ASTRONOMY-THE ORIGINAL SCIENCE

Bellwork: Imagine that it is 5,000 years ago. Clocks and modern calendars have not been invented. How would you tell time or know what day it is?

One way to tell the time is to study the movement of stars, planets and the moon. Studying the ancient skies was so important that ancient people built observatories.

Over time, the study of the night sky became the science of Astronomy. Today Astronomy is known as the study of the universe.

WHO’S WHO OF EARLY ASTRONOMY

• Early astronomers used their eyes and minds to discover the universe.

• They believed that the universe was made up of the sun, moon, and planets. The stars were at the edge of the universe.

PTOLEMY: AN EARTH-CENTERED UNIVERSE

• A Greek Astronomer-around 100 AD

• Ptolemy thought that the Earth was at the center of the universe and that the other planets and the sun revolved around the Earth.

• Although his theory was incorrect, it predicted planetary motion better than any other theory at the time.

• His theory was the most popular for the next 1,500 years. (Geocentric Theory)

NICHOLAS COPERNICUS: A SUN-CENTERED UNIVERSE

•A Polish astronomer (1543)

•New theory changed astronomy forever:

•Heliocentric theory-the sun is at the center of the universe, and all of the planets, including the Earth, orbit the sun.

•The theory correctly explained the movement of the planets around the sun but it did not replace Ptolemy’s theory immediately.

GALILEO: TURNING A TELESCOPE TO THE SKY

•In 1609, Galileo Galilei became one of the first people to use a telescope to observe objects in space.

•He discovered craters and mountains on the Earth’s moon, four of Jupiter's moons, sunspots on the sun, and the phases of Venus.

•These discoveries gave him proof that the planets did indeed revolve around the sun, as Copernicus had stated.

JOHANNES KEPLER: LAWS OF PLANETARY MOTION•In 1609, Kepler concluded that all of the planets revolve around the sun in elliptical orbits and that the sun in not the exact center of the orbits.

JOHANNES KEPLER: LAWS OF PLANETARY MOTION•In 1609, Kepler concluded that all of the planets revolve around the sun in elliptical orbits and that the sun in not the exact center of the orbits.

•Stated his ideas in three laws of planetary motion:

1-the sun is the center of universe and the planets revolve around it in elliptical orbits.

2-the planets move faster when closer to the sun.

3-a mathematical formula to determine the distance of a planet from the sun.

ISAAC NEWTON: THE LAWS OF GRAVITY•In 1687, Isaac Newton showed that all objects in the universe attract each other through gravitational force.

•The force of gravity depends on the mass of the objects and the distance between them.

•Newton’s law of gravity explained why all of the planets orbit the most massive object in the solar system---the sun.

MODERN ASTRONOMY

• The invention of the telescope and the description of gravity were two milestones in the development of modern astronomy.

• More than 200 years later, they discovered what is past our solar system.

EDWIN HUBBLE: BEYOND THE EDGE OF THE MILKY WAY

•In 1924, Edwin Hubble proved that other galaxies existed beyond the edge of the Milky Way.

•His data confirmed the beliefs of some astronomers that the universe is much larger than our galaxy.

REVIEW

Raise your hand if you know the answer to the following questions.

REVIEW

Q: Who was the first to write down the theory drawn to the left?

A: Ptolemy

REVIEW

Q: Who first came up with the idea drawn to the left?

A: Copernicus

REVIEW

Q: Who decided that planets revolve around the sun in elliptical orbits?

A: Kepler

REVIEW

Q: Who used the telescope first?

A: Galileo

REVIEW

Q: Who discovered the galaxies past our own?

A: Hubble