We've all seen images of pens floating weightless in space on films and TV, and we probably haven't ever seen pens falling on the moon. But the moon is in space right? so... yeah, why not, it floats.
And for the guys on the moon, well I haven't got any memories of astronauts without boots on, and those boots sure look big and heavy, they're special gravity boots, I'm sure I heard that on TV once, yeah, that's probably it.
The first principles approach of applying the concept of universal gravitational attraction probably isn't even entering their heads, even if they've been taught it.
This used to get on my nerves, how can people be so stupid? Why won't they just think for a moment!? But recently I've been focussing some effort on learning a language (Spanish) and realise that in that this case the first-principles style of learning that works so well for physics and maths is largely useless, and it's better to turn off the analytical side of your brain and not think too much, just keep exposing yourself, trying to communicate, and let your subconscious do it's stupid fuzzy pattern-matching, and it does a remarkably good job!
There's also the issue of quality of effort. If you apply effort to reason something through, you can weed out obvious misconceptions on your own and give a better answer. Part of the reason why the people that gave ridiculous answers got lower test scores could be that they are not in the habit of applying much effort when asked science-type questions, so they blurt out the first thing that comes to mind and move on. I suspect that on a more-favored subject most of those people would apply effort and give higher-quality answers. Otherwise, they'd be crippled in all aspects of life. This explains why my mom can't use a computer and I can't use her ultra-sophisticated microwave. She doesn't want to expend effort on the computer and I don't want to expend effort in preparing food.
I wonder if there's a reliable way to get people to start using critical analysis on a subject. Such as when you're training someone how to send an email, this would be helpful information!
I had the exact same experience. I'm an Engineer, and my entire life I've only been able to learn (and self-teach) by reasoning through first principles. When I can't reason it through, I don't want to learn it "just because"
I never put any effort into learning a language, and always thought it was "dumb". In high school I could say hello and count to 10 in a couple of languages, but that was it.
When I was 27 I started traveling through Central and South America, and wanted to learn Spanish. I honestly didn't know if I was capable, or if my brain and learning style would allow for it.
For the first couple of months I was frustrated and always saying things like "but that doesn't make any sense", "It should be like this" etc.
After a few months, I just stopped trying to reason it through and started going with it, like you said. After about a year and a half I stopped translating into English in my head, I started dreaming in Spanish, and I can now guess words and verb conjugations without consciously realizing I even know that given word. It first started happening when I was a little drunk, which is a good time for me to actually get stuff done in my head, because I stop trying to reason everything through and just go with it.
Stick with it, you'll get it. I can't more highly recommend immersing yourself for a prolonged period.
Actually I'm living in Madrid now so kind of immersed, the problem is that my girlfriend and I tend to always speak English with each other and I don't need to use Spanish to work either. It's what led me to create my current project: http://readlang.com
While it didn't take long to get the physics of the problem, it took a lot longer for me to grasp the social side of things. Specifically, if your grade six teacher says something stupid like this, there is absolutely nothing to be gained from correcting her. I wish I could go back in time and clue me in.
OTOH, if it's a university lab at a science and engineering school, then give 'em hell.
Perhaps it was irrelevant in your case. Or perhaps your skepticism inspired a fellow student to become an engineer. Who knows?
In the Niven/Pournelle book The Magic Goes Away, one of the wizards takes his apprentices up to a high peak and casts a spell to enable his apprentices to walk on clouds. There is a hidden purpose: In every group class, some of his apprentices goes up the peak and tries to jump on a passing cloud without knowing the spell. This had the effect of raising the intelligence level of his students.
Heinlein proposed that colonists living on the moon would be more intelligent than the general earth population -- simply through natural selection.
Also, your way of learning Spanish is impressive.
If we're discussing reasoning from first principles, is it really so intuitive to disregard the gravity of the Earth in this experiment? Why can you disregard it and still get the correct result?
Even with a physics degree, my kneejerk reaction didn't come from first principles. I, too, was doing "stupid pattern matching" -- the only initial difference between me and the floating-pen-people was that I happened to know that gravitational acceleration could be reasonably approximated as constant on large astronomical bodies (moon is g/6). It took a few seconds for the "otherwise the planetary body would disintegrate" argument to occur to me and even longer for the formal mathematical picture.
The children boldy proclaimed that the reason the hammer and the feather hit the ground at the same time in the famous experiment was because there was less gravity on the moon.
It still rankles with me a year later.
Your daughter presumably understands that it's not about gravity but air resistance. Has she told all her pals? Because that kind of subversive teaching could be really powerful. TEACHERS HATE HER; THE GRAVITY SECRET THEY DON'T WANT YOU TO KNOW!!! etc.
May I ask, hold old was your daughter? What kind of science teaching should she be getting? (Obviously, not anything that wrong).
People just DO NOT think.
Everybody has SEEN (on TV, where they spend more time in front of, than in school or reading books) astronauts in orbit demonstrate they're weighless, by showing a pen float in front of them.
So space = floating pens, in their visual memory.
Moon is in space, therefore pens float.
What about a wrench? Oops, no visual memory to answer, bummer, they'll have to think! And of course, some of the little teaching they had pegged, and they can answer correctly.
That's all. People DO NO think.
Why do you think, IBM had to put up "THINK!" panels in its offices?
Humans have a huge advantage in being able to communicate knowledge across generations, and a huge disadvantage in being able to communicate bullshit across generations.
They just generally do not think about Physics.
A significant part of the article is a reposting of http://www.phys.ufl.edu/~det/phy2060/heavyboots.html
Edit: Changed wording re how much of article is repost
That is an unfair characterisation, I think. The article does indeed reproduce heavyboots in its 725 words entirety (according to pages's word count for what that one's worth), but tacks a further 930 words afterwards. And these 930 are interesting indeed as they're further explorations of the phenomenon and discussion on its underlying reasons.
The reason for choosing b) would have been that the moon's gravity being weak, the earth's gravity nullified the moon's thus having a floating pen.
The reason for choosing d) would be because Moon's gravity is stronger than Earth's.
This is why I think tests are stupids. If I had chosen b) instead of d) I would have gotten a wrong answer. Even though my thought process would be correct. Just missing the right information (which could have been easily found outside a test environment).
So no, I'm pretty sure your thought process wasn't remotely correct.
If Moon was hanging on a stick connected to Earth (instead of orbiting Earth) and Earth gravity forces on a pen were stronger than Moon's gravity forces, then pen would fall in Earth.
Of course you and I know that there are no such strong materials for that Earth-Moon stick, but that's yet another level of complexity that most people don't have to know about.
Technically that's true, but it would require a completely different scenario. Earth's gravity is miniscule at that altitude. For the moon to have a weaker force it would have to be so small that it would likely not even qualify as a moon any more.
You can disagree all you want, it's not because things would just fall towards the moon in practice that it's impossible that the pen stand still.
"Please select all possible conditions under which pen on the Moon would not fall on the ground".
They may not be stupid, but that's pretty much the definition of ignorance.
The interesting part is the discussion of what these wrong mental models look like and how you can teach a correct one.
Absolutely. There was much they did not know, as is true of anyone. "Ignorant" is not an insult, it simply means you do not know something. Would you say Aristotle and Newton knew everything about everything? If not, then they would be, by definition, ignorant of the things they did not know.
By modern standards, absolutely.
By your definition they're ignorant, but not stupid?
The moon has less gravity than the Earth, so a pen is like a feather.
Blah blah atmosphere electro-magnetism blah, the universe is big ad complicated.
They float away because air currents exert forces on them that are greater than their weight. Eventually, in a still-air environment, the feather and the dust will settle to the ground. You can verify this by going to your nearest attic.
> 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 ..."
I was sure at that point he was going to say "dropped it on the floor" but no such luck.
> "...read to him out of it but he cut me off and claimed that what I had read proved his point."
> Physics 324 - Modern Physics for Engineers
> "A body is at rest tends to stay at rest, plus there's no gravity"
> "The gravity of the moon can be said to be negligible, and also the moon's a vacuum, there is no external force on the pen. Therefore it will float where it is."
> "The pen will float away because the gravitational pull of the moon, being approximately 1/6 that of the earth, will not be enough to cause the pen to fall nor remain stationary where it is. The gravatational pull of other objects would influence the pen"
It's a bit scary seeing what the answers are.
I guess we need to remember just how long ago it was that anyone was on the moon, or any distance into space.
An ASCII diagram.
e g m
earth geosynchronous moon
That one's almost correct; it's just an issue of scale; they don't realize how big/heavy the moon actually is.
Is that true? I suspect it's true for people over 30 or who have special interest in STEM, but not so true for anyone else.
One way or another, I think everyone but very small children or reclusive hermits have seen at least some footage of an Apollo astronaut bouncing around on the moon.
25. When the Apollo astronauts were on the Moon, they did not fall off because:
(f) They were on Earth
I recommend browsing Amazon reviews of (non heat pump) electric heaters for statements about which ones are more efficient. (The less efficient one produce more waste heat?)
Because there are few consumer products that exercise people's understanding of gravity, basic thermodynamics might be a good proxy. However the real point of the article isn't all the misconceptions that must be "plucked out" one by one, but the struggle of trying to figure out how to encourage students to form more comprehensive models.
I'd also add that an important goal in teaching is students' facility in applying principles, and confidence to question intuition and consensus.
Then, I think that there are some real differences found in the efficiency of the heaters.
If you have two 1000w heaters, one made from a potato and ten clothes hangers and the other made from the highest quality materials known to man, they will still both heat a room the same amount.
Granted, one might have a better fan or more airflow and might therefore provide a more even heat distribution in the room, but they will both be providing the same amount of heat to the interior of the room. That's just how energy balances work. If 1000w is flowing from the plug into the heater and it's not being stored anywhere in the heater itself there's nowhere for it to go but into heat for the room.
autocorrected, should have been:
>don't realize that they happen to be surrounded by
The proportion giving answer (b) will cause you to sob even more.
(Yes, I have done this. Afterwards, I hid under my bed bewailing the ignorance of my fellow hominids.)
The importance of the heliocentric model comes from the fact that there are more objects in the solar system. With multiple objects you could also hold any one of them still but it makes the model much more complicated and the attraction between the objects less intuitive.
This is confirmed through the phenomena of stellar parallax and stellar aberration, which are only visible from Earth because of its motion. Even back in the 1573, Thomas Digges and many successors realized they could prove the Earth was in motion using parallax (though had trouble detecting it), and in 1729 James Bradley gave the first proof of heliocentrism using aberration. Both of these observations were taken as proof by the scientific world that the Earth orbits the Sun, and not the other way around.
It looks like Jupiter is way faster than I thought it was. My guestimate for gas giant orbits was skewed towards Uranus/Neptune (84/165 years), but Jupiter orbits in only 12!. It's crazy how close Jupiter is to us.
That's incredibly damning of your grade school science curriculum :(
Specialization allows people to stay ignorant about many things.
I blame my uprooting to this retarded planet on people's ignorance in Physics.
>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.
Why is this such a stupid assumption? That's how it works on Earth.
I don't believe that these kids are failing to think; they're using reasonable analogies, but lacking specific knowledge about the environment on the moon.
>"All science is either physics or stamp collecting." - Ernest Rutherford
Basically the authors are complaining that the students haven't collected a specific stamp.
It's a packers vs. mappers question.
The packers collect stamps, and when asked whether the pen falls on the Moon, get out the stamp that says that pens don't fall in space.
The mappers will apply the physics model, the formula, and come out with the right answer (or approximation) corresponding to the right situation.
That's a big problem with packers: you teach them stuff, but they retain only half of it, forgetting the applicability conditions.
"Nothing can go faster than light!" Only material stuff, and only in the vacuum. But there are mediums where light will go slower than a walking human. "There's no perpetual motion machine!" Right, only when you consider a CLOSED system. There's no physical entity smaller than the Universe that's a closed system. Even black holes have inputs AND outputs! And so on.
I find it hard to believe that a high school physics student, just fresh from studying gravity module, wouldn't realize that a rock dropped on the moon would fall down. Doesn't pass the smell test.
Edit: a quiz to maybe prove my point :) On the moon, if you throw a rock, what shape would its arc describe?
Edit2: not a straight line when you drop it, silly!
The arc will approximate a conic section of some kind, depending on how hard you throw it. Within the usual level of ability of a space-suited human throw, it will approximate to an ellipse so close to parabolic as to be impossible to tell the difference before it hits the moon. Throw it harder and it'll approximate to an ellipse. You are only going to be able to approximate a circle if you stand on the highest point on the Moon and throw at exactly the circular orbital speed horizontally, although gravitational perturbations will usually break the orbit. It'll approximate a parabola if you throw at exactly the escape velocity, and a hyperbola if you throw even harder than that.
Please get your wording right, there is a big difference between force and acceleration. It is trivial to prove, that things are not accelerated by gravity at equal rate.
PS: I am not usually wording-nazi but since you started with calculus...
As I was saying, there is difference between force and acceleration.
I read sp332's original comment as having an implicit "in the absence of other external forces" (gravity accelerates things at the same rate regardless of mass) as that's often implied when generally discussing forces and acceleration.
After all, it becomes hard to talk about the relationship between force and acceleration, if you can't even say that the acceleration of an object is proportional to a force acting upon it - because there might be other forces you've not taken into consideration! Yes, I won't accelerate an object if I try to push it into a barrier, because the barrier will exert an opposing force that resists my effort. Yes, an object might fall up if I "drop" it, because it's in an updraft that combined with it's drag coefficient causes more force up than gravity exerts.
But springing those sorts of situations on people as "gotchas" isn't useful in a general discussion about the essence of a concept. Unless otherwise specified, assume ideal point masses in a vacuum (or whatever). If you want to add opposing forces of some kind to complicate^W make the situation more realistic later on as a more advanced topic, that's fine, so long as that's specified up-front.
If complicating factors are not specified up-front, it's assumed that they're absent, because there are an infinte possible set of complicating factors which could be present but have not been mentioned yet.
After all, in an atmosphere it could be accelerated at the same rate, as there's a (previously unmentioned) anemometer and computer-controlled rocket attached to the object which are set up to produce a thrust which exactly compensates for the wind resistence! So ner! :-)
(And, in fact, sp332 specifically stated "even without air resistance" to explicitly constrain the conditions under which their example was valid)
> gravity accelerates things
The confusion is between the transitive and intransitive forms of the word "acceleration". If I say "the pen accelerates", this implies net acceleration of the object. If I say "gravity accelerates the pen", this implies gravity's contribution towards net acceleration. Air resistance diminishes net acceleration, but not the acceleration as contributed by gravity.
sp332 was fine. It's common for astrophysicists to talk about gravitational fields in terms of "acceleration fields" rather than "force fields". This is because the acceleration contributed by gravity only depends on a single argument (distance from the celestial body's center) as opposed to a force-field's two arguments (distance, the pen's mass). And next time you hear "g = 9.81 m/s^2 for all objects on earth's surface", the physicist is referring to gravitational acceleration, regardless of whether or not the object is moving.
After all, a model is only as good as the precision of the results it produces...
Many people don't think.
I believe this is the original:
/edit, well bullshit is a bit strong, but replication failed
That many people suck at "reasoning" about problems boggles my mind. Most these students knew the facts of Newtonian mechanics but could not apply them (in my opinion) to a very simple problem.
Not bragging. I must be good enough at reasoning that I am cognitively unable to comprehend that other people have trouble with it. Everyone knows how to breath or think about future. I assumed everyone can take things they know, combine/apply them to new situations. What I would call reason about things.
Maybe they can. And the results are an artifact of college environment (study/memorize/pass test vs actually learn/challenge/grow).
See, I so can't comprehend it that I'm trying to come up with rationalizations.
I was recently wondering if our terrible road safety problem in South Africa can partly be explained due to a lack of understanding of physics. After all, intuitively Newton's First Law explains why seatbelts are necessary. Concepts like momentum and kinetic energy explain why heavy trucks, speeding down steep inclines are dangerous - authorities don't seem to grasp that very often, and tragedies involving runaway trucks on poorly engineered roads are not infrequent.
But I then realised that two of the most reckless drivers I know are my uncle, an Engineering dropout, and my friend who is a practicing engineer. Being good at physics hasn't saved them from being in multiple car crashes.
Are there any cases where an understanding of physics helps the average person in everyday life?
For your uncle and friend, understanding something doesn't mean you feel it's going to apply to you. Road accident are not only a matter of physics but also a matter of statistics and risk calculation. Some people are reckless because they can't compute the probability of accident and often underestimate it, feeling that since they think they are good drivers it won't happen to them. Humans in general are bad at assessing risk, it's a very difficult matter.
This is the main challenge in teaching people any technical subject - discovering the basic knowledge you have assimilated so deeply that you can't even imagine that others don't share it.
That's an interesting argument to make.
In the context of students taking courses with a physics component it's not so relevant.
Physics 221 - First Semester Calculus-based Introductory Physics
> "Because the gravitational pull of the moon is much weaker than that of the earth. And object such as a pen is so lite that it will float"
Some of the answers are borderline incoherent. I'm not sure if English is their first language, or how old people who take Physics 221 are, but it's kind of scary.
Now, I'm not in favor of teaching creationism in schools. Schools should teach what we as a civilization understand to be true. But as far as what individuals choose to believe? I don't really much care. I think it's an odd thing to get emotional over, but both sides certainly do (this is me preempting emotional replies :-) )
Of course, even when evolution is taught, it's almost always taught wrong. Even a large percentage of graduate biology students have deep misconceptions about what evolution is and how it works.
It just occurred to me that machine learning students would probably have the best understanding of evolution of any group of students. Ha!
Some large percentage of the students got it wrong. Explanations: (i) students limited their "physics know-how" to the textbook context, and this was something different; (ii) textbook problem sets are, over time, edited to weed out confusing problems, even if they're valid.
I've encountered something similar in teaching basic financial present value analysis to engineers - even the students who do well in the class go back to "folk" thinking when we discuss their mortgages and credit cards.
To me, it says that the cue of the classroom, or the awareness that "this is part of Physics 101" is critical to getting some people to apply a particular frame, and without that cue, they go back to "common sense". That does explain what happened (in the blog post) in the Philosophy class, and in the phone poll, but not as well what happened when the blog author tested her physics students.
A ball with no spin on it would travel straight outwards because there would be no force acting on it to make it curve in any other direction.
I think a ball with spin on it would curve outwards because the ball would rotate the air around itself, which would provide the force needed to accelerate it outwards.
The gravitational constant is 1/6 of the Earth's. This means that I can jump on the Moon 6 times higher than here and the pen will tale 6 times longer to fall down.
It will take 6 times longer for gravity to 'kick-in' and cause the perceivable movement, as we got used to here on Earth - where on Earth the pen moved already 6 cm on the Moon the movement is still 1 cm.
It looks as if the things are moving slower. I can catch a falling egg before it reaches the ground, my reactions are like of a fly on Earth.
So I can say that the things are floating on Moon, because they are not accelerating and falling fast enough, in common terms. In interstellar space the pen will fall onto the neighbor galaxy, but will do this so slow, that I will perceive as if it is floating. If the pen will move alongside with an object much smaller than the Moon (a rock), the pen will fall onto the rock with much slower acceleration. For time perception of humans it will float in space.
Another explanation for wrong answers is that if you feed people with stupid questions, you will get stupid answers. Have you asked me to answer these questions I will surely answer wrongly 'pen floats' and 'heavy boots' on purpose only to prove the point. These answers seem to be serious enough to mislead you.
Also, actually try dropping a pen, like right now. Gravity "kicks in" immediately - there's no perceptible delay. (Unless your perception is way different from mine.)
Playing with freefall distance equations showed that time to fall difference is square root of 6. Here we are:
Height = gEarth*timeOnEarth^2/2 = gMoon*timeOnMoon^2/2
gEarth = gMoon * 6
6 * gMoon * timeOnEarth^2/2 = gMoon * timeOnMoon^2/2
6 * timeOnEarth^2 = timeOnMoon^2
timeOnMoon = sqrt(6 * timeOnEarth^2)
timeOnMoon = sqrt(6) * timeOnEarth = 2.45 * timeOnEarth
When you press someone, it's not uncommon for them to just pile on another fact about the subject matter and reassert the claim.
It's like brute force puzzle solving, kind of like I used to do in adventure games - you know the result you want, juggle all the stuff in your inventory or mind until it works.
And for a lot of subjects, for a lot of education, that approach works really well. You're told three facts about some historical event. You're asked a question on a test about the event. List one of those facts to win.
I'm guessing they jump to "boots" because the bootprint on the moon is a pretty widely seen and memorable image, and boots in our normal life are sometimes heavy. Heavy things make it harder to float, that's what heaviness sort of means. Having arrived at "floating's hard," they then call it a day without really understanding anything about how they got there.
There's no underlying theory, they kick away the scaffolding as soon as they get to any answer.
People don't have a list of facts in their heads that are constantly checked for mutual consistency, and people can stubbornly hang on to any premise they want.
In other words, the students (+ phil TA) aren't just stupid on this point, they are so stupid, the physics teachers don't even understand how stupid they are.
space --> weightlessness
People who have not been trained in physics often have a different "intuition" about the laws of physics. An interesting effort to qualify these "physics misconceptions" is the Force Concept Inventory (FCI) questionnaire, which which asks students to answer some basic qualitative problems from Newtonian mechanics. You should try it and see how you fare...
Interestingly, researchers have found that even after taking a Newtonian mechanics class, many students still hold on to their misconceptions---their score on the FCI is only slightly improved...
Of course I understand that and can for instance explain it to them, but it often still remains surprising for me.
No indictment of either (or anyone else who would answer incorrectly). After all, not many people think of physics very often on a day to day basis, particularly physics of extraterrestrial bodies.
(A similar example to your red pebble would be "Cavorite" from the H. G. Wells story "The first men in the moon", which also negated gravity causing objects to shoot violently upwards. The explanation given however was buoyancy, which makes more sense I suppose.)
It's interesting to consider the forces involved. At 10m, with a 100kg astronaut and a 15 ton space station the gravitational force is about 1e-7 Newtons. At that acceleration, if the astronaut kicked off at the speed of 1cm/s--or 36 meters per hour--and assuming the force doesn't change, it would take about 24 days to get back.
This makes an intuitive kind of sense: you would gradually lose weight as you get farther from earth, then after a moment of weightlessness gradually 'gain' weight as you approach the moon.
Obviously this is wrong, but why?
It's not wrong, but it would never happen.
Let's say we've built a moon elevator. Like a space elevator, but tethered to the moon. You travel from the earth; there is a brief period of acceleration, then you settle down to a steady speed for your journey.
After you reach the steady state, you are going to experience normal Earth gravity. As you move further from the earth, however, you will experience less of it. As you approach the moon, its gravity will eventually be stronger - with this transition occurring at the Lagrange point L1 between the earth and the moon, where the gravitational pull from each is equal.
In practice, until we build a moon elevator, this isn't going to happen. Instead, we have to throw you at the moon using a rocket. Most of the energy we use for this is actually spent making you go sideways, instead of directly up. It's kind of cool actually - if you are orbiting the earth in, say, the ISS, you are actually experiencing nearly the same gravitational pull as if you were on the surface. You are just moving so ridiculously quickly in a circle around the earth that the centripetal force cancels out gravity - like someone is swinging you around on an invisible rope. Since this is happening to both you and the spaceship you are in, there is no relative acceleration - so you appear to be weightless.
If we fire some more rockets to accelerate you towards a lunar orbit, nothing else changes - you are still not accelerating relative to your spacecraft (assuming you are strapped in!) and so you continue to appear weightless. You transfer into orbit around the moon - and you are in the same situation you were in when orbiting earth. But if you drop a lunar lander, which slows itself down - it'll fall!
Orbital mechanics and gravity can certainly be counterintuitive, but it's thoroughly fascinating.
On the other hand, most professionals are quite functional in their role (if it wasn't the case, why would employers pay them?).
These two observations mean that understanding of physics is not mandatory for being functional professional.
Too bad this isn't part of current events any more.
I will ask this question on parties, this will be funny :D
Truth: There are dumbasses in this world... those who believe this story, because it gives them a superiority over (mythical) others.
Lol, those stupid uni students who don't even know there's gravity on the moon. Lucky I didn't get a degree and become dumber/Lucky my Uni was better.
It's even a friend of a friend of a friend.
Seriously, why is this on the front page?