Bad Science

Bad Science - what they taught me in school about science and why it was not true. These are some of my personal pet peeves and how they actually impeded my understanding of science as a youngster. There are also a number of preposterous claims by advertisers, developers, and others.

I will entertain email offering corrections to the material here. I appreciate having my mistakes corrected. However, don't be disappointed if your only argument is "it doesn't seem right" or "I know it's wrong." Unless the mistake is obvious, please help me by providing some detail or a reference. Thanks.

Sound does not travel in straight lines and light does

You may have seen this in a textbook. It is the kind of thing that drove Richard Feynman nearly mad when he was asked to be on a textbook commission for California schools.

The argument goes like this. There is a streetlamp around the corner. You can't see it until you move so that the corner is not along a straight line between you and the lamp. Your friend stands around the corner and talks to you. You can still hear your friend. Therefore, light travels in straight lines and sound does not.

First, all of this is incorrect. Second, there are several things wrong about the reasoning.

So, even though sound is a mechanical wave and light is an electromagnetic wave, they both have several rules of propagation in common. Traveling in straight lines (except for reflection, scatter, refraction, and diffraction) is one of them. Now light is also bent by gravity. This observation led Einstein to say that light travels in the shortest distance between two points (the shortest time, really - work it out with refraction and you'll see it's true) so that space must be warped in a gravitational field. That's why light seems to move in a curved path, but really it's just space that's warped. This to me is like the 0g thing. It depends on where you want to stand and make your observation. If you want to stand on the earth and look at star light as it passes near the sun, and say that the sun warped space so that the star light looks like it did not go straight, and then your law about the shortest time between two points holds, so be it. You can look at the same situation in an equivalent way without warped space and get the same answers.

Heat can not be transmitted through a vacuum

This is the way that it is taught that a Thermos bottle (Dewar if you are English) works. Supposedly, heat can not travel through a vacuum and therefore the bottle is a perfect insulator. Ever wonder how the sun warms us then? Actually there are three ways that heat travels:

The vacuum bottle pretty much eliminates 1 and 2, but what about 3? Well, you could eliminate radiation if you could get your emissivity to zero. An approximation to this for room temperatures occurs with something highly reflective in the infrared, such as gold or silver or aluminum. That is why the thermos bottle usually has a silvery coating on the glass.

Plants breathe in carbon dioxide and breathe out oxygen

A lot of you probably know this: plants use oxygen to breathe just as animals do. That is how they consume food and grow and so forth just like animals. So what's this about carbon dioxide? Plants make carbon dioxide just like animals. Hold on. What's going on here?

Well, in sunlight, plants which contain chlorophyll can make lots more oxygen than they use, and can consume lots more carbon dioxide than they make. This is really good or else carbon based life would be in trouble - at least the aerobic stuff. But plants kept out of sunlight go right on consuming oxygen. That is why plants are usually a bad idea in a hospital room. That is why algal blooms (sudden growths of algae) can kill all the fish - they take all the oxygen.

So if you average over all plants over all seasons, you get a net increase in oxygen and a net consumption of carbon dioxide, but remember, that is the simply story and you might get surprising results in a specific situation.

How a laser works

They usually tell about how light can be amplified by a gain medium. This is a material which has been pumped into an upper energy state such that there are more molecules (or atoms or electrons as the case may be) in a upper state than in an immediately lower state. The molecules coming down to the lower state give off energy in the form of photons, adding to the light wave. Normally, this happens spontaneously, but in a laser, the timing is arranged so that a lot of it is stimulated emission. That is, a photon of the same energy comes along and coerces the molecule into releasing a photon. If there is enough gain medium, you get amplified stimulate emission, or ASE. This used to be called super fluorescence, but it was decided that this may have been misleading, so now it is called ASE. Well, everything is pretty much what they told you, but how do you get a laser?

Well, you add enough reflectors to get the been to trace the same path over and over. Two mirrors would allow the beam to go back and forth in a line. More mirrors could be used for a crooked line or a ring. The alpha laser resonator that I have analyzed over the years is quite a bit more complicated, but it is all for the same thing. To get those photons to keep going through the gain medium, sweeping up all available photons.

They told you this before, but how does the beam get out? They told you that the beam gets strong enough to break through one of the mirrors and come out. How silly! One of the mirrors either has a hole in it or is partially reflective so that some light leaks through on every pass. As long as more than enough light is reflected back to keep sweeping the photons in the gain medium, the laser works.

How Dolby works

The Dolby literature simplified the explanation for the masses. But simple explanations generally confuse.

The literature says that under conditions of loud high frequencies, the signal is recorded normally and played back normally. When the sound falls below a certain level at high frequencies, the high frequencies are boosted by 10 dB. On playback, the boosted signal is attenuated by 10 dB, and the noise is attenuated as well. All is back to normal, except that the hiss from the tape is reduced.

On playback, how does the Dolby processor know whether the signal was boosted or not?

Well, it does not really work quite like that. The basic Dolby idea is to use a compander. A compander compresses the dynamic range (sort of like riding the gain control) during record, and undoes the gain riding on playback. The way it works is to have a continuously variable gain boost. For example, if the input is 0 dB, no gain is applied. If it is -2 dB, then 1 dB of gain is applied. If it is -10 dB, then 5 dB of gain is applied. All input levels are mapped to new output levels. Now if you signal on playback is -5 dB, you know that it was originally -10 dB, so 5 dB of attenuation is applied. If you encounter -30 dB, then you attenuate 30 dB. It is a continuously variable gain function, not something that switches at 1 dB levels. dbx made such a compander for professional and home use.

Dolby A was set up for professional use. It divided all of the sound into a dozen or so frequency bands and processed each one through a compander. It worked so well, that a cheaper, simpler version was set up for consumer use. Here, only one band would be companded - the high frequencies. The lower frequencies were left untouched. The consumer version was called Dolby B. A somewhat refined version that played with the tape bias level allowed for some additional headroom on tape - something greatly needed by cassettes. This is called Dolby C.

This particular tidbit of information is obsolete. Dolby is concentrating on digital sound now. Anyone under thirty probably thinks this subject is ridiculous.

Fake experiment shows oxygen consumed by fire

You may have seen this: a candle is lit and placed in a pool of water. A glass is inverted and placed over the candle, which continues to burn for a while, and finally goes out. Behold, the level of the water has risen in the glass. You are told that the water replaced the oxygen that was consumed.

Can you figure out what is wrong? Now think about it a moment. The oxygen was consumed? It disappeared? Of course not. Each molecule of oxygen consumed is converted to either two molecules of water vapor or one molecule of carbon dioxide. You probably remember that to a good approximation all gas molecules occupy the same space at room temperature and pressure. This says that probably there should have been too much gas under the glass and it should bubble out, not pull water in. What gives?

As the air is heated, it quickly expands. It continues expanding, even after the glass is brought down over it. Some of the expanded gas escapes unnoticed as bubbles from the glass. When the candle goes out, the gas rapidly cools and takes up less space, pulling up water as it condenses.

A Radiometer demonstrates the principle of photon pressure

Is Alternating Current deadly?

This is what was claimed by company interests as Edison went against Tesla. The direct current users and sellers did not want to change, because of investment in DC equipment that had already been made, so the first thing they thought of was that AC current might be more dangerous than DC. However, AC had the advantage of being easily stepped up to high voltage for transmission through long distances, like the next town over. It could then be easily stepped down for home use near the home.

That AC was inherently more deadly than DC was asserted in trying to prevent switching over, but it did not work. A lot of people were genuinely afraid of alternating current. One thing that might be said is that because of the body's capacitance, alternating current can cause a tingling sensation at much lower voltages than direct current can. Some people can sense relatively low levels of AC current, but this does not in itself create more danger. .

Centrifugal Force

But there is no real centrifugal force. If there were, then it would balance the centripetal force and you would fly off in a straight line instead of going around in a circle.

If you are inside a box mounted on a rotating arm, and you ignore what is really going on, and pretend that the box is not moving, you then "observe" a force pushing you toward the outside edge of the box, that is the edge further from the center of rotation. You you look at this situation from the outside, you can see that your inertia is resisting being forced to go in a spinning circle. In actuality, the box is pushing on you, forcing you toward the center of rotation. But when you are sitting in the box, it feels like some mysterious force pushing you toward the outside edge of the box. Try releasing a stone while you are in this spinning machine. From your point of view it takes off in a strange looping path. But seen from someone outside your box, not spinning, the stone simply goes off in a straight line.

If there were a real force pushing you out and balancing the force pushing you in, you would feel no net force and you would move in a straight line at a constant velocity. It is the unbalanced centripetal force that makes you move in a circle.

Zero G in Orbit

What do people think of when they hear the term 0g? AT first you might think that something is not accelerating. Next, you may remember that standing on earth you are not accelerating, but you experience 1g. So you then think, well, in orbit, you are so far from the earth that gravity is negligible, so that's it. This is not true, gravity is still alive and well, at about 97.5% of the value at the earth's surface. How can this be?

So actually, you weigh almost the same, and you are accelerated toward the earth almost the same, but you don't feel it. Why? Because the ground is not there pushing back on you to stop your acceleration. Anything in orbit is actually free falling. If you jump off a building, while you are falling, are you in zero G? Well, in the way that we mean 0g and microgravity, yes, you are in 0g in free fall. Only in that since you are falling, blood does not pool in your legs and if you release a ball, it falls right with you. So if you allow yourself to be a (moving) reference frame, you are in zero G. But, if you expect the normal laws of physics apply to your moving frame of reference, such as Newton's laws of motion, you must use an inertial reference frame. An inertial reference frame is one which moves at a constant velocity (acceleration like free falling or orbiting is not allowed). In fact the principle of relativity says that in an inertial reference frame, all of the laws of physics are the same as in any other inertial reference frame, so you can not deduce by any means how fast you are moving. All you can say for sure is that you are moving at a certain velocity relative to another object.

Now suppose you are being forced to go in a circular motion around a planet by gravity. Gravity is constantly pulling you into a circle rather than allowing you to fly off in a straight line. Are you weightless? No, you are still being pulled toward the planet. That is why you do not fly off in a straight line. Everything around you, your spacecraft, your clothes, your hair, your glass of water, is moving in the same circular motion, so if you forget about the motion for a moment, everything seems to be standing still. If you let go of something, it does not change motion, so it seems like there is no gravity. But that's only because you are not used to falling. You are used to resisting gravity by pushing on the ground to stay up.

However, people will sometimes try to use the reference frame of the shuttle or object in orbit and, relative to that, there is microgravity or "zero G." This is just as fictitious as centrifugal force, but people still use the term. (What other term would you use to describe the floating sensation?) The only way you would actually truly experience zero G in an inertial reference frame would be if you were far from any large mass (planets, stars, etc.) Then you would not be moving and not experience any relative acceleration between you and objects around you. It would seem pretty much the same as being in orbit, except you would not be going around anything. Now Einstein reasoned, if there were some large gravitational acceleration in some direction, that affected everything I could see, and I were free falling in that gravitational field how would I be able to tell? Since velocity was relative, maybe acceleration was, too. However, if light were not affected by gravity, you'd be able to measure the acceleration relative to light and deduce the falling. Einstein made a leap of faith to say, I believe that acceleration is like velocity, and you wouldn't be able to tell. He decided that it was like compressing space, so everything thing in that space would be affected the same way, you you could not tell unless you were outside that space looking in. In that way, he predicted the effect of gravity on light. This was astounding, since light has no mass, and was believed not to be affected by gravity. Experiments prove that light is definitely affected by gravity, just as Einstein reasoned it would.

Now the problem with using terms like "weightless", "zero-G", and micro-gravity is that you have to understand that no one really literally means these things in the normal, Newtonian view of the world. To show how seriously confused people get by all this, here a a couple of letters to a well respected aviation magazine from reasonably intelligent readers:

I don't know about you, but I quickly scanned these two letters and thought these guys were really mixed up. However, if you accept a reference frame flying along with the vehicle, they are actually not too far from the truth. Let's take their statements one at a time:

You might look up "weightlessness" on Wikipedia for more information. The last time I checked, this was a fairly accurate article. I have gained a lot of respect for Wikipedia, since misconceptions are usually corrected by someone who knows better in a short length of time.

Retro Firing Slows Down a Spacecraft in Orbit

This is of course, counter intuitive. But air drag or retro firing is only one of the forces acting on the spacecraft.

Air drag, or retro firing removes orbital energy from a satellite. This forces it to fall closer to the earth. But at its new altitude, however, the orbital velocity is higher. Some of the potential energy is converted to kinetic. Thus, firing a retro momentarily slows down the spacecraft, but ultimately speeds it up as it falls closer to earth.

Curved wing supposedly creates lift by Bernoulli effect

They told you an airplane is lifted by lower pressure on top the wing than below. Let's call this Bernoulli lift. Would you believe that much of the lift is created by pushing downward against air? This of course sends the air downward. Let's call this reaction lift.

Try a simple calculation of the Bernoulli effect: take a 2000 lb plane with a wing area of 20 sq feet. Assuming that the air could be made to stick to the wing and move 10% faster over the top than the bottom, you might see a 1% change in air pressure differential from top to bottom, resulting in perhaps of the order of 0.15 lbs per sq inch. The total lift is of the order of 500 lbs. Clearly, the airplane needs more lift than just this (it manages to fly, does it not?). The extra lift comes from throwing some of the air downward to create an equal and opposite force pushing the wing up.

On a typical airliner, you might experience 15-20% of the total lift from Bernoulli effect, but 80-85% of the total lift comes from reaction lift. Ever see a stunt plane fly upside down? How would that be possible if the Bernoulli lift were dominant. Wouldn't flying upside down create a downward force in addition to gravity?

Look again at that jetliner before you board. The wings are not held level, but they stick up in the front and down in the back. That way, they are constantly hitting air and forcing it down, creating lift.

Diode rectifies because of holes and electrons

The standard electronics books and classroom textbooks gave a totally nonsense explanation of how a diode works. The explanation usually goes like this: in the "N" material, conduction usually occurs by the movement of electrons. Electrons flow opposite to the direction of current. (Current flow is defined arbitrarily to be in the direction of positive charge flow.) In "P" material, there is an excess of "holes." (Holes are where an electron should be to fill up an orbital shell, but there is one missing because of the P type doping. So in P material, conduction occurs by the flow of "holes" in the direction of the current. Since holes and electrons flow in opposite directions, at the P-N junction holes and electrons either have to come together (allowed) or flow apart (not allowed.) Some kind of gibberish about holes and electrons can annihilate each other, but holes and electrons can not be created out of nothing is offered. This all falls apart because holes are just a fictitious invention like centrifugal force and coriolis force. Besides, why can electrons and holes flow out of a metal junction with P material?

OK, so what really happens? At a P-N junction, the dopants cause excess charges to be built up at the interface. These charges are held in place by the nature of the materials, on average, so that there is an average permanent electric field in the semiconductor. That mean that for any applied voltage in the same direction as the field, current will flow. For voltages in the opposite direction that are smaller than the permanent field, current will not flow. If a voltage is applied that exceeds this permanent field, it is called "break down" and current does flow, with likely damage to the device.

Atoms are composed of little balls

It is sometimes tempting to describe atoms with electrons and protons and neutrons like miniature solar systems with particles orbiting around others.

There are many problems with thinking of atoms in this way. They simply do not behave like miniature solar systems would. For example, only discrete periods and radii are allowed. And the orbits do not decay by radiating electrical energy into space as you would expect. And you can not predict when and where the electrons will be in the way astronomers predict the configuration of planets.

On top of that, the electron motion is quite complicated for most atoms. The outer electrons act as if they are moving in a very irregular orbit with lots of loops. And if the electrons are fermions (they are) they interfere with each other in ways that planets never do. On the other hand boson particles do not do this.

It has been discovered that a wave function can be defined for each particle such that the square of the wave amplitude represents that the probability that the particle can be found at a position. Wow, that sounds useless or weird or something out of this world. What do you mean the probability that a particle can be found at a particular position. Where is it? Well, the weird thing is, you can't tell very accurately until after you stop it or change it in s ome way. Then you will no where it was when you changed it, but you can't tell accurately just how you changed it! OK, this is really weird right. You mean you don't have instruments good enough, right? No, I mean it is a fundamental property that you can't tell where it is. You can't confine it to a smaller volume than a certain amount, because its position and velocity combination is always a minimum size. This is what keeps matter from collapsing under the weight of gravity. This is just the start of the weirdness. By thinking of the atoms as little planetary systems, you predict everything incorrectly about the way they behave.

Evolution as taught by Darwin explains the diversity of life forms and the complexity of higher life forms

Evolution is supposed to happen by normal variations in species specimens that have a differential advantage in breeding. The most common advantage is survival to breeding age. Somehow this single factor is supposed to account for the whole process.

This explanation for evolution was arrived at by watching domestic animals bred in captivity -- noticeable changes are done in a few generations by selecting for particular characteristics. Couldn't nature perform a selection process based on competition for survival? Of, course. And with millions of generations to work with, couldn't even the smallest competitive advantages be enhanced?

Well, I think the answer is yes and no. The presumption is that the selected characteristics are passed on to the offspring. But consider apple trees. Such a process could never be used to select trees for good tasting apples. The fact is, the seeds from apples when planted only have a 1 in 800 or so chance of producing good tasting apples. Even if the seeds came from inside a good tasting apple. (Most apple bearing trees that produce edible fruit are grafted.)

Ever ask why there still exist so many species when supposedly evolution would have made something better at surviving by now. Whatever was better should have left crocodiles, wolves, elephants, and monkeys in the dust bin by now. And there are not too many intermediate things around, you know, half way between species. Its as if genetics do not really allow an infinite range of variety of species, but maybe there are quantum jumps. Hmm, though, now this is interesting. Evolution as explained by Darwin does not take these ideas into account.

Is it possible that due to imperfections in the genetic copying process that you get an offspring radically different from the parents? Well, yes. Most of the time, we consider these to be birth defects. But once in a while, the changed gene, not inherited from any parents, but an accident is beneficial. It may be something hardly noticeable like a natural immunity to AIDS. (Notice that word, "natural"?) Other times, it might mean a salamander without legs or a snail without a shell, or naked monkey with a big head.

OK, well if a birth defect like this occurs, how would it make a new species -- how would it find a mate? Interesting question, and there are some obvious directions for speculation here.

The fossil record seems to show quantum jumps in species, not a record of continuous change with lots of individuals intermediate between two species. The fossil record seems to indicate quasi-stable species designs which do not vary over long periods of time.

Other factors that may be involved are: population isolation for large periods of time, point mutations, cataclysmic environmental changes on a relatively frequent basis....

It would seem that this whole subject is vastly more complex than the simple rules that you might have been taught like "survival of the fittest." Other factors often outweigh survival of the fittest.

How we approach cosmology

What I intend to talk about: We keep thinking that the latest theoretical breakthroughs can explain nearly everything about the formation of the universe. There are just a few loose ends - dark matter, dark energy, some bad data (it looks like some stars are older than the universe)

It could be that our assumptions about aging stars, planets, galaxies, and the universe are not completely valid over the whole lifetime of the universe. This would make our age estimates significantly off the truth.

Maybe we have forgotten to take relativistic red shift into account with Doppler redshift. How about gravitational redshift? Isn't there enough confusion here to have made some false assumptions about the correlation of size and distance?

Aren't p-branes a contradictory explanation to the one using dark matter/dark energy? Are we really sure the universe is the size it appears to be and that everything can be judged how far away it is by how much redshift (how fast it is moving away from us) it has?

Why is the sky blue?

Why is the ocean blue?

Why are glaciers blue?

The questions were grouped together because we first have to deal with a usually unspoken misconception about color. To illustrate what I mean, can you describe the difference in color between white and silver or between gray and silver? How about the difference in color between yellow and gold?

If you have ever struggled with that, you may realize that the “color” of silver and white is actually the same. What’s different is the directionality of the reflection. Optical scientists usually characterize the difference as something called a Bidirectional Reflectance Distribution Function (BRDF). This differentiates a white sheet of paper --where the light is diffusely reflected in all directions-- from a polished silver surface in which light is reflected out in only one direction for each incoming direction. This type of reflection is called a specular reflection because it is the way a mirror reflects.

We usually think of objects as being one of these two types of reflecting bodies. In fact, we try to think of and speak of most objects as if they were diffuse reflectors. Many objects more or less fit this model.

However, we soon notice that many objects have combinations that words do not describe well. A “red” coffee mug might be ceramic with a clear glaze. So the glassy coating may specularly reflect all colors of light, while the diffuse surface underneath may reflect mostly red light. So what color is it? We usually just say “red”. But it is not red like a “flat” red painted surface is red. So we might call it a glossy red, but again if we look closely, the glossy part is more like white than it is red.

If we look really closely at a lot of objects that we call “white”, we find that they actually have a bit of depth to them, like milk. Light does not just reflect from the upper surface, but it penetrates a bit. White is usually made up of very small clear particles like a cloud. Light refracts from all these particles and eventually leaves through the same surface that it entered. From a distance, it’s just “white.” But really close up, it’s a milky layer.

Suppose we took all those clear particles and melted them together into one single layer. Now instead of “white” we might call it “colorless.” We mislead ourselves with such language. Think of ordinary snow. It is composed of a very large number of clear crystals. All of those surfaces doe so much refracting and reflecting of light that it can be considered a random scattering volume. We like to think of it as a white surface, but that is not really so. Light scatters down some depth into the snow. Think of this: when the snow melts into liquid water, how does it change from white to colorless. Where did all the white go?

If we had many small clear particles with blue dye in them, the substance would appear flat blue from a distance. If we melted them together, we’d have a transparent blue glassy substance. Yet, we still call both objects blue. So, obviously, we mean different things by calling objects “blue.”

Now take ordinary window glass. We tend to call it colorless or clear or transparent. However, when we look through sufficient thickness of the glass we notice that it is greenish.

Water is a little like the glass, only instead of greenish, it is bluish. It is not as strongly bluish as glass is greenish, so it takes more depth of water to appear noticeably blue.

So, ocean water is bluish, but a transparent blue, not like flat blue wall paint, or even glossy blue, but more like a cobalt blue glass mug.

The absorption coefficient of pure water is lowest for blue and green. The impact of the absorption on the color of transmitter light depends on the depth that the light travels to.

Apologies for the quality of these two charts, I was foiled by Microsoft. I will re-do these soon.

Percentage transmission as a function of path length in pure water. Based on the data in the figure above. One meter depth transmits most of the visible with a slight loss of red. At 10 meters, red is being attenuated very significantly. At 50 meters, red is almost gone. Deep blue is all that’s left.

No, the ocean is not blue because it reflects the sky. It’s blue because the water weakly absorbs redish light. Therefore, all that is left after enough depth is just blue light. Blue skylight does play a very minor role, as does chlorophyll fluorescence. But without these factors, the ocean would be almost exactly as blue as you see in satellite photos. A good paper that describes the phenomena is Modeling the reflectance spectra of topical coastal waters by several faculty and staff members of the National University of Singapore. They include a model for the absorption coefficient of seawater. You can also get absorption coefficient data here.

Now, what about the sky. The sky is blue sort of in the way that snow is white. It id due to scatter. I have seen websites where it is claimed that the air is a bluish substance, and that would be the reason why. This is incorrect. If the atmosphere were completely transparent without any scatter, you would see a black sky, same as on the moon. If the air were a bluish substance, you would still see a black sky, but the stars and the sun and the moon would appear blue. In fact, most everything would appear blue because only blue light would filter down from the sun. Obviously, this in not what is happening.

The only way the sky can not be black is if the air is scattering light from the sun into our eyes no matter what direction we look. The light scatters from aerosols, particles of dust, and from the air molecules themselves. It turns out that unless there are volcanic remnants, clouds, or smog, that the scatter from the air molecules is the most important scatter. Some people have claimed with good reason that scatter from man made particulates has made the skies brighter than they were before the industrial revolution. At any rate, scatter from molecules is very strongly wavelength dependent. This type of scattering is called Raleigh scattering after the first person to describe it fairly accurately. The actual dependence on wavelength if λ⁴ meaning that as the wavelength goes from red (600 nm) to blue (400 nm) the strength of the scatter increases 5 fold. So blue light scatters 5 times as strongly as red light. This applies mostly to light that is scattered at large angles from the sun. There is also a strong polarization component to the scatter which you can observe using polarizing filters, but that is really beyond the scope of understanding why the sky is blue. This dependence of the scatter on wavelength can easily be seen in a spectral plot of the skylight.

It is interesting that the sun appears red during a sunset because the blue light has been scattered out of the sunlight, leaving mostly red. The dips and peaks in the sunset red spectrum are largely due to absorption bands in the atmosphere. Note that they are mostly at wavelengths longer than 700 nm, or in the infrared where the atmosphere is much less transparent than it is in the visible.

The daylight spectrum shown above is the result of three things: the blackbody spectrum at the sun’s photosphere temperature (sometimes misleadingly called it surface temperature -- does it have a surface?), the emissivity dependence on wavelength of the photosphere of the sun, and the absorption spectrum of the atmosphere.

So the sky is blue due to some rather complicated scatter phenomena of the atmosphere.

Mendenhall Glacier near Juneau, Alaska appears to be composed of blue-green snow. What gives? If you get a handful of this snow and examine it, it appears to be ordinary white snow. Note that the glacier is backlit and most of the sunlight filters through lots of snow and ice before coming out at the surfaces nearest your eye.

Very unique picture of penguins on a blue iceberg in Antarctica from the Ray I. Doan Photographic Collection shows backlit ice with fairly long light path through the ice. Since ice absorbs red light weakly, the transmitted light is nearly blue. Notice that sun light reflecting from the top surfaces of the ice is still nearly white.

What about glacier ice and snow? We already know now that water is blue, and we now learn that ice is even more blue. Hey wait a minute, isn’t is colorless or white? Actually no. It may seem white in a skating rink, but only because the trapped air in the ice does not let light penetrate very deeply. Glacier ice is more densely packed so that the air bubbles are far fewer and farther between than in ordinary ice. The result is that light penetrates far deeper. Now the light has to traverse much more ice before it reflects or is scattered back This gives a chance for much more red to be absorbed along the path, hence the ice appears much more blue than in “normal” ice or snow. If you visit Juneau, everyone will tell you “the snow is not blue, it’s just an optical illusion.” What they mean is that the glacier is backlit so that you see sun light not bouncing off the top layer of snow, but sunlight filtering through a lot of snow and ice. When that happens, the weak red absorption in the ice plays an important role in what you see.

Another picture of penguins on a blue iceberg in Antarctica from the Ray I. Doan Photographic Collection shows that blue sky is not playing a major role in the apparent color of the iceberg. Here the sky is overcast and gray, and yet the iceberg still appears a deep blue. This photograph is for sale by the photographer very nicely matted and framed.

Does glass flow? Is glass a liquid?

This is a subject taught either in middle school or high school, although it is not at all clear why. It is at the very least misguided and premature. At worst, it is completely false and leads to all sorts of confusion.

The accompanying figure explores what is normally taught about glass flow. Glass is an amorphous solid, they say. The very word implies that glass will flow under normal room temperature conditions.

The truth of the situation is that unlike many solids, glass does not solidify at some well defined temperature. It becomes thicker and thicker (more viscous) as it cools, leading to the mistaken impression that it is still flowing at a measurable rate all the way down to room temperature.

In fact, by the time glass reaches room temperature, it does not flow any more than a solid, and that is at a rate that is too small to be ever observed.

If glass did appreciably flow, this would be a major problem for telescopes. Even as little as 5 microinches would be a noticeable degradation of performance for most telescopes, and as little as 1 microinch would be devastating to the Hubble Space Telescope. Yet the Palomar telescope has been in service for over 50 years without so much as 5 microinches of flow. Since you would need at least 10,000 microinches of flow to easily observe the effect, that means at least 100,000 years would be required at the same rate of flow (assuming that glass flowed just fast enough not to be detected on Palomar yet.)

So what gives with those old windows in buildings and cathedrals? The fundamental flaw in the observation is that glass was not made of uniform thickness when those building were glazed the way glass is today. Today float pans are used in which molten glass floats on a molten layer of tin. As long as sufficient care is taken, this produces glass of very uniform thickness and glass that is very flat.

However, before this method was developed, glass was shaped more or less by hand. This resulted in pieces that were noticeably thicker on one end than on the other. Usually installers tried to put the thicker glass at the bottom of the window frame where it was felt that it would be more stable.

For further discussion on the subject, try doing a search for Robert H. Brill, Research Scientist, The Corning Museum of Glass. You should find a paper he wrote in July of 2000. See also this site and this discussion.

One of the things that telescope owners do have to worry about is gravity sag. This is an elastic deformation that is proportional to the gravity load and disappears when the load is removed. Since telescopes generally have to be re-oriented to see in different directions, this becomes a problem to control. One French approach was to build the telescope so that the glass, deformed under its own weight, was correct in a horizontal orientation. The pointing was then accomplished with a larger turning flat mirror. Thus the main telescope mirrors were always in the “correct” shape. Of course, if gravity had caused the glass to “flow,” this approach would not have worked.

Why Are There Tides?

Note: moon shown much closer than actual scale. Tidal bulges have been greatly exaggerated so that you can see them. The real tidal bulge is less than one millionth of a pixel on this scale. Moon would be more than three feet a way from the earth on this scale.

This subject is so extensively treated in textbooks and on webpages authored by university physicists and astrophysicists that you would think they would have got it right by now.

Unfortunately, the subject is so full of half truth, incomplete information, and serious errors that someone who thinks about what is going on is almost sure to be confused. Also, unfortunately, to truly understand the cause of the tidal bulge on both sides of the earth, you probably need to be a good physics student. You will need to know about non-inertial reference frames and weightlessness in free fall. I will try to guide you a bit, but these concepts usually do not come easily the first time, so if I lose you, don’t give up. Read more.

We will begin for the moment by asserting without proof for the moment that the largest contributor to tides is the gravitational pull of the moon. In doing this we have to realize that the gravitational pull of the sun is much greater than the pull of the moon, and that the rotational effect of the earth does in fact result in a bulging out at the equator. The sun’s effect is less than that of the moon for reasons that we will see shortly. The equatorial bulge is almost exactly constant, so it does not cause a daily movement of the water level. Therefore, we can accept that bulge and ignore it.

Let’s start by dismissing the school textbook non-sense about the earth rotation centrifugal force as the reason for the tidal bulge on the opposite side of the earth from the moon. If your common sense does not tell you that the centrifugal force is constant, then maybe you should not be reading this.

Typical school textbook shows a lot of very misleading and some downright wrong information. Typically no mention is made of the fact the drawing scales are wrong and that centrifugal force is “fictitious” and that it causes a bulge around the entire equator, not just one side. No moving tide results from centrifugal force as shown.

However, in a very non-obvious way, it is due to centrifugal force of the earth’s revolution (orbit) about the moon! This is probably not the best way to describe the situation or understand it so I won’t describe it this way. Read text.

This diagram is also somewhat misleading because the moon is shown in line with the earth’s equator. It actually on average is tilted with respect to the equator.

To be complete, we have to admit here that centrifugal force is not a real force in a physicist’s point of view. There is nothing that causes centrifugal force, because, as I said, it is not a force. Rather it is a force that we have to add to make Newton’s laws of motion work if we insist on standing on a rotating earth and pretending that we are standing still and the laws of motion still hold. This is as ridiculous as being in a car falling off a cliff and saying that there is a force that balances gravity that keeps objects in the car from being attracted to the earth. Everything in the car is in “zero g” or “weightless” is it not. Well, if you say “no, everything is falling at the same rate as the car” you are right. But if you insist in pulling down the shades and pretending your car is motionless, you have to have “zero g” to explain why things are floating (tossing maybe) around in the car.

Illustration of the moon’s orbit being inclined relative to earth’s axis of rotation. The moon is shown too small and too close to the earth relative to the actual scale. Tidal bulge is also enormously exaggerated so that it can be seen.

As earth rotates under tidal bulge, tide appears to go out and come in. Near the equator, the bulge is not large compared to the unperturbed state of the oceans, so tide appears to ebb and flow much less than at mid-lattitudes.

So exactly the same is true for centrifugal force, coriolis force, and “weightlessness” in orbit. These are not real, but they are used for the convenience of working in a reference frame that is either spinning or accelerating. The more accurate description of the situation is that you are choosing to work in a non-inertial reference frame. In this type of reference frame, a force is actually required to accelerate the objects or to force them into a spinning motion, since all objects will in the absence of any force either remain motionless or continue to move with the same velocity. Since velocity means speed in a particular direction, this is equivalent to saying that the object continues to move along a straight line at a constant rate.

Now all of this is absolutely necessary to be very clearly understood to explain the tidal bulges on the earth due to the moon. Some astrophysicists have published web pages and textbooks which say otherwise. The worst of these claim that the tidal bulges would still be the same if the earth and moon were held in place. The claim is that the differential force between the moon pulling on the center of the earth and the ocean is what cause the ocean to take its shape relative to the earth.

Actually, it the earth were held in place, then whatever were holding it in place would be canceling the gravitational force of the moon. The force acting on the ocean would be the vector sum of the force from the earth and from the moon. In this case, there would be a strong bulge of the ocean on the side of the earth toward the moon, and a deep depression on the side away from the moon. Your intuition probably told you that.

If earth and moon were held motionless in space, tidal bulge would be enormous and lopsided to one side. Note: not drawn to scale. Bulge shown much larger than would be to scale and earth shown much closer to moon.

So now, let’s release the earth and let it start falling toward the moon. (The moon will start falling toward the earth as well.) So doesn’t the ocean become “weightless” as the earth falls toward the moon? Well, sort of. In the moving reference fram of the earth, the ocean and the earth are falling at nearly the same rate, so the ocean is nearly weightless with respect to the moon. Of course, the gravity of the earth still pulls on the ocean. In fact the moon and the earth both still pull on the ocean so that the total force on the water molecues is the vector sum of the two forces. But if you insist on standing on the earth and ignoring the fact that you are falling, you would say that some mysterious force has cancelled the pull of the moon.

But notice that the earth is large enough that the pull of the moon’s gravity varies significantly from one side of the earth to the other. The water molecule on the near side of the earth to the moon is attracted more strongly than the earth as a whole. It is trying to fall toward the moon faster than the earth is. Of course, the earth’s overwhelming gravity keeps the water molecule from flying off toward the moon, but it does manage to be a little farther from the center of the earth than it would be without the moon’s gravity.

What about the opposite side of the earth? Isn’t it true that the moon’s gravity pulls on water molecules there, too. Yes, of course, but since the earth is in free fall, the moon is actually pulling more at the center of the earth than on the water molecules on the far side. The earth is falling toward the moon more than the water molecules on the far side. Of course, again, the overwhelming gravity of the earth keeps the water molecules from being left completely behind, but they do lag a bit, enough to raise an ocean tide.

Now, you may be wanting to say, “that’s OK for an earth that is falling toward the moon, but we are staying the same distance away, so what’s happening.” Well, this might be surprising, but the earth is falling toward the moon, or more precisely in a free fall. It turns out that the earth actually orbits around the center of mass of the earth-moon system. This center of mass is actually some 1710 km below the earth’s surface, so most of the time, we tend to ignore this orbital motion as being very slight compared to the orbital motion around the sun.

If you still want to say, but how is the earth “falling toward the moon” when the distance remains constant, you should read the article on “weightlessness in orbit” before continuing. If you have not mastered an understanding of that, the earth-moon orbital motion will not make the slightest bit of sense to you.

If you have followed the discussion thus far, you will understand that in free fall, because the reference frame you are using is a non inertial reference frame like the earth in orbit around the barycenter of the earth-moon, you can use a fictitious force or set of forces to describe the motion of the water molecules in the ocean around the earth. Again, this is analogous to the coriolis force and the centrifugal forces. It is an invention to explain the motion that you would observe in a non-inertial reference frame. If we use this invention, we can ignore the general average pull of the moon on all objects on the earth. Since we are pretending that the earth is standing still, we have to have a fictitious force that cancels that average pull of the moon. Once that is done you are left with the differential force of the moon’s gravity relative to its average (or the pull at the center of the earth.) The differential field is also called the gradient, because it is a vector differential. However, it is not essential to know that anything about gradients to understand the tide. What is important to understand is that the differential pull of the moon is what counts because the earth is in free fall. The instant you constrain the earth (ignoring inertia for the moment) the full force of the moon comes into play, because you have stopped your reference frame from accelerating, and you are working with the real forces, not the fictitious ones that apply in a non-inertial reference frame. With the full gravitational force of the moon, the oceans would be attracted moonward into a lopsided bulge toward the moon.

Differential forces acting on earth and oceans. After the overall large gravitational field of the acting mass (moon) is subtracted out, the remaining field is shown. The reason that the overall average field can be subtracted out is that the earth as a whole is in free fall toward (orbiting) the center of mass between the earth and the moon.

Going back to the free fall reference frame, we can draw the apparent or effective forces on the water molecules as in the diagram. Please note that the tidal bulge is greatly exaggerated so that it is noticeable to the eye and that the moon is shown much closer to the earth than it should be in a scale drawing. This was done to prevent the moon from being off the drawing or the drawing having the earth so small you could not see any detail. This force diagram is essentially the same as you will see on several webpages and in a few textbooks. What they fail to explain is why the differential forces are what actually apply in this non-inertial reference frame.

Sometimes (usually in fact) it is asserted that the differential forces would behave that way even if the earth and moon were being held still. I hope by now you would agree that that would be like saying that centrifugal forces and coriolis forces would still be there if nothing were spinning.

Something like this can usually be understood different ways. It all depends on what reference frame you want to choose to work out the physics in. If you choose an inertial reference frame, and as long as all velocities are small compared to the speed of light, and the gravitational fields are not too large, Newton’s laws of motion will be followed.

Consider for a moment a large hollow space station. Let’s put a little water near the center of this station. Let’s assume that this space station rotates so that the same side faces earth all the time. Let’s call this the down side. Over time, you will notice that if everything is very quiet aboard this space station, water will tend to collect on the down side and upside of the space station. In other words, there will be a very slight “tide” on the station. If the station rotates at some other rate, this tide will roll across the space station, much as the tide rolls across the earth. How does this work? The water on the down side, being closer to earth. It is pulled by earth’s gravity a little harder than the space station as a whole. It must either orbit faster or fall a little bit toward the earth. Once it makes contact with the space station surface, the intermolecular forces make it loosely a part of the space station and it can not get any closer to the earth. Water on the upside is pulled a little bit less strongly by the earth, and is going slightly too fast in orbit, so it does not follow quit as tight a circular path around the earth. From inside the space station, it appears to move up away from the earth until it touches the side of the space station.

Illustration of tidal effect is due to gravity gradient across the dimensions of a large orbiting body.

In orbit, the gravity gradient across the size of the space station will cause an apparent force to push the water away from the center and towards the earth and opposite earth (down and up) sides of the space station.

The space station shown here is extremely large – a couple of thousand miles across – compared to any man made object ever made.

Apparent forces are fictitious, because the forces only exist if you sit in the space station and pretend that you are not moving around the earth. True force is the gravitational force of the earth which always pulls toward the earth, never away.

If earth and moon are held apart by some fixture, and the earth is not rotating, then all the water falls to the earth side of the space station. Gravity does reach out into space.

Suppose you stopped the space station and held it up at a high altitude. Would the tide inside the station continue unchanged? You intuition should tell you that all the water would fall pretty strongly toward the down side of the station. You would be right. Can you think of how this applies to the earth-moon system and tides on the earth? Do you see why the tides would be very different (i.e. one huge bulge on one side of the earth) if the earth and moon were held still in space?

So why is the explanation for the tide taught in a false manner? They reasons for this are complex. In the pre-college text, it is a required subject and therefore must be taught. To teach science without it would be incomplete. Does the high school teacher understand the tides? Usually, no. If the textbook went into the explanation above, not even the teacher could follow it in most cases. So what is the goal of the education? Well, ideally that you should be taught correct science. But that goal really is practically unobtainable. So, the compromise is to teach you something that might be plausible and maybe give you an inkling of the true reasons. Well, why does the astrophysicist teach it incorrectly? It is easy to get confused. Although the earth is an accelerating, non-inertial reference frame, in that it revolves around the sun, the moon (actually the centers of mass between the earth and moon and earth and sun) and rotates on its axis, and revolves around the barycenter with every other planet, we tend to ignore that for everyday things. In our discussion, for example, we conveniently ignored the free fall of the earth, oceans, and moon toward the sun. By free fall, I hope you now immediately think of orbiting the sun. In fact, all of that free fall that we ignored is not exactly constant. When the moon is closer to the sun that the earth is, it is pulled more, and when it is further from the sun than the earth is, it is pulled less by the sun. That causes the moon’s orbit to bulge slightly in both directions. It also causes the oceans to bulge toward and away from the sun.

The sun’s gravitational pull is much greater than the moon’s, but because we are in a non inertial reference frame orbiting the sun, the differential gravity field of the sun applies. That is why both the sun and the moon have significant tidal effects. The sun’s effect is on average about 46% of the moon’s effect, even though the gravitational force of the sun on the earth is much, much larger than the gravitational force of the moon on the earth.

Hopefully, it will have been obvious, that the reason the tide raises and lowers twice a day is that the earth is rotating under the tidal bulges.

More interesting information can be found by looking up "tide" on Wikipedia. On of the interesting things is that since tides are not steady state with the earth simply rotating under them, the waves can be funneled into very large effects where the wave moves up an ever narrowing and shallowing channel. This is why the tides can cause enormous flows in the Bay of Fundy.

Here are some miscellaneous items that I put in a different category: they are not almost universally taught incorrectly, but they somehow seem to be common misconceptions that have developed, probably partly due to newsprint, television, and the movies. Some of it is due to brevity of speech. Rather than give a long explanation and be exact, hopefully most of us scientists have taken to a more layman explanation in everyday life just to keep people from running away from us and going insane. Here are some of the ones that come to mind:

Clouds float in air because the droplets are tiny.

Actually, that plays a role. It should be obvious that large drops would fall immediately. We assume here that we are in the earth’s atmosphere and that gravity is doing it’s usual thing. OK, so tiny droplets is part of the explanation. Another part is that air molecules are constantly bombarding the tiny droplets so that it is difficult for them to fall. Hence they fall at a MUCH lower rate than the simple acceleration due to gravity. [Notice I said “fall at a rate” – this is imprecise, since things do not fall at a constant rate until they reach “terminal velocity.”] So, if nothing else were in effect, a cloud would descend pretty slowly due to the water droplet terminal velocity. However, as the sun shines on the cloud, quite a bit of sun light is absorbed as heat and is transferred to the air in the cloud. This tends to make the air in the cloud rise. This updraft tends to pull the water droplets along with it. Again, this would not be possible if the droplets were much larger, unless some pretty violent updrafts were present (such as in a hail storm.)

Relative humidity is ratio of the moisture in the air to how much the air can hold.

This again is very imprecise language and usually leads to misunderstandings. Generally, unless the pressure gets too high, or some sort of chemical reaction is taking place, how the components in a gas (such as the air) act individually is insensitive to the other components in the gas. For example, the air molecules do not actually hold the water – the water would pretty much do the same thing if the air were not there. So, at a given temperature, water vapor will come to equilibrium with liquid water (by that we mean the rate that water is evaporating is equal to the rate it is condensing) at some vapor pressure of water. This is the same regardless of the air. Relative humidity then represents a state of non-equilibrium. This means that something has swept out some of the water so that less water is in vapor than could be at the given temperature. Alternatively, the area may have just heated up, and the water has not had a chance to catch up. Or there might be very little water around to evaporate and reach equilibrium. This explanation is itself a bit of a simplification. In a state of non-equilibrium, the rate of evaporation can be controlled by the air molecules. They sort of get in the way, hitting the surface of the water and slowing the evaporation. If they were not there, the liquid water would boil until the vapor pressure of water above the water reached the equilibrium pressure for the temperature of the water. Of course, the evaporation process takes energy, and this cools the liquid water. I have had difficulties removing water from a vacuum system, because the water quickly freezes and then starts a very slow evaporation process. I have had to re-pressurize and re-evacuate a system over and over to try to remove water, and organic solvents. But, weathermen and scientists who know better, will often just use the short hand of “how much the air can hold” to describe the equilibrium partial pressure of water vapor.

Something weighs less in air than in a vacuum due to the buoyancy of the air.

This, of course, is shorthand. Does a rock weigh less in water? Is a ship weightless in water (it does not sink at all)? You probably at least agree that the ship weighs the same in water as on land. If you think about it, the rock weighs the same too. What might be confusing, is that the force to lift the rock in the water is now less than its weight. Strictly speaking, the force to lift the rock is the same. It’s just that the water is exerting some of the force on the rock, just like it is exerting all of the force to hold the ship up on the surface. In the same way, air pushes up on objects and makes them appear lighter. Would you say that a helium filled balloon or hot air balloon is weightless, or negative weight? Probably not. So in the same way, saying something “weighs less in the air” is incorrect and misleading.

Is the air weightless.

Of course not. If it were, it wouldn’t stay in place around the earth. In fact, all of the air above every square inch of horizontal surface weighs about 14.7 pounds.

What do raindrops look like?

Actually the exact shape depends on how big the drop is. Smaller drops are sort of egg shaped. Larger ones get to be sort of Kisses™ candy shaped with the point removed. There really is no point at the top of the drop as you so often see it drawn.

Infrared light is “heat waves”

First, infrared is not “light”, so it should be called infrared radiation. More importantly, heat is a property associated with matter, not radiation. Heat content of matter is a measure of the internal energy states that have been occupied. So heat does not equal radiation. But why would people say so? For warm objects on the earth (we mean something warmer than freezing and cooler than say a candle flame) the dominant form of radiation is infrared. This means that a warm object will be constantly giving up some of its heat in the for of infrared radiation. By the same token, if it is in equilibrium with its surroundings, it will be receiving about an equal amount of infrared radiation and absorbing it and converting it back to heat. This expression may have been used for “heat lamps” which radiate predominantly infrared and tend to keep objects hot place under them. It may have been used to describe radiant heating systems for homes. At any rate, it is another shorthand expression that can not be taken literally. If you are confused by the term "heat wave", do not feel bad. It is misused almost constantly so that its meaning is really unclear.

Are the colors of the rainbow “red orange yellow green blue indigo violet”?

Actually, there are many more colors than that. We just divide them more or less into these categories. What about red-orange, and reddish red-orange and so on. We just don’t put names on them.

The north magnetic pole is at a location shown on a map

Well, if you realize two things. The north magnetic pole is opposite to the “north pole” on a compass. Some textbooks like to call the compass the “north seeking pole” So labeling the “north” and “south” magnetic poles has become the choice of the author of a textbook. Ugh. Need for standards.
Secondly, the effective north magnetic pole is hundreds of miles below the surface of the earth. Therefore, one should bear this in mind when thinking of the earth’s magnetic field.

Laser light is perfectly “in phase” and parallel

These are aspects of the coherence of a laser beam. Strictly speaking, a beam can only be perfectly in phase and parallel if it occupies an infinite amount of space and time. Real laser beams only last a finite amount of time and are only “so wide.” Roughly, the angle at which the laser deviates from parallel is at least the wavelength divided by the diameter of the beam (measured in radians.) Real lasers have other physical limitations that prevent them from achieving even this degree of parallelism. But some lasers can come very close. A typical pocket laser pointer will have a divergence angle of about one milliradian – about one fifteenth of a degree. This means that it would form a spot on the moon about 150 miles across. This is obviously not perfectly parallel, but pretty close for everyday work. Another shorthand expression. Lasers are not perfectly in phase, of course. The coherence length is a measure of how far a laser beam can go before the phase of the beam deteriorates so much that it is practically out of phase with itself. Not that is imprecise language. What we really mean is that a laser beam going through two slits will form an interference pattern that is bright/dark where the modulation is close to 100%. After one coherence length, that modulation falls to something like 30%, and it gets worse to where eventually, you get no interference at all.

This teeth whitener or clothes whitener is safe because it only uses oxygen

Oxygen is safe, right? Well, no, not really. Oxygen is high concentrations is explosive. Just think about those Apollo 1 astronauts Grissom, White and Chaffe. Just think of Valujet 592. And that's only regular diatomic oxygen. What about tri-atomic oxygen? That is commonly known as ozone. It is corrosive and harmful. What about monatomic oxygen, frequently just called atomic oxygen. It's the stuff that is so corrosive it eats up satellites. It is what exploded the Kursk submarine (being generated from hydrogen peroxide.) Those whiteners that are oxygen based are really some form of peroxide bleach, no matter how they sell it. It is no more safe than any peroxide.

97% Caffeine free

This does not mean anything until you know what the regular stuff has. In the case of coffee, it was already 94$ caffeine free to begin with. They only took half the caffeine out, but if you don't know that, it sounds like they took a lot more out.

Ring of Fire spark plugs

Some spark plugs were advertised with a surface gap that involved a center electrode, and a grounded ring around the electrode. The animated graphics on the screen lead you to believe that instead of a small thread of spark you would get a spark that filled the whole ring at once. This obviously was better than a tiny spark at igniting the fuel in your car's cylinders. The truth is that once the air (or fuel-air mixture in this case) breaks down (ionizes) all of the rest of the spark is going to follow the same path because it's easier than breaking down more air in a new direction. Bottom line, the spark is about the same as a regular plug. It does have a couple of advantages however. First, the spark is more directly exposed to the mixture in the cylinder so it propagates just a little faster. Secondly, if part of the ground ring gets fouled, the spark just goes to a new spot.

BAD SCIENCE

Why is the ocean blue?

Why are glaciers blue?

Does glass flow? Is glass a liquid?

Why Are There Tides?

Clouds float in air because the droplets are tiny.

Relative humidity is ratio of the moisture in the air to how much the air can hold.

Something weighs less in air than in a vacuum due to the buoyancy of the air.

Is the air weightless.

What do raindrops look like?

Infrared light is “heat waves”

Are the colors of the rainbow “red orange yellow green blue indigo violet”?

The north magnetic pole is at a location shown on a map

Laser light is perfectly “in phase” and parallel

This teeth whitener or clothes whitener is safe because it only uses oxygen

97% Caffeine free

Ring of Fire spark plugs

This jibberish is the opinion of Bill Otto and does not necessarily represent the views of any scientific organization. Copyright © 2005 [Bill Otto]. All rights reserved. Certain graphics have been lifted from other web sites. If you want credit, please email me. Revised: October 19, 2008 .

This jibberish is the opinion of Bill Otto and does not necessarily represent the views of any scientific organization.
Copyright © 2005 [Bill Otto]. All rights reserved. Certain graphics have been lifted from other web sites. If you want credit, please email me.
Revised: October 19, 2008 .