Exam 1 Flashcards
sky motions, tools of astronomy
At the beginning of the semester I mentioned some fundamental questions that humans always ask, including why the sky is blue. Why do we see blue light coming at us from all directions when the Sun is above the horizon?
the air molecules are really good at scattering blue light from the Sun and worse at scattering other colors, so the other colors come from the direction of the Sun and the blue light comes from all other scattered directions
When the Sun is high in the sky we get blue light coming at us from all directions and a yellow Sun, but at sunset the side of the sky with the Sun looks yellow-orange and the Sun looks red. When the Moon is high in the sky it looks white, but when it is rising or setting close to the horizon it looks more yellow (or sometimes even orange). Why do the Sun and Moon look redder when they are closer to the horizon?
their light is passing through more air, so all the colors except for orange and red are scattered away from the direct line of sight to the Sun (or Moon)
Let’s say you go to the Moon, or the planet Mercury, or Jupiter’s moon Europa — all of which have no atmosphere at all. When the Sun is high in the sky, what color is the sky?
Black
At night we see many stars in the sky, but during the day we only see the Sun. Why aren’t the stars up during the day?
the stars are up during the day, the Sun’s light just overwhelms them
From Earth our human eyes can only really see the nearest neighbor stars in the entire galaxy, since our eyes are pretty bad telescopes. Our brains connect dots and pick out shapes that we call constellations. How far would you have to move to see the constellations look different because you would be seeing the stars from a different vantage point?
leave the solar system and move to another part of the galaxy
We see the Sun, Moon, and stars rise roughly in the East and set roughly in the West. What causes this?
rotation, Earth spins on its axis once a day
There is a slow shift in what stars we see at night throughout the whole year. For example Orion is visible at night in the Winter but not in the Summer, and Scorpius is visible at night in the Summer but not in the Winter. What causes this?
orbiting, Earth goes around the Sun once a year
The constellations have the same shapes night after night, year after year. Our neighbor stars do move through space and change position, but it takes a certain amount of time before the changes become noticeable. Roughly how much time do we need to wait until we can noticeably see the stars shifting position around us?
100,000 years
how do you use the Big Dipper to find the North Star?
two stars in the dippler’s bowl (opposite the handle) point to Polaris
is the North Star the brightest star in the sky?
no, it is not very bright
You estimate the North Star is about 59o above the horizon. Roughly where are you?
Stockholm, Sweden (latitude 59o North)
What was true during the time when the pyramids were built 5,000 years ago?
the Earth’s rotation axis slowly wobbles and was pointed toward another star 5000 years ago, a star called Thuban in the constellation of Draco (the dragon)
On Earth our northern rotation axis points very close to the star Polaris, making it our North Star. The southern rotation axis doesn’t point toward a bright star. Well, if we send humans to Mars, what will they see? Read about Mars and then answer this question: does Mars have a bright North Star or South Star?
Mars does not have a North Star and has a very faint South Star
If the Sun is in front of a constellation of the zodiac (for example, Scorpius), it takes about one ______ until it is front of the next zodiac constellation
month
If the Sun is in front of a constellation of the zodiac (for example, Scorpius), it takes about one ______ to pass through all the zodiac constellations and once again be in front of Scorpius
year
