Module 1 Week 2

Question 1

1. What does the Big Bang Theory postulate?

Answer 1

• The Big Bang Theory postulates that 12 to 14 billion years ago, the portion of the universe we can see today was only a few millimeters across. Then, it expanded from this hot dense state into the vast and much cooler cosmos we currently inhabit.

Question 2

2. What are the three main evidence for the Big Bang Theory?

Answer 2

• The expanding universe, the abundance of light elements (H, He, Li), and the uniform cosmic microwave background all prove that the Big Bang Theory might be accurate.

Question 3

3. What is the Red Shift? Why is it proof of an expanding universe?

Answer 3

• The Red Shift is similar to the Doppler effect. It is a concept used by astronomers to explain the displacement of the spectrum of an astronomical object toward longer wavelengths (red). The farther an object goes, the longer the wavelengths are, meaning that there is a shift towards the red end of the spectrum. This suggests and proves that the universe is expanding.

Question 4

4. What were the first elements to form in the Universe?

Answer 4

• The first elements to form in the universe are hydrogen and helium.

Question 5

5. How are stars formed? What is the origin of the energy released by stars?

Answer 5

• As hydrogen and helium started lumping together because of gravity, clouds of dust are formed and eventually collapsed. Nuclear fusion happens due to this collapse and forms the first stars and then the galaxies afterwards.

Question 6

6. Gravitational energy should in theory halt the expansion of the universe. What force is causing the universe to continue to expand?

Answer 6

• The expansion of the universe crucially depends on the ratio or proportion between dark matter and dark energy.

Question 7

7. Compare and contrast the composition of the Earth and the Universe. What are the implications with regard to the possible origin of the Earth?

Answer 7

• The universe and the earth do not have much difference regarding rock forming minerals. However, in terms of volatiles, the universe contains more of it compared to the whole earth. The whole earth, on the other hand, contains more inert gases. This implies that early on the evolution of earth, it contained a lot of hydrogen and helium, but it was swept away by solar winds. This is because the earth is not as big as the other gaseous planets.

Question 8

8. What controls the luminosity of stars?

Answer 8

• Both the surface temperature and surface area of a star control its luminosity.

Question 9

9. What are main sequence stars?

Answer 9

• For the main sequence stars, the cooler they are, the less luminous. The hotter the star, the more luminous it is.

Question 10

10. Why are red giants have high luminousity considering their surface is not that hot?

Answer 10

• The luminosity of a star is not only a function of surface temperature. It is also a function of surface area. Since they are super giants, which means they are very large, they can be very luminous even if they’re not that hot.

Question 11

11. How are stars formed? Will all stars have the same fate? Why?

Answer 11

• Hydrogen and helium begin to collapse due to gravity. Gravitational energy is transformed into heat energy as it collapses to a core. Once a certain temperature is achieved, a star is born by fusing together elements. The fate of a star depends on its mass.

Question 12

12. What is nucleosynthesis? How are elements heavier than Hydrogen formed?

Answer 12

• Nucleosynthesis is the process wherein the energy being released by the sun and other stars, is formed.
• Once hydrogen is used up to form helium, the star burns helium to form progressively heavier elements, carbon, and oxygen and so on, until iron and nickel are formed.

Question 13

13. How are elements heavier than Iron and Nickel formed?

Answer 13

• When carbon, oxygen, and other elements are formed, the hottest fusing of elements in the core forms iron and nickel. They are produced during a supernova explosion.

Question 14

14. Since the Earth and Solar System contain elements heavier than Fe and Ni, what assumption can be made with regard to their origin?

Answer 14

• It can be assumed that a large energy source, even larger than that of a star, is included in the origin of the earth and the solar system.

Question 15

1. Why is the sun considered to be a second-generation star?

Answer 15

• This is due to recycling from earlier times. The sun is considered a 2nd generation star because the 1st one is a red giant which resulted to a supernova explosion. This explosion created another star which is our sun.

Question 16

2. Explain how the solar system was formed according to the Nebular Hypothesis.

Answer 16

• A supernova explosion forms a gas nebula which is mainly composed of gases and dust. Due to gravitational attraction, this mass of gas and dust collapsed into a disc. Mass flowed inward to form the sun and then there was angular momentum surrounding the sun, which later on, because of accretion and bombardment, formed the planets.

Question 17

3. Why are the inner terrestrial planets depleted of Hydrogen and Helium?

Answer 17

• While terrestrial planets gathered from planetesimals made of rocks and metals, they ended up too small to catch large amounts of hydrogen and helium gas in the solar nebula.

Question 18

4. How was the Earth’s moon formed?

Answer 18

• A planet, about the size of Mars, collided with the Earth. The impact of this collision resulted to a part of the Earth’s mantle being ejected. This was captured by the Earth’s gravity and they accreted to form the moon.

Question 19

5. The Earth has an internal heat. What is/are the sources of this heat?

Answer 19

• The first source of heat is the residual heat because of the initial impact of objects into the earth. Its kinetic energy from the collision was transformed into heat energy.
• The second source is due to radioactive decay. New earth had much radioactive material generating heat while decaying.
• The third heat source would be the transformation of gravitational energy to heat energy.

Question 20

6. Explain the Iron Catastrophe in relation to the formation of the Earth’s core, mantle, and the crust. Why is the Iron Catastrophe an example of a positive feedback loop?

Answer 20

• During the formation of the solar system, asteroids impacted and heated the earth. Iron and other metals near the surface melted. These turned into large drops which migrated towards the center, forming the earth’s core. The lighter elements, on the other hand, migrated towards the surface which formed the crust.
• The Iron Catastrophe is an example of a positive feedback loop because when the iron and other metals migrate towards the center due to the accretion of heat and radioactive decay, gravity liberates more heat which causes more heating in the surface. Gravitational energy is transformed into heat energy yet again.

Question 21

7. Trace the evolution of the Earth’s atmosphere. Explain how the current composition is the result of the interaction between the lithosphere, atmosphere, hydrosphere, and the biosphere.

Answer 21

• In the beginning, only helium and hydrogen composed the atmosphere. This was blown away by solar winds and was later replenished by volcanic out gassing. Volcanism and comet impacts resulted to the accumulation of gases. The early atmosphere was dominated by water, carbon dioxide, and with a bit of nitrogen.
• Once the earth started to cool down, precipitation is initiated, which draws out water and carbon dioxide from the atmosphere. This leaves behind nitrogen, which explains why it is the dominant gas in the atmosphere. The hydrologic cycle also resulted to the beginning of sedimentary processes—weathering, erosion, and deposition. Through photosynthesis, life contaminated the atmosphere and generated oxygen.