Test Your Knowledge

How do bats fly in the dark of night at no small speed without colliding with things, when it is well known that they are sightless?
— The bat gives out a sound of very high pitch, which the human ear cannot hear. This sound strikes objects and is reflected off them, and its echo returns to the bat, which senses it by means of a very sensitive nerve within it. By the measure of what it senses, it gauges how far the object is from it, and avoids it as it flies.

What happens to a person if his food is confined to meat alone? Does he die, or does his health fail, or does it stay as it is?
— The famous polar explorer Vilhjalmur Stefansson spent many years with the Eskimos and shared their food, which, as is well known, is made up of meat and fish, with no grains in it, no vegetables, no eggs, no milk, and no butter; and for all that he remained in sound health throughout his stay among them.

Why does the effect of wine show in its drinker faster than the effect of other drinks and foods?
— Because wine needs no digesting: the stomach absorbs it rapidly, above all if the drinker takes it on an empty stomach. Its effect is slower if it is drunk with food.

Why does the cigarette smoker need a single match, while the pipe smoker needs many matches?
— Things burn only if they are supplied with air — or, to be exact, with the oxygen of the air. Cigarette tobacco, besides being more finely shredded, is treated with chemicals containing oxygen that helps combustion. And there is another difference: the cigarette is exposed to the atmosphere and its air, whereas the pipe's air is drawn into it by inhalation. If its owner stops drawing on it for long, its breath dies down as his breath stills, and it goes out.

Why does a water glass break if you pour a hot liquid into it?
— Glass expands with heat. If you pour a hot liquid into the glass, its inner surface expands before its outer surface is given the chance to expand; an opposition arises between the inside of the glass and its outside, and cracking and breakage follow. This is more severe in thick glass. But there are kinds of glass that expand very little with heat, and these are unaffected by having hot or iced water put into them.

The earth revolves in its orbit around the sun: at what time is it nearest to it, and at what time farthest from it?
— The earth's orbit around the sun is not a circle but elliptical in shape. The average distance of the earth from the sun is 93 million miles. This distance is at its greatest in our summer, around the first day of July, and at its smallest in our winter, around the first day of January. The seasons are not produced by the earth's nearness to the sun or its distance from it, but by the fact that its axis inclines upon the plane of its orbit; it is this inclination that produces the seasons.

What are the causes of the stammer that afflicts the tongue?
— It has been observed in stammerers that the letters they find hard to pronounce are linked to words denoting things for which they were punished in childhood, or of which they were afraid, and the like. That is why the "stammer" grows worse whenever a person finds himself in company unfamiliar to him and fears that his speech will leave a bad impression on those present; the stammer rarely comes over its owner when he is alone, or in a gathering of people he knows well and in whose sincerity he trusts.

The best cure for stammering is for the "stammerer" to feel that he has the right to make people hear what he says, and that no one is going to mock him for it, or punish him for it.