PHYSICS FORM FOUR FULL NOTES - ALL TOPICS
Physics Notes Form 4 - All Topics | Lesson Notes based in Tanzania.
ASTRONOMY:- Is the study of the universe and heavenly bodies.
OR
This is the branch of science that deals with the study of the origin, evolution, position, distance and motion of all bodies (objects) and scattered matter in the universe.
ASTRONOMER:Is a person who study astronomy.
IMPORTANCE OF ASTRONOMY TO MANKIND
➢ Astronomy presents a new frontier for exploration.
➢ Astronomy helps us to understand where the earth and the life it supports, originated from and how it evolved.
➢ Astronomy used in navigation. Based on the knowledge of the position of the sun during day time
and the stars at night.
➢ It was the earliest method of measuring time.
➢ It was use to develop calendars that made it possible to predict the seasons.
ASTRONOMICAL THEORIES
• These are the theories that were proposed by scientific astronomers about the study of the universe.
These theories are:
i) Geocentric theory
ii) Heliocentric theory
i) GEOCENTRIC THEORY
• This is the theory that was suggested by the astronomer Claudius Plotemy in 140AD.
❖ He considered the earth to be stationary whiles the moon, sun and planets all moves around the
earth.
FUNDAMENTAL ASSUMPTIONS CONCERNING GEOCENTRIC THEORY
❖ Mr. Claudius Plotemy put on some assumptions regarding his theory.
These are:-
i) The sun, the moon, the planets and the stars revolves in circular orbits around the earth and the earth is at the centre of the system and is stationary.
ii) Each revolving body moved around the earth with uniform speed.
❖ The theory was based on religious beliefs, observations and common sense.
❖ Also it was assumed that, all heavenly bodies are attracted towards the earth.
ii) HELIOCENTRIC THEORY
• This is the theory that was proposed by Nicolous Copernicus in 1512 AD.
❖ He considered the sun to be stationary at the centre and all other heavenly bodies including the earth moves around it in circular path (orbit).
❖ The theory could explain convincingly the occurrence of day and night and based on scientific
proof.
THE SOLAR SYSTEM
• This is the collection of the heavenly bodies that revolve around the sun.
❖ The solar system consist the sun, eight planets, dwarf planets, stars, moon, asteroids, comets, meteoroids, interplanetary dust and other celestial objects
STARS
A star: Is a large celestial body made up of hot gases known as plasma.
Plasma: Refers to an ionized gases in which a certain proportion of electrons are free rather than bound to an atom or molecule.
❖ Stars radiate energy derived from the thermonuclear reactions in the interior region.
GALAXY: Is a giant collection of stars, gas and dust in the universe.
❖ Most stars in the universe are in galaxies. Nearly all stars visible in the night sky are within our own
galaxy and sometimes called Milky Way Galaxy.
