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 usB. Big Bang
2.__M__ where the universe has a low amount of C. Closed universe
mass and will continue expanding foreverD. Cosmic microwave
3.__O__ discovered CMBR in the 1960s and proved background radiation
the Big Bang TheoryE. Dark matter
4.__S__ everything that exists; all the matter and F. Edwin Hubble
Energy, space and timeG. Fred Hoyle
5.__Q__ the small point that everything that exists H. Fundamental forces
was condensed intoI. Georges Lemaitre
6.__H__ gravity, electromagnetism, strong and weak J.Hypothesis
nuclear forcesK. Law
7.__J__ a scientific guess, based on a small amount M. Open universe
of experimental evidence, may change N. Oscillating universe
over timeO. Penzias & Wilson
8.__F__ used red shift to discover the universe is P. Red shift
expanding, in 1920’sQ. Singularity
9.__B__ theory that all that exists now was once in R. Theory
one small point and started expandingS. 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
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
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…
- Formation of atoms (nuclei + electrons)
- The 4 fundamental forces of nature become distinguishable
- Supernova create conditions for the nuclear production of elements heavier than iron
- The first particles form from energy
- Something, not yet understood, causes the early universe (all of space and energy) to begin a process of rapid expansion from a singularity
- The first stars form initiating the nuclear fusion process to create the elements up through iron.
- Formation of galaxies
- 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 10-43 seconds after the initial “bang”?
.000000000000000000000000000000000000000001 sec
We don’t know what happened before that. The models we use rely on 4 “fundamental forces” of physics….gravity, electromagnetism, weak nuclear force, strong nuclear 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.
36. According to Big Bang Theory what significant event occurred approximately 380,000
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 knownThe universe is expanding / 38. if expanding now, was once small in the past / 39. Hubble, 1929
Einstein, 1916
Lemaitre, 1927 / 40. Red shift. Light from galaxies is shifted towards red end of spectrum means its moving away from us (Doppler Effect for light)
Theory of general Relativity says that objects with gravity have to be moving, so universe can’t just stay the same
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.
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 / 45. 74% 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.
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)
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 47 - 49 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)
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 100,000years to cross it!)
56. – 58. There are three shapes to galaxies. Name and draw them. What kind is ours?
Elliptical
Spirals (2 kinds spiral or barred spiral)
Irregular…gravity of nearby objects gives it odd shape