Exam 2 Flashcards
How many seconds in a day
86,400
Why do we sometimes have an extra day in a year
because if we didn’t, we would be off track with the seasons
Where does the sun rise and set on the first day of fall and spring
Due east and due west
Longest day of the year
Summer solstice
Shortest day of the year
Winter solstice
Tropical year
Year based on the seasons; 365 days, 5 hours, 48 minutes, and 45 seconds
Why is a solar day longer than a sidereal day?
Because the earth doesn’t rotate in exactly 24 hours; the extra 4 minute difference makes up that distance
Why does the moon go through its cycle of phases?
Because the earth rotates and revolves at the same time
Why do the sun, moon, and planets always appear on/around the ecliptic?
Because everything in the solar system is essentially on the same plane
Why do the sun, moon, planets, and stars move counter clockwise around the sky once per day?
Because the Earth rotates
Why does the Earth have seasons?
Because of the altitude of the sun. The higher the sun is in the sky, the warmer it will be
Opposition
you look one way to see something and look the opposite way to see something else
When does retrograde motion happen
When an object is at opposition
Conjunction
When something is exactly lined up with something else
Inferior conjunction
when something is in front of and lined up with something
Superior conjunction
something is behind of and lined up with something
Quadrature
When something is at a 90-degree angle in respect to the sun
Greatest elongation
where something is at the highest angle it can be
Greatest elongation of Mercury
23 degrees
Greatest elongation of Venus
47degrees
Which planets can be at any planetary configuration
Mars, Jupiter, and Saturn
Which planets cannot be at any planetary configuration and why
Mercury and Venus cannot be in every position because they are always close to the sun
Does the sun rise exactly due east and set exactly due west every day at the equator
No
Aristotle
Imagined the earth at the center of the universe with everything revolving around it
Ptolemy
Accurately traced the paths of the planets using epicycles • All perfect circles Earth at the center with planets going around in epicycles 150 AD Lived in Alexandria Wrote Almagest
Copernicus
Created the idea of heliocentrism – sun centered solar system Wrote The Revolution of the Celestial Orbs in 1543 Also insisted that the earth rotated every 24 hours 1500’s his model explains why venus and mercury stay near the sun – because their orbits are smaller than earth’s
Tycho Brahe
He built an observatory (Uranobor) in Denmark First true observational astronomer Made the most detailed layout of the solar system of his time
Kepler
1610 Maintained the idea that the sun was the center of the solar system Hypothesized that the planets traveled in ellipses Also discovered as the planets get closer to the sun, they speed up and as they get further away, they slow down Published the book New Astronomy about Mars in 1609 • Summarized the way the Earth travels around the sun and the 3 laws regarding that
Who was the first to find the circumference and radius of the earth
Eratosthenes
circumference of the earth
25,000 mi
Radius of the earth
4,000 mi
Eccentricity
how “ellipse” something is Circular is 0 eccentricity, 1 is the highest eccentricity
Kepler’s 1st Law
Elliptical orbits and the sun is not the center of the solar system
Kepler’s 2nd Law
Planets will move faster as they get closer to the sun
Kepler’s 3rd Law
How a planet’s orbit size is compared to its size (p^2 = a^3)
Order of the planets
Mercury Venus Earth Mars Jupiter Saturn Uranus Neptune
How long does it take the earth to rotate once completely
23 hours and 56 minutes (sidereal day)
How long does it take the moon to go through its phases
29.5 days (synodic period)
How long does it take the moon to go through the constellations of the zodiac
27.3 days (sidereal period)
How many degrees does the moon go around for it to go from full moon to full moon
360 + 30 degrees
The moon’s orbit is very nearly circular.
True
Earth is at the very center of the moon’s orbit.
False
When the moon is close to Earth, the moon appears slightly ___________ than average.
Bigger
What is the eccentricity of the moon’s orbit? Enter your answer as a decimal number.
.055
The date of the vernal equinox is [month] [day].
March 21
The date of the summer solstice is [month] [day].
June 21
The date of the autumnal equinox is [month] [day].
September 21
The date of the winter solstice is [month] [day].
December 21
We add a leap day to our calendar every 4 years.
False, not every four years
Presently, one second is defined as
1/86,400 of the mean solar day
Sally says she saw the full moon in the constellation Cassiopea…
True becasue everything in our solar system passes through the Zodiac constellations
Which of the following planets can be observed at opposition?
Mars, Jupiter, and Saturn
Which of the following planets can be observed at quadrature?
Mars, Jupiter, and Saturn
What can be concluded from this graph? (Grand Haven Graph)
Earth’s rotation rate is gradually slowing
Which of the planets is/are observed to undergo “retrograde loops” in their motion against the background stars?
Mars, Jupiter, and Saturn
Do the yearly average sunrise/set time and the average length of day/night vary with latitude? In other words, do observers at different latitudes see different average sunrise/set times andaverage lengths of days?
It is apparent from the data that the average time of sunrise/set and the average length of the day is the same for all observers on Earth. On the spring and fall equinoxes, the sun rises due east at 6 am and sets due west at 6 pm everywhere on Earth!
Do the +/- variation in sunrise/set time and the +/- variation in the length of the day/night depend on latitude? If so, describe in what sense. For example, if you find that the variation in sunrise/set time decreases the further north you are from the equator, than write something to that effect – and support your conclusion with data from the class-data spreadsheet.
The variation (about the average) of the sunrise/set time and the length of day/night both increase with increasing latitude. Near the equator, there is very little variation in the time of sunrise/set and the length of the day/night; closer to the poles, the variation increases. For example in Alaska, the variation in sunrise/set time is 4 or 5 hours, making the summer solstice day, and the winter solstice night, 20 to 22 hours long! North of the arctic circle, the sun doesn’t set for several (or more) in the summer and doesn’t rise for several (or more) days in the winter.
Does the average azimuth of sunrise/set depend on latitude? Support your answer using the data collected in class.
The average azimuth of sunrise/set does not depend on latitude. All observers on Earth see the sun rise/set at the same place on the horizon: due east and due west.
Does the +/- variation in sunrise/set azimuth depend on latitude? Write an answer, supported with data from the class-data spreadsheet, as in the previous question.
The +/- variation in sunrise/set azimuth does depend on latitude. Near the equator, the variation is minimal – BUT NOT ZERO. (It turns out to be +/- 23 degrees). Further north, the variation in sunrise/set azimuth increases; for example, in Grand Rapids it is about +/- 30 degrees and in Alaska it is about +/- 60 (or more) degrees.
Does the average altitude of the sun at solar noon vary with latitude? Support your answer (quantitatively, if you can) using the data collected in class.
The average altitude of the sun at solar noon – the altitude of the sun on the equinoxes – decreases with increasing latitude. In other words, the sun at noon on the eqinoxes is very high in the sky near the equator, and lower in the sky further north. For example, the equinox altitude of the sun at noon on the equator is 90 degrees, while on the same day in Grand Rapids it is only 47 degrees.
The altitude of the sun at noon on the equinoxes is related to latitude in a simple way: equinox noon-sun altitude equals 90 degrees minus latitude.
Does the +/- variation in the altitude of the sun at noon depend on latitude? Write an answer, supported with data from the class-data spreadsheet, as in the previous question.
The +/- variation of the sun at noon does NOT depend on latitude: all observers see the same variation over the year. The sun is 23 degrees higher (compared to on the equinox) in the summer and 23 degrees lower in the winter.
On Earth’s equator days and nights are nearly equal in length – 12 hours each – every day of the year.
True
For an observer on Mars could Earth ever be at opposition?
No
When Jupiter is in conjunction as viewed from Earth, in which planetary configuration is Earth if viewed from Jupiter?
Superior conjunction.
In what planetary configuration is Mars (as viewed from Earth, of course) when Mars is closest to Earth?
Opposition
The variation in the times of sunrise and sunset over the course of a year for an observer in Grand Rapids is about +/- [h] hours and [m] minutes.
1 hr 30 min
The variation in the altitude of the sun at solar noon over the course of a year for an observer in Grand Rapids is about +/- [d]degrees.
23
Consider by how much the azimuth of the sunrise/set points vary over the seasons, for an observer at the mid latitudes. By how many degrees would you say the most extreme sunrise and sunset azimuths differ from due east and due west? As a point of reference, keep in mind that the directions northeast and due east differ by 45 degrees.
30 degrees
