REPUBLIC OF THE PHILIPPINESBULACAN STATE UNIVERSITYCITY OF MALOLOS, BULACAN

BELEN, Lemuel Kim C. SCI313 ASTRONOMYBEEd Generalist 3 – B MR. GARCIA CIRIACO

THE UNIVERSE

As the totality of everything that exists, including all matter and energy,

the planets, stars, galaxies, and the contents of intergalactic space.

CLAUDIUS PTOLEMY

Ptolemy is most famous for his contribution to astronomy, which is in his 13-book work

called the Almagest.

The Ptolemaic system of astronomy placed the Earth at the center of the universe and explained

all the observed motions of the Sun, Moon, planets, and stars with a system of uniform circular

motions.

Ptolemy borrowed heavily from the previous work of Hipparchus.

The Ptolemaic astronomical system was wrong, but it was a good enough scientific model to last

over 1400 years until the time of Copernicus.

ARISTARCHUS OF SAMOS

Aristarchus (310 BC -230 BC) was a famous Greek mathematician and astronomer,

popular for his theories regarding the heliocentricity of our solar system.

He was the first to say that the Sun, and not the Earth, was the center of our universe. This theory

brought him ridicule during his lifetime. 

Aristarchus was one of the first astronomers to calculate the relative sizes of the Sun, the Moon

and the Earth.

NICOLAS COPERNICUS

The Universe was Earth centered. His theory answered the fact that the planet’s sizes

were different throughout the year and the fact that the orbits of the planets were irregular now

and then would be explained. He wrote his theory in a book, De Revolutionibus Orbium

Coelestium (On the Revolutions of the Heavenly Spheres)

GALILEO GALILEI

In 1609, instrument put together by a lens-grinder in Holland, he constructed the first

complete astronomical telescope.

Galileo discovered that the moon, shining with reflected light, had an uneven, mountainous

surface and that the Milky Way was made up of numerous separate stars.

In 1610 he discovered the four largest satellites of Jupiter, the first satellites of a planet other

than Earth to be detected. He observed and studied the oval shape of Saturn (the limitations of

his telescope prevented the resolving of Saturn's rings), the phases of Venus, and the spots on the

sun. His investigations confirmed his acceptance of the Copernican theory of the solar system;

but he did not openly declare a doctrine so opposed to accepted beliefs until 1613, when he

issued a work on sunspots.

ISAAC NEWTON

Gravity, Newton’s other great contribution, is one of the four fundamental forces in the

universe.

Because of Galileo’s work, Newton knew that an object fell to the Earth at a rate of about

9.8 meters (32 feet) per second. Thus “the apple [that] fell from the tree” fell to the Earth at

about this rate.