Chapter 1: The Earth in Context Slide Set 2

Question 1

Explain the Doppler Effect in terms of universe

Answer 1

Light from sources moving away from us will be “redshifted” (shifted to lower frequency and longer wavelength).
Light from sources moving towards us will be “blueshifted” (shifted to higher frequency and shorter wavelength).

Question 2

How do we know that the universe is expanding?

Answer 2

Light from distant galaxies is redshifted, therefore they are moving away from us (Edwin Hubble)

Question 3

How do we estimate the distance of the galaxies?

Answer 3

Distance of galaxies is estimated from brightness and size.

Question 4

How do we estimate the distance of galaxies from brightness?

Answer 4

Light takes time to travel from far away objects in space to us on Earth. How far we can see is correlated with how far back in time we can see.

Question 5

What do we mean when we say a planet is … light years away?

Answer 5

we are seeing the light 13 billion years after it left the star

Question 6

Explain the Big Bang theory?

Answer 6

• All matter and energy condensed into an infinitesimally small point that appeared 13.8 billion years ago (we don’t know how)
• At first, it was very hot (~1027 K), expanding very quickly (inflation - from the size of an atom to the size of a galaxy in 10-32 seconds), and cooling

Question 7

What happened in the first 10ˆ-10 seconds after the Big Bang?

Answer 7

Quarks – the subatomic particles that form atoms, most of which are annihilated when they collide with each other.

Question 8

What happened in the first 10ˆ-5 seconds after the Big Bang?

Answer 8

Quarks bond to form protons (+ charged, = Hydrogen nuclei), neutrons (neutral charge) and electrons (- charged); in these hot, high pressure conditions, positive and negative particles annihilate each other when they collide

Question 9

What happened in the first 3 minutes after the Big Bang?

Answer 9

nucleosynthesis – fusing of Hydrogen nuclei (i.e. protons) to form Helium, (and other light elements). Hydrogen and helium were essentially the only elements present in the early Universe, and remain to this day, the most abundant elements in the Universe.

Question 10

What happened in the first 380,000 years after the Big Bang?

Answer 10

For atoms (with electrons joined to protons and neutrons) to form, the universe needs to cool and expand more

Question 11

What happened 380,000 years after the Big Bang?

Answer 11

• Negatively charged electrons attached to positively charged protons.
• Matter suddenly becomes electrically neutral, and the earliest light in the Universe is emitted (cosmic microwave background - CMB).
• Atoms and molecules coalesced into gaseous nebulae.

Question 12

What is CMB (Cosmic Microwave Background)?

Answer 12

background energy coming from everywhere in the Universe from when matter went from ionized (+ protons and – electrons are separate, matter full of charge) to electrically neutral.

Question 13

How do we get heavier elements than H and He?

Answer 13

We need to increase the number of protons in the nucleus, which requires a lot of heat. (e.g., to overcome the electrical repulsion exerted by one proton over another)

Question 14

Universe has cooled down a lot but so how do we get the energy to get heavier elements than H and He?

Answer 14

Star formation

Question 15

Explain the process of star formation

Answer 15

1. Gravity caused collapse of gaseous nebulae, building up heat, pressure, energetic collisions of atoms
2. Enough energy for Hydrogen fusion (or “hydrogen burning”). Fusion releases energy at the center of the star, which pushes outwards, resisting gravity and preventing the star from collapsing.
3. Added energy from hydrogen fusion provides enough energy for Helium fusion, which provides enough energy for Carbon fusion, …. Etc.

Question 16

How come the stars don’t collapse during formation?

Answer 16

Fusion releases energy at the center of the star, which pushes outwards, resisting gravity and preventing the star from collapsing

Question 17

What are the burning layers of a star? From exterior to interior

Answer 17

H burning
He burning
C burning
Ne burning
O burning
Si burning 
Fe-Ni burning

Question 18

Explain the process of star destruction (supernova)

Answer 18

1. Silicon (Si) fusion creates iron (Fe) at the center of the star. Fe fusion absorbs energy rather than releasing energy like the fusion of lighter elements, so the push outwards to balance gravity is reduced
2. Gravity wins! Star collapses.
3. Supernova Explosion! Enough energy to create heavier elements.
4. The process repeats, making more heavier elements….

Question 19

Where do elements come from?

Answer 19

• First-generation stars left a legacy of heavier elements.
• Second-generation stars repeated heavy element genesis.
• Succeeding generations contain more heavy elements.
• The sun may be a third-, fourth-, or fifth-generation star.

Question 20

The mix of elements found on Earth include: ______

Answer 20

• Primordial gas from the Big Bang.

- The disgorged contents of exploded stars

Question 21

What is the hypothesis behind the solar system evolution?

Answer 21

Forming the solar system, according to the nebula hypothesis:
A second- or third-generation nebula forms from hydrogen and helium left over from the big bang, as well as from heavier elements that were produced by fusion reactions in stars or during explosion of star

Question 22

How did the solar system form?

Answer 22

1. The nebula condenses into a swirling disc, with a central ball surrounded by rings
2. The ball at the center grows dense and hot enough for fusion to begin (> 5x106oC). It becomes the Sun. Dust (solid particles) condenses in the rings
3. The nature of the matter condensed depends on temperature. At distance of Earth from Sun, temperature ~1500 oC. Iron (melting point 1538 oC), and olivine ((Fe,Mg)2SiO4; melting point 1500 – 1700oC) condense. At distance of Jupiter, water ice (melting point 0 oC) and ammonia (melting point -78oC) condense, and at distance of Neptune, methane (melting point – 182 oC) condenses.
4. Dust particles collide and stick together, forming planetesimals

Question 23

How did the Earth form?

Answer 23

1. Planetesimals grow by continuous collisions.
2. Gradually a proto-Earth develops
3. Gravity reshapes the proto-Earth into a sphere.
4. The Interior heats up (from collisions, high pressure, radioactive decay) and becomes soft.
5. The interior differentiates into:
   - A central iron-rich core (heavy)
   - A rocky outer shell—a mantle (lighter)

Question 24

How did the moon form?

Answer 24

Soon after Earth forms, a small planet collides with it, blasting debris that forms a ring around the Earth.
The Moon forms from the ring of debris

Question 25

How did the atmosphere and oceans form?

Answer 25

Eventually the atmosphere develops from volcanic gases (mainly H2O and CO2). As the Earth cools, moisture condenses, it rains and the oceans fo

Question 26

How old is the oldest rock on Earth and how is that measured?

Answer 26

Age of 4.3-4.4 Ga using the samarium-neodymium dating system

Question 27

What is the oldest rock on Earth and how are its properties interpreted?

Answer 27

Faux Amphibolite - basaltic rocks deposited in a submarine volcanic environment - alternating iron deposition layers --> sediments deposited by bacterial activity in a marine environment?

Question 28

What could the oldest rock tell us about the early Earth?

Answer 28

- Early Earth was generally viewed as inhospitable with lava oceans and constant asteroid bombardment - These rocks tell us there were periods of calm where a water ocean could form - Banded with iron formation tell us that life could have evolved in one of these oceans-much earlier than preciously thought-in a period of calm and stability before the Late Heavy Bombardment

Question 29

What is a planet?

Answer 29

- Is a large solid body orbiting a star (the Sun). - Has a nearly spherical shape. - Has cleared its neighborhood of other objects (by gravity).

Question 30

What is a moon?

Answer 30

a solid body locked in orbit around a planet

Question 31

What are the two groups of planets occur in the Solar System? What are their characteristics and which planets belong to these groups?

Answer 31

1. Terrestrial Planets—small, dense, rocky planets - Mercury, Venus, Earth, and Mars 2. Giant Planets—large, low-density, gas and ice giants - Gas giants: Jupiter, Saturn (hydrogen and helium) - Ice giants: Uranus, Neptune (frozen water, ammonia, methane)

Question 32

What are asteroid belts?

Answer 32

Most meteorites are pieces of rocks broken off asteroids during their collisions with one another. As a result of collisions, their orbit around the Sun is modified and some of these pieces can enter the Earth’s gravitational field.

Question 33

What is a meteorite?

Answer 33

solid extraterrestrial material that survives passage through the Earth’s atmosphere and reaches the Earth’s surface as a recoverable object.

Question 34

Orbiting around Earth, what would the space visitors would notice? (Earth system components)

Answer 34

- Atmosphere—the gaseous envelope. - Hydrosphere—the blue liquid water. - Biosphere—the wealth of life. - Geosphere—the solid Earth.

Question 35

Explain the Earth's Magnetic Field

Answer 35

- The magnetic field of a bar magnet has invisible lines of flux. Flux lines point out from the N pole and in toward the S pole. Lines of flux cause iron filings to align. - Earth’s magnetic field is represented by a giant bar magnet. Earth’s present magnetic field has southern polarity in the north. This is why the N compass needle points north

Question 36

What distorts the Earth's Magnetic field? What shape does it give to it? How is the cosmic radiation intercepted?

Answer 36

- The solar wind distorts the magnetosphere. - Shaped like a teardrop - Deflects most of the solar wind, protecting Earth - The strong magnetic field of the Van Allen belts intercepts dangerous cosmic radiation.

Question 37

How do Northern/Southern lights occur?

Answer 37

- Expression of the interaction of cosmic particles with the Earth’s magnetic field - Some charged particles make it past the Van Allen belts. These are channeled along magnetic field lines. They cause atmospheric gases in polar regions to glow

Question 38

What is the Atmosphere? How was is formed and what is it made out of?

Answer 38

- Our atmosphere is mostly nitrogen (N2) and oxygen (O2). - The remaining gases (totalling less than 1%) include: * *Argon (0.93%), carbon dioxide (0.039%), neon (0. 0018%) * *Other, less common gases (helium, methane, krypton) . - The atmosphere thins away from Earth.

Question 39

What happens to the atmosphere as we go closer to the Earth?

Answer 39

- The atmosphere is more dense closer to Earth. - With increasing elevation: * *Pressure decreases. * *Density decreases. * *Oxygen content decreases.

Question 40

How are atmospheric levels separated? What are the names and the properties of these layers?

Answer 40

Atmospheric layers are separated by pauses: - Troposphere (0–11 km): ** Wind and clouds. ** Weather is confined to this layer. ** Temperature decreases upward. ** Nitrogen and oxygen atoms absorbing incoming solar radiation - Stratosphere (12–47 km) ** Ozone absorbs UV radiation from the sun which, in turn, increases the motion of the ozone molecules, warming the air - Mesosphere (47–82 km) - Thermosphere (82 km+) - Outermost layer.