## The following terms are used to describe a water wave:Crest—the

The following terms are used to describe a water wave:

Crest—the highest elevation above the undisturbed sea surface.

Trough—the lowest depression below the undisturbed sea surface.

Wavelength—the distance between two successive crests or two successive troughs.

Wave height—the vertical distance from the top of the crest to the bottom of the trough.

Amplitude— the distance from either the crest or the trough to the undisturbed water level; one-half the wave height.

Period—the time required for two successive crests (or troughs) to pass a given point. Label the parts of a wave on the following sketch.

## For an easy-to-make model of air pressure, fill a glass

For an easy-to-make model of air pressure, fill a glass with water. Place a piece of cardboard over the top of the glass and hold the cardboard in place with one hand as you turn the glass upside down. Make sure the cardboard does not bend. Now remove your hand from the cardboard. What happens? Does the cardboard fall off and the water flow out? No, the cardboard remains on the glass. Why? The air pressure pushing up on the cardboard is greater than the weight of the water pushing down. For fun, turn the cup sideways, and then turn it all around. The cardboard continues to stick!

## If you tried the above activity, you have discovered that

If you tried the above activity, you have discovered that it is not easy finding yourself amid your many thoughts. Nonetheless, consider it a worthy endeavor and a healthy habit to get to know yourself in such a fashion. Once you feel comfortable staying with your breath, you can practice welcoming in a particular thought, which becomes your focus while your breathing recedes into the background. A good thought to start with is the idea that your bare presence and the bare presence of every other sentient being shine with a wisdom that might be called “basic goodness.” Underneath all the veneer, there is basic goodness in everyone. Try doing this for at least 10 minutes.

## A physical property of any material is its density—its mass

A physical property of any material is its density—its mass per volume. Pennies made after 1982 contain both copper and zinc. Pennies made before 1982 are pure copper. Zinc is less dense than copper, so post-1982 pennies are less dense and have less mass than pre-1982 pennies. Dig into your penny collection and find 20 pre-1982 and 20 post-1982 pennies. Measure their masses on a sensitive scale, such as a home postage scale. Alternatively, hold the pennies in opposite hands to see if you can feel the difference in their masses. How few pennies can you hold and still feel the difference? Try holding single pennies on your left and right index fingers. Can you tell the difference with your eyes closed? Try this with a friend.

## Isopropyl alcohol, also known as rubbing alcohol, is very toxic

Isopropyl alcohol, also known as rubbing alcohol, is very toxic if ingested. This is because it acts to destroy the digestive proteins and other important biomolecules in your stomach. Do this activity to see firsthand the destructive action of isopropyl alcohol on proteins. Crack open an egg and place the egg white and the yolk into two separate bowls. Pour a capful of isopropyl alcohol into the egg white and observe what happens. In the second bowl, stir the yolk with a fork. Add another capful of isopropyl alcohol to the stirred yolk and observe what happens. The same sort of destruction would occur to your own stomach proteins, as well as various tissues, upon ingesting the isopropyl alcohol. Not good! Our skin, however, is more impervious to the destructive powers of isopropyl alcohol, which therefore serves as a good topical antiseptic.

## Throughout the history of life on Earth, there have been

Throughout the history of life on Earth, there have been at least six major mass extinctions. The one that killed off the dinosaurs occurred about 65 million years ago, and it is thought to have been the result of the impact of a large asteroid. The largest mass extinction of them all, however, was the Ordovican mass extinction, which occurred about 450 million years ago. The cause of this mass extinction is uncertain, but scientists have recently demonstrated how this extinction may have been initiated by an intense burst of gamma rays produced by the explosion of a nearby star. A burst as short as 10 s could have led to the loss of Earth’s protective ozone layer, thereby exposing life on Earth to dangerous ultraviolet rays from our Sun. The probability of another nearby star exploding soon is quite low. But take a look around you.Scientists point to the sixth mass extinction as occurring right now. Discuss possible causes of this mass extinction.How long might this mass extinction take? What creatures might survive? Should humans do anything to minimize this mass extinction, or should we just accept it as a natural course of Earth’s history? Throughout the history of life on Earth, there have been at least six major mass extinctions. The one that killed off the dinosaurs occurred about 65 million years ago, and it is thought to have been the result of the impact of a large asteroid. The largest mass extinction of them all, however, was the Ordovican mass extinction, which occurred about 450 million years ago. The cause of this mass extinction is uncertain, but scientists have recently demonstrated how this extinction may have been initiated by an intense burst of gamma rays produced by the explosion of a nearby star. A burst as short as 10 s could have led to the loss of Earth’s protective ozone layer, thereby exposing life on Earth to dangerous ultraviolet rays from our Sun. The probability of another nearby star exploding soon is quite low. But take a look around you. Scientists point to the sixth mass extinction as occurring right now. Discuss possible causes of this mass extinction. How long might this mass extinction take? What creatures might survive? Should humans do anything to minimize this mass extinction, or should we just accept it as a natural course of Earth’s history? Throughout the history of life on Earth, there have been at least six major mass extinctions. The one that killed off the dinosaurs occurred about 65 million years ago, and it is thought to have been the result of the impact of a large asteroid. The largest mass extinction of them all, however, was the Ordovican mass extinction, which occurred about 450 million years ago. The cause of this mass extinction is uncertain, but scientists have recently  demonstrated how this extinction may have been initiated by an intense burst of gamma rays produced by the explosion of a nearby star. A burst as short as 10 s could have led to the loss of Earth’s protective ozone layer, thereby exposing life on Earth to dangerous ultraviolet rays from our Sun. The probability of another nearby star exploding soon is quite low. But take a look around you. Scientists point to the sixth mass extinction as occurring right now. Discuss possible causes of this mass extinction. How long might this mass extinction take? What creatures might survive? Should humans do anything to minimize this mass extinction, or should we just accept it as a natural course of Earth’s history?

## Oxygen, O2, dissolves quite well in a class of compounds

Oxygen, O2, dissolves quite well in a class of compounds known as liquid perfluorocarbons—so well that oxygenated perfluorocarbons can be inhaled in a liquid phase, as is demonstrated by the rodent shown below the water-bound goldfish. Do you suppose perfluorocarbon molecules are polar or nonpolar? Why would the rodent drown if it were brought up to the water layer and the goldfish die if they swam down into the perfluorocarbon layer? How might perfluorocarbons be used to clean our lungs or serve as artificial blood? When is it okay to sacrifice the lives of animals for scientific research?

## You can “quantize” your whistle by whistling down a long

You can “quantize” your whistle by whistling down a long tube, such as the tube from a roll of wrapping paper. First, without the tube, whistle from a high pitch to a low pitch. Do it loudly and in a single breath. (If you can’t whistle, find some one who can.) Next, try the same thing while holding the tube to your lips. Ah ha! Note that some frequencies simply cannot be whistled, no matter how hard you try. These frequencies are forbidden because their wavelengths are not a multiple of the length of the tube.
Try experimenting with tubes of different lengths. To hear yourself more clearly, use a flexible plastic tube, and twist the outer end toward your ear.
When your whistle is confined to the tube, the consequence is a quantization of its frequencies. When an electron wave is confined to an atom, the consequence is a quantization of the electron’s energy.

## After you have given the contemplation of basic goodness a

After you have given the contemplation of basic goodness a fair shake, there are a zillion other thoughts also worthy of your contemplation. Within the context of this chapter, try contemplating the sheer size of the universe. Envision yourself in your chair, and then mentally zoom out to see yourself in the room, then in the building, then on the planet. Zoom out stepwise so that you can experience each stage. Zoom out to the solar system circling within a galaxy that orbits neighboring galaxies within a supercluster that is just one supercluster among billions upon billions of superclusters. Once you have zoomed fully out, focus on that sensation of bigness. When you lose the sensation, start over again, moving as slowly or as fast as is comfortable.