Chapter 1 Cosmology And Earth

Question 1

3,000 years ago people knew…

Answer 1

Thought stars are fixed points in the sky. Planted move against the background of stars.
They didn’t know the earth is a planet
They didn’t know how heavenly bodies move

Question 2

250 BCE

Answer 2

The Greeks first proposed a heliocentric (sun centered) universe

Question 3

Renaissance

Answer 3

A new age of discovery 1400s in Europe.
New scientific exploration:
Copernicus- published evidence for heliocentricity
Galileo- observed moons orbiting Jupiter
Newton-planet motion explained by his theory of gravity.

Question 4

Terrestrial planets

Answer 4

Small, dense, rocky planets.
Mercury, Venus, earth, Mars
Four most interior planets
Between Mars and Jupiter is an asteroid belt

Question 5

Gas-giant planets

Answer 5

Large, low density
Jupiter, Saturn, Uranus and Neptune.
Four most outer planets.

Question 6

Eratosthenes

Answer 6

-Calculated the circumference in 200 BC

-

Question 7

Speed of light

Answer 7

186,000 miles /s (300,000 km/s)

Question 8

The moon

Answer 8

1.3 light seconds 237,000 miles away

Question 9

The sun

Answer 9

8.3 light-minutes - 93 million miles away

Question 10

A light year

Answer 10

Measures a distance 9.5 trillion Km

Question 11

Alpha centauri

Answer 11

The closest star, is 4.3 light years away

Question 12

The Doppler effect

Answer 12

400 nm- blue- higher frequency
700nm- red- low frequency
Sound waves compress or relax with relative motion.
Compressed- shorter wavelength ; higher frequency
Relaxed: longer wavelength; lower frequency.

Question 13

After Big Bang

Answer 13

Hydrogen formed (H2) the fuel of stars

• atoms and molecules formed into gaseous nebulae
• gravity caused compass of nebulae
• collapse resulted increase in: temp, density, rate of rotation
• exploded 13.7 Ga and expanding ever since

Question 14

Cosmology

Answer 14

The scientific study of the universe

Structure and history

Question 15

The expanding universe

Answer 15

Light from galaxies was observed to be “red shifted”
Edwin Hubble.
Hubble decides that whole universe must be expanding (analogous to raisin bread dough)

Question 16

Aftermath of the big bag

Answer 16

• hydrogen atoms within a few seconds
• at 3 min hydrogen atoms fused to form helium atoms
• light nuclei (Be, Li, B) Big Bang nucleosynthesis
• with cooling that followed hydrogen formed - the fuel of stars.

Question 17

Nebulae building

Answer 17

Gravity pulls in sediments and rotation rate is increased developing a disk shape.
Gains mass and density
Central ball of the disk became hit enough to glow
Very early stars

Question 18

Birth of star

Answer 18

Young star- protostar

• pulling in more mass and creating a denser core
• temp rise to 10 million degrees
• these temps, hydrogen nuclei fused to create helium.
• with the start of nuclear fusion, the protostar”ignited”

Question 19

Where do elements come from?

Answer 19

Big Bang nucleosynthesis formed lighted elements (H, He, Li, Be and B)

• heavier elements are from stellar nucleosynthesis ( C to Fe)
• elements with atomic numbers are formed during supernovas

Question 20

Planetesimals

Answer 20

Clump into a lumpy protoplanet.
The interior heats, softens and forms a sphere
The interior differentiates into: a nickel- iron core and a stony silicate mantle

Question 21

Formation of the moon

Answer 21

4. 53 ga a Mars sized planetoids collides with earth
   - the planet and part of earth mantle are disintegrated
   - collision debris forms a ring around the earth
   - the debris coalesces and forms the moon- the moon has a composition similar to earths mantle