IV. Translate at sight. The first stop in a tour of our Solar System is the Moon, which lies about a quarter million miles from the Earth

Our Place In Space

The Solar System

The first stop in a tour of our Solar System is the Moon, which lies about a quarter million miles from the Earth, or about thirty Earth diameters away. If we were to use a miniature model of the Solar System, in which the Earth is only about an inch across (about 500 million times smaller than its actual size), the Moon would be a quarter-inch diameter ball, only about two and a half feet away.

On this scale, the Sun, which is around 93 million miles from the Earth-Moon system, or about four hundred times further than the Moon, would be a ball approximately ten feet in diameter, a thousand feet away from the inch and quarter- inch balls which represent the Earth and Moon.

Lying somewhere within the thousand foot radius circle which approximates the orbit of the Earth would be another one-inch ball, representing Venus, and another ball, a little less than half an inch in size, representing Mercury. Mercury's half-inch model would be three to five hundred feet from the Sun, depending upon where it was in its somewhat eccentric orbit, while Venus would be about seven hundred feet from the Sun. If passing between the Earth and Sun, it would be three hundred feet from us, but if on the other side of the Sun, it would be seventeen hundred feet away.

Now think about what these objects would look like, as seen from the inch-wide Earth. The Moon, although only a quarter-inch across, is only two and a half feet away, and as a result, would be seen as a small ball, about half a degree in size. The Sun, although much further away, is much larger than the Moon, and would appear to be about the same half degree in size. (Which is the way they look in our sky.)

Mercury and Venus, however, being not much larger than the Moon and smaller than the Earth, would be so tiny, given their huge distances from us, that they would only be dots as seen from the Earth, unless viewed with some kind of magnifying device (e.g., a telescope). And when we look at the night sky, that is exactly how we see them and every other individual object in the Universe, save for the Moon and Sun. Only the planet we live on, its satellite, and the star it orbits are big enough or close enough for us to see them as anything other than infinitesimal dots, without optical aid.

Дата добавления: 2015-09-04