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34 Cards in this Set
- Front
- Back
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How old is the universe? |
14 billion years old |
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How large is the galaxy? |
100,000 light years across |
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Copernican principle |
Under the modified Copernican principle, neither the Sun nor the Earth are in a central, specially favored position in the universe.[1] In some sense, it is equivalent to the mediocrity principle. |
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Describe the scientific method (With diagram) |
Observation ----> theory --- >prediction (With problem in the middle) - Observations leads to theory explaining it, theory leads to prediction consistent with previous observations, predictions of new phenomenon are observed. If the observations agree with the predictions, more predictions can be made. |
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How many stars are visible at one time? |
About 3000 |
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Constellations Vs Asterisms |
Constellations: a group of stars forming a recognizable pattern that is traditionally named after its apparent form or identified with a mythological figure. Modern astronomers divide the sky into eighty-eight constellations with defined boundaries. |
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What is the North Star? |
Polaris |
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Angular Measure? |
Angular measure, each degree contains 60' (arc minutes)- Each arc minute contains 60" (arc seconds) |
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What is diurnal motion? |
Diurnal motion is the daily motion of stars and other celestial bodies across the sky. This motion is due to the Earth's rotation from west to east, which causes celestial bodies to have an apparent motion from east to west. |
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What angle does the Earth’s axis make to its equator? |
90® and is the same for all planets |
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What angle does the celestial equator (or for that matter the Earth’sequator make with the ecliptic since the celestial equator is simply anextension of the Earth’s equator!) |
23.5® which is not the same for all planets |
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4. What is the eccentricity of the Earth’s orbit? |
e ≈ 0.02 Nearly circular (actually off by only ≈ 2%approximately |
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7. Make a statement about what causes these common sense seasonalvariations on the Earth. (Hint, the answer is not that we are closer to orfarther from the Sun.) |
The tilt of the earth’s axis to its orbit plane (≈ 23.5®)2coupled with its orbit about the sun, causes the rays of the sun to hit more/ less obliquely for different seasons and changing the length of daylighthours. This affects directly the average temperature of that season. |
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8, Is the Earth closer or farther from the Sun when it is winter in the northernhemisphere? |
Closer to the Sun for northern the hemisphere winter (essentially look this up on the net) |
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Generically, what is one complete spin of the Earth called? |
Solar Day |
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13. Are the winters &/or summers more intense in the northern hemisphereor southern hemisphere? |
The Southern Hemisphere For example in the southern summer (occurring at the same time as northern winter), since the earth is slightly closer to the sun then the southern hemisphere gets hit with a double whammy, tilt toward the sun and slightly closer to the sun giving higher average temperatures in the southern hemisphere summer. |
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Give the names of the planets according to the ancients (7) |
Sun, moon, mercury, Venus, mars, Jupiter, saturn |
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3. State the definition of a planet according to the ancients. |
A planet is defined as celestial object which moved amongst the stars |
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What 2 objects are always in the ecliptic plane? |
The sun and the earth |
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What are inferior planets? |
The planets inside the orbit of the earth are called the Inferior Planets: Mercury and Venus. |
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What are superior planets? |
The planets outside the orbit of the earth are called the Superior Planets: Mars, Jupiter, Saturn, Uranus, Neptune, and Pluto. |
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What is precession? |
The rotation of the earth's axis itself: makes one complete circle in about 26,000 years (Currently pointing to north star, Polaris) |
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Tropical year vs. sidereal year |
A tropical year (also known as a solar year), for general purposes, is the time that the Sun takes to return to the same position in the cycle of seasons, as seen from Earth; for example, the time from vernal equinox to vernal equinox, or from summer solstice to summer solstice. Because of the precession of the equinoxes, the seasonal cycle does not remain exactly synchronized with the position of the Earth in its orbit around the Sun. As a consequence, the tropical year is about 20 minutes shorter than the time it takes Earth to complete one full orbit around the Sun as measured with respect to the fixed stars (the sidereal year). A sidereal year (from Latin sidus "asterism, star") is the time taken by the Earth to orbit the Sun once with respect to the fixed stars. Hence it is also the time taken for the Sun to return to the same position with respect to the fixed stars after apparently travelling once around the ecliptic. It equals 365.25636 SI days for the J2000.0 epoch.[1] |
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Do all planets follow the ecliptic? |
Turns out their orbits are tipped only a little bit with respect to Earth's. In other words,all eight planets essentially lie in the same flat plane. As each orbits the sun, theyfollow the same familiar ecliptic path and pass through the same dozen zodiac constellations. |
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What is the Zodiac? |
An area of the sky 10 degrees on either side of the ecliptic
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Triangulation vs. Parallax |
Triangulation measures baseline and angles, and can calculate distance. Parallax is similar to triangulation, but looks at apparent motion of objects against distant background from 2 vantage points. |
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What is the planetary problem?
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Planets: 1. Move in respect to fixed stars. 2. Change in brightness 3. Change speed. 4. Undergo retrograde maotion. Why do they do this? |
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What were early observations in the Geocentric model? |
Inferior planets never too far from sun, superior planets not tied to sun and experience retrograde motion, superior planets brightest at opposition, inferior planets brightnest near inferior conjunction. |
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What are Kepler's Laws? |
Kepler's three laws of planetary motion can be described as follows:The path of the planets about the sun is elliptical in shape, with the center of the sun being located at one focus. (The Law of Ellipses) An imaginary line drawn from the center of the sun to the center of the planet will sweep out equal areas in equal intervals of time. (The Law of Equal Areas) The ratio of the squares of the periods of any two planets is equal to the ratio of the cubes of their average distances from the sun. (The Law of Harmonies) |
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When can an eclipse (sun or moon) occur? |
Moon 1. full moon 2. moon in the ecliptic plane Sun 1. new moon 2. moon in the ecliptic plane |
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Describe Ptolemy |
- Greeks thought the earth was the center of the solar system, that the sun, moon and planets revolved around it on crystalline circular paths and that stars were fixed to a huge sphere that rotated once per day. - These ideas were brought together by Ptolemy in the Almagest, or "Great One" Ptolmey lived from 120 A.D to 180 A.D |
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Describe Copernicus |
Suggested that the earth and all other planets traveled around the sun. This idea was gaining support (Had been suggested before by people like Astarchus) but the Catholic church felt it was a hereitcal idea. |
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Describe Tycho Brahe |
Danish observor, made many accurate measurements of the changing positions of the planets. |
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Describe Kepler |
Used Tycho Brahe's observations and measurements to derive his laws, that the planets move around the sun, and that they move not in cricles, but in ellipses. Keplers |
