Index | Comments and Contributions | previous:2.6 learning physics
physics
[Top of page]
[Bottom of page]
[Index]
[Send comment]
The following story was submitted by Russell Bray. It illustrates something that we Physicists have to live with... people who remain completely convinced of something that is incorrect even when corrected by someone who knows more about the subject than they do. I am a Arizona State Secondary Ed Major with emphasis in Physics. In a class of Secondary Ed students (none of which are Physics), we were having group discussions. The dude giving his lecture (Theatre Major) asked the class what makes the sky blue. We were to get in groups of five, discuss, and come up with a collective answer. I was not surprised when two groups decided that the sky was blue because the reflection of the ocean. I come to expect that, deal with it, and realize that they were lied to by their parents or second grade teacher. What I didn't expect was that the guy asking didn't know either. After I gave my response of scattering of the sun's light waves through the atmosphere, he said close, but no. Interesting. "What pray tell, is it" I ask. He says, "Because our atmosphere is mostly Nitrogen Oxide, all the rays of the sun are absorbed by the molecules but blue, just like this blue folder absorbes all but blue rays." To a certain degree I see his point, but I couldn't leave it alone. "Why is a sunset red" I ask. "Pollution. We have beautiful sunsets because we have dirty air." He says confidently.
physics
[Top of page]
[Bottom of page]
[Index]
[Send comment]
July 20
From: sirius#NoSpam.wam.umd.edu (The Human Neutrino)
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."
physics
[Top of page]
[Bottom of page]
[Index]
[Send comment]
From: RICHARD#NoSpam.lane.cc.ukans.edu (Richard Kershenbaum)
The following was sent to me by Dr.Adrian Melott, Associate Professor of
Physics and Astronomy here at the University of Kansas:
THE BURNING QUESTION OF HEAVY BOOTS
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.
physics
[Top of page]
[Bottom of page]
[Index]
[Send comment]
From: Joseph Voros http://www.swinburne.edu.au/afi/about/personnel.htm jvoros#NoSpam.No.Spam.swin.edu.au The recent business of Heavy Boots (TM) was being discussed by my Engies the other day when I arrived to take them for a class. (I tutor a couple of freshman Engineer classes in Physics for the University.) Anyway, they were arguing about this, and decided they'd ask me what the situation was. I talked about gravity and how all matter/energy gravitates, etc. The Sun gravitates and all the stars, etc etc. I had to also explain that, contrary to what some of them thought, gravity acts even when there is no air (!!); that the Moon has gravity despite having no atmosphere. This took some convincing(!), but I clinched it with the experiment with the hammer and feather -- they weren't wearing Heavy Boots, and yet still fell. I then proceeded to discuss the nature of scientific theories, testing hypotheses, keeping an open mind but remaining sceptical, the usual stuff. I tend to get very animated when I talk Physics, and raise my voice, gesticulate, pace, and generally carry on. After some 20 minutes of this talk about Science (TM) and Scientific Method (TM), I finished up with something like "So that is how Science is done. Formulate theories, test them and believe them only when and how far they predict experimental results. ... Now, any questions?" One girl up the back raises her hand, "Yes, I have one. You got very worked up over this -- are you a Scorpio?" Oi veh! joe ps Of course I'm not a Scorpio!! I have a very balanced approach to these things -- I'm a *Libra*.
physics
[Top of page]
[Bottom of page]
[Index]
[Send comment]
From: partee#NoSpam.iastate.edu (Jonathan Partee)
We read an article claiming that the average American does not know the
correct answer to the following question:
If a pen is dropped on a moon, will it:
A) Float away
B) Float where it is
C) Fall to the surface of the moon
So a bunch of us TA's got together and gave our physics classes quizzes asking
this question. Out of 168 people taking the quiz, 48 missed the question.
The responses are below. Some people didn't write comments. The spelling and
grammer were not changed, however, clarifying comments are enclosed in []'s.
{ed A report is that only 3 of the 48 were in this course. The rest were
from lesser courses.}
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"
Physics 222 - Second Semester Calculus-based Introductory Physics
"Because moon has gravitation 1/6 of the gravitation of earth the force will
be small toward the moon [so it will float away]"
Physics 221 - First Semester Calculus-based Introductory Physics
"It will fall to the earth by force of gravity and by the attraction between
the earth and the moon"
"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"
"Because there are no external forces if you let go [it will float where it is]
"External forces that are present on the moon will attract the pen. There
isn't gravity on the moon as there is on earth so the pen won't drop."
"Since there is no gravity it will float and fall slowly. It will not fall
like in the ground quickly because there is no gravity"
"The force of gravity on the moon is a fraction of the gravity on the earth,
so the moon would not be able to attract the pen to inself. Rather, it would
only be able to suspend the pen"
"It will eventually fall to the surface of the moon because of the slight
gravitational field plus the moment of inertia about the moon. Also with
angular momentum being conserved, it must fall. I=MR^2" [We were studying
conservation of angular momentum when I gave this quiz]
"The pen will fall to the surface of the moon. As we let go we will
introduce some initial enerty into the pen thus putting it in a forward
downward motion. Since on the moon there is no force of resistance the pen
will fall very slowly towards the surface"
"If you are standing on the moon holding a pen and you let go, it will float
where it is. It will not fall to the surface of the moon because a
gravitational force strong enough to cause this does not exist. In addition,
the pen does not have a lot of external force on it, so it will not be likely
to move"
"The pen will fall to the surface of the moon because the moon generates a
gravitational field by rotating and the pen must act under this force".
Physics 111 - First semester Non-calculus Physics
"It will float where it is because there is no gravity force on the moon.
Also, if you just let go there isno acceleration so it should just float
where it is."
"There is no gravitational force on the moon, the pen therefore has no
weight so its mass has no effect on 'where it goes'. Plus, you know, there
is no wind to blow the pen up there! =)"
Astronomy 150 - Physics for humanities majors
"[It will float where it is] Because there isn't a real strong gravity force
on the moon. Actually it is like having none at all. If I remember right,
it is only like 2.9m/s (force of gravity)"
"It will float away because the gravity of the moon won't pull it down to the
surface, but it won't stay where it is because there is always some force
acting on mass - (even though the gravity of the moon isn't strong enough)"
"The gravity of the earth will pull it more than that of the moon, so it will
float toward earth"
"It'll float away because your body is not able to stay completely still. So
it would float in the direction your hand was shaking"
"There is not much gravitational pull on the moon to have it fall to the
surface. The pen is so small and light, it probably would not be affected
by the gravitation of the moon so it would float away."
"There is no gravity in space so if you just let it go, it will just gently
float away."
"It will float away because the gravitational force is less than here on the
Earth where it would fall. I think it will float away because of what I have
seen of the space rooms NASA uses to get astronauts ready for flight."
"Theoretically, it should float away because it has no mass, gravity does not
pull the pen towards the surface at a great enough rate to make it fall,
however it does have enough force to keep it floating and ultimately it will
drift away."
"Because there is no gravity on the moon. Therefore it would float away
because there is nothing to hold it there or to pull it to the surface of
the moon"
"[It will float away] Because there would be no gravitational force to hold
it there or make it fall to the surface of the moon"
"There is no gravitational pull on the moon to cause pen to come back towards
surface. The pen would float away probably toward the gravitational pull of
the earth."
"[It will float where it is] Because there is no gravitational pull. It will
neither fall towards the moon because there is no gravity to pull it there
nor is there any other gravitational force that will pull it away from the
moon."
"Float where it is and will not move because there is no gravitational pull,
it will not float away unless it is pushed."
"The gravity on the moon is such that it won't be pulled to the surface, and
since the pen won't make any movement it should float where it is."
"It will float where it is until a force acts upon it. There is no gravity
to act upon it."
Astronomy 120 - Physics for brain-dead
"[It will float away because there is] no gravity to hold it and no atmosphere"
"[It will float away] because the gravity on the moon is not as great as it
is on the earth"
"Because the earth is a greater mass and the pen will be pulled toward the
greater body because of gravity. The moon doesn't have that great of a
gravitational pull"
"No gravitatational pull so it won't fall and no force pulling it away so it
will float where it is"
"Lack of gravity on moon allows pen to float in space"
"Because there is no gravitational pull on the moon, there is no pull towards
the moon or away from."
"The moon doesn't have gravity like the earth which would bring the pen down
to the surface instead the moon's atmosphere would cause it to float above
the moon's surface."
"Gravity will not pull it down, because there is less of it. It shouldn't
float away just because I've never seen it happen. There's a balance between
gravity and the opposite force."
"It would float where it is because gravity would not let it fall to the
surface (there is no gravity) on the moon. It would not float away because
it has no mass."
physics
[Top of page]
[Bottom of page]
[Index]
[Send comment]
From: "West, Alexander NAM-WOOD-STORK" <Alexander.West#NoSpam.shell.com> When I explained "Heavy Boots" to my son, he had a follow up story. He was telling a friend the tale that whilst NASA spent millions of taxpayers' dollars developing a pen that would work in space, the Russians used a pencil. She said:- "But why did they need a special pen to work in space?" "Because in an ordinary biro, you need gravity to force the ink to the ball of the pen" "OK" she said, "but that still doesn't make sense, because the astronauts aren't upside down all of the time" My son was copying a couple of CDs for her later. The first one took about 20 minutes to copy. "The second one won't take so long", she said. "There aren't as many instruments playing on that one" My son gave up trying to explain that one.
physics
[Top of page]
[Bottom of page]
[Index]
[Send comment]
From: pankaj#NoSpam.bu-pub.bu.edu
About eight years ago, when I was studying in high school in
India, my Chemistry professor was trying to explain the "screening
effect" of electrons (a phenomenon that makes metals bind their
electrons less losely then other elements, resulting in conductivity).
He tried to give an analogy, using earth and moon.
He said, "Imagine if their was another moon orbiting earth, then the
pull that our true moon faces will be smaller." I was puzzled and
declared that it is not possible. To which he further explained," Well
it's like this. The earth now has to pull two moons instead of one
hence it has to divide its force among the too, hence its pull on the
moon will be halved."
At this point I argued that all the artificial satellites in
the sky must face lesser pull by earth when ever a new satellite is
launched. " That's true," he said,"and that's why the cost of
launching satellites is going up these days...."
physics
[Top of page]
[Bottom of page]
[Index]
[Send comment]
From: rusty#NoSpam.rlyeh.engr.sgi.com (Rusty Ballinger) pankaj#NoSpam.bu-pub.bu.edu's story reminded me of something I learned in my high school physics class. We were talking about surface tension, and the teacher had just demonstrated a floating razor blade and a drop of detergent. Out of curiosity, I asked whether surface tension could have any effect on something the size of a battleship. "Well, yes," he said. "That's how they float." Seeing our amazement, he even shared an anecdote to support this. "Sure, when I was your age, some friends and I went down to the pond one night and threw in a bunch of soap. The next morning, all the rowboats were at the bottom of the pond!" He wasn't the only one laughing about that.
physics
[Top of page]
[Bottom of page]
[Index]
[Send comment]
Januari 1
From: "Girdle Popper" <G_Popper#NoSpam.Hotmail.Com>
Asteroid Science According to NBC
* Asteroids travel through space making a noise like a powerful but subdued
engine.
* Asteroids are usually locked into orbits, but if a comet comes by, they
can be bumped out of their rut and become dangerously unstable.
* It's only the fact that everything is locked into an orbit which prevents
collisions in our solar system. Any asteroid that gets loose is certain to
crash into Earth within a matter of hours.
* It's just barely possible to evacuate Kansas City to a distance of 100
miles in 48 hours. This requires lots of airplanes. It also requires
martial law, so that 'looters will be arrested on sight'. (Have they no
mercy?) With 30+ hours to go, people will panic in the streets and run
around at random.
* A mile-wide asteroid can mostly burn up in the atmosphere, causing it to
do only a relatively small amount of damage (bursting a dam) when it
strikes.
* A river from a burst dam can exactly keep pace with a pickup truck for
several minutes. It will then obligingly pause as the pickup truck turns
around and goes in another direction.
* When a raging river washes over a pickup truck on a bridge, the bridge
won't be damaged, the truck won't be swept off the bridge, and people in
the open back of the truck won't be swept away.
* A four-mile-wide nickel asteroid (which would mass about a *trillion*
tons) can be destroyed -- literally destroyed, so that nothing remains --
by three airplane-mounted lasers.
* But with only two airplane-mounted lasers, it instead instantly explodes
into thousands of pieces. Astronomers are very surprised that it wasn't
literally destroyed.
* Laser beams are easily visible in space.
* Incoming asteroids spend several minutes in Earth's atmosphere.
* Asteroids made of softer or more volatile stuff than nickel will
harmlessly burn up in the atmosphere regardless of size.
* Asteroids that land in the ocean will do no damage regardless of size.
* Asteroids are discovered by astronomers peering directly through their
telescopes in brightly lit observatories. Whatever they see will appear on
computer monitors, however.
* Asteroid positions are reported in plainly audible 75 BPS Baudot teletype
signals.
* Oddly, there will be no dog to be rescued at the last possible moment.
Maybe only tornadoes and volcanoes come equipped with dogs. Would you
settle for goldfish?
physics
[Top of page]
[Bottom of page]
[Index]
[Send comment]
From: jasonp#NoSpam.wam.umd.edu (Jason Stratos Papadopoulos)
PROOF THE EARTH IS FLAT
Hello. If anyone out there watched a Learning Channel show "In Search of
the Edge of the World", they heard some pretty bizarre (though creative)
conclusive proofs the earth is flat. A sampler:
According to the theory of continental drift, all the continents can
shift about the surface of the earth as if on a bed of some viscous
fluid. Were the earth round and rotating, centrifugal force would make
all the continents slosh to the equator, but this is a contradiction,
as it is not the actual case. QED
A plumb bob always points to the center of the earth (assuming the
earth is a sphere). Then a plumb bob used by someone else in a different
place would make a different angle to an impartial observer. Since
builders use plumb bobs to make buildings stick straight up, any
building of sufficient size would then be larger on the top floor than
on the bottom floor, but this is a contradiction. QED
And a few refutations of established results:
Ptolemy (?) proposed the earth was round and proved it by figuring its
radius based on the angle the sun made with Alexandria on the same day
it was directly over another city (7.2 deg.). Flat Earthers insist that
this is only an assumption; if the earth was flat the experiment would
still yield meaningful results, since the system is then a right tri-
angle and the sun would therefore be 4,000 miles away.
And for all those who need visual proof and are satisfied with satellite
photos, Flat Earthers cite Einstein's general theory of relativity and
its proclaiming that light bends in the presence of massive objects;
thus what is actually flat appears to cameras as round. This phenomenon
also explains why ships appear to rise out of the horizon.
Finally, a story I read elsewhere: a researcher at some lab once got a
letter from a very distressed Flat Earther, who had heard that the
Soviets (I guess 1950s?) were going to detonate a nuclear bomb. Newton's
third law would then dictate that the (flat) earth would then tilt toward
the USSR, and everybody would slide off. The researcher wrote back that
all was well, and that we in U.S. of A. planned to detonate a similar
bomb at the same instant on OUR end of the world, thus cancelling the
torque the Soviet bomb created.
The researcher was given a dressing-down when the Flat Earther wrote
a letter of commendation and praise to the researcher's boss.
physics
[Top of page]
[Bottom of page]
[Index]
[Send comment]
A fellow was following a truck in heavy traffic. Every block or so, when they were stopped at a stop light, the driver of the truck would jump out of the cab with a big stick and bang on the side of the cargo bay. He'd then jump back into the cab in time to drive away when the signal changed. The first fellow observed this for several miles, until he could stand it no longer. The next time the truck driver jumped out with the stick, the first fellow jumped out and ran up to him. "I'm sorry to bother you," he said, over the din of the banging, "but I am very curious; could you tell me what you are doing?" Without breaking rhythm, the truck driver replied, "Sure, Mac. Ya see, this here's a six-ton truck but I've got eight tons of canaries aboard, so I've gotta keep two ton of them flying all the time so I don't break an axle".
physics
[Top of page]
[Bottom of page]
[Index]
[Send comment]
From: ken#NoSpam.aiai.ed.ac.uk (Ken Johnson) Subject: English one-pound notes (True.) The English one-pound note has been out of circulation for a couple of years now, replaced by a gold-coloured coin. The note went through several designs; this story refers to the last of them. Try to get hold of an English one-pound note. If you turn the note over, there is an engraving of Sir Isaac Newton and a copy of a diagram from his great book describing the motion of planets. As you would expect, the diagram shows a planet (P) whose path is an ellipse, at one focus of which is the sun (S). However, the engravers draw the Sun at the centre (C) of the ellipse instead of at a focus. Nobody who had looked at the diagram for which Newton was renowned had understood what it meant. From Andrew Taylor: So the ः1 note had a physics error? It's lucky we have the ः2 coin instead now. It features a circle of cogs around its perimeter which would lock up if anyone tried turning them since there is an odd number of them.
physics
[Top of page]
[Bottom of page]
[Index]
[Send comment]
From: Larry Brown <astronomer#NoSpam.mars.net> In 1976 the British astronomer Patrick Moore announced on BBC Radio 2 that at 9:47 AM a once-in-a-lifetime astronomical event was going to occur that listeners could experience in their very own homes. The planet Pluto would pass behind Jupiter, temporarily causing a gravitational alignment that would counteract and lessen the Earth's own gravity. Moore told his listeners that if they jumped in the air at the exact moment that this planetary alignment occurred, they would experience a strange floating sensation. When 9:47 AM arrived, BBC2 began to receive hundreds of phone calls from listeners claiming to have felt the sensation. One woman even reported that she and her eleven friends had risen from their chairs and floated around the room. From: Chuck Taylor Those of us in the US, being on the opposite side of the planet, experienced an opposite effect. I stepped on the scales at the exact moment, and found for the duration of the transit, my weight increased approximately 37.317639 %. Fortunately it was all lost when Pluto reappeared. However even with the uncertainties involved with the weight scale, this would not have been enough (if applied in the opposite direction) to have cause me to float around the room. So we must discount the one woman's story.
next:2.8 physical proofs | Index | Comments and Contributions
Member of the Science Humor Net Ring
[
Previous 5 Sites
|
Previous
|
Next
|
Next 5 Sites
]
[
Random Site
|
List Sites
]