Pretest Ch 20: Origins of the Universe

Transcription

1 Name: _Answer key Pretest: _2_/ 58 Posttest: _58_/ 58 Pretest Ch 20: Origins of the Universe Vocab/Matching: Match the definition on the left with the term on the right by placing the letter of the term on the blank. 1. P the Doppler effect applied to light, shows A. Albert Einstein galaxies are moving away from us B. Big Bang 2. M where the universe has a low amount of C. Closed universe mass and will continue expanding forever D. Cosmic microwave 3. O discovered CMBR in the 1960s and proved background radiation the Big Bang Theory E. Dark matter 4. S everything that exists; all the matter and F. Edwin Hubble energy G. Fred Hoyle 5. Q the small point that everything that exists H. Fundamental forces was condensed into I. Georges Lemaitre 6. H gravity, electromagnetism, strong and weak J. Hypothesis molecular forces K. Law 7. J a scientific guess, based on a small amount M. Open universe of experimental evidence, may change N. Oscillating universe over time O. Penzias & Wilson 8. F used red shift to discover the universe is P. Red shift expanding, in 1920 s Q. Singularity 9. B theory that all that exists now was once in R. Theory one small point and started expanding S. Universe 10. E we can not see it, but can measure its effects; black holes are an example 11. R an explanation for a natural phenomenon, has much evidence to back it up, tends to be complex 12. A had the idea that the universe must not be static (unchanging) but had no evidence 13. D microwave energy left over from the Big Bang event that we can still measure today 14. N this is just one Big Bang in a series of Big Bangs/Big Crunches/Big Bangs/Big Crunches

2 15. G gave the Big Bang Theory its name while trying to make fun of it 16. I started the Big Bang theory, though he had no evidence to support it 17. K a simple statement that describes what happens in natural phenomenon 18. C the amount of matter in the universe is finite (set); the universe will collapse back in on itself or stay one size forever. If the following statement applies to a hypothesis, put a letter H. If it applies to a scientific theory, put the letter T. If it applies to a scientific law, put the letter L. It is possible to have more than one letter or no letters at all on a blank. 19. H an educated guess about a phenomenon 20. H can become a law 21. H T L can be changed 22. L describes a phenomenon (answers what ) 23. is more important than a theory 24. L tends to be simple, often just a mathematical equation 25. _T L has a lot of evidence to back it up 26. T explains a phenomenon (answers why or how ) 27. _T L is considered to be true or a fact by the scientific community 28. H can become a theory 29. H may not have evidence to back it up 30. _H T L can be proven false with further evidence/experimentation/observation 31. T tends to be very detailed and complex 32. _H T L_ can be used to make predictions

3 33. The following list identifies some of the events that have taken place according to Big Bang Theory. Put this list in a proper sequential order in time A. Formation of atoms (nuclei + electrons) B. The 4 fundamental forces of nature become distinguishable C. Supernova create conditions for the nuclear production of elements heavier than iron D. The first particles form from energy E. Something, not yet understood, causes the early universe (all of space and energy) to begin a process of rapid expansion from a singularity F. The first stars form initiating the nuclear fusion process to create the elements up through iron. G. Formation of galaxies H. Formation of simple atomic nuclei (combinations of protons and neutrons) E B D H A G F C 34. What needed to happen in the universe before it was possible for the first atoms to form? Cool down so energy could become matter (quarks eventually form atomic nuclei (protons & neutrons) then atoms) 35. What is so special about the time seconds after the initial bang? sec We don t know what happened before that. The models we use rely on 4 fundamental forces of physics.gravity, electromagnetism, weak molecular force, strong molecular force. Those forces had not existed before then they were all one superforce so we can t use science to explain what was happening, because science (as we know it) wasn t working then.

4 36. According to Big Bang Theory what significant event occurred approximately 300,000 years after the initial bang? first atoms were made (H & He) cooled down enough (about 3000 K). That cleared up the soup and allowed light to shine through. We detect this now as CMBR. 37. A very common misconception about the Big Bang is that people tend to view it as some giant explosion. Scientist wouldn t describe it this way. What would be a more appropriate description for what occurred at the very beginning according to Big Bang Theory? Rapid expansion from size of atom to 8x solar system in less than a second. The list on the left contains a few significant pieces of evidence that support some aspect of Big Bang Theory. For each item listed, describe the way in which it supports Big Bang Theory, briefly describe how this information is known, and identify the scientist(s) associated with the evidence. Evidence How it supports BBT Scientist(s) How is this known The universe is expanding 38. if expanding now, was once small in the past 39. Hubble, Red shift. Light from galaxies is shifted towards red end of spectrum means its moving away from us (Doppler Effect for light) Einstein, 1916 Theory of general Relativity says that objects with gravity

5 have to be moving, so universe can t just stay the same Lemaitre, 1927 Based on Einstein, predicted it would expand, couldn t prove, people ignored him Cosmic Microwave Background Radiation 41. The energy left over from the formation of the universe. Over time, it has shifted towards microwave end of spectrum. This light existed in early universe, but was blocked by all the unorganized matter. By 300,000 years after the Event, the universe had cooled down enough for the light to be seen. 42. Penzias & Wilson, 1964 (was predicted by others before that, but they actually found it) 43. BBT predicts there would be some residual energy left over that s not coming from 1 place in space, but has expanded (as the universe did) to come from all over. That s what CMBR does comes from everywhere.

6 Abundance of light elements (hydrogen and helium) in the universe 44. The conditions in the early universe would only make the simplest of elements Hydrogen and Helium. Thus we should find a lot of hydrogen and helium in the universe today. There have been many contributors to identifying composition % of the universe is Hydrogen and 25% is Helium. Other heavier elements came from stars processes (fusion) and supernovas (star explosions) as predicted by Hoyle. 46. Measurements of the red shift of light from distant galaxies informs scientists that the universe is expanding. What is red shift? Why does this show something is moving away from us? Red shift Doppler Effect applied to light. As objects move away from us, their wavelengths are stretched out (become longer) this shifts it towards the red end of the spectrum. The more it shifts the faster it is moving. If things move towards us, the wavelengths are compressed (shortened) and shifted towards the blue end of the spectrum.

7 Given the notion that the universe is currently expanding as described by Big Bang Theory, there are, in general, three possible outcomes for the future. Identify/describe those three possibilities for the fate of the universe: 47. Keep expanding forever (open universe, Big Rip) 48. Expand to a certain point and stop (flat universe, Big Freeze) 49. Expand to a certain point and contract again (closed universe, Big Crunch/Oscillating Universe)

8 50. What will determine which of the above scenarios actually happens? The amount of mass in the universe. The problem is that there is a lot of matter we can t see, but know it s there because of its gravitational effects (dark matter). So it s hard to measure the amount of mass. Describe how #50 will do this for each of #47 - #49 above. 51. If the amount of mass is over a certain limit, the universe will collapse back in on itself (closed universe/big Crunch) 52. If the amount of mass is just right the universe will grow to a certain size and stay there (Flat universe/big Freeze) 53. If the amount of mass is under the certain limit, it will just keep expanding forever (open universe, Big Rip) 54. Which of the three outcomes identified in seems to be supported by current data? Universe expanding forever (open universe/big Rip) there appears to be too low of an amount of mass for the gravity to stop the expansion or to stop it and bring everything back together. Hubble found that galaxies are speeding up the farther away they are, the faster they move (speeding up, not slowing down)

9 55. What is a galaxy and what is ours called? Collection of billions of stars. Ours is called the Milky Way and is estimated to contain between 200,000,000,000 and 400,000,000,000 stars. It is 100,000 ly across (light takes 100,000 years to cross it!) There are three shapes to galaxies. Name and draw them. What kind is ours? Elliptical Spirals (2 kinds spiral or barred spiral)

10 Irregular gravity of nearby objects gives it odd shape