered and shaded darker on the left it creates the illusion of it actually being in the middle (the darkness somehow makes our brain think it is more voluminous).
It’s also possible the two arcs in the backgroung help create the illusion because they seem to be arced differently than the ones in the foreground. The right one should have a much higher gradient because of perspective.
And as said before, symmetry is always fun!
Hey there!
Mathias, I agree with you. The human brain is a weird “machine”…
I’ve got my pic like facebook users do, but I use gravatar instead. Is this why it requires the e-mail to post a comment? I think so…
Well, anyway, really cool one!
Cheers!
i have seen this before never got that it actually works until just before i saw the solution
Typo in the link above and didn’t see a way to edit it. http://facebook.com/BowlingTracker
It’s because we can’t see it that our brain assumes that the apex of the arch is somewhere behind the column, but not on its left edge.
This is probably the kind of thing our primitive brains have done for millions of years (and is therefore the stronger instinct). It’s only now with our modern brains do we start looking at things with a mathematical eye.
Imagine how an animal might see it, they have no idea what a parabola is, but might still need to make a fair guess at where a semi-obscured escape-hole is placed.
Oh that is so bizarre…!
I’d like to see how the interior arch works. It seems even worse than the outer one.
nice one.
It has something to do with the column off-centered. the brain assumes it would be in the middle of the top of the arch, but we see that it’s not. therefore, we think it’s not aligned.
besides that, it also occured to me that we assume that the most upper left brick would be a “full” brick, instead of the left half one of the top.
Very nice illusion!
I grabbed http://www.facebook.com/Dalixam – as that’s been my nick for som 8-9 years… There is another guy using the same nick. He has dalixam.com, I have dalixam.dk :)
I made sure to log in the first hour it was possible to get the personalized URL :D
actually the column starts on the top middle part of the arch. so it’s not really an illusion at all ;)
Hello! I don’t comment much, but I’m here every day. Love the site! I frequently use your illusion of the day for my wallpaper. Make it a little more interesting when people walk by.
Thanks for keeping me entertained.
Why has our brain presumed the column is aligned differently than it actually is?
[b] BECAUSE THE POLE ISN’T IN THE MIDDLE OF THE ARC! IT’S ON THE SIDE!!! [/b]
This appears to be a variation of the Poggendorf illusion. There is no one commonly accepted explanation. There are physiological ( Huble and Wiss), visual consistency and cultural explainations.
Ther is no doubt that the length and intersection of Vertical lines accounts for the effect. Reduce or eliminate the intersection of the vertical and curved lines and the effect reduces. rotate the vertiacl lines and the effect reduces. this is one of the strongest illusions of its kind.
There are a variety of of explainations here: .http://www.psychologie.tu-dresden.de/i1/kaw/diverses%20Material/www.illusionworks.com/html/poggendorf.html
cool. I saw how the first arch worked. Its the second arch, behind that looks off to me.
This is simply another Poggendorff Illusion: an illusion that confuses the human brain when trying to join a diagonal line when it is obstructed by a vertical or horizontal bar. The only difference is that this is in a real life situation where most Poggendorff illusions are just lines.
This has nothing to do with symmetry Zwaan; the pillar is clearly off centre in this pic.
Vurdlak you posted more of these Poggendorff illusions on 10th Feb ‘09.
Peace!
Actually, no one above has noticed that the eye and the brain are both working normally here, and nothing is wrong at all with the misperception.
Look at the right half of the arch, now look closely at the vertical support for it. Notice how it is shaded. Notice how the vertical support for the left side are not shaded.
Shading, without any other clues such as just what is causing less light to reach the right side, naturally make the shaded item appear further away or smaller, but definitely NOT in the same plain as the unshaded side.
Do note that the shadows case by the column in the middle ore not the cause. Its just the artist shading the right half and left half in different manners.
It has nothing to do with the apex, or the offset of the obscuring column, its all in the shading of the right side vertical support. Our brains would naturally extend the line of the arch correctly, but for the shading, it doe snot make sense for it to be in the same plane.
Without the column, the shading on the right side would be correctly perceived by the eye/brain as ‘wrong’.
Dumb illusion. the column isn’t “tricking” us into thinking that the apex is behind the column. We’re expecting the arch to be circular instead of having a point, so when the point is hidden, we expect it to go a different way.
It’s like putting something in the road that obscures a turn and saying “HA! The road turned, but you didn’t see it because something was in the way! What an impossible road!”
Great illusion. My brain just doesn’t want to connect those lines, especially for the more distant arch. I put up an animated gif “solution” at http://s933.photobucket.com/albums/ad179/fizzix137/?action=view¤t=arch-illusion-soln.gif
Cool! (I read what you post and took your advice; Facebook: schnallity)
You can also see that the center dividing column and the arch support columns on the right side have their shading on opposite sides, differing light sources. This also works to confuse the eye/brain.
Yea, I expected the solution. When I viewed it in igoogle, the image was smaller and I could not see anything wrong with the arches. But when I expanded the image, it looked off. Cool illusion!
I did not believe it, but I reconstructed the drawing by
mirroring the left side and paste to the right to a completely symmetric
arch, and then paste the column back in, – the result can be seen here:
http://www.logicoders.dk/arch.jpg
Yes, it works!
This arch is possible.
Fyi, it’s just like the front one, Trevoir.
Cheers!
Cool! Indeed!
Love this site.
Wonderful! One of your best I guess!
it’s probably because when the eye sees the curve or the arch the first thing we think is the arch is rounded. also because the column is in the middle we assume that it goes between the middle of the arch.
If you put your finger in front of the column, it looks more normal.
Great!
I think its confusing because the pole is not in line with the peak of the arch.
~Asianpearlkeeper
It works because the bricks in the wall fool you, if they were aligned it wouldn’t work..
on the left side its about 3 inches higher than the right of the pole :?
ive seen this in a book, the pole isnt in the middle its off to the side a bit