Presentation on theme: "P1 - The Earth in the Universe. Big Bang 14 thousand million years ago Theory was proposed by the Catholic Priest George Lemaitre."— Presentation transcript:
P1 - The Earth in the Universe
Big Bang 14 thousand million years ago Theory was proposed by the Catholic Priest George Lemaitre
The solar system was formed from clouds of gases and dust in space about 5 thousand million years ago
The Earth must be older than its oldest rocks which are about 4 thousand million years old
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
Fusion Fusion of hydrogen nuclei is the source of the Suns energy All chemical elements larger than helium were made in earlier stars
1.Milky Way Galaxy: – light years – Spins around a black hole 2.Sun: – 1.4 million km – Centre of Solar system 3.Planet: – km – Orbits sun 4.Moons: – 3500km – Orbits Planets 5.Asteroids: – 1000km – Orbits Sun (between Mars and Jupiter) 6.Comets: – 3km – Orbits Sun Diameters and Motion Biggest > Smallest
Information about distant stars and galaxies comes only from the radiation astronomers can detect Light pollution interferes with observations of the night sky How we know about the Universe
Speed of Light Light travels at 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
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
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
Future of the Universe Understand why the ultimate fate of the Universe is difficult to predict.
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
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
Be able to label the Core, Mantle, Crust Structure of the Earth
Theory of Continental Drift Proposed by Alfred Wegener The movement of the Earth's continents Evidence for it: 1.Geometric fit of continents 2.Matching fossils 3.Matching mountain chains 4.Matching rocks
Reasons for the rejection of Wegeners theory by geologists of his time: 1.Movement of continents not detectable 2.Wegener was an outsider to the community of geologists 3.Too big an idea from limited evidence 4.Simpler explanations of the same evidence
Seafloor Spreading 1.A consequence of movement of the solid mantle 2.Seafloors spread by about 10 cm a year 3.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.
Tectonic Plates The following occur at plate boundaries: 1.Volcanoes: Plates moving apart 2.Mountains: Plates move towards one another. One plate dives underneath another 3.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
Rocks provide evidence for changes in the Earth Erosion, sedimentation, fossils, folding, radioactive dating, craters.
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
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
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.
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
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.
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)
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.
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
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.
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.