Can you make it rain artificially?

Hopi Indians in the southwestern United States still invoke rain by sacrificing golden eagles and dancing with live rattlesnakes between their teeth. While this is happening, others have adopted a scientific method to make it rain.

In 1946, Vincent Schaefer and Irving Longmuir of General Electric's Research Laboratories in Schenectady, United States, began their work, which proved that rain could be artificially provoked.

Clouds are made up of millions of particles of water too small to precipitate as rain. Only when drops of a quarter of a millimeter or more form do they cause a fine drizzle. The smallest droplets evaporate before reaching land.

One way to make the droplets grow is to turn them into ice. In a cloud with ice particles and water droplets, the former grow rapidly when water vapor is absolved. Since the temperature of the clouds is almost always lower than the freezing point, one would expect the drops to freeze easily. But the water can be below that point without freezing.

This is because the water in the clouds is absolutely pure; it has no dust or contaminants that can form the center of an ice crystal. If particles are added, the droplets freeze, grow rapidly to a size large enough to precipitate, and then melt as the temperature rises to form rain.

Schaefer and Longmuir proved that adding particles to clouds, usually silver iodide, could produce rapidly growing ice crystals. These particles are launched from airplanes, by rockets or by air currents that raise them from the surface.

In the former Soviet Union, 70 mm artillery pieces were used to shoot silver iodide particles into the clouds. Although the technique can work when the clouds have the right temperature, it is impossible to know how much it would have rained without resorting to artifice. And this raises questions about the cost-effectiveness and efficiency of the method.

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How do you make dice?

Dice must be carefully made so that each cube is perfectly balanced on all six sides. If not, some sides of the cube will come out more than others.

Currently, most dice are made of plastic, either by hand or machine. After the cube is formed, a certain number of dots are punched into the die faces.

Then each hole is filled with a drop of paint that weighs exactly the same as the plastic that was removed to make the hole. In this way, the six sides of the die remain balanced, no matter how many holes each face has.

The "loaded" dice - the ones made for cheating - contain an extra weight inside one of their six sides. When a loaded die is rolled, the extra weight helps the cube often fall on the heavier side, so the side opposite that side will show up more often than it should.

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How do you assemble a ship inside a bottle?

The steps to introduce a ship in a bottle are not difficult: the masts are fixed on hinges and folded against the deck as they pass through the neck of the glass container; once inside, they are placed in a vertical position by pulling them by means of threads which are then trimmed and glued to a ''sea'' of moldable resin.

The first step in this art is to carve the hull out of hardwood and then assemble the boat; deck pieces such as the rudder and boats are removed so that the masts can be folded, and once the model is inside the bottle with the masts upright, the accessories are glued back into place by pushing them with the tip of a wire.

The sails, made of cloth or paper, are partially attached to the masts so that they can be rolled up and put into the bottle, and the sticks holding them are placed parallel to the hull so that they pass through the hull's neck.

But before putting the boat the model builders form a sea in the bottle with blue moldable resin that they introduce under pressure with steel rods.

The model is put into the bottle through the stern, as one of the control threads passes through the bowsprit, the bow pole that should be close to the neck of the container. When the model is almost in position, the threads are pulled to lift the masts; the sails are carefully unrolled and then glued into place. The bowsprit thread is also attached with glue, and the other threads are embedded in the sea of resin after the hull is secured. The remaining thread is trimmed with a long, slender-handled razor.

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