![]() ![]() Get a string and pass it trough the earth and moon beads.It should be about 70 cm in diameter (2.5 feet). Get the largest orange or yellow balloon that you can find to be the sun in your model.This will be the size of a chick pea or about 6 to 7 mm in diameter. Get a larger plastic or glass bead to be the Earth.The diameter of the moon in your model must be about 1.5 millimeters. This must be the size of a small circle like this º. Get a very small white glass or plastic bead to be the moon.Proportional diameters in your scale model Make a scale model of the sun, Earth and the moon to demonstrate their proportional diameters and distances. What fraction of the moon is usually exposed to sunlight? Observe and compare the shadow and sunlight on the ball and on the moon.Ĭan you use this experiment to explain why doesn’t the moon look round? ![]() Hold a ball in the sunlight, next to the moon so you can see both moon and the ball at the same time. If it is the third quarter of the month, you can see the moon in the west in mornings. If it is the first quarter of the month, you can see the moon in the east in the afternoon. A series of experiments that includes a control is called a “controlled experiment.” Experiment 1: Without a control you cannot be sure that changing the variable causes your observations. They can be the hardest part of a project. ![]() Dependable controls are sometimes very hard to develop. A control is a neutral “reference point” for comparison that allows you to see what changing a variable does by comparing it to not changing anything. The only difference is that no experimental variables are changed. It is a separate experiment, done exactly like the others. For an experiment to give answers you can trust, it must have a “control.” A control is an additional experimental trial or run. This list is called an experimental procedure. ![]() Make a step-by-step list of what you will do to answer each question. Pretty much half the world qualifies!ĭesign an experiment to test each hypothesis. So, instead of having to be in a rather narrow path, as happens for solar eclipses, you only have to be in a part of the world from which the Moon is visible at the time of the eclipse. The reason is that when the Moon gets dark, it is because it does not receive the sunlight, and it then is dark for anyone who can see it. And you are far more likely to be able to observe one than a solar one. They do happen at least twice a year, though. Lunar EclipsesĪs explained above, lunar eclipses do not occur every month because of the inclination of the Moon’s orbit. It is estimated that, on the average, a given spot on the Earth will be on the path of an eclipse only about once every 370 years, so if you like to see an eclipse, it is better to move to an eclipse than to wait for one to come to you. To see a total solar eclipse you have to be inside this rather small region. As the Earth moves, this circle traces a path on its surface, called the path of totality. In a solar eclipse, the dark part of the Moon’s shadow on the surface of the Earth is a circle of only about 160 miles in diameter. If the Moon is further away from the Earth, then its disk will not be big enough to cover the Sun completely, and we get an annular eclipse, where most of the sun is covered, but an annulus remains, surrounding the dark disk of the Moon. This is the most spectacular kind, where the day changes into darkness, and one can see the stars in plain day. If the Moon is close enough to the Earth, it will cover it completely, and we get a total solar eclipse. Because of this, when there is a solar eclipse, the Moon is about the right size to completely cover the disk of the Sun. The Moon is about 400 times smaller than the Sun, but at the same time the Sun is about 400 times farther away from the Earth than the Moon. The Moon and the Sun appear to have the same size when viewed from the Earth. As noted above, these are not as frequent as one might expect, but there are still at least two each year. Solar EclipsesĪ solar eclipse occurs, when the Moon is directly between the Earth and the Sun. Whether you will be able to observe a total or partial eclipse will depend on which of the two regions you are located in. It is important to notice that the shadow is more complicated than just a cone: it actually consists of a darker cone, or umbra, where no sunlight reaches, and a lighter region, the penumbra, where only some of the sunlight is blocked. Whether it is the Moon between the Earth and Sun, or the other way around, the phenomenon is basically the same: the body in the middle casts a cone of shadow, and if the outer body happens to move into this cone, we have an eclipse. ![]()
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