MIDTERM 1 Flashcards
(97 cards)
1
Q
What is a light year, and what doe it describe?
A
The distance travelled by light in one Earth year; distance
2
Q
Why do astronomy think our Universe started with a “Big Bang”?
A
The galaxies are getting further apart, so a long time ago they must have been very close together
3
Q
Why do far away galaxy look young?
A
The light from far away galaxies was emitted a long time ago when they were young
4
Q
Approximately how old is the Universe?
A
14 billions years
5
Q
What is the “Local Group”?
A
The set of nearby galaxies, spanning about 10 million light years
6
Q
What is your “Address” in the Universe, in the correct order?
A
You, Earth, Solar System, Milky Way Galaxy, Local Group, Universe
7
Q
About where is our solar system located within the Milky Way Galaxy?
A
about half of the way from the centre of the galaxy to the outskirts of the galactic disk
8
Q
What was the early Universe (about 15 minutes after the Big Bang) made of?
A
hydrogen and helium, with very little heavier elements
9
Q
What is the Sun mostly made of?
A
hydrogen and helium
10
Q
Astronomers define any element but hydrogen, helium and lithium as “metals”. Under this definition, the Earth’s crust is mad mostly of “metallic” substances. Where did these come from originally?
A
They were formed by fusion by fusion processes in stars
11
Q
Why can’t we see further away than about 14 billion light years?
A
The light has not yet had time to reach us
12
Q
How did an ancient Egyptian “hour” compare to the one we use today?
A
It varied in length depending on the seasons, because the relative length of day and night changes during the seasons
13
Q
How did Eratosthenes determine the size of the Earth?
A
Measuring the distance between two cities and considering the position of the sun at noon on the summer solstice in both places
14
Q
Ptolemy created an astronomical model that allowed for very accurate predictions of the positions of the stars and planets. Why is his model no longer favoured today?
A
His model had the Earth as the centre of the solar system
15
Q
During the Dark Ages, a time when scientific thinking was rapidly regressing in Europe, where did the majority of scientific advancement take place?
A
The Middle East
16
Q
What was Nicholas Copernicus’ most notable contribution to modern day Astronomy?
A
Her proposed a simplified heliocentric model of the solar system
17
Q
How did Tycho Brahe contribute to the field of Astronomy?
A
- He recruited Kepler as his assistant for analyzing his observational data
- He determined that comets and novae occur much further away than the moon
- He took extremely detailed and accurate measurements of the positions of heavenly bodies
18
Q
How did Johannes Kepler contribute to Astronomy?
A
He determined that planets move in ellipses with the Sun in one of the focal points, and proposed Kepler’s Law of Planetary Motion
19
Q
What is not a possible orbit in the context of Kepler’s First Law?
A
A planet moves in an ellipse with the Sun at the centre
20
Q
Kepler’s Second Law tells us that a planet with an elliptical orbit will
A
Move are slowly when it is further from the Sun
21
Q
Kepler’s Third Law relates the following characteristics of a planet
A
average distance and period
22
Q
How did Galileo contribute to modern Astronomy?
A
- He refined the telescope for use as a scientific instrument
- He discovered the largest 4 moons around Jupiter
- He showed that Venus actually rotated around the Sun, not the Earth
23
Q
What is a Watt?
A
A unit of power
24
Q
What property of light determines its “colour”?
A
Wavelength
25
A camera flash appears to be bright white in colour. What does this tell you about the light that was emitted?
It contains a mixture of light from across the visible spectrum
26
A particle of light (a photon) hits an electron. All of the photon's energy is turned into kinetic energy in the electron, and not photons are left after the collision. What light/matter interaction has taken place?
Absorption
27
What phase of a material is the hottest?
Plasma
28
A transparent material
transmits light very well
29
Why I grass green?
It reflects green light and absorbs all other colours
30
An atom is missing an electron in one of its electron energy levels, and another electron moves in to fill the space. Which transition would emit the most energetic photon?
An electron drops in energy from the 4th energy level to the lowest (first) energy level
31
You are looking at a tungsten lamp, which emits a very smooth, continuous spectrum in the wavelengths your are looking in. Suddenly, a dense cloud of hydrogen passes between you and the lamp. How does the spectrum change?
You start to see hydrogen absorption lines
32
Which effect makes emission lines from far away galaxies look redder than they should, and why?
The Doppler effect; the galaxies are receding from us, so their light looks redder
33
You find an ion of a rare isotope of the (hitherto undetected) element Unobtanium while on a family vacation to Pandora. The nucleus of this isotope has 215 protons and 285 neutrons, and it has 213 elections surrounding it. Which of the following are the correct atomic number, weight and charge (in that order)?
215,500, +2
34
An optometrist finds that the focal plane of your eye does not coincide with your retina when you look at objects that are far away from you. What problem would you notice with your eyesight?
Everything you see is blurry
35
A motorcycle and a car are driving side by side on a highway at night. The motorcycle's headlight is twice as bright as each car headlight, so that the total light coming from each vehicle is the sam. You are standing far enough from the vehicles that the angular separation of the car's headlights is much lower than the angular resolution of your eye. Can you tell which vehicle is which?
No, each will appear as a point source of equally bright light
36
What is the main benefit of using CCD cameras over standard film cameras?
CCDs detect a higher fraction of photons
37
If you have a camera (but not a spectrometer) hooked up to your telescope, which of the following experiments can you not perform?
Find out how fast a star is rotating
38
If you hav a spectrometer attached to your telescope, and are not capable of direct imaging, which of the following experiments can you not perform?
Determine that size o a galaxy
39
Which of the following experiments is least likely to yield useful results?
A sea-level X-ray imaging telescope
40
Which of the following is not a good reason to laugh a telescope into space?
It is closer to the objects it is measuring
41
Why must you cool an extreme infrared space-based telescope down to observe faint objects?
A warm telescope will emit its own infrared spectrum
42
Which of the following is not an advantage of reflection (mirror) telescopes over refraction (lens) telescopes?
Reflectors collect more light than a refractor of the same size
43
What is a star?
A large, glowing ball of gas that generates heat and light through nuclear fusion
44
What is a planet?
A moderately large object that orbits a star; it shines by reflected light. Planets may be rocky, icy, or gaseous in composition
45
What is a comet?
A relatively small and icy object that orbits a star
46
What is a nebula?
An interstellar cloud of gas and/or dust (and stars)
47
What is a galaxy?
A great island of stars in space, all held together by gravity and orbiting a common center
48
What is a galaxy group?
A gravitationally bond group of up to a few dozen galaxies, typically a few million light years across
49
What is the universe?
The sum total of all matter and energy; that is, everything within and between all galaxies
50
What is the speed of light?
Light travels at a finite speed - 300,000 km/s - THUS we see objects as they were in the past
51
What is a light-year?
The distance light can travel in 1 year
| - about 10 trillion kilometres (6 trillion miles)
52
Why can't we see a galaxy 15 billion light-years away?
Because looking 15 billion light-years away means looking to a time before the universe existed
53
What is our physical place in the universe?
Earth is part of the solar system, which is in the Milky Way Galaxy, which is a member of the Local Group of galaxies in the Local Supercluster
54
How did we come to be?
=The matter in our bodies cameo from the Big Bang
- The light elements H, He, Li, were produced right after the Big Bang
- All heavier elements were constructed from H and He in stars then recycled into new star systems, including our solar system
55
How can we know what the universe was like in the past?
When we look to great distances, we are seeing events that happened long ago because light travels at a finite speed
56
Can we see the entire universe?
No. The observable portion of the universe I about 1.4 billion light-years in radius because the universe is about 14 billion years old
57
How is Earth moving in our solar system?
Contrary to our perception, we are not "sitting still"
| We are moving with Earth in several ways, and at surprisingly fast speeds
58
How is our Sun moving in the Milky Way Galaxy?
Our Sun moves randomly relative to the other stars in the local solar neighbourhood
- orbits the galaxy every 230 million years
59
What is one of the greatest mysteries in astronomy about the Milky Way?
Most of Milky Way's light comes from disk and bulge but most of the mass is in its halo
60
How do galaxies move within the universe?
Galaxies are carried along with the expansion of the universe. But how did Hubble figure out that the universe is expanding?
61
How is our solar system moving in the Milky Way Galaxy?
Stars in the Local Neighbourhood move randomly relative to one another and orbit the centre of the Milky Way in about 230 million years
62
How do galaxies move within the universe?
All galaxies beyond the Local Group are moving away from us with expansion of the universe: the more distant they are, the faster they're moving
63
Are we ever sitting still?
No. Earth is constantly in motion, even though we don't notice it
64
How did astronomical observations benefit ancient societies?
Keeping track of time and seasons
- for practices purposes, including agriculture
- for religious and ceremonial purposes
Aid to navigation
65
What did ancient civilizations achieve in astronomy?
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Tracking the seasons
Daily timekeeping
Calendar
Monitoring lunar cycles
Monitoring planets an stars
Predicting eclipses
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66
Why does modern science trace its root to the Greeks?
They developed models of nature and emphasized that the predictions of models should agree with observations
67
How did Ptolemy explain planetary motion?
The Ptolemaic model ha each planet move on a small circle whose centre moves around Earth on a larger circle
68
Hoe did Copernicus, Tycho and Kepler challenge the Earth-centered idea?
Copernicus created a sun-centered model; Tycho provided that data needed to improve this model; Kepler found a model that fit Tycho's data
69
What are Kepler's three laws of planetary motion?
- The orbit of each planet is an eclipse with the Sun at one focus
- As a planet moves around its orbit it sweeps out equal areas in equal times
- More distant planets orbit the Sun at slower average speeds: p2=a3
70
What was Galileo's role in solidifying the Copernican revolution?
His experiments and observations overcame the remaining objections to the Sun-centered solar system model
71
How do we experience light?
Light is a form of energy
| Light comes in many colours that combine to form white light
72
How do light and matter interact?
Matter can emit light, absorb light, transmit light, and reflect (or scatter) light.
Interactions between light and matter determine the appearance of everything we see
73
What is light?
Light can behave like either a way or a particle
A light wave is a vibration of electric and magnetic fields
Light waves have a wavelength and a frequency
74
What is the electromagnetic spectrum?
Human eyes cannot see most forums of light
| The entire range of wavelengths of light is know as the electromagnetic spectrum
75
What is the structure of matter?
Matter is made of atoms, which consist of a nucleus of protons and neutrons surrounded by a cloud of electrons
76
What are the phases of matter?
Adding heat to a substance changes it phase by breaking chemical bonds
As temperature rises, a substance transforms from a solid to a liquid to a gas, then the molecules can dissociate into atoms
Stropping of electrons from atoms (ionization) turns the substance into a plasma
77
How is energy stored in atoms?
The energies of electrons in atoms correspond to particular energy levels
Atoms gain and lose energy only in amounts corresponding to particular changes in energy levels
78
Continuous specturm
Has continuously varying intensity distribution as a function of wavelength or frequency
Emitted by dense materials (e.g. dense gas or solid)
79
Emission line spectrum
Has emission lines for particular wavelengths or frequencies
Emitted by thin gas
80
Absorption line spectrum
has dark absorption lines for particular wavelengths or frequencies. Occurs if light is sent through a this gas
81
Which colour of star is the hottest?
blue star
82
Why don't we glow in the dark?
people only emit light that is invisible to our eyes
83
What are the three basic type of spectra?
Continuous spectrum, emission line spectrum, absorption line spectrum
84
How does light tell us what things are made of?
Each atom has a unique fingerprint
| We can determine which atoms something is made of by looking or their fingerprints in the spectrum
85
How does light tell us the temperatures of planets and stars?
Nearly all large or dense objets emit a continuous spectrum that depend on temperature
The spectrum of that thermal radiation tells us the object's temperature
86
How do we interpret an actual spectrum?
By carefully studying the features in a spectrum, we can learn a great deal about the object that created it
87
Hoe does light tell us the speed of a distant object?
The Doppler effect tells us how fast an object is moving toward or away from us
Blueshift- object moving toward us
Redshift- objets moving away from us
88
How does light tell us the rotation rate of an object?
The width of an object's spectral lines can tell us how fast it is rotating
89
How does your eye form an image?
It uses refraction to bend parallel light ray so that they form an image
The image is in focus if the focal plane is at the retina
90
How do we record images?
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Cameras focus light like your eye and record the image with a detector
The detectors (CCDS) in digital cameras are like those used on modern telescopes
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91
What are the two most important properties of a telescope?
Collecting area determines how much light a telescope can gather
Angular resolution is the minimum angular separation a telescope can distinguish
92
What are the two basic designs of telescopes?
Refracting telescopes focus light with lenses
Reflecting telescopes focus light with mirrors
* The vast majority of professional telescopes are reflectors
93
What do astronomers do with telescopes?
Imaging
Spectroscopy
Timing
94
How does Earth's atmosphere affect ground-based observations
Telescope sites are chosen to minimize the problems of light pollution atmospheric turbulence (----> "twinkling" of stars), and bad weather
95
Why do we put telescopes into space?
Forms of light other than radio and visible do not pass through Earth's atmosphere
Also, much sharper images are possible because there is not turbulence
96
How can we observe invisible light?
Telescopes for invisible light are usually modified versions of reflecting telescopes
Many of the telescopes used for observing invisible light are in space
97
Visible light and radio waves can be observed with ground based telescopes
The largest optical telescopes currently un use have diameters of about 10 meters
The largest radio telescope has a diameter of 500 meters
