Heavy Boots
About 6-7 years ago, I was in a philosophy class at the University
of Wisconsin, Madison (good science/engineering school) and the
teaching assistant was explaining Descartes.
He was trying to show how things don't always happen the way we
think they will and explained that, while a pen always falls when
you drop it on Earth, it would just float away if you let go of it
on the Moon. My jaw dropped a little. I blurted "What?!" Looking
around the room, I saw that only my friend Mark and one other
student looked confused by the TA's statement. The other 17 people
just looked at me like "What's your problem?" "But a pen would fall
if you dropped it on the Moon, just more slowly." I protested.
"No it wouldn't." the TA explained calmly, "because you're too
far away from the Earth's gravity." Think. Think. Aha! "You saw the
APOLLO astronauts walking around on the Moon, didn't you?"
I countered, "why
didn't they float away?"
"Because they were wearing heavy boots." he responded, as if
this made perfect sense (remember, this is a Philosophy TA who's
had plenty of logic classes). By then I realized that we were each
living in totally different worlds, and did not speak each others
language, so I gave up.
As we left the room, my friend Mark was raging. "My God! How can
all those people be so stupid?" I tried to be understanding. "Mark,
they knew this stuff at one time, but it's not part of their basic
view of the world, so they've forgotten it. Most people could
probably make the same mistake."
To prove my point, we went back to our dorm room and began
randomly selecting names from the campus phone book. We called
about 30 people and asked each this question: 1
1. If you're standing on the Moon holding a pen, and you let go,
will it
a) float away,
b) float where it is,
or c) fall to the ground?
About 47 percent got this question correct. Of the ones who got
it wrong, we asked the obvious follow-up question:
2. You've seen films of the APOLLO astronauts walking around on
the Moon, why didn't they fall off?
About 20 percent of the people changed their answer to the first
question when they heard this one! But the most amazing part was
that about half of them confidently answered, "Because they were
wearing heavy boots."
MORE ON THE BURNING QUESTION OF HEAVY BOOTS
I decided to settle this question once and for all. Therefore, I
put two multiple choice questions on my Physics 111 test, after the
study of elementary mechanics and gravity.
13. If you are standing on the Moon, and holding a rock, and you
let it go, it will:
(a) float away
(b) float where it is
(c) move sideways
(d) fall to the ground
(e) none of the above
25. When the Apollo astronauts wre on the Moon, they did not
fall off because:
(a) the Earth's gravity extends to the Moon
(b) the Moon has gravity
(c) they wore heavy boots
(d) they had safety ropes
(e) they had spiked shoes
The response showed some interesting patterns! The first
question was generally of average difficulty, compared with the
rest of the test: 57% got it right. The second question was easier:
73% got it right. So, we need more research to explain the people
who got #25 right but did not get #13 right!
The second interesting point is that these questions proved to
be excellent discriminators: that is, success on these two
questions proved to be an extremely good predictor of overall
success on the test. On the first question, 92% of those in the
upper quarter of the test score got it right; only 20% of those in
the bottom quarter did. They generally chose answers (a) or (b). On
the second question, 97% in the upper quarter got it right and 33%
in the lower quarter did. The big popular choice of this group was
(c)...33% chose heavy boots, followed closely by safety ropes at
27%.
A telling comment on the issue of fairness in teaching
elementary physics: Two students asked if I was going to continue
asking them about things they had never studied in the class.