1. 1.1 Early Views about the Cosmos
Space Exploration
1.1 Early Views about the Cosmos

2. Celestial objects have fascinated humans throughout history
Celestial objects have fascinated humans throughout history. These include:
The sun
The moon
The stars
Constellations
Planets
Meteors
Falling stars
Northern lights

3. Celestial events of particular interest to humans were / are:
Solar and lunar eclipses
Meteor showers
Aurora borealis
Comets
The Greeks were the first
to explain how the universe
worked in a logical, systematic manner.

4. Models of Planetary Motion
1. Geocentric model: Aristotle 2000 years ago
The earth is the center of the universe
Heliocentric model: Copernicus about 1500 AD
- The sun is the center of the universe and all other planets orbit around it.

5. Models of Planetary Motion
Geocentric Model
Heliocentric Model
Proposed by / when:
Aristotle – over 2000 years ago
Copernicus – 1530 AD
Description:
Earth is center of universe
Sun is center of universe
Supported by:
Euclidian and Pythagorean math used to calculate the size of the spheres
Telescopes allowed scientists to see mountains on the moon and the rings of Saturn
What wasn’t explained:
Movement of the planets was irregular
Planetary motion didn’t follow a circular pathway
What next:
Replaced with the heliocentric model
Updated to account for elliptical pathways of the planets

6. Geocentric Model - Aristotle

7. Heliocentric Model - Copernicus

8. Copernicus’ Model
(Heliocentric)
Confirmed by Galileo and Kepler
Aristotle’s Model
(Geocentric)
Assisted by Pythagoras
and Euclid

9. Revisions to the Heliocentric Model
Galileo Galilei – saw mountains on the moon with a telescope and confirmed Copernicus’ ideas
Tycho Brahe – observed and recorded the movement of the planets, confirmed a circular orbit was not likely
Johannes Kepler – proposed the planets followed elliptical orbits around the sun

10. Cosmological Events
Solstice means “sun” “stop” and represent the shortest and longest periods of daylight.
June 21 – the summer solstice is the longest day of the year
Dec 21 – the winter solstice is the shortest day of the year

11. Equinox
Means “equal” “night” and represents periods of equal day and night.
Vernal Equinox - March 21 – spring equinox
Autumnal Equinox - Sept 22 – fall equinox

13. Ancient peoples celebrated the solstice and equinox occasions by creating large structures
Chichen Itza
Pyramids at Giza
Stonehenge
Medicine Wheel

14. Our solar system – size and scale

15. Astronomy tools
Sundial: have been used for more than 7000 years to measure the passage of time - based on the sun's position in the sky
Merkhet: invented by the Ancient Egyptians to chart astronomical positions and predict the movement of stars
Quadrant: Invented in the 2nd century AD by the Egyptian astronomers to measure a star's height above the horizon

16. Astrolabe: Used by Arabian astronomers to make accurate charts of star positions
Cross-staff: invented by Levi ben Gurson to measure the angle between the Moon and any given star
Early Telescope (late 16th century): invented in the late 16th century and it allowed astronomers such as Galileo to discover details about Earth's closet planetary neighbors and the relative size and distance of what laid beyond Earth

17. Optical/Radio Telescopes and Space-Based Telescopes: operating from Earth, satellites orbiting around Earth and space-based telescopes have reveals the immensity of objects in space and distances across the universe. Also have discovered that our sun is simply one in the corner of our galaxy that is among of billions of other galaxies.

18. Measuring Distance and Time in Space
Astronomical Units (AU) - Used for….measuring "local distances", inside our solar system
1 AU = average distance from the center of Earth to the center of the Sun = km
Used when…describing positions of the planets relative to the Sun
less than 1 = closer to the sun than Earth
greater than 1 = further from the sun than Earth
The furthest planet (Pluto) from the sun is 39.5 AU away

19. Light Years
Used for….when the vast distances beyond the solar system, out to the stars and galaxies are too great for astronomical units.
It equals the distance that light travels in one year
Speed of light is… km/s
Light travels 9.5 trillion km in 1 year
The nearest star (after the sun) is 4 light years away.

20. Looking In the Past
The light we seen has taken time to get to us therefore the images we see are from the past. The time delay for the images coming from the following places is…
Light travelling from… Time Delay
The moon second
The sun minutes
Pluto hours
Stars in the center years
of the galaxy
Light captured by the 13 billion years
Hubble light telescope
Do Check and Reflect p. 383, # 1-8