The moon illusion - Andrew Vanden Heuvel
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Not SyncedHave you ever noticed
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Not Syncedhow the full moon looks bigger
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Not Syncedwhen it's near the horizon
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Not Syncedthan when it's high over head?
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Not SyncedIf so, you're not alone.
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Not SyncedPeople have wondered about this strange effect
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Not Syncedsince ancient times,
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Not Syncedand surprisingly, we still don't have
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Not Synceda great explanation,
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Not Syncedbut that's not for lack of trying.
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Not SyncedSome of the greatest minds of history --
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Not SyncedAristotle,
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Not SyncedPtolemy,
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Not SyncedDa Vinci,
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Not SyncedDecartes
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Not Synced-- have all wrestled with this problem
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Not Syncedand failed to generate an adequate explanation.
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Not SyncedOne of the first ideas suggested
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Not Syncedwas that the image of the moon in the sky
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Not Syncedreally is bigger near the horizon.
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Not SyncedPerhaps the Earth's atmosphere acts
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Not Syncedas a giant lens,
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Not Syncedmagnifying the moon as it rises and sets.
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Not SyncedBut this explanation doesn't cut it.
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Not SyncedIf anything, the refraction of the atmosphere
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Not Syncedwould make the moon look slightly smaller.
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Not SyncedPlus, if you actually measure
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Not Syncedthe size of the visible moon
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Not Syncedat different positions,
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Not Syncedit doesn't change at all.
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Not SyncedBut then, why does it still seem bigger
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Not Syncedwhen it's rising?
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Not SyncedThis must be some kind of optical illusion.
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Not SyncedThe question is, which one?
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Not SyncedOne explanation is the Ebbinghaus Illusion,
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Not Syncedwhere two identical objects look different
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Not Syncedbecause of the relative size
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Not Syncedof the objects they're surrounded by.
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Not SyncedHere the two center circles are actually the same size.
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Not SyncedMaybe the moon looks bigger near the horizon
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Not Syncedbecause it's next to tiny trees,
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Not Syncedhouses,
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Not Syncedand towers in the distance.
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Not SyncedBut when the moon is higher up,
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Not Syncedit's surrounded by the vast darkness of the night sky
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Not Syncedand looks tiny by comparison.
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Not SyncedAnother possibility is the famous Ponzo Illusion.
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Not SyncedIf you've ever tried to draw in perspective,
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Not Syncedyou know that the closer something is to the horizon,
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Not Syncedthe smaller you should draw it.
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Not SyncedOur brain compensates automatically for this
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Not Syncedby perceiving objects near the horizon
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Not Syncedas larger than they actually appear.
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Not SyncedThe two yellow lines in this drawing
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Not Syncedare the same size,
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Not Syncedbut the upper one seems bigger
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Not Syncedbecause we interpret it as receding
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Not Syncedfarther into the horizon.
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Not SyncedSo, between Ponzo and Ebbinghaus,
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Not Syncedit seems like we've solved the mystery
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Not Syncedof the moon illusion,
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Not Syncedbut, unfortunately, there are a few details
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Not Syncedthat complicate things.
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Not SyncedFor one thing, if this was just the Ebbinghaus effect,
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Not Syncedthen we would expect the moon illusion
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Not Syncedto disappear for pilots flying high above the clouds
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Not Syncedsince there wouldn't be any other smaller objects
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Not Syncednear the horizon.
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Not SyncedBut in fact, pilots and sailors out on the ocean
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Not Syncedstill claim to see the moon illusion.
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Not SyncedOn the other hand, if it's just our brain's autocorrecting
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Not Syncedthe size of objects near the horizon,
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Not Syncedthen we'd expect the moon illusion
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Not Syncedto be visible inside a planetarium,
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Not Syncedwhere the whole sky,
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Not Syncedincluding the horizon,
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Not Syncedis displayed on a spherical dome overhead.
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Not SyncedStudies have shown, though,
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Not Syncedthat this is not the case.
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Not SyncedTo make matters worse,
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Not Syncedit seems the moon illusion disappears entirely
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Not Syncedif you just bend over
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Not Syncedand look at the moon between your legs.
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Not SyncedNow, this is just getting ridiculous!
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Not SyncedOne of the most promising explanations today
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Not Syncedis known as Convergence Micropsia.
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Not SyncedOur brains judge the distance to objects
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Not Syncedand their apparent size
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Not Syncedby the focus of our eyes.
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Not SyncedWhen looking at the horizon,
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Not Syncedyour eyes focus far-off into the distance
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Not Syncedso your brain knows you're looking far away.
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Not SyncedThe moon appears a certain size.
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Not SyncedYour brain thinks it's far away,
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Not Syncedwhich it is,
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Not Syncedso you naturally conclude
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Not Syncedthat the moon must be big.
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Not SyncedBut when looking up at the night sky,
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Not Syncedthere's nothing for your eyes to focus on,
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Not Syncedso they default to their rest focus,
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Not Syncedwhich is point just a few meters away.
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Not SyncedNow your brain thinks the moon is much closer
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Not Syncedthan it really is,
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Not Syncedso you naturally conclude
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Not Syncedthat the moon is not as big as you thought it was.
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Not SyncedRather than explain why the moon
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Not Syncedlooks so big near the horizon,
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Not SyncedConvergence Microspia explains
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Not Syncedwhy the moon looks so small when overhead.
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Not SyncedStill not satisfied?
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Not SyncedWell, frankly, neither are many scientists
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Not Syncedso the debate over the moon illusion still rages on
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Not Syncedand may continue as long as we still see it
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Not Syncedin the night sky.
- Title:
- The moon illusion - Andrew Vanden Heuvel
- Speaker:
- Andrew Vanden Heuvel
- Description:
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View full lesson: http://ed.ted.com/lessons/the-moon-illusion-andrew-vanden-heuvel
Have you noticed how the full moon looks bigger on the horizon than high overhead? Actually, the two images are exactly the same size -- so why do we perceive them differently? Scientists aren't sure, but there are plenty of intriguing theories. Andrew Vanden Heuvel unravels the details of focus, distance and proportion that contribute to this mystifying optical illusion.
Lesson by Andrew Vanden Heuvel, animation by Kozmonot Animation Studio.
- Video Language:
- English
- Team:
- closed TED
- Project:
- TED-Ed
- Duration:
- 04:09
TED edited English subtitles for The moon illusion | ||
Jenny Zurawell edited English subtitles for The moon illusion | ||
Jessica Ruby approved English subtitles for The moon illusion | ||
Jessica Ruby accepted English subtitles for The moon illusion | ||
Jessica Ruby edited English subtitles for The moon illusion | ||
Jessica Ruby edited English subtitles for The moon illusion | ||
Andrea McDonough edited English subtitles for The moon illusion | ||
Andrea McDonough edited English subtitles for The moon illusion |