If we are to understand the nature of heavenly bodies, it is essential to know how far away they are; only then can we calculate the sizes and energy outputs of planets, stars, and galaxies, and ultimately determine the scale of the Universe itself. So far as we can tell, mankind has always considered the […]
This chapter describes the properties of stars that can be derived from observations. Stars may be the most important component of the Universe, and to illustrate this point we may note that life on Earth is sustained by light and heat from the nearest star, our Sun. The stare themselves make up the great galaxies, […]
Before the brightest stars and globular clusters galaxies fade below our limits of detection, and well before the hydrogen clouds can no longer be measured we come face to face with one of the most amazing properties of our world: the Universe is expanding The space between galaxies is increasing. Smaller parts of the Universe […]
Our Galaxy is some 5 x 1017 kilometres in radius, and our journey is still far from complete. Around us in space, far beyond the edge of our Galaxy, lie other spiral forms reminiscent of the Milky Way but still further away. The metre is not a convenient unit for astronomy, nor is the kilometre, […]
The stars that form our Galaxy, the Milky Way, are still remote, but not untouched by our travels. Parallax has no theoretical limit in its application ; the distances to all visible objects in the Universe could, in principle, be determined by this method. If our eyes could detect shifts in angles ninny times smaller […]
From our vantage point on Earth, it is possible to observe the motions of the planets and to map out their relative distances from the Sun with great accuracy. This was first done over 300 years ago but it required most of the intervening centuries before the key to the absolute distance scale within the […]
Fundamental to the absolute determinations of distances in astronomy is the trigonometrical parallax. Although the name is not common outside of astronomy, the principle is in constant use by us all: we are walking in a field, the grass at our feet quickly brushes past us, a tree in the distance more slowly shifts its […]
In everyday life, when we cannot directly pace off a distance we confidently go beyond the metre stick and employ the tried and true methods of geometry and trigonometry. These become our new tools. But the way in which we use these tools is governed By completely different,”more subtle principle our belief in the.Uniformity of […]
Perspectives of astronomy We are surrounded by the sounds and slowly fading images of a distant world. As each sound is recognized, each new sight put into perspective, we hopefully come to a clearer view of the Universe as a whole. In the present we find evidence of our origin and this evi¬dence is not […]