The scientific study of the universe has evolved over time as new evidence and theories have emerged. Originally, it was thought that Earth was at the center of the universe with objects orbiting in perfect circles (the geocentric model). However, careful observations found inaccuracies, leading to proposals of sun-centered models by Copernicus and Kepler. Kepler determined planets orbit in ellipses with the sun at one focus. Galileo's telescope provided further evidence supporting a heliocentric model. Today astronomers use various telescopes to study and better understand the universe.

2. The scientific study of the universe
Astronomy:

3. Originally suggested the universe had
a large stationary Earth in the center,
and the sun, moon, and the stars were
arranged around the Earth in perfect
spheres orbiting in perfect or constant
speeds
OriginalThoughts:

5. As careful mathematical observations
were made, they found the Sun, the
Moon, and some of the “stars” did not
follow paths as thoughts
OriginalThoughts

6. The “stars” that did not follow the
predicted path, rather they
“wandered” across the sky, and thus
were called “planets”, the Greek word
for “wander”
OriginalThoughts

7. Aristotle’sTheories:
• The Earth was in the center, and the Sun, the
Moon, the stars, and the planets orbited on
separate spheres that encased each other and
spun at different rates
• Motion caused by a supernatural being
• Earth was a sphere (could see shadow on moon
during eclipse) and non-moving (because we
could not feel it and falling objects would not
drop straight down)

8. Earth centered, model of the Universe
Geocentric Universe:

9. Retrograde Motion:
A problem with Aristotle’s theory
was that objects would travel one
direction across, the sky, stop,
and go backwards

10. Ptolemy’sTheories:
• Geo-centric
• Each planet was fixed to a small
sphere that was fixed to a larger
sphere
• No changes made for a 1,000 years
until the inaccuracies in predictions
became to big to blame on primitive
equipment

11. Copernicus’Theories
• Proposed a sun-centered universe
with the Earth spinning on its axis
once a day
• Orbits were perfect circles
• Did not publish his findings until his
death because it contradicted the
Church’s beliefs

12. Sun-centered universe
Heliocentric Universe:

13. Tycho Brahe’s Contribution
Built a top of line observatory,
gathered and kept tremendous
amounts of data

14. Johannes Kepler’sTheories
Laws of Planetary Motion:
• Each planet revolves around the Sun in an elliptical
orbit with the sun at one of the foci
• Planets do not move at a constant velocity (due to
gravity pulling)
• There is a mathematical relationship between the
time it takes a planet to revolve around the sun and
its average distance from the sun

15. Galileo Galilei’s Contribution
Developed and refined the
telescope for view distant objects

16. Explosion of matter that occurred 14
billion years ago, and thus the universe
expanding since that point
Big BangTheory:

18. Universe:
The entirety of what we call outer
space

19. A collection of stars, dust, and gas
bound together by gravity (ours is the
Milky Way Galaxy)
Galaxy

20. A collection of planets that revolve
around a star (sun)
Solar System

21. The average distance between the
Earth and the sun; approximately 150
million kilometers
Astronomical Unit:

22. The speed of light is 300,000 km/s
Light Speed

23. The distance that light can travel in
one year (9.46 km x 1012)
LightYear

24. All the frequencies or wavelengths of
electromagnetic waves (energy)
Electromagnetic Spectrum

26. Notes on the Elec. Spec.
• What we see falls into the visible
light spectrum
• Only stars emit visible light,
everything else (planets & moons)
are reflecting light
• Other instruments can detect the
other electromagnetic waves

27. An instrument that collects
electromagnetic radiation from the sky
and concentrates it for better
observation
Telescopes

28. Telescopes that only collect visible
light
OpticalTelescopes

29. RefractingTelescope: Uses a set lenses
to focus light
ReflectingTelescope: Uses a set of
mirrors to focus light
OpticalTelescopes

30. Used to detect radio waves, gamma
rays, and infrared rays
Invisible Electromagnetic Radiation
Telescopes

31. Telescopes that
were launched into
space to escape
obstructive Earth’s
atmosphere
(HubbleTelescope)
SpaceTelescopes