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I just came across your site. Great stuff. I think even many adults
with only a kind of amateur interest in physics would do well to read your
material on misconceptions.
In the text:
You'd only weigh about fifteen percent less than you do on the ground. While 300 miles out in space, a 115lb person would weigh about 100lb.
The example is wrong.
[ No it's not. Read it again, and pay attention to an important word that you missed. I said, "You'd only weight *ABOUT* fifteen percent less." At that altitude it's not exactly 15% decrease, but it's about 15%. Also their weight decreases to *ABOUT* 100lbs but not exactly 100lbs. If you're not an English speaker, perhaps you didn't realize that "about" means "approximately." -billb ]
You wanted to say "a 100lb person would weight 85lb". Otherwise you lead the reader to conclusion that 15% od 115lb is 15lb, which is not.
Brno, Czech Republic - Thursday, January 12, 2006 at 06:18:28 (PST)
what is the main reason behind earth's changing magnetic field?what are proposed theories ? can i propose one of my own?
puneet mehrotra <email@example.com>
kanpur, u.p india - Wednesday, January 11, 2006 at 05:41:33 (PST)
I just read the explanation on transistor theory by William Beaty. It is truly excellent. This is the first time that I can truly say that I understand transistor theory. Thanks so much.
john cope <firstname.lastname@example.org>
bellingham, wa USA - Monday, January 09, 2006 at 14:31:20 (PST)
Wonderful to find someone who doesn't just regurgitate errors and misconceptios. Try to find definitive quotes on whether ac or dc is more dangerous and why and you'll see one of the problems I've had.
The other is to do with musical instruments - one example: The reason for the hole in the front of the guitar is to allow the sound that bounces round the inside to get out?
Stu Wright <email@example.com>
poulton le Fylde, lancs UK - Friday, January 06, 2006 at 05:52:20 (PST)
Many thinks for the chapters on transistor operation. I have several books on the subject and they made absolutely no sense, just like you described. But after reading your description of it, I understand them a whole lot better - and it seems to simple and common sense! Great articles, I'll personally bookmark this and enlighten anyone else who may be interested in this subject.
George Veskov <jkxxster)*at*(gmail.com>
Westminster, CO USA - Friday, December 23, 2005 at 20:29:22 (PST)
I wish people would stop talking about lift when they speak of aircraft wings. It is not lift, it is push.
Air moving across the top of a wing produces a vaccum of sorts, greater air pressure from beneath the wing PUSHES the wing up. Lift is when you pull something from above, to push up is when you apply pressure from underneath.
I am not a scientist or anything, it is just that it sounds so dumb to talk about lift, when it is pressure from below. Tell me I'm wrong.
USA - Tuesday, December 20, 2005 at 21:42:49 (PST)
1. The earth does NOT orbit the sun. Nor do they orbit a common point (another popular misconception). Because the planets have mass, each will tug on the others AND the sun itself. They ALL orbit whatever happens to be the center of gravity for the solar system at that time. Because the mass is unevenly distributed and the planets move with very different shaped orbits at very different velocities, the center of gravity will be constantly moving. That the center of gravity of the solar system will always lie within the sun is merely incidental and may not be true of solar systems in general.
2. The acceleration of a relatively small object due to gravity is independent of the mass of the object. Actually, as all objects have mass (and therefore gravity), any two objects must fall towards a common point. If you are talking about a golf ball and the planet earth, then the planet earth isn't going to be moving very far. For that reason, you can opt to neglect that part of the calculation. The classic textbook example of dropping two objects at the same time is also invalid, as they are typically described as being dropped at nearly identical positions at the same time. If the earth were to accelerate significantly towards one, it would necessarily accelerate by the same amount to the other.
3. A planet is NOT at the bottom of its gravity well (a.k.a. the gravitational field of a moving object is NOT spherical). It can't be. Information can't travel faster than light and that includes information on where a given mass is. Gravity must therefore drag as a function of relative velocity. If you want to get picky, it must actually drag a bit more than that - space is not infinitely elastic, so must take a non-zero time to react to any changes in state.
4. Light might not be a particle, wave, or both. In fact, it is not at all clear how to regard light, as there are plenty of conflicting experiments. For example, there are experiments which suggest it is possible to have the slits seperated by time rather than space. There is also the problem of quantum entanglement, where two photons are coupled in a way that connects the state of one to the state of the other, regardless of distance. This cannot be used to break the limits on the speed of information, but that is not the problem I'm concerned with. I'm much more concerned with the fact that entanglement exists at all, when the only components we're allowing a photon to have cannot possibly interact with the components of another photon at a distance. One or more of the definitions used have to be incomplete for the above observations to make any sense.
5. The digits of Pi are NOT random. This is a bit of a cheat, as it's not really physics, although Pi is used extensively within physics. There have been two discoveries, in recent years. First, it is possible to calculate any specific digit of Pi - not a trait normally associated with random or pseudorandom streams. Also, although the overall distribution of digits is as close to normal as you could want, over any large sequence, that's not the only criteria for randomness.
Jonathan Day <firstname.lastname@example.org>
Portland, OR USA - Sunday, December 18, 2005 at 01:04:49 (PST)
This Comment is not to debate if lift is caused by Newton's third law or by Barnouli's principle. It is to correct Your statement of "a symetrical wing would produce no lift or a wing could not fly inverted if the venturi lift explanation is beleived". Your explanation leaves out "angle of attack". When an airfoil is tilted to the free airstream (relative Wind) a greater distance across one side and a shorter distance accross the other will thus be created along with the fact You have Your downwash effect. This neither disproves or proves Your Theory of Lift being caused by the downwash only.
Bruce McGinnis <email@example.com>
Colton, Ca. USA - Friday, December 09, 2005 at 10:25:46 (PST)
this is boring but thanks for making pitsco it helps me !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!! E-mail me back please! at firstname.lastname@example.org
Brittany Simmons <email@example.com>
Easley, S.C. USA - Thursday, November 17, 2005 at 06:20:15 (PST)
The section on gravity in space is a bit of a strawman argument, isn't it? The example you give is still within the earth's gravitational field. 300 miles is not very far when you're talking about space travel. Gravity
[ I guess it still wasn't clear enough. ASTRONAUTS' WEIGHTLESSNESS IS NOT CAUSED BY LOW GRAVITY. The incorrect books I've seen were talking about actual astronauts in low Earth orbit and trying to explain their weightlessness. They were NOT talking about some theoretical astronaut far from the earth. But in any case, astronauts look just as weightless when they're in low earth orbit, or when they're part way to the moon. If we could orbit a few feet above the Lunar surface, or if we could travel outside the solar system, astronauts in either ship would still look just as weightless. How can this be? It's very simple: the weightlessness of astronauts is caused by falling, and is not caused by lack of gravity. -billb]
requires a large body of mass. In your example, that would be the earth, leaving the earth's gravitational field, but outside the earth's gravitational field, it may be safe to say that there would at least be a negligible amount of gravity.
Knoxville, TN USA - Wednesday, November 02, 2005 at 21:39:01 (PST)
I agree with the general misconceptions that we see in schools, in fact, I wrote an article about it; feel free to read if you like.
Montreal, Qc Canada - Friday, October 28, 2005 at 11:39:16 (PDT)
Re: Gravity in Space is Zero - Wrong!
Correct, but it depends where you define space to be.
[ My complaint is about something clear and simple: textbook descriptions of weightless astronauts in Earth orbit, and photos of those astronauts "proving" that gravity there is zero. Maybe I could change the title to read "gravity in spaceships is zero" ? No, because the misconception is always about floating astronauts, not about the gravity of very distant locations. The original error was in old books with photos of Mercury astronauts with floating objects in the craft, or of the first Gemini space walks. Now most important: as long as a spacecraft is in free fall, the effect of gravity is not visible, and the people inside will appear weightless only because they are falling. The weightlessness is entirely caused by falling and they are apparently weightless regardless of the strength of gravity at that location: they appear just as weightless whether they're orbiting very close to Earth, or whether they're at some special gravity null-point between the Earth and Moon. So yes, the gravity far out in space is nearly zero... but this has nothing to do with the misconception about "weightlessness" of floating astronauts in low earth orbit. -billb]
300 miles above the Earth is technically space, because there is essentially no atmosphere, but gravity is comparable to the surface - as you point out, free fall makes gravity only "appear" to be zero. But far away from any "massive" influences gravity is very small indeed; in fact in intergalactic space its effects are tiny and are only evident over millions of years of universal expansion or stellar evolution. Having said that our perceptions of time are relative - who is to say that an aggregation of diffuse gas separated by millions of light years being drawn together over millions of years by "tiny" gravitational effects are not significant in somebody else's universe; or that the effects of a nearby black hole are a mere bgatelle to someone else's - essentially as we live in a "massive" universe we cannot escape gravity and hence where ever we are gravity is present and its strength can only be described as relative. Yet again ( I am waffling now ) if the resultant gravitational effects of a number of bodies on an object ( i suppose this must include the whole universe ) is zero then in this case gravity is - for that observer - zero. I'll stop now!!
David Matkin <firstname.lastname@example.org>
Peterborough, UK - Tuesday, October 25, 2005 at 15:41:20 (PDT)
I don't agree that the air is blue. The sky is blue because of rayleigh scattering, plain and simple. You wouldn't call a prism "rainbow-colored" because a rainbow comes out!
[Yet soap films made from transparent water are rainbow colored? :) But note carefully the object above us which is blue. Ask yourself: is there any solid surface up there? No. Does a solid dome called "the sky" exist? Nope: the only thing up there is a layer of air; air backed up by the black of outer space. The air up there is blue in color. (And if the air isn't blue, then what up there is blue?) But yes I agree that the blue of the air is caused by preferential scattering of shorter wavelengths. And this color varies with viewing angle: the color of sunsets is caused by the red color of the air. The red (or the sky-blue) color is not caused by a pigment; by a resonant absorption-band of a dye molecule. - billb]
The color of an object is the light which reflects or transmits when the object is illuminated by white light. For example, an object is blue when it absorbs incident red and green light. When you look through a transparent blue sheet of plastic,everything you see will be blue because all of the green and red light is absorbed.
However, when you look through air something completely different happens. Things viewed through air become *less* blue! For example, the sun is a bluish-white color in space, but is yellow-orange at zenith and red when it is low on the horizon.
Curtis Volin <cevolinatyahoo>
Atlanta, Ga USA - Tuesday, October 25, 2005 at 14:49:07 (PDT)
Another few thoughts on the colour of the ocean.
1) I think that we are in agreement that white light transmitted through water has more red absorbed than blue and hence looks blue. By definition, therefore, if we consider transmitted light then water is, of course, blue.
2) I also suspect that the fact the amount of reflected light observed from a body of water depends on the angle from which we are observing is something that we are also in agreement with. I.e. the shallower the angle the greater the fraction of incident light that is reflected.
3) The colour of a body of water must therefore depend on the original source of light - either above or below the surface - and the angle that we are observing the water from.
4) Looking at your reflection from a position standing on a pier, I conceed, will be dominated by the colour blue; but this is reflected and scattered up from the water itself as your reflection forms a small proportion of the light that you observe.
5) Looking at the ocean from above ( your pictues of the aircraft carrier and the tropical beach for example ) also show the sea to be blue as we are viewing from above - or there abouts. The light from below has of course had an amount of red "removed" from it and hence looks blue.
6) If we darken an apparently "white" sky - thunder clouds, evening sky etc does this not "appear" blue as well? And hence a reflection from the sea's surface of an apparently white sky actually is just a darker version of the blue already present - just a thought!!
7) I do maintain, however, that the vast majority of water that we observe we only see because of reflected light, check your e-m theory ( I genuinely do not wish to seem patronising here ), otherwise we would see shoals of fish, coral reefs, plants and so on from above the water surface as a matter of course BUT WE DO NOT - even on a completely calm lake we cannot see below the suface at any real distance - see later) - hence the light that we do see MUST be reflected. (I do conceed, however, that the amount of reflected light may also depend on wavelength and hence "blue" may dominate.)
8) I do not disagree with you that water is blue but I do maintain that the appearance of a body of water is significantly affected by the nature of the incident light upon its surface - if not dominated by it! An average man is about 6 feet tall. This means that when standing on a beach at sea level 10 degrees corresponds to a distance of only 34 feet. The whole of the ocean beyond that is dominated by reflected light - and that is by your figures!!
9) In short reflected light dominates at an "angle" and the blueness of water becomes more and more significant as the observer becomes perpendicular to the surface.
10 Yes, water IS blue - but reflection dominates.
David Matkin <email@example.com>
peterborough, UK - Tuesday, October 25, 2005 at 14:43:18 (PDT)
i'd like to take issue with your statement that aerodynamic lift is caused by the trailing edge angle and that leading edge geometry have little effect.
i agree with a later statement that unless a wing is "tilted" or cambered it won't create lift. Please don't "nit-pick", as i'm trying not to. Lift is created by the circulation of the fluid around the wing. a result of this circulation is downwash. a more cambered wing (like a wing with leading edge slats and trailing edge flaps) creates more lift at low speed, as so is used at take-off. in cruise, the plane is moving much faster, and doesn't need as much camber in it's wing (and so the slats and flaps are retracted) and it's lift is contrilled by slight changes in "tilt" (by changing the attitude of the plane).
The point is leading edge geometry has a very large affect on the effectiveness of a wing. Wings with a fat leading edge are used only at slow speed (because of their drag penalty), a key advantage is that they allow the airflow to remain attached at high angles of attack ("tilt"). Very fast planes have very sharp leading edges, and so slats (leading edge flaps) were invented, increasing the camber of the wing and changing the geometry of the leading edge radius.
btw, "angle of attack" is, measured between at the leading edge of the wing, the angle between the on-coming airflow and the wing's chordline (joinig the leading edge and the trailing edge (see wiki)
try this link ... http://www.grc.nasa.gov/WWW/K-12/airplane/inclind.html
russell blake <RrEbMlOaVkEeC1A2P2S5@rogers.com>
pickering, ON CANADA - Monday, October 24, 2005 at 12:57:21 (PDT)
You've got the idea that a re-entering spacecraft is heated by "compression" of the air it hits... Well...??? Yeaaasss, kinda. Kinda not too I would have said. "temperature" of gas is really a measure of the average velocity (well actually average kinetic energy) of the atoms and molecules of the gas. Normally the average velocity of a gas is around the speed of sound. When gas molecules bang into a solid (like a shuttle tile when it's sitting on the ground) then there is an exchange of energy between the atoms of the solid and the atoms of the gas. If the average energy of the atoms in the solid is higher than the average engergy of the gas then interactions between them tend to on average remove energy from the solid and pass it to the gas. (hot solid cools down and doing so heats up the gas). Same thing happens in reverse.
Now look at a reentry. Viewed from the point of view of a gas atom (or molecule) it's zipping along minding it's own business at an average of the speed of sound. Suddenly something travelling at 25 times the speed of sound runs into it. (a molecule of tile material). Suddenly it gains a lot of energy! It's "temperature" (average velocity) goes up and it becomes what we would call "hot". Same thing happens to the tile molecules. They're along for the ride with the rest of the shuttle. They're used to being hit by air molecules or atoms at about the speed of sound, then after a few days of not being hit by anything (and having their temperature controlled by radiation) suddenly there are all these air molecules hitting them! Ouch! They gain energy from each interaction with each of the collisions as the gas that they're seeing is hitting them at 25 times the speed of sound. They get hot too!!! It seems like a lot of energy is coming from nowhere to make this temperature, heating everything up, but it's not. Each collision slows down the shuttle and the kinetic energy of the shuttle is transferred to each molecule of air and tile material. Cheers Jason =:)
Jason Rogers <firstname.lastname@example.org>
Grafton, nsw australia - Monday, October 24, 2005 at 05:21:25 (PDT)
I read the piece on the colour of the sky, and have looked at the pictures of Earth from space showing the blue ring around the Earth. What I don't understand is, why does the sky become less blue and more white as it moves towards the horizon?
[Good question! Very thick layers of air are like milk: they scatter all the light that hits them. But thinner layers of air scatter the bluish wavelengths of light while allowing the reddish wavelengths to pass through. Thin sparse air layers are splitting the light into separate red and blue. But thick dense layers are scattering the red light too, so the red and blue are recombined again. If you had a gigantic ball of dense air hanging out in space, it should appear white, but with a blue border. -billb]
Raglan, New Zealand - Sunday, October 23, 2005 at 03:14:31 (PDT)
Great site there!
I was taught Red-Orange-Yellow-Green-Blue-Indigo-Violet
The interesting thing about teaching rainbows, not just the number but the type of colours that are typically taught and illistrated in K-12 books. They always include Violet below Blue. Most human eyes have three colour sensitive cells. The sensation that you get of colour depends on the relative stimulation of each of these three cells. Generally speaking there is considerable overlap in sensitivity between the three cells for any one frequency of light. So a "red" light will stimulate the red cells strongly, the green cell less so and the blue cell not at all. A "green" light will stimulate the green cells strongly and both the red and blue cells weakly and be perceived as green. However there is no overlap at the highest frequencies and up around the "violet" end of the spectrum (nearly "ultra violet") only the blue cells will be stimulated and the red and green cells not at all. The perceived colour will be **BLUE** not violet. In order to trigger the sensation of Violet in the human you need to have a mixture of frequencies, some low (red) and some high (blue). Look at a real rainbow, there just isn't a violet band in it at all! Well, actually there can be, but not in the place that it's "supposed" to be. When there is blue sky behind the rainbow (as sometimes happens) then the red light reflected by the raindrops mixes with the blue light coming from the air behind to produce a stimulation of the blue sensitive cells and the red senstive cells and you see violet.
Jason Rogers <email@example.com>
Grafton, NSW Australia - Saturday, October 22, 2005 at 23:26:39 (PDT)
I stole this from IPS and you should remove that disclaimer from my email.
The discussion of the weight of air is long and extensive. Why not simplify?
Does gas have weight?
It's much easier for your average elementary school teacher to do the following simple demonstration than it is to vacuum pump a container.
Mass 1/2 an alka-seltzer tablet, water and a small glass bottle* with a screw-on-lid on a balance. *Because you are building up pressure, the glass bottle should be reinforced with tape. Two pieces of duct tape around the middle should stop the bottle from shattering.
Add the alka-seltzer to the water. Put the lid on quickly and tightly. Remass the bottle. The mass should be the same (especially if you are using a Scout or electronic balance).
Unscrew the lid and let the gas escape. The bottle should be about 0.80 grams lighter. The gas did have weight and when you release the gas, you can see the mass decrease.
I always thought this would be a great demo with a pop bottle, but I've never confirmed how much soda you need in order to show a measurable change in mass.
I would guess that a 2L bottle would be better because you would have an increased volume of carbonic acid with which to generate CO2.
Becca Kreidler <firstname.lastname@example.org>
Denver, CO USA - Tuesday, October 18, 2005 at 17:05:22 (PDT)
Re: Gases do not expand to fill their containers.
It's not really appropriate to say that gases at very high pressures have densities comparable to liquids, and that the "real difference" between the gas and liquid phases is that... they're different phases. Gases at very high pressures are above the critical point of the liquid-gas phase transition. In this regime you can go from "liquid" to "gas" without a phase transition, so in this regime they are not distincly separate phases. You can even go from liquid to gas at normal temperature and pressure without a phase transition by increasing the pressure beyond the critical point, raising the temperature, and then lowering the pressure. The liquid-gas phase transition doesn't cause any symmetry breaking, so it's not an "interesting" phase transition. The order parameter that properly distinguishes the two phases is density; that's the only thing that's really changing between the two phases.
Also, I think it's confusing to say that there are bonds between the molecules making up a liquid. There may be temporary bonds, to an extent, but there are not bonds in the sense that the molecules in a solid are connected by bonds.
Also, gases in the normal environment *do* expand to fill their containers, even if there is other gas present. However, if there are two gases in a container and one is more dense, the two will separate, to an extent. But if you took two bottles of oxygen and "tagged" the molecules A and B and then combined the gases, both would fill the container they were sharing equally.
Of course, liquids in a liquid evironment are going to do the same thing, and to say that anything doesn't fill its container is disingenous. That's why liquids have vapor pressures.
Judson Powers <email@example.com>
USA - Thursday, October 13, 2005 at 23:53:53 (PDT)
Seven colours in the rainbow. To find out what ACTUALLY happened, we should
have a look at what Netwon has to say about the matter. Specifically, the place
to look is in Newton's "Optics", Book 0ne, Part II, Proposition III, Problem I.
There, he mentions that the reason for the seven colors of the rainbow is analogy
to the seven notes of the musical scale. To back up this claim, Newton makes an
interesting experiment. He says that he had "an Assistant, whose eyes for
distinguishing colours were more critical than mine" look at the spectrum cast by
a prism and mark out the the boundaries between colors. Then Newton measured the
distances of these boundary lines points and found out that they were "divided after
the manner of a musical chord", i.e. they were laid out in nearly the same
proportions as the frets on a stringed instrument.
Form this description, it seems clear to me that the reason for Newton wanting to
have a seventh colour was not wanting to be consonant with religious authority, but
consonant with Pythagoras. Given that he rejected the Trinity, Newton was not
very likely to pay much heed to religious authority in such a minor matter as
the number 6 vs. 7. (By the way, the arguments about 7 orifices, 7 days, and
the like were arguments that were leveled against Galileo, not against Newton.)
However, Newton, like Kepler, Leibniz, and other seventeenth-century scientists,
had an extremely high regard for Pythagoras, even to the extent of believing that
many of his discoveries were actually rediscoveries of facts known to Pythagoras.
For instance, in his essay "The Pipes of Pan", Newton argues that the
Pythagoreans actually knew the inverse square law of gravitation!! Therefore,
Newton must have found it very comforting that there was a mathematical analogy
between the seven colors of and the seven musical tones.
It might also be pointed out that this point of view about the seven colours is
actually in rather good agreement with modern understanding. If one could
somehow slow down the frequency of light waves by several orders of magnitude
and convert them into sound waves, we would find that the range of visible light
indeed corresponds to an octave and that the different colors do correspond to the
different notes of the musical scale. One might object that this is merely a
lucky guess because Newton believed that light was a stream of particles,
not a wave. But recall that Newton also believed that his corpuscles of light
came with characteristic vibrational frequncies which depended on their colour.
In book two, part 3, when Newton dicusses interference by thin films, he bases
his explanation on a theory of "Fits of refraction and reflection". That is to
say, he assume that his corpuscles undergo some sort of an oscillation and that,
if they should encounter a srface during a certain part of the oscillation, they
are more prone to be reflected off the surface whilst, if they encounter the
surface during other parts of the oscillation, they are more prone to be refracted.
Furthermore, to explain the differnt colors of "Newton's rings", he
assumes that the frequency of these vibrations is related to the colour of the
light. Hence, it is more than pure luck that Newton was right about the
analogy between colours and notes.
(Aside: Some people see Newton's idea of fits of reflection and refraction as a
rather contrived scheme to accomodate wave-like behaviour in a corpuscular theory
but, to me, this idea seems rather natural. If one tries to visualize a
corpuscle, the usual picture would be of tiny spheres of whatever stuff light
is made out of. It is natural that the stuff would have some elastic properties
(In fact, Hyghens makes a point of discussing the fact that EVERY known substance
has elastic properties.) hence a sphere of that stuff would vibrate at a
certain frequency which depends on the elastic properties of the substance, its
density, and the size of the sphere. One could easily enough envision a mechanical
model of Newton's fits of refraction and reflection. For instance, suppose that
the surface of an interface is some sort of screen with tiny holes through which
the corpuscles pass. During that phase of the oscillation where the corpuscles
have the smallest radius, they would easiest pass through the screen, hence "fit of
refraction" whilst, during the phase of the refraction where they have the greatest
radius, they are most likely to bump into the screen and bounce off of it, hence
"fit of reflection".)
Putting too much emphasis on Newton's seven colors in teaching elementary optics
can actually obscure Newton's contribution. Before Newton, it was generally
assumed that there only were a finite number of discrete colors. Aristotle
taught that all colors were actually combinations of black an white. When
Renaissance artists started to mix colours (before then, mixing colours was
frowned upon as adulteration) it became apparent that this was not the case.
(In fact, as a young man, Newton made the experiment of mixing black and white
paint but, no matter how hard he tried, all he could produce were different shades
of gray, not colours.) Based on this, seventeenth century opticians advanced
theories in which light was made out of several primary colours. What amazed the
scientific community about Newton's theory when it first came out was that it
claimed there were actually a continuous infinity of primary colours.
Therefore, I think that the right way to teach Newton's seven colours is as Newton
himself did it --- as analogy to the different notes of the musical scale. Just as
one can vary the pitch of a note continuously, so too one can vary the colour of a
light beam continousously. Just as the ear tends to hear this infinity of pitches
in terms of a few notes, so too the eye regards the infinity of frequencies in
terms of a few colours. A frequency of 256 cycles per second is the note "middle
C". If one plays a slightly lower frequency, say 250 c.p.s., that is also heard as
the note C, but a bit flat. If one plays a pitch of 260 c.p.s., it will be
percieved as a slightly sharp middle C. As one raises the pitch, one gets to an
in-between pitch which could be described either as C sharp or D flat. Raising
the pitch more, it becomes a D. Likewise, a certain frequency will give one a
yellow light. Lowering the frequency a bit, it wil still look yellow, but a
slightly reddish shade of yellow. Raising it a bit will yield a different shade
of yellow. Raising the frequency even more will give rise to yellow-green, and
eventually to green. Taught this way, there is no danger of falling into the
trap that rainbows consist of exactly seven (or whatever other number) of
distinct bands of colour any more than one could fall into the trap that a
stringed instrument can only produce the notes of the scale and no others. (If
this were the case, piano tuners would be unnnecesary.) Rather, nature presents
us with a continuum, but we percieve it in terms of several discrete bands.
Raymond Puzio <puzio"one""at".excite"dot"com>
Passaic, NJ USA - Friday, October 07, 2005 at 17:00:06 (PDT)
I was looking for something else and ran into your site. Fascinating. But I disagree with your statements on wings and flight. The books do have it right. Or more correct than your version. Angle of attack is very important and a symetrical shape can produce lift. But your statment that a wing cannot produce lift without deflecting air down is wrong. And using F=Ma is inappropriate in this context. A wing generates lift not by deflecting air. Infact, that deflected air usually creates drag which decreases an aircrafts chance at flight. The early aircraft designs that tried to use the F=Ma foundations never left the ground. The wing shape creates low pressure above the wing which then pulls the wing up. Yes it is a simplistic version of the system, but this is the bernoulli model. Instead of looking at the air as racing to catch up as it crosses the wing lets use the model that really lets planes fly. We are not in a wind tunnel today. The air is dead calm and the plane rolls down the runway. In a frictionless world, the wing pushes the air molecules out of its way. It splits them, sending some up. These molecules merely move up and down. No wind, the air is not moving, its the wing. So two molecules that we aligned vertically before the wing separates them, end up aligned vertically after the wing passes through. Now since the top molecule had to move it has gained kinetic energy. If we look at the system as a closed system, the sum of the kinetic energy and the potential energy must remain constant. If the molecules gain kinetic energy, then they must lose potential energy (air pressure). So the air pressure drops. The drop in air pressure creates an imbalance with the higher pressure below the wing which accelerates the wing vertically. Want a static proof. Look at wind over a roof. The roof is deflecting the air up. So by F=Ma, the shingles should be driven down firmly into your roof. But as we know, the wind will lift the shingle up, and it is not from cracks that the wind gets under. Look at the super dome in New Orleans.
Russell Jack <firstname.lastname@example.org>
Houston, Tx USA - Friday, September 30, 2005 at 13:59:19 (PDT)
With regrads to your comments in the "ELECTRONS IN WIRES JUMP FROM ATOM TO ATOM DURING A CURRENT" is mostly right. However there
is a case where electrons do jump from atom to atom during a current.
With Semiconductors electrons do jump from atom to atom.
[Nope, sorry. In semiconductors the electrons are jumping all the time, and not just during a current. In other words, the semiconductor doesn't turn into an insulator as the current goes to zero.-billb]
David Formosa <email@example.com>
Sydney, NSW AUS - Monday, September 26, 2005 at 06:34:03 (PDT)
I love all the misconceptions that you have gathered and put in one place. I didn't notice any on the topic of waves. I'm sure there are some....any thoughts?
Nancy Easterly <firstname.lastname@example.org>
Houston, TX USA - Thursday, September 01, 2005 at 05:14:39 (PDT)
Speaking as a junior high student, I know firsthand how inaccurate many textbooks are. It's especially bad when the teacher has no experience in the subject either. At least 120 12-year-old kids are taking their confused version as unquestionable fact. Our system doesn't teach enough and what it does is apocryphal. A suggestion to textbook authors- offer one candy bar or equivalent for every error a student catches. This work very well on math books. I know of one person who went through 32 cases of Snickers on one calculus textbook.
Moscow, ID USA - Monday, August 29, 2005 at 12:26:02 (PDT)
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!
USA - Thursday, July 28, 2005 at 15:32:18 (PDT)
A simple observation.
In the article GRAVITY IN SPACE IS ZERO? you state that, "You'd only weigh about fifteen percent less than you do on the ground. While 300 miles out in space, a 115lb person would weigh about 100lb."
The only problem I see in this statement is that fifteen percent less than 115lb is not 100lb, but 97.75lb.
[ Fifteen percent less than 115 lbs is ABOUT 100 lbs. It's not very fair to change my words and then criticize the altered version. -billb ]
Thank you for your page.
Guadalajara, JAL MEXICO - Wednesday, July 06, 2005 at 11:57:34 (PDT)
I am writing a science workbook in which I am encouraging students to think critically about scientific theories. I would like to use some of your information, but do not wnt to break any copyright laws. I would very much like to use two or three of your writings in their entirity and give you credit. May I have your permission to do so?
San Antonio, TX USA - Saturday, July 02, 2005 at 13:22:43 (PDT)
The analysis of air being blue is completely incorrect. Air is not blue. The "color" of a gas is determined by absorbed and transmitted light, which are processes completely different than Rayleigh scattering.
[Nope. Color has many causes: absorption as with dyes, interference as with interference filters, and scattering as with smoke and aerogel. But further, color is a property perceived by humans and created by human retinas and minds response to incoming light. Regardless of the physical mechanism, if blue light comes from an object illuminated with white light, then we say that the object is "colored blue." Aerogel is blue/white in color. So are opals. So are thick layers of gas. If I look at a gas and see blue, then the color of the gas is blue. That's what the word "color" means. The spectral distribution of the light striking the retina is critical, while the details of the physics which produced that distribution are irrelevant, because if it looks blue, it really is blue. Your reasoning is also wrong because, in order to be consistent, we'd have to say that interference coatings and blue-jay feathers and Morpho butterfly wings are NOT COLORED. After all, interference coatings and morpho wings and bluejay feathers are entirely made of transparent materials, and their perceived colors are created by wave interference rather than by dyes. Bluejays are blue, yet there are no blue dyes in their feathers at all. Air is analogous: when air is lit from the side, the air is colored blue, even though the color is created by wave mechanics rather than by resonant absorption. (And of course air is also red/orange, as during a sunset. The color of air varies with viewing angle. Hmmm. Perhaps you would say that, if the color of an object will change in proportion to angle, then the color is not real?) Finally, if we say that the sky is blue, well, what exactly is "the sky?" There is no solid "sky surface" up there; the only thing above is is a layer of air. Since "the sky" is an illusion, we're forced to connect the blue color with "the atmosphere" or to "the air." -billb ]
Your statement that "air is blue" is a gross oversimplification. If the scientific explanation for something is too complicated, I see no reason why you can't simply say that instead of offering a completely incorrect explanation.
[ Why is the sky blue? Whenver someone says that a concept is too complicated to be explained without math, I become extremely skeptical. Usually they mean this: "I've not bothered to spend the time and the careful thinking necessary to come up with a simple explanation." Either that, or they assume that a simple explanation is trivial to create, and they could produce a good one if they bothered. In reality, math can be a crutch which prevents understanding of physics, and simple explanations are "simple" only in hindsight. Einstein said "You do not really understand something unless you can explain it to your grandmother" Give it a try yourself. Try to explain advanced concepts to the general public. If you can do a good job, then post your efforts on a website and I'll link to them. - billb]
Rob Cook <email@example.com>
Stanford, CA USA - Monday, June 20, 2005 at 13:24:48 (PDT)
Under the misconceptions about heat, I am unsure if heat does actually rise or not? Could you please send me some information on this topic to clear up my misconceptions? I plan to be an elementary teacher and would like to know the correct answer to provide students when asked? [Actually, warmer air is less dense than cooler air, so warmer air rises and cooler air falls. - billb]
Christa Tandle <CTandle@mail.keuka.edu>
Waterloo, NY USA - Monday, June 13, 2005 at 10:52:58 (PDT)
Here's a simple demonstration of an airfoil. Turn on a faucet so that the water forms a steady hard stream (this is our 'airflow'). Now loosely hold the handle end of a spoon between your thumb and index finger letting the other end dangle downwards (the back of the spoon is our 'wing'). Now gently move the spoon towards the water flow until the back of the spoon makes contact with water. At this point, you will feel a definite and surprisingly strong pull on the spoon. The force will pull the spoon into the stream and part way through it -- a good portion of the spoon will end up completely on the other side of the initial water flow. You can see how the direction of the water flow follows the shape of the spoon and leaves the spoon in the same direction as the trailing edge. I definitely recommend that you try this.
Glenn C. Rhoads <rhoads at paul dot rutgers dot edu>
Highland Park, NJ USA - Thursday, May 26, 2005 at 13:40:06 (PDT)
Thanks, great informative site. I particularly liked your explanation of transistors, I have felt the same way you did, that no one ever clearly explains how they work and we are meant to just accept their mathematical descriptions. In fact I feel that way about alot of subjects in that same area, having to do with quantum physics or electronics.
Urbana-Champaign, IL USA - Tuesday, May 17, 2005 at 19:53:12 (PDT)
I am a science teacher in the UK, and you have made it very clear that I need to go back to school! My understanding of Physics is clearly not up to the job.
UK - Sunday, May 01, 2005 at 06:31:42 (PDT)
If the air is tinted blue as you claim
then distant clouds should appear bluer
than nearby clouds.
[Sunlit clouds are too bright, so I doubt you can see the dim blue light added by the air in front of them. On the other hand, a distant dark object should look far more blue than a nearby dark object ...such as distant forested hills in shadow. - billb]
cyber_rigger <cyber_riggerAT yahoo DOT com>
USA - Monday, April 25, 2005 at 07:15:16 (PDT)
very intresting reading, as for those seeking the circuits for the herf guns ive collected them before and they can be found in the electronics lab site , in the forums and as for the electromagnetic levitation, stuff theres circuits for that to there,
perth, w.a australia - Saturday, April 23, 2005 at 08:30:38 (PDT)
Are these misconceptions general? Or did you conduct some kind of survey to find out these misconceptions. I'm just wondering. If you could send me an e-mail that would be nice. Thank you.
[ I found these misconceptions in grade-school textbooks and in children's science reference books. Because I was looking for widespread misconceptions, I only recorded the ones which appeared in several different books. - billb]
Glen Rock, NJ USA - Monday, April 18, 2005 at 04:58:08 (PDT)
My comment has to do more with scientific philosophy than science. I recently had a little debate with the editors of Discover magazine over the concept of infinity. I was responding to a quote in the magazine over the difference between science and the unfathomable. I put infinity in the unfathomable category. They responded that infinity was an accepted mathematical concept and that it was used in science. My contention is that just because infinity is accepted in mathematics and "used" in science does not make it a verifiable concept. No one has ever verified an infinite value of any scientific parameter. A simple equation like f=ma allows for an infinte mass and infinite acceleration, but have infinite masses and infinite accelerations ever been measured? When Riemann spaces came on the scene, the door was opened for spaces that do not naturally extend to infinity in nature. Hence, verifying infinity may not be either necessary or possible. I suggest that we leave infinity in the unfathomable category. Any thoughts?
[ How about Xeno's paradox and continuous space: I can divide the space between my fingers into an infinite number of slices. Or I can move my fingers to an infinite number of different positions. Unless space itself is discontinuous, that is. The concept of infinity is not just associated with discussions of "no upper limit." It's also connected with smoothly continuous values and the number of tickmarks you can put on a ruler. - billb]
Scott Jackson <firstname.lastname@example.org>
Irvine, CA USA - Saturday, April 02, 2005 at 14:25:09 (PST)
my thoughts of causes of flight....as an airfoil moves through the air, the air hitting the leading edge of the wing is thrust/ramped up into the airstream above, creating a zone of high pressure. This high pressure zone rides over the now "low pressure" zone right above the wing, created by the absence of the air that got pushed up at the leading edge in the first place.(The airflow beneath the leading edge is largely undisturbed and parallel,per smoke stream photos) As shown by the various wing gradient pressure charts seen at (and ignored) other sections of this site, a substantial difference in pressure is created, attracting the air below the wing and the wing itself upward. The high pressure zone above the low pressure also flows to the low pressure area, but by the time it arrives, the wing(and the plane) has allready flown past, so this air continues.....in the downward direction that is frequently discussed.This is the downward airflow that occurs, having little to do with direct deflection from air contacting bottom of wing.
There is,however,a net deflection of air from the total body of the aircraft passing
through the air, similar to the waves of water thrust aside when a boat trasvels through the water, or
an 18 wheeler throwing about vast amounts of air as it tunnels through the air, at "super hi-way" speeds.
THis outward blast can be easier seen during a light mist or drizzle, and on dry days
can be seen by the violent disruption of the grass on the side of the road just as the front of the truck passes.
The causes of trailing wake vortices? Well, the normal pressured air below wing, in trying to get to the highly low
pressure air above, has only one direction it can go, and thats up and around the end of the wingtip. It
cant go up and around the front, blocked by the oncoming airstream. It cant come from up behind
the wing, that way is blocked from the air stram from the hi pressure area present on top of the
wing. So that leaves the wingtips. And ,as the lo pressure(and the wing, and the plane) has flown by
before this incoming airstream gets there, this stream flows in, from outside to inside, thereby
creating the circular wake vortice streaming back from the wingtips.Of course, there is also the "surfing"
/planeing of the wings through through the aerial medium that also contributes to lift,
but the vast majority of the work is done by this "magic" that occurs above the wing.
Any other flow of air other than that at the leading edge is a waste product(like the water exiting out
the bottom of a hydroelectric dam,after the turbines have been turned by the incoming water, the outgoing water
flow is now something to get rid of, as its usefullness is done), as the majority of the work has been done.
Wing shaping is critical to successful wing design and performance, as shown by the research performed by the early architects of flight,
and hundreds of variations of wing shapes and lift performance tabulated by NACA. As promised, this link...
has a section (AERIAL DEMONSTRATIONS)where a USAF manual depicting pilot operations during air show demos, answering the question
of how planes fly upside down (by addition of either rudder or elevator input, depending on attitude
of the aircraft at the time.
I dont believe the assertion that wings, propellers, and helicopter
blades operate the same. It seems that they operate
in two separate modes. Props and especially helicopter blades are
oriented at 10-30 degrees in order to
fling air backwards, creating thrust. No airplane wing has an angle on
incidence that would support deflection
as the main source of lift.In fact, most aircraft wings stall at this
angle of attack.
If water seeks its own level, then why would the water level increase world wide as the polar ice cap melts? An ice cube in a glass of water, doesn't raise the level inside the glass as the ice melts.
Ron Seto <email@example.com>
Vancleave, Ms USA - Sunday, March 27, 2005 at 12:03:50 (PST)
This is GREAT!!! I'm going to give this site to everyone i know. It'll make 'em flip out.... hehehe.......
Yo Momma <firstname.lastname@example.org................................>
nowheresville, arbitrary cambodia - Thursday, March 24, 2005 at 20:10:44 (PST)
I only just found this site but it looks pretty good. It is pretty in depth and I will consider using a link on my own web site once I spend some more time on your site. I look forward to that. Mike Stahl (www.respectfulempiricist.com)
Mike Stahl <email@example.com>
Towson, MD USA - Wednesday, March 23, 2005 at 07:56:50 (PST)
What sets some people apart from others in understanding science questions is often that the details have been "mulled over" for some time, that is, they have been allowed to be digested or to sink into the ol' noggin. Youngsters frequently are put under pressure to perform in the classroom or in public and even an adult would find the process of learning under these circumstances to be difficult. Thinking about puzzling concepts in the quiet of one's own thoughts is how science is learned. I sometimes want to shout this from the rooftops. AVC
Tehachapi, CA USA - Tuesday, March 22, 2005 at 14:45:30 (PST)
Your article about why the sky is blue is intriguing, but nevertheless erroneous. In the article you state, "Each molecule of air behaves like a bluish-looking mote of dust." Molecules of "air" do not exist. Air is a mixture. A container of air will have molecules of oxygen, nitrogen, carbon dioxide, etc. So which molecule exactly are you saying is blue [ Yes, that's right: a molecule of nitrogen gas scatters blue light and appears bluish, and so does a lone oxygen molecule. The skies of Mars, heavy in CO2, are also blue. In other words, "air molecules" look blue regardless of which type they are. Only a molecule with a resonance frequency near the visible band will appear otherwise. - billb] or is blue some magical property of the mixture of different molecules. If your argument is correct why don't astronauts in space see a bright blue halo effect around the earth. When they look past the earth, but near the edge of its disk, they are actually looking through twice the thickness of atmosphere that we normally look through. So why don't they see blue?
[They don't?!! Perhaps you aren't familiar with all those photos taken by shuttle astronauts. Try these: Astronomy Picture of the Day: Moonrise - Spacewalk, Spacewalk 2 - billb]
Marvin Champion <mchampatmemberdotafadotorg>
Warner Robins, GA USA - Tuesday, March 22, 2005 at 13:49:24 (PST)
With regards to sound traveling better in liquids/solid than air: This is more of a question than an argument (ok it is both realy). I know (or at least I am fairly confident) that explosions (sound/shockwaves) are more intense underwater. For example, unless my Naval training was wrong, the relative power of an underwater explosion can be as much as 4-10 times stronger than the same explosion above water. I have witnessed such examples but do not rule out that there could be any number of influential variables that I do not recognize or fully understand. My gutt says that the reasoning is in the density of the propogating material providing much more contact with the surface of the material receiving the damage than there would be contact between air and receiving object. I look forward to any comments as I am simply a curious person and not a scientist. Note on my background: I was an ETRO in the Navy (Electronics Tech/Reactor Operator) however, having been Enlisted rather than an Officer I recognize that most of my Heat Tranfer/Fluid Flow, Electronics, and Nuclear Chemistry training are strongly skewed toward usefullness to my job rather than deep scientific understanding at the mathematical level. Cheers, Scot
Scot <scot (at) scot gabriel . com>
Joplin, mo USA - Tuesday, March 22, 2005 at 09:01:57 (PST)
A line from one of Shakespeare's sonnets (#66) may well sum up most of the difficulty: "And simple truth miscalled simplicity". The simple truth is that both the laws of conservation of mass and momentum must be observed. Air does not magically appear or disappear above or below the wing to result in a difference in airflow in the real world outside of the artificial constraints imposed within wind tunnels and forces created in the airfoil must be balanced by equal and opposite motion generated in the air. Any Bernoulli Effect that occurs results in slowing down as well as the more generally recognized speeding up of flow over curvatures in the airfoil surfaces and it generates a twisting force on it rather than lift. The reaction to this in the air is some creation of vortices at the trailing edge and this is normally not a good thing. More important than these unending controversies and all but unknown universally is the tremendous mass weight of air in quantity, adding up to many hundreds of tons in hardly any space at all. Aircraft are flying through a thick soup that is no less weighty for its invisibility. The same applies to the creation of energy from wind turbines, which must be built strong to accept the forces imposed on them from even light winds. It is a good exercise for homework to calculate just how heavy air is ( despite its buoyancy ) in ordinary spaces from its density of about one and a quarter ounces per cubic foot. Thanks for providing this forum for everyone's benefit in learning about some of these realities of creation as it exists.
Anthony Chessick <see www.integenercom>
Tehachapi, CA USA - Tuesday, March 22, 2005 at 07:01:11 (PST)
People who have not "mulled over" Science questions should be disqualified from making any comments about them. I am thinking about the Bernoulli principle as it relates to aerodynamic lift. Many don't even know how the Bernoulli principle works in the first place. It takes some mulling over, you know. The other thing that needs mulling over is the weight of ordinary air as it helps create lift. One million cubic feet of air has a mass weight of 38 tons!!!!!!! This is the air contained in a box only 100 feet on a side or just an envelope surrounding a medium sized aircraft. 38 tons!!!! Just ordinary air!!!!!!!! It takes lots of mulling to come to the realization that air is very, very heavy in large quantities and it doesn't fall because it is buoyant!!!!!!! No wonder that aircraft can find support in this medium, whether or not any of the various lift theories are correct!!!!!!!!
Anthony Chessick <integener at inreach.com>
Tehachapi, CA USA - Monday, March 21, 2005 at 21:07:06 (PST)
n/0 is undefined. Defining it as infinity leads to paradoxes. See this page in the wikipedia for enough paradoxes to float your boat. http://en.wikipedia.org/wiki/Division_by_zero
[Thanks for that link! But if you read "Limits and division by zero" in that entry, you'll find no paradox. They say that 0/0 is undefined, not that, say 2/0 is undefined. -billb]
I certainly enjoy your site, and I find your attitude towards
authority a healthy and useful one, but oversimplification will often
produce faulty logic. Your problem with the definition of science and the
scientific method, the latter of which applies to natural science only,
undermines your approach. Your attitude towards grammar and spelling are
not particularly useful either, not because those are essential to
understanding, but because too much license is usually taken in the
process. On the best day, it is difficult to express scientific
information with precision, outside of mathematical equations, as you have
noted in your personal reformulation of your understanding of electricity.
Using imprecise language and spelling and grammar just contribute to the
confusion. They may not be intrinsic to the meaning, but ignoring and
perpetuating such errors when you are aware of them is not laziness, but
deliberate contribution to the sea of confusion that already threatens to
drown us. Everything I read here tells me that is not your intention, but
we all know how that contributes to the paving business.
Now, let us discuss your odd attitude toward the scientific method. You
casually toss off several "examples" that purport to defeat the basic
definition of the scientific method as you state it. Those casual
thoughts do not hold up to close examination.
Having read your main misconceptions page, I'd say that you may have
created as many confusions as you have resolved.
[ But you don't say what they are! -billb]
Only a few of your
points are clear winners. The rest would probably do as well unsaid, as
they appear to be alternate simplifications as lacking in rigor as the
recent news said that a star was cast out of the center of the milkyway and that it was going faster than light speed now from what they said it the star was traviling at 1.5 million mph. now did the star leave the center of milkyway the other day or did it happen years ago also why did it not get larger as too speed and time there is a problim in the math.
monte robinson <firstname.lastname@example.org>
santee, ca USA - Tuesday, March 08, 2005 at 17:42:52 (PST)
First,your website(s) are awesome. For me they take the place of Scientific American's Amateur Scientist column, which I grew up with but which no longer exists. I have a few comments to this page:
1. Regarding the burning of a candle to show that CO2 is consumed: I've done this with my kids, and I'm reasonably sure air didn't leak out the bottom. My theory was that, since CO2 is highly soluble in water, it is rapidly removed through the water, and therefore the experiment might have a smidgen of validity.
2. An experiment I saw in FIRST GRADE (35 years ago...) didn't make sense then, and it still doesn't: two balloons of equal size were suspended from opposite ends of a stick, balanced. If you pop one, the system is unbalanced, and the deflated balloon goes up. This was supposed to demonstrate that air does have "weight." The problem is that as long as you're in the atmosphere, the balloons are isobuoyant, and it shouldn't make any difference whether or not one is inflated. The only reason it seems to work is that the weight of the popped balloon is redistributed across the lever.
3. The peanut butter jar barometer: A balloon stretched across a jar, with a straw sticking out sideways, is often used as a basic barometer for kids learning about weather. Most of my kids had to make one. The problem is that temperature changes also cause the air inside to expand and contract (my kids actually had explicit instructions to place them outside). The end of the straw moves a couple of centimeters, and the kids think the pressure has changed. I kept one at (approx.) constant temperature, and it did work, when compared to reported barometric pressure, but the change was TINY - about 2mm at the end of a 9 inch straw. Any comments?
David E. Hunt <talidavid@TTTTTTTearthlink.net>
Quote "Because the flowing air adheres to the TOP of the wing, the tilt of the wing also causes the upper surface of the wing to pull downwards upon the air above it. The air ABOVE the wing moves down and the wing is forced upwards."
I want you to explain a general approach illustrating air being "pulled". I can not imagine air being pulled; like a sickly ball of cotton candy tugged by a child from a parent. I can imagine air being pushed (entrained) by other surrounding air.
David Anderson has no idea how wings work, and my review on Amazon attempts to explain why.
Ug its Me <email@example.com>
A comment on your explanation of why lakes and seas appear
blue. Basically I disagree with your explanation.
It is true to say that water absorbs longer wavelengths better
than short and hence white light transmitted through water appears blue (
ask a SCUBA dver what colour every thing looks at 30 metres ) but the
overwhelming majority of light visible from the surface of the sea is
1) There are no light sources below the water The only light
source is the sky ( and surrounding scenery ).
2) The sea does NOT look blue on a cloudy grey day it looks GREY. Go out
and look if you don't believe me.
3) A significant amount of light is absorbed by the ocean - water
is transparent after all ( even allowing for surface reflections )- so
the water appears to be the same colour as the sky but darker.
4)( The clincher ) If you are lucky enough to find a perfectly
calm lake then you will observe a perfect reflection in it of the sky and
surrounding scenery WHICH INCLUDES ALL OF THE COLOURS PRESENT PERFECTLY
There are minor points involving the polarisation of light which produces uneven darkening in places but this is not relevent.
In conclusion water "is" blue but this is NOT the reason why lakes and oceans appear blue. THEY PREDOMINANTLY REFLECT THE SKY.
My work is related to a particular science curriculum, which is based on students "doing science." While a lot of it follows the scientific method which you comment on, I think very importantly it begins with "observation," which you seem to support. Students observe...something, whether it's a flame, a piece of ice, a field of grass...and they try to notice something that they want to explore further. Then, they go from there to ask a question, develop a hypothesis or an idea, and test that through an experiment. It seems to work very well, and allows the kids to learn a lot of information as well as science process. So, I agree with you, methods of science do go beyond what traditionally has been taught, but you have to start somewhere, and don't a lot of innovations come through trying things out: experimentation of a sort?
[ If books explained the "methods of science," then the NSTA wouldn't have turned against scientific method in favor of teaching the "nature of science. If they avoided listing "The Scientific Method," then the scientists linked on my site wouldn't be complaining. Or if the books listed the simple series of steps always performed by physics researchers (and to a lesser extent Chemists and Biologists,) then there would be little confusion. Instead the books try to turn these methods into a requirement for all scientists, turning it into a definition of Science, a short list of unquestionable rules written in gothic capital letters, The Scientific Method, where Thou Shalt Perform Experiments, (and if you don't perform experiments, then you're not doing science.) But that's just wrong, because science is not physics, and there is no simple list, no Scientific Method which applies to all sciences. The various "methods of science" exist. But if there is no Scientific Method, doesn't this make it very hard to define what Science is? Yes. That's the actual situation: Science is very hard to define, whole books have been written about the problem. Grade school teachers are put in a bad situation if they're expected to explain what science is. Top minds in science and philosophy have failed, and the topic is controversial. Ah, I see an analogy: telling kids that all scientists always follow The Scientific Method is much like telling them that electrons in an atom orbit the nucleus just like planets orbit a sun. This isn't a misconception as long as we make clear that REAL electrons behave quite differently (just as real scientists often do things very differently than the list of steps in The Scientific Method.) -billb]
Mark J. Smith, MA <firstname.lastname@example.org>
Albuquerque, NM USA - Wednesday, January 19, 2005 at 09:53:56 (PST)
Can you tell me why Einsein's equation is mc^2 and not (mc^2)/2. I understand that (mv^2)/2 is the normal relation for kinetic energhy of motion. and it would appear that the particles emitted in nuclear reacion leave at the volocity of light.
Leonard Greiner <email@example.com>
Santa Ana, CA USA - Monday, January 10, 2005 at 08:54:35 (PST)
Despite what your physics teacher would tell you, weight and mass *are* one and the same. The confusion lies with the extraordinarily poor choice of term chosen by scientists/physicists to describe the pull of the earth or other body on an object. They chose "weight", and they shouldn't have since that term was already in use.
One thousand years ago and earlier, merchants and laypeople would use balance scales to 'weigh' objects by comparing the 'weight' of the object against the 'weight' of other objects. Since they were using balance scales it is an undeniable fact that our millennial ancestors were measuring what is now referred to as mass, except they called it "weight" (the word "mass" didn't exist yet in English). If you were to send an ancient merchant to the moon with his scales he would conclude that objects weighed the same on the moon as on Earth (although he would of course notice that the pull of the moon on the object was substantially less than that of the Earth). Then along came Science. Somewhere along the way 'weight' became known as 'mass'. Then the definition of weight, according to physics, along with the units that measure it, became a force, something it had theretofore never been. And how could it have? The tools to measure forces were created by science itself - force-based spring scales simply did not exist one thousand years ago! So, weight according to its "scientific" definition was not even measurable despite the fact that the term had been in use for centuries.
Conclusion: weight = mass and physics needs to come up with a term for the pull of a large body on an object that doesn't contradict over a millennium of common usage. I suggest 'pull' - the pull of the Earth on an object is X newtons or Y poundals (not pounds since those are a unit of mass).