Relativity: The Special and The general Theory by Albert Einstein

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The present book is intended, as far as possible, to give an
exact insight into the theory of Relativity to those readers who,
from a general scientific and philosophical point of view, are
interested in the theory, but who are not conversant with the
mathematical apparatus1 of theoretical physics. The work presumes
a standard of education corresponding to that of a university
matriculation examination, and, despite the shortness
of the book, a fair amount of patience and force of will on the
part of the reader. The author has spared himself no pains in his
endeavor to present the main ideas in the simplest and most intelligible
form, and on the whole, in the sequence and connection
in which they actually originated. In the interest of clearness, it
appeared to me inevitable that I should repeat myself frequently,
without paying the slightest attention to the elegance of the presentation.
I adhered scrupulously to the precept of that brilliant
theoretical physicist L. Boltzmann, according to whom matters
of elegance ought to be left to the tailor and to the cobbler. I
make no pretence of having withheld from the reader difficulties.

Astronomy Principles and Practice Fourth Edition - AE ROY and D Clarke

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The etymology of the word ‘Astronomy’ implies that it was the discipline involved in ‘the arranging of the stars’. Today we might say that astronomy is our attempt to study and understand celestial phenomena, part of the never-ending urge to discover order in nature. We do not know who were the first astronomers—what we do know is that the science of astronomy was well advanced in parts of Europe by the middle of the third millennium BC and that the Chinese people had astronomical schools as early as 2000 BC. In all ages, from the burgeoning of man’s intelligence, there have been people fascinated by the heavens and their changing aspect and these people, as far as their cultural environment has allowed them, have tried to formulate cosmologies. We are no different today.

Nowadays, the word ‘Astrophysics’ is also used to describe the study of the celestial bodies. Infact, many astronomers use both terms quite generally and it is not infrequent to find Departments of Astronomy and Astrophysics within educational establishments. The question may well be asked ‘What is the difference between Astronomy and Astrophysics?’ Very loosely, Astronomy might be defined as the subject of the ‘where and when related to the description of a celestial body with the ‘why and how’ being covered more by Astrophysics. Rather than trying to provide a hard and fast rule for the terminology, we will simply use Astronomy to cover all aspects of the description of the skies and the Universe.