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Earth and Ocean Systems > The Earth, the Universe and Everything > Flashcards

The Earth, the Universe and Everything Flashcards

Lectures 1.1-1.5

1
Q

What are the two theories on the configuration of our solar system? Which is correct?

A

Geocentric - Things orbit around the earth
Heliocentric - Things orbit around the sun (correct)

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2
Q

What did the Babylonian’s and Greeks observe about the stars?

A

They are fixed relative to each other and rotate around a fixed point.

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3
Q

Why and when was the geocentric theory popular?

A

In the early ADs and middle ages due to the influence of Ptolemy and church leaders, due to the comforting idea of the universe centered around us.

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4
Q

When did this change?

A

The Renaissance due to the new age of scientific discovery such as under Galileo. Backed up when Newton discovered gravity and explained the attractive force that objects exert on one another.

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5
Q

How did we discover the size/shape of the earth?

A

Ships disappearing in the distance. Size from measuring shadows in deep wells 800km apart.

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6
Q

What is perihelion?

A

The point in earths orbit in which it is closest to the sun.

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7
Q

What is aphelion?

A

The point in earths orbit in which it is furthest from the sun.

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8
Q

What is the ecliptic?

A

The plane of earths orbit about the sun.

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9
Q

Is the axis of earths rotation perpendicular to the ecliptic?

A

No. This means the ecliptic crosses over the equator rather than always being on it.

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10
Q

Why do we have seasons?

A

The earths tilt. Higher tilt means more sunlight to poles, causing those month long arctic days.

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11
Q

What is the importance of earths orbit being eccentric?

A

It is not a circle, so the distance to the sun varies throughout the seasons.

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12
Q

What causes the North Star to change?

A

The precession of earths axis. This cycle takes 26,000 years and is the process of earths axis spinning so the direction the north is facing is not constant.

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13
Q

What are milankovitch cycles?

A

The 3 earth cycles that control climate. Eccentricity, Obliquity, and Precession.

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14
Q

What state to these cycles need to be in for an ice age to occur?

A
  • High tilt for seasonal contrast
  • NH summers during perihelion
  • High eccentricity
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15
Q

What are the moons 3 key roles?

A
  1. Stabilises tilt from 22.2 to 24.5 degrees
  2. Generates lunar tides
  3. Slows earths rate of rotation
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16
Q

What is a spring tide?

A

A tide when the moon and sun are aligned.

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17
Q

What is a neap tide?

A

When the sun and moon are at 90 degrees.

18
Q

Why are tides created by the moon so important?

A

Essential to evolution of land walking animals which first needed inter tidal zones to get used to being out of water.

19
Q

What is the term for when the earth is closest/furthest to the moon?

A

Perigee is when closest. Apogee is furthest.

20
Q

What is the umbra? What happens if the moon passes through it?

A

The shadow created by earth over the moon. If the entire moon surface enters the umbra an eclipse occurs.

21
Q

How does a solar eclipse occur?

A

When the new moon passes infront of the sun. Only occurs when moon is on plane of ecliptic and aligned with the sun.

22
Q

How do we measure distance in space?

A

Parallax: Observe the object from two spaced points. Twice the distance to the Sun, divided by the distance to the star (which is unknown so far) is equal to the tangent of the parallax angle of the star

23
Q

What is the term for the moon when closest/furthest from the sun?

A

Moon closest to the sun = Perigee
Moon furthest from the sun = Apogee

24
Q

What is the doppler effect?

A

The change in wave frequency that occurs when a wave source moves. (For example how noise changes as a train moves by you, frequency + pitch decreasing as it moves away from you and increasing as it moves towards you).

25
Q

What happens to wavelength as light moves further away?

A

It increases, causing redshift.

26
Q

How does redshift act on moving stars?

A

A moving star expresses redshift when moving away/expanding, and blueshift wen approaching as it is being compressed.

27
Q

What have we discovered about our universe by measuring Redshift?

A

Light from galaxies was observed to be red shifted, but not at great speed. Observed that entire universe must be expanding, with expansion increasing with distance from earth.

28
Q

When was the big bang? What was it?

A

13.8 billion years ago, it was an event in which space expanded rapidly.

29
Q

What did the big bang create?

A

Protons and neutrons. New elements stopped being formed after rapid cooling.

30
Q

What was going on immediately after the big bang?

A

‘Not much’. All atoms are ionised due to high temperatures and light finds it hard to move through this.

31
Q

What was the composition of the universe after the big bang happened and cooled?

A

75% H and 25% He.

32
Q

When and what caused light to occur for the first time?

A

Plasma cooled enough to allow neutral hydrogen atoms to form. Photons decoupled from matter, allowing light to escape.

33
Q

What is the CMB?

A

Cosmic Microwave Background. The cooled remnant of the first light that traveled throughout the universe, which has minute temperature fluctuations.

34
Q

What can we use the CMB for?

A

Temperature fluctuations correspond to density variations that were the seeds for future structures. Provides a map for new galaxies to be found.

35
Q

How are stars formed?

A

Stellar nucleosynthesis - When outward pressure from nuclear fusion of H ignites to form He, balancing gravitational collapse.

36
Q

What causes a red giant phase?

A
  1. Stars mass must be above 0.8M and very hot.
  2. Balance between H consumed by gravitational collapse and thermal expansion if broken, the
  3. Stars internal temperature rises.
  4. Causes expansion of stars exterior and fusion of helium.
37
Q

What causes a star to be a red giant or a white dwarf?

A

H being used causes a red giant. He causes a white dwarf. Any star larger than 11M continues to collapse (supernova).

38
Q

How does a supernova occur?

A
  • Stellar fusion only continues until 56Fe, only releases energy until mass of 56.
  • Once Fe fuel of core has run out, hydrostatic balance is lost.
  • Core collapses and is compressed a lot.
  • Rebounds with shockwave (supernova).
39
Q

What is supernova nucleosynthesis?

A

Hot radioactive fallout explodes into space, decays until stable isotopes remain. They form a stardust that eventually emerges into planets.

40
Q

Why is the inner region of the galaxy inhabitable?

A
  1. Stars far too dense, too many supernova
  2. Lethal neutron stars
41
Q

Why is the outer region of the galaxy inhabitable?

A
  • Not enough stars
  • Not enough heavy elements

Earth and Ocean Systems (5 decks)

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