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Use tracing paper to
draw along the top(^2) curve on this page.
Line your curve up with
the bottom one. Which is
longer? How strange—even
though the bottom one
looked longer, you’ve just
discovered that they’re both
the same length!
3
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O
U
S
C
U
RVES
This visual trick is known as
the Jastrow illusion.Scientists don’t really know why
the bottom curve looks longer. They
think it might be because your brain
compares the short inner curve of the
top shape with the long outer curve of
the bottom shape since they are next
to each other. You see a similar illusion
with these photos of the Leaning Tower
of Pisa. Which tower is leaning more?
It looks like the one on the right...
but the images are identical!SCIENCE
PART...
THE
US_056-057_Curious_curves.indd 57 12/09/2018 15:50