earth

Question 1

how do we know the age pf the universe?

Answer 1

• the red shift = look at an object and record light as a particular freq
• dopler effect = pitch increases as it comes close and decreases as it moves away

Question 2

how did elements initially form in the universe?

Answer 2

hot elements began to cool and clump together

Question 3

what is the lightest element?

Answer 3

H+

Question 4

what does the sun do to H?

Answer 4

it burns to produce He

Question 5

what do large stars do?

Answer 5

burn He and then C until Fe is formed

Question 6

how are the rest of the elements made?

Answer 6

during a star’s evolution/ rapidly when a giant star explodes = supernova explosion

Question 7

what type of nebula is left over from an explosion?

Answer 7

orion

Question 8

rocky planet formation

Answer 8

coagulation: 10^4, dust grains collide to form cm size particles and these grow to km size

Question 9

what is runaway accretion?

Answer 9

coagulation: 10^4-10^5
grow by collision to ~1000km planetesimals
growth rate increases with mass so large objects grow faster hence ‘runaway’

Question 10

oligarchs

Answer 10

10^5-10^6
grow by accreting planets and merging with one another to form ~100 planetary embyros, well spaces and residing in gaps in the planetesimal field

Question 11

merger of embryo planets

Answer 11

on the time scales 10^7-10^8 embryos collide on this slow time scale, leaving 2-5 earth sized planets

Question 12

what planet could be a failed embryo?

Answer 12

mars

Question 13

how do giant planets and ice asteroids form?

Answer 13

• beyond the snow line when water condenses, adding many times by the mass
• cores accrete by similar process to rocky planets
• once a critical mass of 10xearth is reached, accretion of gas can occur to produce gas giants

Question 14

examples of gas giants

Answer 14

Jupiter and Saturn

Question 15

why are Uranus and Neptune not gas giants?

Answer 15

may have reached critical mass too late

Question 16

what do some larger asteroids also contain?

Answer 16

water ice

Question 17

how was the interior of the earth heated?

Answer 17

by the release of gravitational energy, once grown to 10% of its present size melting began

Question 18

how did the core form?

Answer 18

dense droplets of Fe descended through the deep magma ocean to form the core

Question 19

when was core formation complete?

Answer 19

by 50 Ma

Question 20

what were required to form first before heavy elements could form?

Answer 20

giant stars to form and synthesise through nuclear fusion and explosion

Question 21

what allowed the differentiation of the inner earth?

Answer 21

the heat of collision and radioactivity which melts rock