P1 - The Earth in the Universe

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P1 - The Earth in the Universe
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Big Bang

• 14 thousand million years ago
• Theory was proposed by the Catholic Priest George
  Lemaitre

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The solar system was formed from clouds of gases
and dust in space about 5 thousand million years
ago
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The Earth must be older than its oldest rocks
which are about 4 thousand million years old
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The Sun is a Star

• The Sun is a star in the Milky Way galaxy
• All stars have a life cycle
• There are thousands of millions of galaxies, each
  containing thousands of millions of stars, and
  that all of these make up the Universe

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Fusion

• Fusion of hydrogen nuclei is the source of the
  Suns energy
• All chemical elements larger than helium were
  made in earlier stars

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Diameters and MotionBiggest gt Smallest

• Milky Way Galaxy
• 100 000 light years
• Spins around a black hole
• Sun
• 1.4 million km
• Centre of Solar system
• Planet
• 120 000km
• Orbits sun
• Moons
• 3500km
• Orbits Planets
• Asteroids
• 1000km
• Orbits Sun (between Mars and Jupiter)
• Comets
• 3km
• Orbits Sun

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How we know about the Universe

• Information about distant stars and galaxies
  comes only from the radiation astronomers can
  detect
• Light pollution interferes with observations of
  the night sky

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Speed of Light

• Light travels at 300 000 km/s
• The speed of light means distant objects are
  observed as younger than they are now
• Light-year the distance travelled by light in a
  year

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Parallax or Relative Brightness

• Can be used to measure the distance to stars
• The difficulty of observations makes the distance
  of stars and galaxies uncertain

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Hubbles Law

• All Galaxies are moving away from us.
• The further away the galaxy, the quicker it is
  moving.
• This suggests that the universe is expanding

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Future of the Universe

• Understand why the ultimate fate of the Universe
  is difficult to predict.

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Aliens

• Astronomers have detected planets around nearby
  stars
• Even if a small proportion of stars have planets,
  many scientists think that it is likely that life
  exists elsewhere in the Universe
• No evidence of alien life has so far been
  detected

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Asteroid Collisions

• The frequency of a 15km asteroid hitting Earth
  is 1 in every 65 million years.
• The last one was in Mexico, 65 million years
  ago. Evidence indicates that this led to the
  extinction of the dinosaurs

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Structure of the Earth

• Be able to label the Core, Mantle, Crust

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Theory of Continental Drift

• Proposed by Alfred Wegener
• The movement of the Earth's continents
• Evidence for it
• Geometric fit of continents
• Matching fossils
• Matching mountain chains
• Matching rocks

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• Reasons for the rejection of Wegeners theory by
  geologists of his time
• Movement of continents not detectable
• Wegener was an outsider to the community of
  geologists
• Too big an idea from limited evidence
• Simpler explanations of the same evidence

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Seafloor Spreading

• A consequence of movement of the solid mantle
• Seafloors spread by about 10 cm a year
• Produces a pattern in the magnetism recorded in
  ocean floors, due to reversals of the Earths
  magnetic field and solidification of molten magma
  at oceanic ridges.

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Tectonic Plates

• The following occur at plate boundaries
• Volcanoes Plates moving apart
• Mountains Plates move towards one another. One
  plate dives underneath another
• Earthquakes Plate slide past one another
• Rock processes seen today explain past changes
• Continents would be worn down to sea level, if
  mountains were not being continuously formed.
  Therefore the above are an important part of the
  rock cycle

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Rocks provide evidence for changes in the Earth

• Erosion, sedimentation, fossils, folding,
  radioactive dating, craters.

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Actions that Public Authorities can take to
Reduce Damage caused by Geo-Hazards

1. Enforce building regulations to limit the effect
   of earthquakes
2. provide education and training
3. monitor natural hazards in the local area to look
   for early signs of earthquakes or volcanic
   activity
4. take part in international research

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Data

• Data statements tell you facts, and may contain
  measurements. For example, look at these three
  statements
• Asteroids are small objects orbiting the Sun
• Some asteroids have orbits close to the Earth
• The dinosaurs died out at about the same time as
  a large crater was made in Mexico

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Explanations

• Explanations seek to explain the data, and
  formulating an explanation requires imagination
  and creativity.
• One explanation is that an asteroid collision may
  have killed off the dinosaurs. The asteroid
  impact would have created dust which blocked out
  the Sun.

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Predictions

• A good explanation will explain data, and link
  together things which were not thought to be
  related. It should also make predictions.
• Asteroids often contain the rare metal iridium -
  data
• A huge asteroid impact would send iridium dust
  throughout the world - prediction
• Sedimentary rocks from the time the dinosaurs
  died out contain iridium - data
• When the asteroid crashed, the iridium came from
  the dust which blocked out the Sun - explanation

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Observations

• Data and predictions can be used to test an
  explanation, but you have to be careful. When an
  observation agrees with the prediction, it makes
  you more confident in the explanation, but it
  does not prove that the explanation is true.
• The opposite is also correct. When an observation
  disagrees with a prediction, it makes you less
  confident in the explanation, but it does not
  prove that the explanation is wrong. The data may
  be faulty.

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Other Theories

• The asteroid theory is not the only theory about
  the death of the dinosaurs.
• There were huge volcanic eruptions in India at
  the time the dinosaurs died out (data)
• Big volcanic eruptions cause dust clouds which
  block out the Sun (data)
• The big Indian eruptions could have killed out
  the dinosaurs by cooling the Earth (explanation)

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Publishing and Peer Review

• Scientists report their ideas to the scientific
  community, which is made up of all the other
  scientists. They present them at conferences and
  then write them up in journals or books.
• At conferences, other scientists will listen and
  debate the new ideas. Before journals or books
  are published, other expert scientists read the
  new ideas and decide if they are sensible. This
  is called peer review.

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Repeating Experiments

• Scientists do not usually accept the results of
  experiments until someone else has repeated the
  experiment to get the same results.
• It is hard to set up experiments in geology and
  astronomy, so new theories here need support from
  different observations

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Different Explanations

• Data often allows more than one possible
  explanation, so different scientists can have
  different explanations for the same observations.
• Wegeners ideas could certainly explain similar
  fossils in different continents, but other
  geologists thought that there were once land
  bridges between continents, allowing animals to
  travel between them.
• The different backgrounds of different scientists
  can affect their judgements, so they may have
  quite different explanations for the same data.

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New Explanation Become Accepted

• A scientific explanation is rarely abandoned just
  because some data does not correspond to it. It
  is safer to stick with a theory that has worked
  well in the past.
• Old geological theory - mountains as wrinkles
  made by the Earth shrinking as it cools down.
• No clear explanation how continents could move
  about.
• In the 1950s, evidence from magnetism in the
  ocean floor showed that the seafloors were
  spreading by a few centimetres each year. This
  showed movement of large parts of the Earths
  crust, now called tectonic plates.