Why didn’t astronauts float off the moon?

From phys.ufl.edu

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.”


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.

14 thoughts on “Why didn’t astronauts float off the moon?

  1. Mr. Right

    The moon has gravity. Therefore, anything heavier than the atmosphere (which virtually non-existent on the moon) will fall towards it. The Earth’s gravity has nothing to do with it. That TA was an idiot.

  2. corpower

    The ‘professor’ is not an idiot, but he happens to be a typical academic jerk. The difference between a teacher and a professor is that the former actually tell you the answer clearly.

    This professor has you deduce the answer from the entire article. Very annoying! We are not his students…

  3. Looney

    As a philosophy TA (at UConn), I must express extreme disappointment in my colleague from Wisconsin. Such scientific ignorance is inexcusable in a philosopher, as it is impossible to do philosophy effectively without at least an educated layman’s understanding of scientific principles. In order to discuss determinism, one must have a basic understanding of quantum indeterminacy. In order to do epistemology, one must be aware of the relativistic limit on the propagation of information. In order to engage in the philosophy of mind, one must be aware of neuroscientists’ research on the same topic. And clearly none of this is possible if one can’t even understand plain old Newtonian gravitation.

  4. corpower

    Yeah!! What Looney said. Stick it, Wisconsin U!

    Uh, quantum indeterminacy is a concept beyond your grasp. Call for details: 1-888-jaggoff

    btw – looney is precisely the type of academic shmuck I referred to earlier.

    If an academic is decapitated on the moon, will his head and blood float upwards, hover around the neck, or fall to his moon boots?

  5. e

    It’s a nice article written over the way people interpretate stuff.

    bravo:) really made your point!

  6. Zufolek

    Hilarious. How do they think the Moon stays together? And how the hell are heavy boots going to help if there’s no gravity?

  7. Casey

    “so I gave up.”

    I realize how frustrating it may be to try and teach someone unwilling to learn. I hope next time you will press on them that a small amount of inquiry will resolve the dispute, and to challenge them not to take comfort in their ignorance.

  8. FluckFaps

    No, you damn fool, no assthrownaughts were on the Moon, and those who were wore magnetic boots, not golf shoes, as it’s made of iron, like mars.

  9. jeet

    The research effort that went into the question and the results received are commendable…
    I hope fluckfaps is not a TA.

  10. Esquire

    Nice article, informative and funny at the same time.


    Although you will probably never make it back here, you must have known writing a comment like that would draw personal attacks. So, this is for the other hundreds just like you out there.

    First, it is written from a viewpoint from so high on your high-horse that you lose your audience in the first paragraph.

    Second, being a TA does not qualify you as a philosopher. You still need to learn how to relate to an audience you are speaking to, instead of deliberately trying to speak over them. Try reading something other than textbooks once in a while. When not in class, relax. This is exactly the mistake the TA made in the article.

    Third, you do not DO epistemology. Besides, people understand the law of gravity. What they have trouble with is the environment the problem is placed in.

    Loosen up! How clear is that?

  11. Teelo

    Hmm, what about the dust on the moons surface?

    Surely it would float away because its not wearing ‘heavy boots’.

    p.s. you probably were sounding like a bit of an ass, and thats why he gave up on learning so quick. Even if you were right.

  12. Matthew

    What is the answer? I am seven and trying to figure this out. I was told there was gravity on the moon, but no one can tell me why rocks won’t float away, but i am lead to beleive that the asrtonauts would have floated away if not for the boots. This is what my teacher tells me.

    1. PO8

      It’s so hard to tell who here is serious and who is trolling. Bravo to the skilled trolls, and condolences to those who are serious.

      matthew, just in case you are seriously a seven year old with a confused teacher, your teacher is simply wrong. Every object, even something as small as a baseball, pulls every other object, even something as far away as the Space Station, toward it due to gravity. It’s just that the more stuff that makes up the objects and the closer they are, the more they are pulled toward each other. The earth is made of a lot more stuff than the moon, so it pulls on everything a lot harder when you’re standing on it. But whatever you let go of on the Moon would be pulled down by the gravity of the Moon acting on the thing (and the other way around).

      There’s only a few places in the vicinity of the Earth-Moon system where there is actually no net gravity: these are called Lagrange Points and are places where the pull of Moon and Earth are in opposite directions and cancel each other out.

      When you see astronauts floating in “zero gravity”, they actually are falling to Earth pretty fast: it’s just that they’re going sideways really fast at the same time, so they keep “missing” the Earth. This is called an orbit. Galilean relativity, which you will learn about when you are older, says that from the astronaut’s point of view they are in zero gravity, but from the Earth’s point of view they are in orbit—it’s all just point of view.

      corpower, if you are, as your tone implies, an adult, and yet you had to “deduce the answer from the entire article”, I’d strongly suggest taking a physics class. The piece is funny to anyone with a competent 12th grade education precisely because a seemingly obvious fact, “the moon has gravity, so things near it fall onto it unless you stop them”, is apparently so confusing to so many people.

      Esquire, no, the TA’s mistake was not that he used the wrong tone with the class. It was that he didn’t understand how gravity works, yet tried to use it in an example. Except for the bit about quantum indeterminacy (and you’re correct there, corpower), I found Looney’s post to be either a well-thought-out response or a well-written troll. Either way, nice.

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