NO SPAMMERS! The entries you submit are NOT posted here automatically. They first are reviewed by the site owner who will complain to the ISP of guestbook-spammers. If you want to advertize on the internet you should pay for it.
Great site -- keep it up! |
Al Johnson <altonjatflash.net>
Plano, TX USA - Friday, December 24, 1999 at 08:32:39 (PST)
in response to "Electricity is not energy" first off baterries do not "produce" electricity, and light bulbs do not consume it, it is changed into heat and light energy and dissipated
Grant Gugel <grunt108athotmailcom>
Port St. Jhn, FL USA - Tuesday, December 21, 1999 at 05:43:02 (PST)
I think your site is very good!
Jason Stark <sci-manatjunocom>
Rexburg, I.D. USA - Thursday, December 16, 1999 at 14:41:16 (PST)
OLD GLASS is thicker at the bottom because glass is an amorphic solid - its chemical structure is irregular. in fact, given long enough, glass will flow like an extremely viscous liquid! You can check out any first-year chem text, in the "solids" section. [Unfortunately it is a myth that widely 'infects' textbooks. See SCI.PHYSICS f.a.q. for the true story. - Bill B.]
anon, anon Anon - Wednesday, December 15, 1999 at 22:45:45 (PST)
A misconception I recently noticed in the materials for a private tutoring service where I work had to do with the tides. In a paragraph about gravity, the booklet stated that "The moon causes tides while the sun does not, because the moon is closer to the Earth and therefore pulls more strongly on the oceans." This is blatantly wrong; the force exerted on Earth by the sun is MUCH greater than that of the moon, or we'd be orbiting the moon! In fact, the tides from the moon are due to the fact that the distance from one side of the Earth to the other is a signifigant fraction of the distance to the moon, so the inverse square nature of gravity predicts a sizeable difference in the force exerted by the moon on the nearer and further sides. This distance is a negligible fraction of the distance from Earth to the sun, though, so the difference in force exerted by the sun is relatively strong. But there are tides from the sun. Ask any sailor, they will tell you that the strength of the tides varies throughout the month. This is due to the enhancing or negating effect of the sun's tides.
Surrey, BC Canada - Wednesday, December 15, 1999 at 22:41:21 (PST)
I have seen many children who think that motion only occurs when something is going straight.
Michelle Turrell <liveforfunathotmailcom>
xxx, xx USA - Sunday, December 05, 1999 at 23:14:58 (PST)
Circles cannot be measured in square feet.
Berkeley, CA USA - Thursday, December 02, 1999 at 11:16:37 (PST)
GLASS THICKER AT THE BOTTOM *+*+*+* There was an article on this in New Scientist within the last six months or so. They must have an index that would permit you to find it.
Richard Miller <richardmilleratrocketmailcom>
Santa, CA USA - Saturday, November 27, 1999 at 10:08:29 (PST)
I'm interested in the belief that old glass is thicker at the bottom than new glass. I read in the Journal of Chem Education that the reason that the bottom of the glass is thicker is due an old method of making the glass. Do you have any futher information on this topic? Ed [See the SCI.PHYSICS f.a.q. for the true story. - Bill B.]
Ed Farrar <efarraratstartext.net>
ft worth, tx USA - Tuesday, November 23, 1999 at 21:53:15 (PST)
Sorry!I don't know all of them!Can you help me?
Hong Kong, Single Hong Kong - Sunday, November 21, 1999 at 21:03:19 (PST)
Although i haven't had time to read it thougherly it is a good idea, i have bad science teachers(one is good- Mr Barker)and i have my mock Exams and they have told me all incorrect stuff. I still havent got a clue about left hand grip-could u put some info on please?
England - Saturday, November 20, 1999 at 12:56:36 (PST)
THE FAITH in SCIENCE *+*+*+* It is never too early to be disabused of the idea that science is a reaction to faith. It is, rather, faith rorganized about a new ethos. I was made aware of this in reading Whitehead's "Science and the Modern World" and have been red flagging items since then, sometimes. Here are a few: *+*+* That there is order to Nature and that it is worthwhile to divine it. *+*+* That the rational powers of homo sapiens sapiens are equal to that task, especially the rational powers of MY mind. *+*+* That effect follows from cause, space is infinite, time linear. *+*+* The notion of a quantitative permanence underlying all change. *+*+* That conservation laws, and a good deal else, are consonant with out sense of the fitness of things. *+*+* That in the beginning there was geometry, mathematics, and Newton's hard little balls. *+*+* The 12/14/96 issue of New Scientist adds these: *+*+* Science promotes rational thinking; A scientifically informed citizenry is vital to a democratic society; Science is essential for economic prosperity. *+*+* A quote to sign off: "All our science, measured against reality, is primitive and childlike - and yet it is the most precious thing we have." Pure faith, and rather niave, that despite the fact the author is Albert Einstein.
Richard Miller <richardmilleratrocketmailcom>
Santa Cruz, Ca USA - Saturday, November 20, 1999 at 10:30:22 (PST)
Newton's Third Law speaks of an equal and opposite reaction. There are
actually two versions of the third law, the strong form and a weak form.
In electromagnetic interactions, e.g., a charged particle moving in a
magnetic field, the reaction force is not always opposite. In this
context physicists apply the weak form of the third law.|
W. Horne <bds136ataolcom>
Newton, MA USA - Sunday, November 14, 1999 at 20:02:29 (PST)
Re observing the actual water vapour at the spout of a tea kettle - that's quite right, but don't put your finger in the vapour. Water vapour is extremely good at transporting energy, which it will transfer to your finger giving you a nasty burn, even though the steam cloud feels only warm. Steam engines, turbines, heat pipes and so on use this heat content very effective ly to transfer energy.
David Boyes <dboyesatcompuserve.com>
Brussels, Belgium - Friday, November 12, 1999 at 09:40:41 (PST)
I would feel morecomfortable if you would distinguish between an atom (no charge) and an ion.(either positive or negative) Several times the term atom is used when ion, cation, or anion would have been the correct term. Thanks for the site, it does cause us to at least think about both scientific information and misinformation.
Charles Besancon <csbesanconatprodigy.net>
Fort Smith, AR USA - Thursday, November 11, 1999 at 15:44:38 (PST)
I have read the debate about what is responsible for lift - angle of attack versus the Bernoulli Effect. While the angle of attack argument is more intuitive it does not explain stalls. Stalls arecommonly attributed to the disruption of the air flow above the wing which arecommonly caused by an excessive angle of attack. If the Bernoulli Effect is the main source of lift then any disruption of air flow over the wing would logically result in a stall. I fail to see why an aircraft would ever stall if the main source of lift was from the angle of attack of its wings.
Terence Blakely <terence_blakelyatdellcom>
Austin, TX USA - Thursday, November 11, 1999 at 15:43:13 (PST)
AS A SAILOR AND SAILING INSTRUCTOR I HAVE HAD THE CHANCE TO INSTRUCT A FEW PILOTS. THEY CAN UNDERSTAND THE ANGLE OF ATTACK WITH THE THRUST OF THEIR ENGINES BUT DON'T UNDERSTAND HOW YOU MAKE A SAILBOAT SAIL WITH THE THRUST IN FRONT OF YOU INSTEAD OF FR OM BEHIND. YOU PILOTS NEED TO LEARN TO SAIL AND YOU WOULD HAVE SOME RESPECT FOR THE OTHER THEORY.
ORVILLE F. OTTO <orvillefloydatwebtv.net>
ST. PETERSBURG, FL USA - Thursday, November 11, 1999 at 13:04:48 (PST)
Look at a map of the United States. We've all seen it a thousand times. Everything is where you expect. Coasts, mountains, rivers, lakes, political divisions. Now, turn the map upside-down. Nothing looks familiar anymore, right? Right! But is it wrong? You decide.
If you look at photos of distant galaxies, you'll
notice that some resemble flat pinwheels, others are
inclined at any number of angles, still others are on
edge, much the same as our Milky Way.
The point is that our sense of orientation is highly
parochial, in terms of the greater universe. There
are innumerable places in space from which the Earth,
indeed our entire solar system, must appear upside-down.
Visitors arriving from some distant nebula might well
sense that Australia is in the "northern" hemisphere
and Greenland is "down under", that our sun rises in
the "west" and sets in the "east"!
Some astronomers now believe the "Big Bang" may be
just one phase of what amounts to an open-ended process.
One scenario is that the universe periodically expands
and contracts. Big bangs evolve into blackholes, setting
the stage for another big bang. (Assume the reader is
a little acquainted with these terms)
One way scientists determine if a distant object is
moving toward or away from the Earth is by observing
its "red shift" or spectral distribution.
Here's the dilemma. By most accounts, the universe is
expanding faster at the greater distances. Were it all
expanding at the same rate, we would not see any red
shifts. And we could "look back" and observe an ever
growing void in space, the epicenter of the Big Bang.
On the other hand, analyses of black holes seem to
favor the idea that objects caught in their pull
are being drawn in at an ever increasing speed
proportional to the closing distance.
In other words, if you could observe an object closer
to a black hole then yourself, it would appear to be
pulling away from you, according to its red shift.
Conversely, an object further away from a black hole
(then yourself) would also appear to be pulling away,
since your rate of acceleration was constantly increasing.
Which all boils down to - are we acomin' (black hole)
or a goin' (Big Bang) Or both ??
AGGREGATING MOMENTUM -+-+-+- One hundred - 100 - pingpong balls fall, simultaneously, from a given height, on a horizontal plate just sufficiently large to acommodate them. We designate X as the force of their collective impact. We now pour a stream of 100s, 1000s of pingpong balls on the plate in a steady steam. The force registered on the plate is now substantially in excess of X. How much it doesn't matter; what matters are the dynamics of AGGREGATING MOMENTUM as the stream approaches and impact s the plate, that the ball 4d. from the surface is transferring some portion of its momentum to the decelerating ball ahead of it, and that, with the 4d. ball at its back, to the one below it, and the lot to the one in contact with the surface, which has come to a full stop. -+-+-+- Now, was that so difficult? It's really all that's necessary to account for the shortfall of the Newtonian/sing-square/direct-contact-transfer-of-momentum model that was based on impact = X, above, the one still in fashion t oday; all that's required to explain the discrepancy with the measured force, which was substantially greater than the one calculated by trigonometric means. Isn't it remarkable that 300 years went by and nobody thought of that?
Richard Millerwww.sant <richardmilleratrocketmailcom>
Santa Cruz, Ca USA - Tuesday, November 09, 1999 at 10:26:50 (PST)
AND TO CONCLUDE -+-+-+- 1. There are demonstrable variations in dynamic pressure at appreciable distances from the source of resistance to a fluid flow, as, one chord length ahead of an airfoil. These have been measured, photographed, and are to be inferred from the velocity changes that are assumed to acompany vertical variations in the spacing of the streamlines. [Velocity and pressure, remember, are reciprocals.] Thus, the dynamic pressure at any designated point within the volume of air affect ed by the passage of the airfoil is distinct from, and greater than (or lesser than) that within the ambient flow. -+-+-+- 2. The existence of such a variation in dynamic pressure can only [excuse me, this is where I bcome - um, well, kind of dogmatic] b e assumed on the basis of the AGGREGATION OF MOMENTUM (or its extenuation) along the lines of force extending from the source of the flow to the source of the resistance to that flow, what we customarily call the relative wind. -+-+-+- 3. The profile of the pressure force, plotted from the source of resistance outward, as forward from the airfoil, or upward, or downward, is the reciprocal of that of the airstream, and thus varies inversely with the square of the distance from its source. It is the recip rocal of the v-sq. in, among other sources, the lift equation. This much Newton states in that 33rd Proposition of Book 11 of the Principia. -+-+-+- 4. Thus we have identified an ATMOSPHERIC FIELD, one with exactly the topography and dynamics of a gravi tational or electromagnetic field. Lift is a field effect. All fluid dynamics are field dynamics. -+-+-+- How remarkable the degree of incuriosity about this all these years. And how curious I am to see how much longer it goes on.
Richard Millerw <richardmilleratrocketmailcom>
Santa Cruz, Ca USA - Monday, November 08, 1999 at 10:28:40 (PST)
DYNAMIC PRESSURES ONE MORE TIME -+-+-+- We have a model, snow settling one flake at a time on a flat roof; and a second model, all that snow falling at once. Both these are unacceptable in terms of force as regards flight. Let's see what happens in t he range between these extremes. -+-+-+- We accelerate the rate of flow, first to 4 hours, then 2, then 1, then increments of that. With each decrement of time there is an increment of the force of the impact on the roof. There is, that is, as soon as o ne flake begins to press upon the back of the one before it, AGGREGATING momentum. This might not happen till the last few minutes of the process. That's not important. What is is that momentum DOES begin, at some point, to aggregate. -+-+-+- That seem s simple enough, doesn't it? Air pressure builds with the aggregation of momentum every time the wind blows. That's not just theory. It's measured every day. What is curious is how little consideration is given to this simple fact in classical aerodynam ics. Momentum within a flow does not just aggregate, but does so in a mathematically precise manner. Newton recognized this and set it down as the 37th Proposition in Book 11 of the Principia. He was a little over his depth in that book, however, and fai led to recognize that the INVERSE ratio he identified as a cocomitant to the v-sq. in the velocity, which engendered accrual of pressure, was identical, topographically, to the gravitational field with which his name is so intimately linked. Some irony, n'est-ce pas? -+-+-+- And if Newton didn't get it, why should anybody else, except maybe Einstein, who thought in field terms, but was too busy with other stuff. Lift is a field effect. All fluid dynamics is field dynamics. It's been hanging out ther e for 300 years now, and nobody's picked up on it, and I doubt anybody will pay attention now.
Richard Miller <richardmilleratrocketmailcom>
Santa Cruz, Ca USA - Saturday, November 06, 1999 at 10:50:37 (PST)
NEGATIVE DYNAMIC PRESSURE +++ This is really the unsolved problem of aerodynamics, or such is my conviction, and just now it's got a hold on me, so I'm going to go ahead until somebody stops me. +++ On a still, cold winter night snow falls on a f lat roof. In 8 hours it falls to a depth of one foot and weighs one ton. Let this be the one-at-a-time model; each snowflake falls with a discrete impact. +++ A rod hangs from a pivot with a short crossbar at its bottom. To one end of the crossbar there is a plate inclined slightly to the vertical against which a line or stream, a stream-line, of steel balls fall. The other end is calibrated so that the resultant force on the plate can be measured. This is another example of the one-at-a-time mod el, aligned vertically for convenience, and meant to represent the version derived from the Principia by followers of Newton, that of an inclined plate exposed to a steady horizontal flow. That was theory, derived via trigonometry, from - well, more theo ry, and when the time came to measure the actual force the theory was found to be off by a factor of 30. Notwithstanding this discrepancy the one-at-a-time, momentum-exchange-by-direct-contact model is alive and well even unto this day. It is justified by - appearances are saved by (and a great deal of science consists in saving appearances) - the contention that the shortfall is made up for the negative pressure forces acting on the upper surface of the wing. There is no description nor explanation of how this happens - at least I've not been able to find any - just the contention. +++ Time Out to define lift as a 50-50 process, half a result of the transmission of momentum to the lower surface, half as the -?- extraction of momentum from the upper. Wouldn't simple conservation law, as of energy or momentum, require such a dist ribution? +++ Let's go back to our snow covered roof. It is now mounted on springs equal in depth and force to the snowfall. Thus, as the fall proceeds theycompress. The day breaks suddenly and a bright sun shines on the roof and the snow evaporate s and the springs expand. One could use a pulley mechanism under the roof to lift a bucket of water, say, do useful work. If the roof with the evaporting snow could be incorporated in the wing of an aircraft it would contribute to lift. +++ Next, let 's take the whole ton of snow and drop it on the roof. This is our all-at-once model and it crushes the structure. This is obviously not the way that air strikes a wing, and it is obviously too much. The one-at-a-time model is too little, the all-at-on ce to much. What actually happens lies somewhere between the two. Any ideas of what it is?
Richard Miller <richardmilleratrocketmailcom>
Santa Cruz, Ca USA - Friday, November 05, 1999 at 10:47:56 (PST)
DYNAMIC PRESSURES ++ The science is called aerodynamics, and you'd think that had something to do with the dynamics of the air, wouldn't you? You'd think that the definition of positive and negative dynamic pressures would be the first thing any aut hor would concern himself with, n'est-ce pas? Well, such is not the case. I have ransacked the literature and never found any attempt to define or describe negative dynamic pressure in a suitable way. The entire upper surface of the airfoil has been ign ored right from the start.
I'm pretty sure I know why this is. Our ability, as humans, to conceptualize, is anchored in our Intuitions. That word is spelled with a capital "I" to distinguish it from smalll "i" intuition, as in "The phone's going to ring, honey. Aunt Mildred's g
oing to call about..." Capital "I" Intuition is the one we employ in the expression counter-intuitive (as is [-] dynamic pressure), that related to our deepest, and typically unconscious convictions, those so deeply ingrained that it never, or rarely occ
urs to us to even question them. Get a copy of "The Critique of Pure Reason" and consult the index for some exposition of this concept.
I have kicked this matter around for the last 20 years and the best I've been able to do is to devise some similies and metaphors to help me understand it. Note that we don't even have a terminology that iscomprehensible for what happens on the upper
surface of the airfoil. About the exchange of momentum with the lower, Newtonian mechanics, we hear ad nauseum. We understand, being immersed in the phenomena daily, the transfer of momentum TO a surface or an object: We hit balls with bats n' like that
all the time. Momentum extraction FROM a surface? That confuses us. Well, it confuses me.
It happens when I throw a ball to you. When the ball plunked into my glove I understood, Intuitively, the transfer of momentum TO a surface. When I tossed the ball back, imparted momentum to it, there was, in an instant, less momentum in the ball-in-
hand entity, but I wasn't aware of that. Are you aware of it?
Or this. A large, very light rigid sheet of plastic floats 15 ft. off the floor. It's sink rate is offset by a small army of little folk shooting upward with pingpong ball dispensers. X number of balls hitting with X force transfer enough momentum T
O the sheet to keep it at a constant height. The process of the extraction of momentum - sounds funny, doesn't it, the extrction of momentum - takes place as a cocomitant on the upper surface. Provide some mechanism to define, describe, rationalize THA
That's a start. There's a lot more to be said, and that will depend on the ensuing correspondence, if any.
H. Hurn wrote:
] The word "suction" greatly serves to further the confusion on this subject
Good point. I originally avoided getting into that because it's beyond the K-6 grade level, but that was years ago, and this website exceeded the sixt
h-grader level long ago.
PS, suction does exist in liquids, but not in gases. In theory it is possible to drink through a straw even in a vacuum environment, and genuine negative pressures can exist within liquids.
About vacuums in the open air, and static vs. dynamic pressure... Watch out when thinking about surface waves on water. Yes, its easy to make a hole in the water's surface. But it's also easy to exceed the wave speed and to create "sonic booms". Th e speed of water waves is very low, and if you look closely, you'll find that you can only create "holes" when you move your hand significantly faster than the wave speed. To make a similar hole in the air, you'd have to move your hand faster than the speed of sound. Unrestrained air moves VERY fast, and it fills any low-pressure regions almost instantly. When I flap my hands back and forth, do I create changes in absolute pressure? No, because if I did, these changes in pressure would be sound waves, just as high-speed airplanes produce sound waves (sonic booms.) My flapping hands create air motions rather than air pressure. Here's an analogy: stir a liquid slowly, and the surface of the liquid remains flat, even though your stirring actions will cause the liquid to flow. This is how wings work: they cause the air to move, but the "level" of the air (the density and the stat ic pressure) does not change much. Stir fast, and not only can you make holes in the surface, but you also make ripples (sound) and shocks (sonic booms). Only when the relative motions of the air approach the speed of sound does the absolute pressure of the air begin to change.
I only managed to figure out the above stuff recently. Up until then I took the books' word that absolute pressure around the aircraft is almost constant. Simple rule: if the wing moves slowly, it TRIES to change the pressure of the air, but instead the
air just moves, and the energy goes into the KE of moving air, not into the PE of altered air pressure.
I recently had a spirited debate about "lift" with two members of my family who made their living as pilots, each having several thousand hours ofcommerical or military flying time. I was flabergasted that neither of them understood the Bernoulli exp lanation that higher relative pressure on the lower surfaces of the wing pushed the wing up. They vigoursly argued that it was "suction" on top of the wing that provided lift.
When I read your explanation in an attempt to find material to enlighten them, I see where they get their misconception. Yours and other materials make the same mistake of explaining the Bernouilli principal by using the word "suction". In high school p
hysics, I think we all learned that "suction" is not a real thing itself, rather it is simply higher air pressure trying to equalize a lower air pressure volume or area (vacum).
In the Bernouilli Principal of lift (and perhaps in the angle of attack principal also), please cease using the term "suction" and explain that lift is created by higher air pressure pushing up on the lower wing surfaces because of less air pressure on th
e top wing surfaces. The word "suction" greatly serves to further the confusion on this subject.
need more advace sites
none of your Business <theman16_2atexcitecom>
i'm lost, lb japan - Monday, November 01, 1999 at 14:10:10 (PST)
Dear Dennis; ++ More learned or not, certainly a debatable point, but I have devoted a *lot* of thought to the matter which I feel should amount to something. As for static and dynamic pressures and a cu.ft. of air being a cu.ft. of air, let me sugge st a gedanken Experiment. +++ A box with an interior dimension of one cubic foot. The lid, one foot square, is able to slide up and down within the walls, and, the reason this has to be in the realm of thought and not that of reality, admits no leakage.
Thus, you could apply as much pressure to the top, bearing downward, as you please, and no air would escape. ++ You have at your disposal a quantity of lead slabs. Begin piling them on top of the lid. How many - and let us assume an atmospheric pressu
re of 15lbs./sq.in. for simplicity's sake - slabs, how much weight would be required before the space within the box occupied less than one cu.ft.? When you've done it for air, do it for water. ++ I'll look forward to your reply.
Dear Mr. Miller, you obviously are more learned than myself about aerodynamics. While I am sorting out the finer points of what you are saying, I also continue to maintain that partial vacuums do occur in "open" air, not only in flasks. The failure of this principle would result in a gross violation of the "laws" of both Newtonian and modern physics. If I place my hand in a tank of water and sweep it swiftly from right to left, I create a partial vacuum on the right of my hand which can literally be se en, as water rushes in behind it to fill the vacuum created. The same is true in open air. In fact, trailing turbulence is due in large part to this effect. Molecular distance therefore is not always consistent, i.e., a cubic foot of air does not always c ontain the same number of molecules. If the vacuum effect did not occur, it would violate physical laws because it would mean "instantaneous" movement of a parcel of air to prevent formation of a vacuum. That would, mathematically, infinite power. To reph rase, WORK = FORCE(mass) x DISTANCE. POWER = WORK divided by time. Zero time would be required to prevent said vacuum from occurring. That would result in POWER being infinite, a clear violation of physical law. In other words, the packet of air would hav e to be traveling at infinite speed to prevent formation of said vacuum.
Dr. Dennis Hudson <sheanneatzianetcom>
Las Cruces, NM USA - Sunday, October 31, 1999 at 12:32:46 (PST)
After reading your sections on electricity, i feel like I finally understand it. And I have a PE (mechanical)! Now maybe I can go back a re-read my EE notes. Meanwhile another misconception I havecome across is that radios, radars tranmit electrons and that the elctrons reflect off objects or is picked up by antennae etc. . I didn't know if you had captured that one?
Arlington, VA USA - Friday, October 29, 1999 at 10:01:00 (PDT)
i love your web site icome on this page every day and always orget to sighn the guest book but now i hav't forgot about it i. Your pagew is the best page i've been on so i hope you never ever ever ever ever ever ever ever ever ever ever ever ever ever ever ever ever ever ever ever ever ever ever ever close it down
Liverpool, England - Thursday, October 28, 1999 at 08:45:04 (PDT)
ANGLE of ATTACK and CHAMBER +++ Dr. Hudson There is no good reason I can imagine for a flat plate to produce lift at zero A/A. Chamber or, in its absence, angle of attack, are required in order to produce a pressure differential. I tried to make th is clear in what I wrote some days ago about the differential translatory flow. That's the key point in the phenomenon of lift, and it begins ahead of the wing. Whatever shape procudes it qualifies as an airfoil, but it must have the equivalent of chamb er or a/a.
Richard Miller <richardmilleratrocketmailcom>
Santa Cruz, Ca USA - Tuesday, October 26, 1999 at 10:45:00 (PDT)
STATIC AND DYNAMIC PRESSURES +++ Dear Dr. Hudson et al. There appears to be continued confusion about two fundamental aspects of aerodynamics: static and dynamic pressures. In the broadest terms, static pressures are contained, as the air in the tire s of your car, and dynamic pressures manifest in a free atmosphere. The concept of vacuum obtains only in the first instance, as when air is pumped out of a flask. +++ As for dynamic pressures, those on which lift depends, and with the qualification that we are dealing only with sub-sonic velocities, a cu.ft. of air is always a cu.ft. of air. Put another way, the intermolecular distance, whether the air passing the flat-plate wing of a small balsa glider, or the Clark Y of a Cub, or the wing of a DC-3, is always the same. Its static pressure is always uniform. +++ Dynamic pressure is the result of aggregated momentum. One great large fullback hurling himself against a tackle dummy might do as an example of the concept of the DIRECT CONTACT TRANSFER OF MOMENTUM, the one assumed in the Newtonian model. Now imagine a line of ten such fullbacks hitting the same dummy. There is an aggregation of their collective mass in that case. This is what accounts for the (positive) dynamic pressure on the under s urface of an airfoil, the aggregated momentum of the air (molecules) stacked up ahead of the wing. The inverse process occurs above the wing. You have a sample of this when you stand with your back to a strong wind and have trouble breathing. +++ One cu .ft. of air is always one cu.ct. of air.
Richard Miller <richardmilleratrocketmailcom>
Santa Cruz, Ca USA - Tuesday, October 26, 1999 at 10:34:26 (PDT)
I am trying tocombine angle of attack and Bernoulli. I wonder if this works. Any airfoil (paper airplane, plywood sheet, or 747) can be thought of dimensionally as a rectangular solid, more or less. Each looks like this, in end-view: A B
________________ W==> |________________| <<----direction of flightNow, at leading edge "A" a force "W" (wind) is encountered which "at first" acts equally across the vertical face of "A", in a sense "stopping" "A" in midair. Think of "W" as the hinge of a gate, or imagine we have nailed our plywood example, only at "A ", to a post. In that case, the rest of our wing will tend to sag downwards, "B" representing the low end of the sag. This would naturally produce a positive angle of attack, with wind being "thrown downwards" from the underside of the airfoil. It would a lso produce, due to fluid dynamics, lift due to a partial VACUUM above the airfoil. But vacuum-lift depends on air pressing against the underside of the airfoil, i.e., air is trying to get in to fill the vacuum and so pushes the airfoil upwards ahead of i t. Thus the vacuum-lift idea seems inconsistent with the notion that we are "hurling" parcels of air downwards. But perhaps not: it may simply be that some portion of those parcels is also acting upwardly, eh? Still, there are a couple of obvious problems. Planes with flat wings do manage to fly with zero AOA, don't they? And, if my little theory is credible at all, how then does a flat-wing craft get off the ground to begin with, unless it first configu res to a positive AOA? My "hitching-post" theory doesn't seem to answer these questions. Any ideas?
Dr. Dennis Hudson <sheanneatzianetcom>
Las Cruces, NM USA - Monday, October 25, 1999 at 23:30:53 (PDT)
To clarify some of the stuff on the "lifting force" page...
The physicists and aerodynamicists agree: it is wrong to imagine that
pressure-difference provides 60% of lift, while AOA provides 40% (or
whatever %). Instead, pressure difference explains 100% of the lifting
force... and AOA explains 100% too!
AOA and pressure-difference are proportional. They are linked together,
and changing the AOA will change the pressure difference. Confusion
arises when we look at cambered wings, since cambered wings can deflect
air downwards even when their AOA is zero. Think of a thin, sheetlike
wing which is curved (like the Wright brother's flyer.) At zero AOA it
still gives lift. Why? Beause air has inertia, and even though the
airfoil as a whole is at zero AOA, the trailing edge of the airfoil is
pointing downwards. As the airfoil moves forwards, it flings air
downwards from its trailing edge. It also pulls air upwards at the
leading edge, but this "upwash" is small, and only occurs near the wing.
The "downwash" behind the wing keeps moving down ideally forever. (In
reality, it bcomes part of the downward-moving wingtip vorticies, and
eventually is slowed by viscosity.)
Air has inertia, and for this reason, "sucking" is different than
"blowing". A rocket ship can fly by spewing out a jet of exhaust, but a
"backwards rocket" which only sucks gas into an intake cannot fly.
"Suction" happens in all directions, like a contracting sphere, while
"blowing" creates a narrow jet. "Blowing" a jet of air will create large
reaction forces, but "sucking" air inwards will not. The difference is
caused by the inertia of the air. With wings, air is pulled upwards
towards the leading edge, but it is "blown" downwards by the trailing
edge, and the two effects are not equal. And with wings, the air starts
out motionless before the airplane arrives, but after the airplane has
passed, the air is moving downwards.
For another confusing aspect about "airfoil shape", see figure 4 on this
Bill Beaty <>
In reference to your angle of attack liftingcomments. Both pressure differential(low pressure on top) and angle of attack contribute to lift over the operational range of an airfoil. AOA does contribute to the lift on an F18 flying at 45 degrees AOA, doesn't it? This airplane is surely flying below it's airfoils stall speed. If your theory was entirley correct then any airplane that had the same size wing and the same weight would stall at the same speed and angle of attack. This is surely not the case. I would surely like it if AOA was the deciding factor because then I could get rid of that slow old wing on my Super Cub ,trade it in for a fast one and still have the STOL performance. Not likely. Good Day
Jason Mummery <jmummeryatgolden.net>
Guelph, Ont Canada - Sunday, October 24, 1999 at 16:40:38 (PDT)
Re: Bernoulli effect vs downward force discussion. As a boy I went to school and got a Bill-Nye-type explanation of lift. Then I went home with my friends and made all sorts of paper airplanes with flat wings that actually flew. We had contests. We experimented with wing designs: large small, tapered, ben t up or down. We put paper clips and other things on the fuselage. We had fun. We discovered stuff and had fun. In school, on the other hand, wehad to orget all "that childish stuff" so we could learn real science...and not have so much fun.
Paul Tevlin <tevlinatitsa.ucsf.edu>
San Francisco, caCAca USA - Tuesday, October 12, 1999 at 15:04:31 (PDT)
THE WING AS TURNING VANE +++ At the heart of the Newtonian, or momentum-transfer concept of the generation of the lift is the idea that the wing acts as a turning vane, that it deflects a volume of air downward and derives the force we call lift as a reaction to that process. Th is is not what happens. A wing operates in a different manner than a vane. This can easily be determined by acomparison of the velocity and pressure profiles; they are quite different and distinct. This, of course, should have been done a long time ago and the turning-van c oncept rejected. Nobody seemed to care. Nobody seems to care about the fact that two quantities of an icompressible fluid cannot occupy the same space, not at least at normal day-to-day pressures. Consider a boat in hydroplaning mode. It is, as the wing is supposed to do, turning the surf ace layer of the water over which it travels into the layer below: surface layer into subsurface layer. This is a state of disequilibrium which the watercompensates for in two ways: It generates an upward force which we observe as the phenomenon of hydr oplaning, a correlate to aerodynamic lift; and it spills around the sides and rear of the hull, most noticably as the roostertail aft of the transome. If the wing does, in fact, turn a column of air downward in the act of producing lift, why is there no manifestation of simple conservation law as a result of one layer of air being forced into the one below? Why does the air not pop up at the trailin g edge, but in fact continue downward? P.S. I anticipate no answer to these questions. I've been putting them to the aerodynamiccommunity for years and no one ever answers, nor even attempts to.
Richard Miller <richardmilleratrocketmailcom>
Santa Cruz, Ca USA - Monday, October 11, 1999 at 10:33:05 (PDT)
MR. PAT BRANCH +++ I am shocked and dismayed at your reference to a big vacuum above the wing. Do you not, with all your stated experience, know the difference between static and dynamic pressure?
Richard Miller <richardmilleratrockeetmailcom>
Santa Cruz, Ca USA - Monday, October 11, 1999 at 10:13:34 (PDT)
Your expaination of aircraft lift does not explain why the aircraft shown can fly much slower than 100 mph. As an aerospace engineer who helped work on the C-17 and B-2 I can assure you the Bernoulli effect accounts quite well for the forces on an air craft. Although it is actually the Navier-Stokes equation that describes the forces. The pushing of the air down might be a good way to describe how it works to K-6 grades, but it is that big vacuum above the wing that actually pulls it up. How do plan es fly at 0 angle of attack? Your balsa airplane will nose straight into the ground if you make the wings level. The truth will set you free - but someone telling you something does not make it true.
Pat Branch <brancwiatmail.northgrumcom>
Melbourne, Fl USA - Sunday, October 10, 1999 at 08:33:07 (PDT)
Here's the correct version...Guess I was too interested in your site to read my owncomments critically... I love your site with its brief and understandablecomments about what's wrong with science education. And I do agree - we're taught from books too much rather than applying critical thinking. I'll be sure to link your web site to mine as many teachers vi sit my site. Even the National Science Teachers Association featured an article on skating & melting ice this year!!! .......Please add the following to your "magnetic materials"comments: Not all steels are magnetic. Most stainless steels are nonmagnetic due to the existence of a different phase structure in stainless steel (austenitic) verses regular steel (ferritic). HOWEVER, many scientists/engineers believe that ALL stainless steels are nonmagnetic. On the contrary, there are certain types such as th e 400 series that are magnetic but still in the "stainless steel" category. - ... Dr. Kain Materials Engineering Scientist/Engineer 15-years of practical applications (not theory!) ... drkainatsciencespiderscom .... www.sciencespiderscom
Dr. Kain <drkainatsciencespiders.com>
Columbia, SC USA - Wednesday, October 06, 1999 at 16:52:24 (PDT)
Ooops - meant to say some believe that ALL stainless steels are NONmagnetic!
Dr. Kain <drkainatsciencespiderscom>
Columbia, SC USA - Wednesday, October 06, 1999 at 16:49:49 (PDT)
I love your site with its brief and understandablecomments about what's wrong with science education. And I do agree - we're taught from books too much rather than applying critical thinking. I'll be sure to link your web site to mine as many teache rs visit my site. Even the National Science Teachers Association featured an article on skating & melting ice this year!!! Please add the following to your "magnetic materials"comments: Not all steels are magnetic. Most stainless steels are nonmagnetic due to the existence of a different phase structure in stainless steel (austenitic) verses regular steel (ferritic). HOWEV ER, many scientists/engineers believe that ALL stainless steels are magnetic. On the contrary, there are certain types such as the 400 series that are nonmagnetic but still in the "stainless steel" category. -Dr. Kain Materials Engineering Scientist/Engineer 15-years of practical applications (not theory!) drkainatsciencespiderscom www.sciencespiderscom
Dr. Kathleen Kain <drkainatsciencespiders.com>
Columbia, SC USA - Wednesday, October 06, 1999 at 16:48:16 (PDT)
Brave man! Well done! For "nit-picker" read "rigorous thinker" - (which is the sine qua non of science)- and then plead "guily as charged"! I learned about Franklin, the "transparency" of air to sound, and liquid films an water. Always interesting to learn. I hope you get many more contributions. Here are my first, not very interesting thoughts. (The singular of phenomena is phenomenon ... oh, and whilst on English, I squirm when I hear "dissect" mispronounced to sound like bisect). When taking on advocates of the "longer route" argument re. airplane wings, my simple argument is that if the wings experience a net upward force, they must exert a net downward force on some air, which is accelerated downwards - all very understandable w ithout resorting to fluid dynamics. A more interesting idea about colours and rainbows. Yes, of course there is a continuous change in "colour". The number, and perception of those colours is affected by culture and vocabulary. Just as those most experienced in it have more words for wha t others regard as "snow", the number of words for colours gradually increases with time in societies. I have heard - and it sounds very plausible - that if you go backwards far enough in time the number of words for colours, and therefore the number of colours discriminated decreases. Ancient societies acquired words for colours gradually, and, interestingly, roughly in the same order - starting with what had practical significe for them - and as far as I can remember went something like white, dark, r ed, yellow, green, blue, although the borders of their colours need not correspond exactly to ours. The ancient Greeks did not distinguish between green and blue, but had one word which corresponds to roughly what we call green and blue.
Jonathan Reece <jon.reeceatzetnet.co.uk>
Oxford, UK - Friday, October 01, 1999 at 16:00:03 (PDT)
Regarding how an airplane flies, attack angle vs. airfoil shape - Balsa wood toy planes are proof that attack angle alone can make a plane fly. Maybe airfoil shape helps too, and maybe especially at higher speeds (?), but there is proof that things ca n fly without it.
Andy Gillespie <andy_gillespieathpcom>
Corvallis, OR USA - Thursday, September 30, 1999 at 19:47:23 (PDT)
Congratulations on creating and maintaining this kind of site. I have acomment and a question... Comment: In the topic about infrared and heat you use thecommon phrase "infrared light". I was taught in college (in a class on photographic science) that "light" is defined as the portion of the electromagnetic spectrum that the typical human eye can pe rceive. Those areas immediately outside that range are referred to as infrared and ultraviolet. The "infra" and "ultra" prefixes indicate that they are not in the perceivable range, thus not qualifying as light. They drove home the terms "infrared radiation" and "ultraviolet radiation", and took points off if you used the word "light" incorrectly. This seems to be a very human-centric definition, and maybe exists only within the photographic industry (or maybe on ly within R.I.T.??) Question: The description of table salt mixed with water no longer being a salt, but being sodium and chloride (chlorine? I orget which). Sounds reasonable, but is that process reverseable? One method of obtaining table salt is to put ocean water in a pa n and let it evaporate. If the sodium and chloride are in solution, do they reform into a salt when the water is removed? How? Thanks!
John Bell <johnbellaterolscom>
Ashburn, VA USA - Wednesday, September 29, 1999 at 07:03:05 (PDT)
There is no such thing as a "sodiumchloride Molecule". Your Misconception is that you believe a sodium chloride crystal is formed of these molecules, which dissolve into Ions when dissolved in water. This is wrong. A sodium chloride crystal is formed of Na+ and Cl- Ions.
Hagen, Germany - Thursday, September 23, 1999 at 08:45:13 (PDT)
I like your web page a lot and I think that you give out good information. I also think you should put more picturesand illustrations.All in all I think your site is very cool and agian I'd like to say that I liked it a lot.Thank you for putting this w ebsite online!!!!!!!
houston, tx USA - Wednesday, September 22, 1999 at 19:44:07 (PDT)
I ran across your site while constructing a detailed outline of chemistry history that I feltcompelled to start because my chemistry textbook is so full of factual errors and misleading simplifications. My own contention is that the reason "science" i s so confusing is that the Models (i.e. analogies or images using familiar references) used to describe and explain phenomena have utterly replaced observations of the phenomena themselves and thinking about the problems these observations present. As lon g as you don't know what's being described or solved, you can't possibly understand it. Unfortunately, this kind of misunderstanding is cumulative.
boston, ma USA - Monday, September 20, 1999 at 16:13:22 (PDT)
THE JUSTIFICATION OF BERNOULLI +++
Aerodynamic theory has been bedeviled from the outset by the
perceptions of those who see with the eyes of the flesh; those who see the
structural, not the functional aspect of physical phenomena. Dear old
Prandlt removed the rotor from the Magnus configuration - and the axis
from that - as a model for all like-minded investigators, and left the
relative wind blowing slowly in the relative wind.
What Prandtl discarded was the DIFFERENTIAL TRANSLATORY FLOW that is
the proximate cause of lift. It is the vertical pressure potential across
the airfoil that holds up the wing, and next in order the relative flow:
an upper stream covering a longer transit at a faster velocity; a lower,
its counterpart, with a shorter transit and a slower speed.
The INCEPTION POINT of these collateral flows lies a number of chord
lengths ahead of the airfoil - how far depends on the lift coefficient,
wing loading, airspeed - and below the horizontal plane of the wing. From
here a line runs to what is called, but is not, the stagnation point at
the airfoil leading edge. This line is parabolic, being a transit through
a field, and a] delineates the upwash, and b] serves as the shear boundry
between the upper and the lower flows. [You probably do not know much, if
anything, about these concepts; they appear nowhere in airfoil theory, not
to my knowledge in any event.]
The DIFFERENTIAL TRANSLATORY FLOW, the air that flows over the wing and
the air that flows under it, begin at the INCEPTION POINT, and they have
reached their min- and maxima, or very close to it, by the time they reach
the leading edge of the airfoil. This can be confirmed by the most
cursory glance at the streamline separation in smoke-flow pictures and the
cocomitant plots of pressure across the airfoil, especially those
vertical spikes at the leading edge of the wing section.
The airfoil - the structure - is thus at one further remove from the
process of lift than the DIFFERENTIAL FLOW, and it can be defined as ANY
shape, a hand held out the window of a car, a frisbee, an inverted
section, symetrical or not, a membrane, even a barn door, that will induce
the required flow differential.
There is not, nor has there ever been, a problem - How does a plane fly
upside down? - with the explanation of lift based on the Bernoulli
theorem, only the failure to discriminate properly between structure and
function, the visible and the invisible, the obvious and the implicit.
Thanks for the page and handy way to make additions to it. I have acommentary on airfoil theory that I willl enter as soon as I have confirmation that name, URL, all that sort of stuff is in order.
Richard Miller <richardmilleratrocketmailcom>
Santa Cruz, CA USA - Saturday, September 11, 1999 at 10:36:40 (PDT)
OK, the rainbow does not have 7 distincts bands of color, but it still has bands of color. So the question is: why do we see non-homogeneous color patterns from a homogeneous light sprectrum ?
Pierre Dragito <Pierre.Dragitoatcaramailcom>
USA - Tuesday, September 07, 1999 at 07:46:10 (PDT)
Very informative. I learnt a lot. However, every time I got to the end of an article I thought "What a dick he is". Yes you are a nitpicker, with not much to do judging by the size of your site. Then again, I'm sitting at home on the internet readi ng every word of every page I look at and tonite (saturday) I am babysitting for a friend so my life is about as exciting!
Wellington, NZ - Friday, September 03, 1999 at 20:36:48 (PDT)
There is one gross misconception that is still popular which should be addressed: some people are taught from an early age that the Earth has gravity "because it spins". This is very wrong. The Earth exerts a graviational force on massive objects bec ause it has mass. It's rotation is irrelevant. (In fact, our inertia would carry us off the planets surface as it spun, but gravity holds us down.)
W. Blaine Dowler <wdowleratualberta.ca>
Canada - Wednesday, August 25, 1999 at 08:49:29 (PDT)
Great page, although there are surely misconceptions in it. I know another one: To demonstrate "mass inertia" in class, some teachers use an iron ball which hangs from some thin thread. It has another hook at the bottom, with another thread and a handl e hanging down from it. Now, if you "pull slowly", the upper thread will break, and the ball will fall down. But if you "pull fast", then the lower thread will break! You then suggest that the ball "cannot follow the fast movement because of its inertia". This is wrong. Pulling the handle will cause the system to absorb energy by starting oscillations governed by the ball's mass and elastic/plastic properties of the thread. As the amplitude increases, one of the threads will reach its breaking tension. T his can in theory be the lower OR upper one, depending on many influences. The experiment *WORKS*, however! Can anyone tell me why?
Carsten Kuss <b_c.kussatt_online.de>
Bonn, Germany - Monday, August 02, 1999 at 10:49:42 (PDT)
The inventor of Radio was not Marconi. Though Marconi popularized the use of radio his patent was struck down after a long and bitter court battle. Radio was invented by Tesla who demonstrated a working radio over a year prior to Marconi's application.
Daniel Ketchum <ketchum.danielatoscsystemscom>
germantown, MD USA - Friday, July 30, 1999 at 13:24:49 (PDT)
The does-air-have-weight? controversy is an illustration of the problem that few authors bother to give an adequate definition of "weigh." Most students realize that "weight" is not the same as "mass." "Mass" (which is measured in grams or slugs (I t hink the English unit is called)) is an inherent property of matter (at least in a Newtonian universe) while "weight" is a force (measued in Newtons or pounds.) Unfortunatly it is not clear exactly *which* force we mean by "weight." Is is the force caus ed by the local gravitational field? Is it the gravitional force minus the centripital force of the Earth's rotation? Is it those effects minus the buoyancy of the surrounding air (or water as the case may be?) I favor the definition that "weight" is t hat force measured by your bathroom scale (a spring scale) so that "weight" is gravity's pull minus the centripital force minus the buoyancy. By this definition, your weight will vary with changes in latitude, altitude, and weather condition (because of air pressure differences.) Also, by this definition, air (not in a stretchy balloon) has zero weight. If you don't like this result you can adopt the definition that "weight" is the force due to gravity regardless of the other forces involved. Then the sealed vs. unsealed vacuum bottle will *almost* give you the weight of the air inside (you still must add in the calculated centripital force.) It would be more practial to define "weight" as gravitational + centripital forces so that the bottle experiment will give you the answe r. Be warned, however, that your results will vary with your distance from the equator. Makes you wish your teacher had asked you for the *mass* of the air instead. By the way, the opened/closed umbrella trick shows off the mass of the air but says not hing about its weight.
Sunnyvale, CA USA - Thursday, July 22, 1999 at 18:43:01 (PDT)
Help! I am looking for a book that describes all introductory aspects of electricity which uses flowing water as an analog to electon theory. Can anyone help me locate this book?
USA - Saturday, June 26, 1999 at 13:28:34 (PDT)
I AM SUPPOSE TO GRADUATE AS B.S. IN PHYSICS FOR TEACHERS IN PHILIPPINES.....BUT NOW I AM AFRAID IF I AM GOING TO TEACH PHYSICS REALLY....
Ezrel M. Alucilja <macsegambitathotmailcom>
Manila, USA - Sunday, June 20, 1999 at 21:00:51 (PDT)
re: Bernoulli Baloney Two Principles I did not see in yourcomments. The Magnus Principle: The inertia of the air flowing over the curved wing creates an area of lower pressure over the top of the wing. The Coander Principle: The Magnus effect deflects the flow of air downward along the surface of the wing. Even the low air pressure over the wing is mostly caused by Newton. Questions: Has any one ever used Bernoulli's formula to show what a small part it actually plays in lift? Don't orget to subtract the downward lift from the bottom of the wing.
If airplanes fly by Bernoulli, why do jet airliners increase the width of
their wing on landing? (Thin wings increase Bernoulli differential.)
If NASCAR racecars are lifted by Bernoulli, how can such a small spoiler
counter the whole upper surface of the car?
Why isn't the perfect wing semi-circular in cross section? (To increase
upper air speed.)
This is a classic example of a site which has great information but terrible design. If you would take the time to rorganize this information in a clear, concise, and attractive manner, I'm certain you could help spread the truth about science to many, many more.
Robby Slaughter <sciencemisconceptionsatrobbyslaughter.com>
Austin, TX USA - Thursday, June 17, 1999 at 15:44:51 (PDT)
I think Aspden's Law just about explains it all. The reason textbook electromagnetism is so hard to understand is because the current explanations assume Einstein was correct. Aspden shows that he was not. Good searchin'! Sebby
Eugene, OR USA - Wednesday, June 16, 1999 at 17:14:17 (PDT)
Iam not shore what are the thoughts that block understanding .I do agree that many teaching books are misleading.I met someone who collects books that only a few ever gets to consumers.one book Iwish Icould buy or steel,was on car repair.It was mostly pictures ,by an elect.engneer.for his son of 6.I understood it all at a glance finaly, after doing tune ups for yeares.
Terry O' <Fly175276>
Phila. , pa USA - Thursday, June 10, 1999 at 13:38:42 (PDT)
Funny points, but textbooks are only a poor souls attempt in describing allready established theories. Do holes move or electrons, who cares as long as a person eventually predicts the result and visualizes (somehow) the why and how. And along with these human conditionscome some really wacked out descriptions of electricity. Analogy of water to electricity has allways been my favorite. Questioning, asking why, making fun of things, its what we all do sometimes for the good of science and sometimes just for the fun. The only diff between famous people in science and the science soldiers(workers) is they decided to run with their crazy id ea to the ends of the earth.
Orlando, fl USA - Tuesday, June 08, 1999 at 06:25:58 (PDT)
Like so many people out there - I feel that there is a terrible amount of discrepencies in our understanding of Physics and Chemistry. My only hope is that one day both shall find eachother morecomplementary rather than seperate ideals.
Dean Sarelius <desleyatenternetcom.au>
USA - Monday, June 07, 1999 at 04:00:18 (PDT)
About how planes fly: Unfortunately your explanation is just as misleading as the one you cite. There has been a long discussion in sci.physics just this spring and the result is as follows: A reasonable thick asymetrical airfoil (curved atop, flat bottom) at zero degree angle of attack and 200 mph produces as much lift as a thin symetrical (i.e. both sides curved) airfoil at 11 degrees AoA. The lift is produced not be the 'downwash' (which h appens way behind the airfoil in any case and is a result) but by pressure differences. 1/3 of the lift usually is produced underneath the wing (higher pressure than normal), 2/3 above the wing (lower than normal). Also there's acommon misconception abou t the air packets: when they meet again behind the wing, it's not the twin brothers rejoicing: the lower one is behind the upper one (in time and space) and they never meet again. The downwash is a result of the pressure differences, happens behind the wi ng and has nothing to do whatsoever with the production of the lift. Look up the discussion in s.p. and please correct your page.
Lorenz Borsche <lbsysataolcom>
Heidelberg, Germany - Wednesday, June 02, 1999 at 02:16:00 (PDT)
I like your site, but I think the part on the parallel light from lasers is somewhat misleading. You state that laser light is not necessarily parallel but can be made parallel using a lens, while it is impossible to do that with light from an ordinary light source. In fact neither laser light can be transformed into a perfectly parallel beam. A laser beam will always be divergent at a sufficiently large distance no matter what lenses you try to condense the beam with. It is true though that it is gene rally easier to obtain an "almost parallel" beam from a laser than from other light sources. There is no such thing as a perfect point source, lasers are simply better approximations of a point source than most other light sources. Also, the statement that the divergent beam from He-Ne lasers is because of the concave end mirror is wrong, or at least gives a false impression that the concave shape itself makes the beam divergent. The cavity parameters (shape of end the mirrors, dist ance between them and their reflectivity) are important to get the laser working in the first place, but once the arrangement is lasing the divergence of the beam is determined only by the diameter of the beam at the exit aperture and the wavelength.< br> Johannes Swartling <j_swartlingathotmailcom>
Sweden - Tuesday, May 25, 1999 at 09:37:57 (PDT)
I hate to ruin some of this sites visitors dreams, but it appears that there are some poorly missinformed people out there.. I ahve read some disturbingcomments about Nikola Teslas ethnicity. Nikola Tesla was born to Serbian parents, his father being a Serbian Orthodox priest. If this is not enough to convince you otherwise then the very fact the Croatia itself was not around when Mr Tesla was born... Do you not know simple history. I find it amusing that people who claim that such falcities to satisfy their own nationalistic ego's.
Ned Tesic <nedatprimuscom>
- Monday, May 24, 1999 at 21:10:58 (PDT)
ELECTRICAL ENERGY IS LOST IN TRANSMISSION DEW TO THE INHERINT RESISTIVE NATURE OF ALL WIRE AKA HEAT.
Billie Malone <bmale44atpeppersnetcom>
CAMPWOOD, TX USA - Saturday, May 22, 1999 at 21:05:49 (PDT)
This site is good.I never noticed any of this stuff (partly because I never knew it was wrong)
Somewhere , MA USA - Friday, May 21, 1999 at 11:14:06 (PDT)
I like this site, but you are too specific. Also, it seems pathetic that someone would waste all that time on this.
Ithaca, NY USA - Friday, May 21, 1999 at 11:11:29 (PDT)
I NEED SOMETHING ON CURRENT ELECTRICITY FOR MY CLASS PROJECT. I GO TO MONTEBELLO HIGH SCHOOL, I'D APPRECIATE IT IF YOU'D HELP ME OUT. I'M HAVING A HARD TIME TRYING TO FIND SOMETHING ON THIS SUBJECT.
Rosalie Christenson <r0xy65athotmailcom>
Los Angeles, CA USA - Thursday, May 20, 1999 at 08:41:53 (PDT)
Regarding the arifoil explanation controversy, I was also misled in pilot school by being taught that a wing does not deflect air downwards. A good way to make someone realize that this is wrong is to tell him to imagine a propeller which creates a for ward force with the Bernoulli effect, but without blasting a stream of air backwards. People seem to have an intuitive grasp of propellers, but their early physics lessons have taught them wings are somehow different.
Curtis Cameron <curtisc1atcyberramp.net>
Plano, Tx USA - Monday, May 17, 1999 at 07:43:44 (PDT)
The most frequently asked question by the students in the physics class is " What is an electric charge ". Is it a special kind of matter or is it a special kind of property which is exhibited by matter? Can we say electric charge is a kind of property of matter by virtue of which forces are produced, exerted & modified at a distance?
New Delhi, Del India - Sunday, May 16, 1999 at 21:30:06 (PDT)
Its every were I look 7 energies all inerg changable me wears out thinging about lightning try turning hubble check out lifes little classroom?
VLD, NJ USA - Sunday, May 16, 1999 at 03:20:50 (PDT)
Astonishing! I'm not a stupid person, yet I have never EVER been able to understand anything about electricity other than the most basic wiring. The more people have tried to explain it to me the more I found myself getting ucomfortable. Nothing made sense. NOW I KNOW WHY! The way electricity is taught iscompletely contradictory and misleading, especially to the literal thinker like myself. Thanks for breaking it down for me.
USA - Thursday, May 13, 1999 at 06:50:01 (PDT)
i am looking for information regarding students and their misconception in science.I need info on how to avoid,rectify and assess and strategies taken place . Please help.
stuart hassett <shas1atstuadents.bendigo.latrobe.edu.au>
bendigo, vic australia - Wednesday, May 12, 1999 at 23:18:10 (PDT)
Bill, Yourcomments are quite accurate. Some people who are supposed experts barely take any physics classes, and learn these experiments tot ry to explain it. Since they lack the technical background and mathematical background, they get lost! Very Lost! So, it does no tsurpirse me that these kinds of errors still exist. Plus, as you can see from some of these idiots posting "Seymore butts", students are losing the motivation to laern, all they learn is that violence and stealing, etc. is the way to succeed, like in the video games. Hence, the importance of having accurate textbooks to motivate those prized few who want to succeed legitimately and live beyond age 23 or so need to have a solid background. I hold my BSE in Engineering Physics and my MS in Materials Science Engineering. I work in an Electrical Failure Analysis group, so I could definitelycompare notes! You provide a comprehensive somewhat simple explanation, whereas the derivations of what you say would blow most people away. Your useageof analogies is critical and well placed, kudos! I just hope more people access your website in search of answers to Electricity and ESD.
we used this project for our 4th quarter project and it sucks help us pleasse
semore butts <semore butts at yahoocom>
anderson, pa USA - Wednesday, May 05, 1999 at 09:33:27 (PDT)
The sun will never burn out. The sun is not a star.
schenectady, ny USA - Tuesday, May 04, 1999 at 17:13:50 (PDT)
Do you have any theories on light speed? If it isn't to far from your field, let me know and I will tell you something very interesting...
San Antonio, TX USA - Saturday, May 01, 1999 at 17:09:17 (PDT)
sparks an lighting when your bed light up and you see little lights in your eyes an then they fly across the nite an make a thunderous racket ......
Mark Sadow <M2catwebtv.net>
USA - Saturday, May 01, 1999 at 05:57:12 (PDT)
I have a question about something in our new text. It says that the magnetic pole by the geographic pole is the magnetic south pole (since the needle of acompass is magnitized as n and opposites attract). Any ideas? Am I leading them astray?
Sharon S. <sstrefliatgate.net>
Woodbine, GA USA - Wednesday, April 28, 1999 at 19:12:13 (PDT)
I LOVE YOUR SITE
BRITTANY MENDEZ <CARLOS.MENDEZ 5 at GTE .NET>
MESQUITE, TX USA - Saturday, April 24, 1999 at 08:21:54 (PDT)
One:I used to build magnetometers and often brought up the question of the Earth's polarity. I am glad to see that someone else sees things as cock-eyed as I do. I wonder what would happen if someone dragged a wire from one end of the planet to the other and plugged it in. Sounds like something for acomicbook superhero to save the Earth from.
Two:Maybe you can shed some light on the subject(pun intended).
Nobody seems to know just where lightcomes from. Is it the nucleus as in the sun or the electron as it shifts from one orbit to the next similar to a comet's tail. Teachers and scientists still don't seem to know the truth. What do you think?
I've been trying to find a simple experiment on how to make a geyser.But having no luck.Can anyone help? Thanks
Nathanael Fleming <ljfatgte.net>
Coos Bay, OR USA - Monday, April 12, 1999 at 22:13:33 (PDT)
The Bernoulli issue raises such learnedcomments. I'd just like to comment/question on experimental methods. In hydraulic and windtunnel tests, is the airfoil "freestanding" in the medium, like an actual wing with air all about it (except where supported by a post)? Or is the airfoil, at its ends, in sealed contact with the chamber? It would seem to make a difference, since an open end would allow some diffusion of forces laterally, while the closed end model would allow no lateral diffusion.
Dennis Hudson <sheanneatzianetcom>
las cruces, nm USA - Sunday, April 11, 1999 at 01:45:33 (PDT)
Don't understand your statement about electricity in a circuit moving at inches per minute. I assumed that electricity and electron movement (or hole flow) were synonymous in your discussion. That would be "c" (speed o' light). In the discussion of the usage or misusage of the word electricity I use the "potential" argument. Electricity is similar to a jar of gasoline. It is not energy but the potential for energy. Even after you light it the gasoline you see under the flames is still not energy. The event taking place just above causing your hair to singe is the energy. I also have a problem with the Electriccompany charging me for "Electricity". And it doesn't even matter whether it's AC or DC. If it's AC the only thing that the power company is doing is moving the electrons that I already had in my wires back and fo rth. If it's DC I'm sending just as many electrons back to the powercompany as they are sending me. What a jip ;-)
Jeff Francis <jfrancisatjagunetcom>
Baltimore, Md USA - Saturday, April 03, 1999 at 02:00:53 (PST)
Hi Wes! (below)
Before I post, I'd just like to say that I think that the work done by Mr. Beatty inorganisingcomposing these websites is the greatest thing since the invention of dirt floors (...it's a Georgia joke...sorry...) Anyway, I do have a question concerni ng a statement made by Mr. Beatty about the true nature of "electricity". He states that "...if the polarity in an electric circuit is reversed AND THE ELECTRCITY DOES NOT CHANGE DIRECTION, then the flow of electrical energy is reversed. I'm kinda confu sed. How can the polarity change and the flow of electricity- talkin' about electric charge here- not change direction? This statement was made in the article entitled "Electricity is not Electrical Energy". If anyone can answer my question, I'd be ete rnally greatful. Thanks!
Wes Marshall <marshallatathens.net>
Lawrenceville, GA USA - Tuesday, March 30, 1999 at 16:06:05 (PST)
air craft fly because of verying amounts of streamlined drag, and verying air pressure. When air hits the underside of a surface tilted at alow angle, drag is produced. The low tilt angle also has produced stremelining. Keep tilting the surface up towa rd 90 degrees, where you have lost all stream lining, but have great drag. Thus no lift. Now for the top surface. If the surface is flat, it produces no drag,or lift. Keep introducing more and more streamlined protrusion, and you create drag and subsequen tially lift. Keep adding the protrusion,bcoming more bulbuous, and less streamlined, and you loose lift and drag is increased greatly. Also I have a theory that if you could inject an air pressure into a moving slip stream, and using tha t air pressure t o cause an air pressure shape, you could obtain lift.
hartsville, sc USA - Tuesday, March 09, 1999 at 12:53:45 (PST)
Thank you for a great site--but I have a question regarding sound travelling thru water. I've seen experiments where a firecracker exploded a few inches from a glass won't break the glass above water but will when both the 'cracker and the glass are submerged. Similarly, I've been told that dolphins use their echolocation to stun fish which is possible because water conveys sound better than air. What am I missing?
Mike Cherry <voxhomonaataolcom>
Orlando, FL USA - Sunday, March 07, 1999 at 20:25:55 (PST)
The airfoil idea of wing lift is incorrect. The Pitts Special, a popular aerobatic bi-plane has symmetrical wings, with the same shape on the top and bottom of the wing. It flies 100% by applying angle-of-attack. Also if the airfoil theory was correct, military and sports airplanes would not be able to fly UPSIDE DOWN.
Rod Rikimaru <rodmeisteratworldnet.att.net>
Los Angeles, CA USA - Saturday, March 06, 1999 at 23:56:51 (PST)
This site is great!! Electricity was my least favourite topic in Physics simply because no one was ever able to explain all these difficulties away convincingly. I am somewhat unpopular with the more wishy-washy among my teachers because I tend to ques tion everything , and so the teaching of the subject when I was younger was incredibly inefficient, and I had learnt little. I am grateful that others besides me find the same and have gone to the trouble of trying to set things right. In my case, it may havecome a little too late, but I'll make sure I show others lower down in the school this web-site and fewer people will be turned off the topic.
London , England - Thursday, March 04, 1999 at 06:50:13 (PST)
Re: what makes a wing work Our 6th graders make a 7" helicopter on a dowel rod. In a demonstration I show 4 similiar wing setups. 1: a flat wing (which dosen't fly anywhere and just drops) 2: a flat wing with 15 degrees of angle of attack (which flys up a few feet) 3: an airfoil w ing made of white pine at the same 15 degrees of attack (which flys up 20 or 30 feet) 4: an airfoil wing made of red oak at the same 15 degrees of attack (which flys up 10 or 15 feet).. Students find out about reducing drag (via the rounded streamlined s hape and smooth sanded surface), angle of attack, reduction of weight (light weight wood and removing excess wood from the hub), and airfoil shape (shown in smoke tunnel video tests of many shapes and angles). Theycome to understand that it takes all fo ur modifications to obtain the higest flights (greatest lift). SEEING IS BELIEVING !
Phil Horan <horanpataolcom>
Syracuse, NY USA - Tuesday, March 02, 1999 at 15:58:30 (PST)
I believe you state that the balloon experiment would not show a difference between an inflated water balloon and an uninflated balloon if balanced underwater. This seems clearly wrong to me. It is the elasticity of the rubber of the baloon that causes it's contents (when inflated) to be under higher pressure (and thus density) than the same substance around it (otherwise the balloon would not be "inflated"). Why should this be any different underwater? [Try the experiment, see if the inflated balloon sinks -billb] The water in an "inflated" water balloon will still be denser than the water around that balloon. I would not be surprised, however, to find that the elasticity of the balloon has a more difficult time increasing the pressure of water significantly (as opposed to the more easily- compressable air), such that the difference in mass between the two balloons might be very small.
Keith Blackwell <keptatsecret.to.avoid.spam>
Loveland, CO USA - Monday, February 22, 1999 at 09:36:06 (PST)
in mycoment before i said some thing which i got answered by your website. What kinda of project should i do so i may get closer to understanding the maglev cradke?
USA - Thursday, February 11, 1999 at 17:03:49 (PST)
Love it. I teach Biology - and love science. But I turned off on electricity in 9th grade when the text book our school used said "lightning doesn't strike something that isn't grounded because it knows there is no place to go." This also explained, I assume, why electrons don't continue falling out of electrical sockets when you remove the plug. I decided at the age of 14 that some areas of science must have been invented to give certain groups of people something to entertain themselves with. Since t hat time, I have to admit, I have always taken everything anyone said about electricity with a grain of salt. Now, in my middle years with 20 years of teaching behind me, I am finally willing to re-investigate the topic of electricity. I have signed up fo r an electrical home repair course - you don't necessarily have to understand the beast to tame it, and I am willing to relearn all the terms and formulas in hopes that in 30 years they have learned something about teaching it.
Laurel A. Palmisano <laurelatworldnet.att.net>
Richfield, OH USA - Sunday, January 31, 1999 at 02:50:32 (PST)
Acommon misconception is that the primary colors of paint are red, yellow, and blue. The primary colors of paint (or printing) are cyan, magenta, and yellow, while the primary colors of light are red, green , and blue. The traditional color wheel is also wrong. By the way, I think your site is great.
Dr. Lawrence Woolf <Larry.Woolfatgatcom>
USA - Wednesday, January 27, 1999 at 14:41:46 (PST)
Great Page-been here many times. (And have done some of your microwave tricks--big kick!) Appreciate yourcomments on these and when I taught (now in research) used several of your examples in class. Thanks!
Oh, well, a little more nit picking.
RE Lasers and stuff. It seems slightly incorrect to be talking about both
waves and photons. And especially the phase of a photon. The photon is a
particle, w/o a phase only an energy count on a detector. It just seems a
bit wrong to discuss one or the other without specifying the context in
which you choose to measure and what observables you are considering.
(But Oh yes! there 'is' only one wave)
And the onto the balloon: doesn't your solution with the bag and the less
dense air do the same thing as the balloon and the more dense air?
Yes your are a nitpicker, thank you very much! Although almost all of us seem to get along quite well with our electrical misconceptions it is always interesting to be recalibrated so that we can distinguish fact from fiction. Our second grade son was assigned a science project. That is how I ended up in your pages. It looks like we will both be learning a little something from this endeavor.
Mark Sugar <msugaratEBmailcom>
Groton , CT USA - Tuesday, January 12, 1999 at 15:12:24 (PST)
Re. the below... Physics defines "negative charge" as being the polarity of the charge on the electron, and it defines "North" as being the magnetic polarity of the north-pointing end of a magnet. It's arbitrary, but then the length of the Meter is arbitrary, and the mass of the Kilogram is also arbitrary. It might have been better if electrons were declared "positive", and if the "N" polarity of a magnet was declared to be the same as the northern pole of the earth. The north-pointing end of a magnet or acompass needle would then have an "S" painted on it, and everyone would be constantly reminded that OPPOSITE polarities attract!
Bill Beaty <>
Seattle, WA USA - Tuesday, October 26, 1999 at 02:34:35 (PDT)
I was struck by your assertion that the magnetic north pole MUST actually be the south magnetic pole, because the "North" pointer on a compass is "attracted" in that direction.
Acompass is only intended to INDICATE which direction the north magnetic
pole is in, and there is nothing in or on acompass to indicate what the
polarity of the magnetic arrow might be, other than the obvious fact that
the south pole of one magnet would be attracted to the north pole of
In fact, on mycompass, the letter N is painted on the background, not on
I believe your assertion that the north pole is actually the south
magnetic pole is rather silly, even allowing for the fact that these
definitions are arbitrary.
SPAM ADVERTIZEMENT from Storm &company removed 12/24/98. -Bill Beaty
As a pre-service secondary science teacher, your site has proven extremely interesting. Many of the professors in the science education department at my university teach about misconceptions...but never from this perspective. Some of my professors have even used these same experiments to prove to us that we have such misconceptions. The trouble is, some of them have used the very same experiments to demonstrate the very same wrong evidence. The balloon experiment about the weight of air comes to mind. I might have to share this sight with my department (after grades are passed out) to see how they react and what they think. Thanks for the great information!
Greenville, NC USA - Thursday, December 10, 1998 at 19:16:53 (PST)
I was very glad tocome across your document. As a pilot and physicist, I've frequently been asked how airplanes can fly upside down. The longer upper path description implies that a plane should be able to fly backwards but not inverted. I'll point to your document to answer future queries. I've usually explained lift by a simplified derivation of the Navier-Stokes equations. The stable atmosphere is modeled as many small balls (air molecules) moving in random directions equally distributed in all directions. The wing is simplified to a right triangle with horizontal bottom, vertical front and long sloping back. The distribution of molecule directions that hit the wing above, below, and in front explains lift, induced drag, stall, the sound barrier, wake turbulence, and tip vortices. If you are interested, I will draft an elaboration for addition to your page. Thank you
Dr. Robert J. Meier <worselattircom>
Rochester, MI USA - Thursday, December 10, 1998 at 17:48:32 (PST)
Many people imagine that we live in an especially enlightened era. OBVIOUSLY this is the age of "science"- look at all the gizmos we have! OBVIOUSLY the average person today is far more educated than his medieval ancestors- we know about "gravity" and "inertia" while they supposedly thought that the earth was flat.
This iscomplete nonsense. We live in the new Dark Ages- in some
respects, darker than the old one. (The Council of Paderborn declared
witches and werewolves to be figments of superstition, whereas today
almost everyone and his brother believes in the little green men).
We live in a world filled with marvelous technology- airplanes,computers,
television, microwave ovens, lasers, etc ad nauseam. All of this,
however, is just magic for most people. For the most part, we do not know
how our toys work; we just use them. We talk about "forces," "energy,"
"atoms," "fields"- but what do these mean? These words function for most
people like the spirits, ghosts and hoodoo powers that fill the lives of
That a man has a wristwatch and a radio is no guarantee that his knowledge
of reality is more advanced than that of an Australian aborigine or a
In fact, the "industrial animist" is in a worse position than his more
"primitive" contemporaries. When so-called primitive peoples first saw
airplanes zipping through the air, they knew that they had not the
foggiest as to how these things work. But when we climb aboard a jet
liner, we think we know at least the principles of how we're getting from
NY to LA. We do not receive our technology from the gods or from
Promethean titans; itcomes shrink-wrapped in an ideology of science- or
rather, science fiction, for what people talk about has nothing to do with
Newton, Planck or Einstein.
Our technological world depends upon a very thin stratum of the
population- a stratum bcoming ever thinner thanks to the wonders of
public education. It is a minority of scientists, engineers, technicians,
etc. who keep the circus running. But for the most part, even they do not
understand what they are doing. They have bcome habituated in the use of
calculation. They "know the math," and they know how to apply it to
physical reality for practical effect. But do they understand what these
formulas mean? As our pathbreaking host confesses, he only understood the
science underlying his math after he got his BS in electrical engineering.
How many people with degrees have the courage to discover their own
errors, and correct them?
One related misconception is that *turning on* a light causes your electric bill to go up a lot, every time you do it. Implication is that enormous amounts of current are drawn. Actually, it can be true, because a cold lamp filament has low resistance, but the warmup time is too short to matter. I'd love to know where this idea came from. (Fuses don't blow, and breakers don't trip!)
Nicholas Bodley <nbodleyattiac.net>
Waltham, MA USA - Sunday, November 29, 1998 at 15:56:21 (PST)
Your page is very good. But you use yourself a misconception... When you say "Like it or not, we are stuck with negative electrons,[...] centimeters which are about as wide as a small finger, etc."
A centimeter is 1/100th of a meter, which is defined as the distance
covered by the radiation of the isotope 86 of krypton in vacuum in
1/299792458th of a second. It was first defined by the 1/10 000 000th of
the quarter of the terrestrial meridian. The use of laser to calculate the
"exact" speed of light in vacuum leaded to the new definition...
Only the US system (vs the metric system) have units refering to the human
body (feet, inch, even temperature in a way (ok, he had some fever...))...
Shouldn't many of these misconseptions have been cleared up by parents prior to kindergarten? I must admit that I did get a better understanding of some gerneral concepts.
Sudbury, ON Canada - Tuesday, November 24, 1998 at 19:34:17 (PST)
What a wonderful insight into how wrong school physics teachers can be. I found this page most interesting and informative, i am currently studying physics of my own teaching and i would be grateful if you could rcomend some text books, if so email me with the titles Thanks, and once again very intresting matierial
nicola white <nickyrocksusaatyahoocom.>
atlanta, ga USA - Monday, November 23, 1998 at 09:17:44 (PST)
I found your site very interesting. I am a junior high physical science teacher (who actually majored in physiology/biology, and trying to prepare students for state proficiency tests, so I am always looking for reliable sources. In taking a TOYS for chem and physics class, an interesting thought came about as to why art teachers teach primary COLORS instead of primary pigments, which would certainly help students. There are a lot of misconceptions out there that are difficult to talk teenagers into "unlearning!"
Andi Schmidt <schmidtandiathotmailcom>
Mason, OH USA - Saturday, November 21, 1998 at 17:32:43 (PST)
This is a cool site.
Bradley Frodge <RFrodge>
Locust, NC USA - Monday, November 16, 1998 at 08:30:03 (PST)
REFERENCE Q3:IS THERE A CONSPIRACY TO SUPPRESS THESE DEVICES?
Wake up from your slumber and great naivete'. Alleged conspiracy against
women is minuscule whencompared to billion dollar losses to energy
magnets who keep our planet in tow and financial slavery. Neither do
black holes, plate tectonics, spacecraft etc. threaten the existence of
super rich energy providers. Until you have mastered the art and science
of politics and global economics you cannot successfully predict the
oucome of scientific advancement or anything else on this planet. Orbit
in a smaller sphere until your horizons have widened and do not give
advice to others on subjects that are out of your league.
Refer to http://www.2xtremenet/pea_research/inventns.txt to find the
historical fate of free energy devices ofcommended and patented
performance strewn across the refuse pile.
About the misconception of batteries and generators creating electricity... Energy can neither be created nor destroyed, you hit it right on, one thing though, ya you knew it wascoming. Energy can be converted from one form to another. In the case of the battery, it's chemical to electrical in the case of the generator it's magnetic to electrical. If you would like to talk about it further, drop me a line, I really like you page !!!
Thomas Reeder <treeder3atbellatlantic.net>
Millvale, PA USA - Friday, November 13, 1998 at 03:08:06 (PST)
A year or so ago I watched a t.v. program that showed a big, two-story house being powered by a truck. The truck was specially designed for this purpose. There was some kind of a box on the side of the truck that the guy somehow "hooked" the house into. I don't remember the details, I just remember that they showed a demo and were talking about how wonderful this technology would be for people up north during winter. Did anyone else see this? If so, what was the name of the technology and what was the name of thecompany (or person) that was demonstrating this. Thanks for any help you can provide.
Raleigh, NC USA - Wednesday, November 11, 1998 at 03:42:32 (PST)
You've met your match. I am more of a nit picker than you ( and since I have three children - now grown - I have probably literally picked more nits than you). What about the north pole really being the south pole, the fact that there are more than just plants and animals thatcomprise the livingorganisms on this planet and the fact that gravity is a two way street, not a pulling of one object tword the other. More later, my class has just arrived.
Joanne Suttile <jsuttileatsmes.org>
San Juan Capist5rano, CA USA - Monday, November 09, 1998 at 13:06:25 (PST)
A plane is mainly sucked in the air by its wings: If an airplane flies upside down, it will fly a ballistic trajectory, because during this time there will be no lift. Of this reason the pilot has to correct his track with the flaps! A very difficult exercise with an RC-controlled airplane is to fly a spiral near the ground. In this case you have a ballistic trajectory, too. You will never know in which position you will be, when you end the spiral. If you are in the right position, it's o.k.If you are in the upside-down-position, you have correct your fligth with the flaps immediaetly, otherwise you'l smash the plane into the airfield. Thomas Pruss, prussatjahr-verlag.de, Hamburg, Gemany
Thomas Pruss <prussatjahr-verlag.de>
Hamburg, D Germany - Tuesday, November 03, 1998 at 06:03:36 (PST)
Great page! Here are a couple of interesting tidbits: In the section on sound travelling through solids, one big reason why the watch-ruler-ear setup sounds louder is because of bone-conducted sound; that is, the ruler vibrates your skull, which vibrates the sensory receptors in your ear. Try this experiment: hit a tuning fork against a table, and hold the base of it near your ear. Listen to how loud it sounds. Next, touch the base of it to the bone above your ear. The sound will get much louder. The reason for this is because of impedance matching -- in the first case, it's much easier for the energy to bounce back and forth within the tuning fork than to escape to the air, but in the second case it's relatively easy for the energy to escape into the skull to vibrate the inner ear.
In the section on prisms, the two prism experiment will
work just fine, with one caveat -- you can't leave any
space between the prisms! The explanation is right in
your drawing. When the rainbow emerges from the prism,
the colors are all closely spaced, but as we move further
away from the prism, they spread out. This means that
what goes into the second prism won't be the same thing
thatcomes out of the first, so we shouldn't expect white
light out of the second prism -- unless the two prisms
You argue that air friction does not slow down cars (etc.) That is not correct; air friction does indeed cause the slowing. The other phenomena you describe -- shedding vortices, for example -- are themselves caused by friction. Without friction due to viscosity, there is no drag.
Rich Griffiths <richgatone.net>
Cincinnati, OH USA - Monday, October 26, 1998 at 11:48:18 (PST)
THANK YOU! I teach multiple, integrated sciences at the Junior High level. My father has been an electrical engineer for many years with many electronic aerospace designs to his credit. We know about and regret the ways in which science has been taught. The "touchy-feely," "new-age" approaches to teaching science are robbing our students of the very solid foundation which you refer to. Precise language at every level is the key!
Mrs. Kathryn Ervin <KathyETutorsatjunocom>
Clovis, CA USA - Sunday, October 25, 1998 at 11:35:22 (PST)
IT DIDN'T HELP ME BUT MAYBE IT'LL HELP SOMEONE ELSE!!!!
DALLAS, TX USA - Friday, October 23, 1998 at 07:56:03 (PDT)
This is a *very* fascinating page. I'm just finishing year 12, my final year (about 3 more weeks to go!!), and my jaw DROPPED when I read the headlines... then I read the articles and it all made sense. I truly enjoyed reading your page.
Juliet Holwill <the_mexican_muleathotmailcom>
melbourne, vic austrlia - Thursday, October 22, 1998 at 01:14:06 (PDT)
You are perfectly right, except for your bow to Einstein!
Dipl.-Ing. Norbert Derksen <Norbert.Derksenatkst.siemens.de>
Konstanz, Germany - Tuesday, October 20, 1998 at 12:59:11 (PDT)
There ARE 92 elements present on earth, though they are not the ones we learned about. According to the Los Alamos site, http://cst.lanl.gov/CST/imagemap/periodic/93.html http://cst.lanl.gov/CST/imagemap/periodic/94.html both Neptunium and Plutonium are found at trace levels in nature. Thiscompensates for the missing ones (Tc and Pm) and brings the total back to 92!
Gorges-Émile April <georgesatvlsi.polymtl.ca>
Montréal, Qc Canada - Thursday, October 15, 1998 at 14:11:23 (PDT)
I am a maltese university student doing the B.Ed course. I am doing my thesis about teachers' misconceptions in electricity and magnetism. I found this page very helpful and I would be very grateful to anyone who is willing to send me more information about this topic. Thank You
Malta - Wednesday, October 07, 1998 at 13:33:29 (PDT)
about how a plane flies the way you explain about the angle of attack, what about when a plane is landing or rather descending.according to your theory a plane starting to descend would not fly down but crash
bhupen kharawala <bhupenkharawalaathotmailcom>
ahmedabad, india - Saturday, October 03, 1998 at 03:33:43 (PDT)
This is so cool!!!%2
Brandy Simmons <none>
tiptonville, Tn USA - Wednesday, September 30, 1998 at 09:12:46 (PDT)
Bravo Mr. Bill ... ;-) Continue U r not alone ...
Deliakos Argiris <amysaatthe.forthnet.gr>
Thessaloniki, Greece - Tuesday, September 15, 1998 at 10:30:52 (PDT)
It's the third time I visit this beautifull site and I willcome back ! It's just what I was looking for,thank you. Here I find good food for my ideas.I soon will work some of them out and tell you more about them !BTW sorry for my bad Englisch but I a m from Belgium and unfortunaly the second language they teatche here in shool is French , what I think is verry stupid to do so, while the www and the most scientific articels are written in Englich ! I am also looking for somebody in the USA for e-mai l with me to discus all kinds off scientific ideas .Thank you .
WILLIAM D. <william.datplanetinternet.be>
BRUGES, WEST VL. BELGIUM - Friday, September 04, 1998 at 17:51:04 (PDT)
science is more about constructing models to explain the world than it is about collecting facts. All models are flawed. When a model is taught as the one, truecomplete and only explanation (as is often the case with teachers and other authorities) misinformation will result. I taught science for a while and I was amazed at how simplistic the books were.
John Kroll <krolljlatyahoo.com>
USA - Wednesday, September 02, 1998 at 08:20:58 (PDT)
We are very glad to have found your cool side. My 11year old daugter will use your , anti bubble, experiment for her school demo. Thank you very much.
Sydney, N.S.W. Australia - Monday, August 31, 1998 at 04:01:31 (PDT)
Excellent sites! I do hope these texts are pressed as soon as possible!
Park Inseog <epistemeatunitel.co.kr>
Seoul, Korea - Sunday, August 30, 1998 at 23:45:45 (PDT)
I'm glad to see a site such as this. Recently, I saw a (Canadian) science show where they explained the circular motion of the moon by stating there is a force causing the moon to want to flee away from the Earth, etc. It also had the following question: If you weigh 30 kg on Earth, how much would you weigh on the moon? They then went on to say you would weigh fewer kilograms on the moon than on Earth. I could not believe it! In their attempt to convert to mertic, they muddied the issue of mass and weight.
Thanks for the sounding board.
P.S. Consider asking your site designer to add wrap=virtual
to your textarea tag. I saves a lot of enters on the part
of your guests.
Seven colours in the rainbow. What seems to have happened was this. Isaac Newton saw that white light could be made into a rainbow, and the human eye could readily distinguish 6 colours: Red Orange Yellow Green Blue Violet Unfortunately 6 is the devil's number (666 is worse) whereas 7 is God's number (7 stars in the sky (=planets) days of the week, orifices in the head etc. It was therefore necessary to invent Indigo as an imagined colour between Blue and Violet, or his optical work would have been criticized on religious grounds!
Martin Pitt <m.j.pittatsheffield.ac.uk>
Sheffield, UK - Wednesday, August 19, 1998 at 06:11:51 (PDT)
I have directed my children's school district to these sites. A lot of the "new age" touchy feely emotional pseudo-science crap that's being shoveled into our kids these days has its roots in the very misconceptions your pages address. I've explored your pages with much interest.
Mike Stempo <stempomjatapcicom>
Allentown, PA USA - Sunday, July 26, 1998 at 10:33:13 (PDT)
On balloons below: a good point! I have problems only because pressure is never mentioned in the versions of "balloon experiment" I've seen. The demo would not be misleading if, rather than full and empty balloons, it instead used nearly-inflated and extremely-inflated balloons. These balloons would have nearly the same size, but very different internal pressure. Their weights would be different. On the other hand, if the demonstration is said to illustrate that full and empty balloons weigh differently, then it is wrong. Use full and empty paper bags instead, and use the experiment to show that the bags DON'T weigh differently. Then launch into a lecture on bouyancy!
USA - Friday, July 17, 1998 at 19:08:08 (PDT)
In yourcomments regarding the filled/empty balloon experiment, you are missing the point of the experiment. The experiment (as I have seen it written up, anyway) is supposed to demonstrate that air DOES have mass. The experiment does indicate this, even in your own words: "The experiment secretly relies on the fact that the air within a high-pressure balloon is denser than air within a low pressure balloon." What is density? It is MASS divided by volume. Since high-pressure air is more dense than low-pressure air, then air must have mass. Now I agree that you can't measure the mass of air by weighing a balloon, but that is NOT what the experiment (as I have seen it written up) demonstrates. The fact is, a filled balloon IS heavier than an empty balloon. Thus, air MUST have mass, or that would not be the case.
Dr. Jay L. Wile (Ph.D. in nuclear chemistry) <jlwileathighschooldscience.com>
Anderson, IN USA - Thursday, July 16, 1998 at 03:23:37 (PDT)
I don't believe at all that your 'Science Misconceptions' page is nitpicky. Possibly I'm wrong, but many of the errors may be in an effort to make relativelycomplex topics more understandable to the non-scientific consumer, child or adult. For most, the minor inaccuracies are meaningless in their jobs, hobbies, and lives, since many have little concept of the applications of science incommon events of every day (how sad). The point you make about critical thinking, however, is most valid. In effect, those who learn of textbook errors through experimental failure or simply more detailed study, will frequently retain the new (and correct) information longer. I occasionally present formal instruction in scientific topics as part of my job. In some cases the draft copy of a visual aid may contain a small error, which I frequently elect not to correct. If an audience member 'catches' it, Icompliment them and indicate it was a 'test'. If not, I'll point out the error, especially if the visual aid covered an important point. I feel that emphasis of an 'error' will tend to reinforce the point being made. By the way, you have a superb site; keep up the excellent work! -Ted
Theodore J. Rieth <tjriethatepix.net>
Towanda, PA USA - Sunday, July 12, 1998 at 18:53:14 (PDT)
Excellent site! Question: Is there a difference in the spelling of Technetium in the US vs. the UK? I've not seen it spelled Technicium before...
tom lee <tomleeatee.stanford.edu>
Stanford, CA USA - Tuesday, June 16, 1998 at 17:54:10 (PDT)
That URL might be wrong. The state I live in is NSW, the box wouldn't take. Small but significant nitpick. You do not feel your own weight. You feel the static reaction of the surface on which you stand, sit, etc. You can tell this because you feel the force pushing UP on you whereas the force of gravity (weight by definition) is in the opposite direction. You have to get children to concentrate to feel SR as we do a very good job at ignoring it, Unless you sit on a thumbtack or you are a princess with a pea under the matress. It is, incidently, the source of much of the dicomfort of heroin addicts going cold turkey. Ordinary folk will notice its absence. You are so used to the pelvis and peritoneum pressing up on your gut that when you go over a cres t in a fast travelling car and go into orbit for just a moment you feel its absence. The lack of SR in space is caused, as you say, by the falling of BOTH the craft and the astronaut. Tell the good folk if they went over a cliff in a large crate or a carg o container they would be able to "float" about in it just like the astronauts in space, for a little while.
Rob Gooley <rgooleyatyahoo.com>
braidwood, N AUSTRALIA - Monday, May 18, 1998 at 06:02:57 (PDT)
This a tremendous service to American Youth. Science should be taught from these pages! Technology is at an all time low point in the US (I have witnessed it from pre-Apollo days to the present) The mis-representation of phenomena in the media is so al l-pervasive that something like this site makes a difference. Thanks.
USA - Sunday, May 17, 1998 at 20:55:25 (PDT)
Concerning the speed of electrons, I believe they flow faster in a cathode ray tube (CRT) where the electrons are accelerated in a near vacuum and made to sweep across the screen.
Michael Gilsdorf <GilsdorfMataolcom>
USA - Friday, May 15, 1998 at 21:56:09 (PDT)
This is a much needed site, I hope the people behind it will be able to continue tospread the truth! Why should people continue to teach myths to the younger generations? Fight on!
Abdulhadi Ayyad <aayyadathotmailcom>
Kuwait - Wednesday, May 13, 1998 at 22:12:40 (PDT)
As to sound traveling better through solids: Youcompletely missed the acoustic-impedance mismatches between the ruler and the air!
Nicholas Bodley <nbodleyattiac.net>
Waltham, MA USA - Thursday, May 07, 1998 at 22:04:08 (PDT)
In the "two prisms can't rcomine white light", you miss a verycommon optics trick. With the diagram marked "wrong", all you need to do is put a plane mirror on the thick collimated side. The rays retrace and you get the same, white collimated beamcoming out in the opposite direction. We use this "prism-pair" geometry incompressing ultrafast laser pulses. (incidentally, instead of a mirror, you could just as well put two more prisms in a mirror-image of the first two)
Kevin Kubarych <kjkatlphys.chem.utoronto.ca>
Toronto, ON Canada - Wednesday, April 22, 1998 at 16:54:52 (PDT)
Great site. Loved it, but...I'm sure you know The Dexter Magnetics graphic link you use as a correction of one of the three earth b-field misconceptions is guilty of the other two. Keep up the good fight.
David Howard <dhowardaterdascom>
Atlanta , GA USA - Friday, April 17, 1998 at 18:43:47 (PDT)
Open for business. Let fly with verbose prose.
W Beaty <>
Seattle, WA USA - Tuesday, April 07, 1998 at 20:58:29 (PDT)