Place a pair of binoculars in an open window in the direct path of the sun’s rays.

Stand a mirror in front of one eyepiece so that it throws an image of the sun on to the

opposite wall of the room. Adjust the mirror until the image is sharp, and darken the

room.

You would risk damaging your eyes if you looked directly at the sun through

binoculars, but you can view the bright disc on the wall as large and clear as in the

movies. Clouds and birds passing over can also be distinguished and. if the binoculars

are good even sunspots. These are a few hot areas on the glowing sphere, some so big

that many terrestrial globes could fit into them. Because of the earth’s rotation, the

sun’s image moves quite quickly across the wall. Do not forget to re-align the

binoculars from time to time onto the sun. The moon and stars cannot be observed in

this way because the light coming from them is too weak.

Place a flowerpot with a long stick fixed into the hole at the bottom in a spot, which is sunny, all day. The stick’s shadow moves along the rim of the pot as the sun moves. Each hour by the clock mark the position of the shadow on the pot. If the sun is shining, you can read off the time. Because of the rotation of the earth the sun apparently passes over us in a semi-circle. In the morning and evening its shadow strikes the pot superficially, while; it midday, around 12 o’clock, the light incidence is greatest. The shadow can be seen particularly clearly on the sloping wall of the pot.

=====================================

Hold a watch horizontally, with the hour hand pointing directly to the sun. If you halve the distance between the hour hand and the 12 with a match, the end of the match points directly to the south.

In 24 hours the sun ‘moves’, because of the earth’s rotation, once around the earth. But the hour hand of the watch goes twice round the dial. Therefore before midday we halve the distance from the hour hand to the 12, and after midday from the 12 to the hour hand. The match always points to the south. At midday, at 12 o’clock, the hour hand and the 12 both point to the sun standing in the south

The earth rotates in 24 hours from west to east once on its axis. In this time the sun shines on all regions of the globe one after the other and determines their time of day. To enable a practical calculation of the time, the earth is divided into 24 time zones, which are very simply shown on the map below.

Since in a few areas, which belong together, a uniform time has been

introduced, the boundaries of the time zones sometimes run along state boundaries. For example, Mexico has Central time. The West European countries including Great Britain has together with the Middle European countries, Middle-European time.

According to the map, when it is 13.00 hours there it is only 7 o’clock in the morning on the East Coast of the U.S.A. in Japan it is already 21 .00 hours and on the right edge (dateline) a new day is beginning.

The time zones are shown on the world time disk pictured below.

Copy or stick this onto a piece of cardboard and cut it out. Color the panel corresponding to time zone were you live red. Remove the casing and glass from an alarm clock, push the minute hand through the hole in the paper disk and fix it firmly to the hour hand. Make sure that the red-colored panel is exactly over the hour hand. If you rotate the disk with this, it should not stick. The clock will tell you all time of the day on the earth. Read off first on the red panel the time of the place where you live.

If you rotate the disk to the left, you will find the time zones of places west of you. In each panel, the time is an hour earlier. If you rotate to the right, you will find the places east of you. In each panel the time is an hour later. The outer circle continues into the inner circle at the crossed arrows and vice-versa. For example: in New York it is 6.15 in the morning. Then it is already 20.15 in Tokyo and in New Zealand a new day will begin in 45 minutes. Or in London it is 20.03. What time is it in

San Francisco? Look at the world map: San Francisco lies in the time zone of Los Angeles. On the rotating disk go to the left to the Los Angeles panel. The time is: 11.03.

=====================================

Download full e-book attached below (you have to login to download this book)

• 204 Science Experiments.pdf
  (818 downloads)

=====================================