Myth: The astronauts didn’t float away because they had heavy boots

by Stephanie Chasteen on November 9, 2009

Below I am reposting a rather long piece taken verbatim from the website of Steve Detweiler who just says that it’s an “amusing anecdote from a friend of mine.”  So, I’m not sure of the veracity of the story, and some claim that it’s an urban legend.  It may well be.  But it opened up some deep discussion on the PHYSLRNR email list, which I attempt to summarize below.

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. 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 were 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.

———————————

First off, here’s the physics.  Earth is not the only thing with gravity.  The moon exerts a gravitational force on things, but it just exerts less force, mostly because it’s just got less stuff.  Stuff attracts stuff, and so less stuff will attract other stuff less strongly.  If you drop a pen, it will fall slowly, because the acceleration due to gravity is weaker.  Earth is far away, but that doesn’t really matter — when you are on the surface of the moon, the gravitational attraction of the moon is stronger than that of the earth.  That’s why the astronauts could jump very high on the moon.  You would weigh less on the moon than you do on the earth.  If the astronauts jumped really really really hard, they could float away from the moon.  The same is true on the earth (but to jump that hard, you need rockets, and that’s what the space shuttle does).

So, here’s the discussion.  One instructor said that she had used similar questions in her class, and gotten similar results.  Many students thought the pen would float away.  One year, she asked them instead about a crescent wrench instead of the “apocryphal pen.”  They all answered that question correctly!  Another instructor, however, gave a similar set of questions to his class, and most of them answered correctly.  What’s he doing differently?

What’s the problem?  This question forces students to challenge a preconception that they had walking in the door — perhaps that “things float in space” or “heavy things get weighed down.”  Apparently the misconception that the moon has no gravitational attraction persists through most physics courses.  Even though they might be able to state that the moon has gravity (as evidenced by correct answering of the second question, as to why the astronauts stayed on the moon), they have trouble transferring that understanding to the “what happens when you drop a pen on the moon” question.  They are thinking, argued one instructor, in terms of the surface features of the problem (we’re on the moon!) rather than the underlying features (all chunks of matter have gravity).  Students transfer more when they’re interactively engaged in the material, says the research (e.g., Cognitive Development, 6, 449-468 (1991), Learning and Transfer: Instructional Conditions and Conceptual Change, Michelle Perry).

John Clement gave a few ideas for ways to address this misconception in class:

Given enough time you could propose a number of what-if questions which might help the TA understand what is going on.  Why did the rocket have to fire its engines to prevent a crash?  Why don’t rocks fly away from the moon?  What force pulled Apollo 13 around the Moon?  Whey when the astronaut dropped a feather and hammer did they both fall to the surface of the Moon? This last one has no heavy boots!!!

Another really important question is to ask why they think there is no gravitational attraction on the Moon.  A number of students will reply “because there is no air”.  The common misconception is think that “gravity” is due to the air pressing you down.  Or they may say because the Moon does not rotate, as this is another common misconception.  These are explained in the teachers manual for Minds on Physics, and students are asked questions
to bring out these misconceptions while building a coherent model of gravitational attraction.

So rather than attacking the “heavy boots” conception, the student has to internalize the model that there is (at least in classical mechanics) no threshold to the action of forces, and that unbalanced forces cause acceleration.  Then they have to apply it to a variety of cases, of course, along the way.  It helps to have them apply these conceptions to objects on other planets.  So blocks of wood in a water filled bowl all float at the same level on the Moon and the Earth, but springs supporting masses are stretched less on the Moon.

So the “heavy boots” is not the primary concern.  The concept of forces and acceleration are the primary concern.  Once the students have a firm model of forces, and of NTNs general gravitational law, the idea that things can float on the Moon will go away.

A few more comments that I liked:

Can the boots be heavy if the astronaut is not?  Are the boots heavier than the astronaut?  If not, do the boots weigh down the astronaut or does the astronaut way down the boots?  I think a few questions like this can make the logical inconsistency evident. (Jerry Touger)

But, countered Dave Van Domelen:

Actually, it goes along with ideas like blankets being intrinsically warm.  Qualities as properties of things, rather than the result of interactions.

And from John Clement, an idea I’d never heard before:

This comes from the concept that “gravity” exhibits a threshold effect.  You have to have enough of it to be pulled down, otherwise you float.

Which, pointed out a discussant, suggests that students are using buoyancy as an analogy — if you’re heavy enough you sink, if you’re light enough you float.  Or, perhaps, friction is the correct model — there is a threshold at which the force becomes effective.

Of course, trying to address these misconceptions as “problems” to be plucked out of the students minds won’t work.  They’re using these ideas because they fit with their experience of the world.  Trying to understand their underlying conceptions (without perjoratively labeling them as misconceptions) and working from there, will be most productive.  Dewey Dykstra has written quite a bit about this, and you can see my previous post on that.

Other resources:

  • Minds on Physics (vol 4) has a good section on moon/earth comparisons
  • An entire thesis was written on the “heavy boots” problem
  • Chapter 4 (p 44-46) of another thesis also deals with this problem
  • David Hammer, More Than Misconceptions” published in AJP in 1996.

{ 26 comments… read them below or add one }

Joshua Lutes November 9, 2009 at 4:05 pm

I answered gravity on a physics test in high school for the question “What force works at a distance” and got it wrong because the professor wanted electromagnetism. When I took the paper up to him to contest it, he told me that gravity doesn’t count because it only exists between planets. I got the physics book and read to him out of it but he cut me off and claimed that what I had read proved his point. He … he was kind of a jerk?

Oh, right. Guess what chapter we ended up skipping over that school year.

Peter Lyons November 10, 2009 at 6:02 am

Here’s comedian Mitch Hedberg’s take on the whole gravity issue: “My belt holds up my pants and my pants have belt loops that hold up the belt. What the f***’s really goin on down there? Who is the real hero?”

http://en.wikiquote.org/wiki/Mitch_Hedberg

Ilya Lisenker November 10, 2009 at 7:22 am

Somehow, Russian middle school students were able to absorb that fact in 6th grade (physics was not an elective). What we did have was a giant glass tube which could be evacuated with a hand pump and which contained a feather, a BB and a small block of wood. What we did not have was computers that make pretty pictures out of such experiments making them seem like another computer game where anything happens. You just can’t replace first hand experience with virtual learning and have it become truly a part of you. Same way as the (otherwise dumb) kid who burnt holes in his uniform in eighth grade chemistry (also not elective) will never forget that sulfuric acid is not volatile so even dilute acid will become concentrated once the water evaporates.

Robert Pearlman November 10, 2009 at 9:24 pm

I found this both fascinating and nostalgic as in 1995, I led a student group that conducted the “Heavy Boots” survey at the University of Maryland at College Park.

At the time I was president of the Maryland Students for the Exploration of Space (MSEDS), a chapter of the larger national organizations SEDS-USA. Largely comprised of astronomy and physics majors, the members of MSEDS decided one night to randomly call students listed in the campus directory and ask the question, “What would happen if you were to stand on the Moon and release a pen from your hand?”

If the person’s reply was not “drop to the surface of the Moon” then we asked the follow-up question about why the astronauts who walked on the Moon didn’t also float or float away.

Our poll differed from the one described by Steve Detweiler in that we didn’t ask it as a set of multiple choice questions. All the replies were free form.

In addition to asking the two questions, we also asked for the student’s year and major.

We found at least one physic student (a junior if I remember correctly) whose answer to the first question was incorrect. Overall, the correct responses were not as high as Detweiler’s example — I suspect because we did not offer choices.

But it was the follow-up question that was more interesting (at least to me). We received explanations that the astronauts were tethered to the “space shuttle”, that the astronauts wore “anti-gravity” spacesuits and that they “held on” to the Moon. Two replied with surprise that astronauts had even been to the Moon.

And without prompting, three said some version of “they were wearing heavy boots”.

Since reading your blog last night, I have tried to locate the summary we wrote up afterwards of the results but have yet to find it. I remember copying it a few years ago to a backup CD, but what happened to it in the intervening years (and moves) has escaped me. I am going to reach out to some of our members from back then to see if they retained copies.

I do not recall what led us to conduct the poll that night; I am fairly certain it was not an impromptu thought on any of our parts, though I wonder where we learned about it…

jessy March 3, 2010 at 7:31 pm

rubbish

sciencegeekgirl March 3, 2010 at 8:46 pm

Exactly. That’s why it’s called a myth. If that’s what you mean.

interestingfellow February 22, 2012 at 7:35 pm

It seemed such an illogical and jovial assumption, that I didn’t understand the “myth”. I had to get through the beginning of the article to understand that there are, somehow, people out there that just don’t “get it”.
I’m not saying we all have to be astrophysicists, but definitely not idiots.
I have little tolerance or patience for people who do not wish to know “why.”
That being said, I realize I’m not the smartest peanut in the turd.

Pam June 23, 2012 at 7:37 pm

My 8 year old student is reading The Magic Tree House: Midnight on the Moon. We were looking for information about moon boots and came across your article. She got all of the questions correct. I asked her what would happen to a pencil if it were dropped on the moon. She said it would float down slowly, then bounce a little before landing. I asked her if it would float away, and she said, “Of course not – there is still gravity on the moon, it just isn’t that strong.” Isn’t it interesting how easily college classrooms are able to affect the way otherwise intelligent people view what is common sense to an 8 year old?

Sandy April 4, 2013 at 11:17 am

Hi thank u soooo much, you helped me to solve a question for my child..keep it up

phryk November 28, 2013 at 2:21 pm

One thing that might have made the students think that a pen would float on the moon is the lack of atmosphere – the sky on the moon looks pitch black, just like “in space”.

You could try asking the same question with Mars instead of the Moon and see what happens…

rob November 28, 2013 at 3:44 pm

It is interesting how the author calls it the inability to transfer the understanding of a particular concept from one thing to another.

They were unable to connect two very connectable details.

They need to focus more of their time on heightening their ability to make connections in physics, or maybe just in general, because perhaps the lacking of that skill is another piece of the puzzle.

Schmitt November 28, 2013 at 10:22 pm

Whether we like it or not, a lot of what people know about foreign environments comes from movies. They’re visceral and real in ways which words on a page in a textbook are not. In the absence of actual knowledge, and confidence in that knowledge, it’s easy to subconsciously substitute movie knowledge, even when we know intellectually it’s wrong.

And there have been so many movies that get space so very wrong. You’re fighting against Star Wars here. That’s a tough battle.

I like John Clement’s “Apollo 13” question for this reason. Everybody’s seen that movie, and so everybody feels in their bones what it means for a spacecraft (with no engines) to go around the moon. You spend most of the movie sitting in a disabled spacecraft being pulled by the moon’s gravity.

There’s a great miniseries called “From the Earth to the Moon”, which is like that, but for every Apollo mission. The climax of one episode, “Galileo Was Right”, shows an astronaut on the moon simultaneously dropping a feather and a hammer.

If TV is ruining science for people, then let’s use TV to fix this problem!

King November 29, 2013 at 10:15 am

Maybe its because I’m from a different county but I’ve never met anyone who would not know that thing fall to the ground on the moon in exactly the same way as they would on earth. WTF America! Is your education system that bad!

King November 29, 2013 at 10:21 am

I just did a straw poll at work here (6 other people). All said that the pen would drop to the ground, 5 said that the moons gravity would do it and 5 also (without prompting) said that they thought the moons gravity was about a sixth of earths. Most of them I was asking a trick question or making a joke.

Alan Z November 30, 2013 at 2:16 am

Original “heavy boots” post to usenet from Russ Brown in September 1989:
http://goo.gl/Xk7oKA

Mike Scott November 30, 2013 at 11:49 am

Of course, it’s true that an astronaut (of sufficiently low density) could float away on the Earth if not held down by heavy boots. But not on the Moon.

Simon Howard November 30, 2013 at 6:57 pm

“If you drop a pen, it will fall slowly, because the acceleration due to gravity is weaker”

WRONG! Things fall at the same speed regardless of their mass. Look up the “Hammer vs Feather” video on Youtube of astronauts demonstrating this on the moon’s surface.

Stephanie Chasteen November 30, 2013 at 8:10 pm

Simon, “the acceleration due to gravity is weaker” is not referring to a pen versus a heavier objects, but to the acceleration due to gravity on the moon versus the earth.

Michael October 30, 2015 at 3:58 am

Of course there is gravity on the moon. The thing that surprises me when I watch the moon landing clips is that the astronauts seem unable to move as one might expect they would in 1/6 earth gravity. How heavy are their suits, packs and boots? I think they weigh ~200 pounds, and assuming a generous body weight of 200 pounds, that is 400 pounds, or ~67 pounds on the moon. After a short trip to the moon, their muscular strength should not have diminished much. Why aren’t these astronauts jumping ten feet or more off the surface of the moon?

Don Straub December 8, 2015 at 4:03 pm

Maybe something was trashed in translation, but “ground” in most English dictionaries is “surface of the Earth/earth,” not “surface of the Moon / lunar soil.” With that definition in one’s vocabulary, the “none of the above” option, when offered, is a better answer than “fall to the ground.”
A little bit aside, some people (indoor types?) go to the extreme of referring to every foot-level surface as “floor.” Lawns and sidewalks become the floor. At least on the Moon, there are floors outdoors, the floors of craters.
Alternate poser: The pen wouldn’t do any of the above because it is tethered to the writing slate.

fred January 24, 2016 at 5:56 am

“Of course there is gravity on the moon. The thing that surprises me when I watch the moon landing clips is that the astronauts seem unable to move as one might expect they would in 1/6 earth gravity. How heavy are their suits, packs and boots? I think they weigh ~200 pounds, and assuming a generous body weight of 200 pounds, that is 400 pounds, or ~67 pounds on the moon. After a short trip to the moon, their muscular strength should not have diminished much. Why aren’t these astronauts jumping ten feet or more off the surface of the moon?”

They probably could have jumped higher… how smart do you think that would be considering they might fall over on landing and tear a hole in their suit?

Michael March 6, 2016 at 5:47 am

A more interesting question would be why the astronauts were not able to jump very high in 1/6 earth’s gravity. Why the dust they kicked up didn’t fly up into a cloud, but settled right back down. Why NASA would fake a moon landing?

??? February 7, 2017 at 1:33 am

Truth be told, the current operating environment is challenging.

chris March 10, 2017 at 11:00 pm

My opinion it does not matter how much something weighs if there is no gravity it will float away.

Pam April 22, 2017 at 9:12 pm

That was my husband Russ Brown that wrote this heavy boots story years ago ( happened around 1982.) Great to see it’s still making the rounds. Sadly, some people still don’t understand.

Rubin April 27, 2017 at 9:09 am

Cardisa, I was preparing to change my profile today, so I
value every one of these excellent tips for aligning its material with my
different subjects.

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