The Distance Of The Stars

The distance of the star Alpha Ceutauri may be stated In round numbers to be 20,000,000,000,000 of miles. Now, a billion means a million of millions, so that the distance of Alpha Centauri may be stated to be twenty millions of millions of miles. Let us now try to form some conception, however imperfect, of the amazing distance. Let us suppose a railway train to leave the earth traveling day and night at the rate of fifty miles an hour without stoppages. In six months it would reach the moon, in 200 years it would reach the Sun and in 6,000 years it would reach the planet Neptune, the orbit of which forms the extreme known limit of the planetary system. The same train, however, would not reach the star Alpha Centauri in less than 42,000,000 years.
One more illustration may be useful. Comets, in general, revolve in very eccentric orbits. When a comet is in the perihelion of it orbit it is comparatively near to tho earth; on the other hand, when it is at the aphelion it is remote - in many instances very remote - from the earth. For instance, the celebrated cornet of 1858, known as Donati's comet, one of the greatest comets of modern times, at the time of its passage of the perihelion was distant from the sun 50,000,000 miles; but when it has attained the aphelion of its orbit (which will occur in about 1,000 years hereafter) its distance from the earth will not be less than 30,000,000,000 miles. Now our typical railway train starting from the earth would not reach the aphelion of the orbit of Donati's comet in less than 60,000 years, and yet the aphelion distance of Donati's comet is only one seven-hundredth part of the distance from the earth to Alpha Centauri, the nearest of the fixed stars. - Good Words.