The center of mass of objects in space is the unique point where the weighted relative position of the distributed mass sums to zero. The center of mass plays an important role in astronomy and astrophysics, where it is referred to as the barycenter. The barycenter is the point between two objects where they balance each other; it is the center of mass where two or more bodies orbit each other. When a moon orbits a planet, or a planet orbits a star, both bodies are actually orbiting around a point that lies away from the center of a larger body. For example, the Moon does not orbit the exact center of the Earth, but a point on a line between the center of the Earth and the Moon, approximately 1,710 km (1062 miles) below the surface of the Earth, where their respective masses balance.
To find the barycenter of two bodies one can use a formula
Where
a - is the distance between the centers of the two bodies;
m1 - and m2 are the masses of the two bodies.
Depending on the masses of the stellar bodies, there are different cases of rotation around the center of the masses. In each of these cases, the position of the center of the mass will depend on the masses of the objects involved.
1. The masses are approximately the same.
In this case, the center of the masses will be exactly in the middle between these two objects and consequently they both will rotate around the same barycenter.
2. Mass of one of the bodies is bigger than the mass of another body. In this case, the center of the masses will be external for both bodies.
3. One body has sufficiently greater mass than another body. In this case, the center of masses will be internal for a body with a bigger mass. This model depicts the algorithm of motion of Earth and Moon.
4. One body has much more greater mass than another body. In this case, the center of masses will be internal for a body with a huge mass. This model depicts the algorithm of motion of Sun and Earth.
5. Two bodies with the same mass orbiting a common barycenter, external to both bodies, with eccentric elliptic orbits (a common situation for binary stars).
If the difference in mass is big, enough it may cause wobbling of one body. If the body wobbles, it causes the Doppler Effect. The Doppler Effect is observed whenever the source of waves is moving with respect to an observer. The Doppler Effect can be described as the effect produced by a moving source of waves in which there is an apparent upward shift in frequency for observers towards whom the source is approaching and an apparent downward shift in frequency for observers from whom the source is receding. When this happens to light, it is known as a blue or red shift. By measuring this shift in the color of the light, scientists can work out how big the planet is and how fast it orbits.
Red and Blue spectrums which are used to find the wobbling stars.
ANCIENT AND MEDIEVAL HISTORY OF UKRAINE
Manual for students of the faculties with the teaching
in English
Kyiv-2011
UKRAINE
NATIONAL UNIVERSITY of LIFE and ENVIRONMENTAL SCIENCES of UKRAINE
Natural Humanitarian Scientific Educational Institute
Department of History and Political Sciences
N. ISAKOVA
ANCIENT AND MEDIEVAL HISTORY OF UKRAINE
Manual for students of the faculties with the teaching
in English
Kyiv-2011
ÓÄÊ 93 [477] "0/2" - "04/14": 811.111(07)
ÁÁÊ: 63.3 (0)3
È-85
The manual covers the stages of the historical development of Ukraine from the ancient times till second half of XV- th century. The special attention is paid to the problem of the creation of the ancient Rus state and main stages of its development. The composition contains materials for self-study (quizzes, projects), chronology and recommended literature.
Recommended for publication by the research board of the Natural Humanitarian Scientific Educational Institute .
Author: candidate of historical science, docent Isakova N.P.
Reviewers: Doctor of Historical Science, professor Berenshtein L.Y. (National University of Life and Environmental Sciences of Ukraine);
ñandidate of historical science, docent Palamarchuk N.I. (National Technical University of Ukraine "KPI"),
Practical-methodical edition
ANCIENT AND MEDIEVAL HISTORY OF UKRAINE
Manual for students of the faculties with the teaching
in English
Author: Isakova N.P.
Publication is edited by the author
Signed for printing 25.05.2011 Format 60õ84 1/16
Relative number of printed pages 3,1 Reg. edited pages 3,3
Edition 50 Order ¹
Druk TOV «Anwa-Print»
Vul. Solomjanska, 1, Kiev-35, 03035.
All rights reserved. The text of this publication may not be reproduced or transmitted without prior permission of the publisher.
1. A primitive society on the territory of Ukraine
2.The first state like formations on Ukraine’s territory
3. Eastern Slavs
Chapter II. Medieval Ukraine
1. Origin of Ukrainian Statehood. Kyivan Rus
2. Halytsko-Volynsk Principality
3. The Ukrainian lands making part of the Great Lithuanian Principality and of other States
Quizzes
Chronology
Literature
Preface
History of Ukraine plays an extremely important role in the educational-training process of each educational establishment, as native history is not only an educational study but a part of a national outlook, important part of a common culture of the society and all its members.
Without knowledge of history it is not only difficult to understand the present, foresee and successfully build the future, but to bring up a conscious citizen, real patriot of the Ukrainian state.
The manual “Ancient and Medieval history of Ukraine. Advanced composition for students of the faculties with the teaching in English” is targeted for the students of the higher agricultural institutes of the III – IV levels of accreditation, which follow the baccalaureate program in English.
The stages of the historical development of Ukraine from ancient times to the end of the XV century are covered. The structure of the textbook constitutes of the two sections, corresponding to the new approaches of the division into periods of the Ukrainian history: “Ancient history of Ukraine”, “Medieval Ukraine”. The special attention is brought to the problems of the statehood, social-political, social-economic, cultural, and intellectual development of the Ukrainian people during the various historical stages. It is very actual and useful.
The basis of the educational-methodical textbook is formed by the author lectures and educational-methodical works of the last years, provided according to the requirements of the module-rate system of education and principles of the typical program “History of Ukraine. Syllabus of the subject for students of the facilities with the teaching of several subjects in English”.
In the textbook an attempt to collect and briefly but clearly provide the most important and characteristic events and facts has been made. The special attention is paid to the complex and controversial issues, processes in the history of social-political, social-economic and cultural life of Ukraine from the arousal of first state units on the territory of Ukraine up to joining Rzeczpospolyta by the Ukrainian lands. The detailed consideration of the processes of formation of ancient Rus state and the main stages of its development are provided as well as social-economic and political order of Kyivan Rus and Halytsko-Volynsk statehood.
The characteristic feature of the textbook is its formation in accordance with the first module of the course “History of Ukraine”.
In order to master the study material at the end of each chapter the quiz on every topic is provided. The quizzes are also related to the material that goes beyond the information given in the textbook. The purpose of that is to deepen the self-study of the extra-curriculum literature by the students. For the same reasons at the end of each chapter there are projects.
The project consists of the composition assignment, which develops the student’s writing skills, the ability to express their own ideas. In all cases the composition topic relates to the reading. It enables to expand the themes of the text and gives the students an opportunity to do their own research. Projects will encourage students to take an active part in the learning process.
At the end of the textbook there is a chronological table of the main historical events from the ancient times to the end of XV century as well as an extended list of the recommended literature on the subject “History of Ukraine”.
The manual is a first part of a planned by the author edition of the course of the history of Ukraine in English.