October Test Flashcards
Why are we “star stuff”?
The universe started with the Big Bang, which produced helium and hydrogen. Everything else was brought by stars.
What is our physical place in the universe?
Earth, in the Milky Way Galaxy, in the Local Group, in the Local Supercluster, in the universe
Why does looking into space mean looking back in time
Light takes time to travel through space.
How do human scales compare to the age of the Universe?
On a cosmic calender, human civilization is just a few seconds old
Describe the basic motions of Earth
Earth rotates on its axis once each day and orbits around the sun once each year.
How do we know that the universe is expanding
All galaxies are moving away from us
What is a constellation?
A region of the sky
What is the celestial sphere
An imaginary sphere surrounding Earth that contains the stars, Sun, Moon, and planets
Why do we see a band of light called the Milky Way in the sky
It traces the Galactic plane
Describe the basic features of the sky
The horizon is the boundary between Earth and sky.
How does the sky vary with latitude
As the celestial sphere rotates, we see different portions of paths of stars from different latitudes.
Why are some stars above the horizon at all times?
All stars appear to make a daily circle. Circumpolar stars which are above horizon
What is the cause of the seasons on Earth?
As the Earth orbits, different portions of Earth receive more or less sunlight.
Summer Solstice - Northern gets most sunlight
Winter Solstice - southern gets most sunlight
Equinoxes - equal sunlight
How does the night sky change through the year?
The visible constellations depend on where the Earth is in its orbit around the sun
Why do we see phases of the moon?
Phases of the moon are due to parts of the moon being in darkness while other parts are illuminated by the sun
Why do planets seem to move backwards relative to the stars?
Retrograde motion occurs when the Earth passes by another planet in its orbit
What are Kepler’s laws of planetary motion?
- The orbit of each planet is an ellipse with the Sun at one focus.
- As a planet moves around its orbit, it sweeps out equal areas in equal time
- More distant planets orbit the sun at slower speeds
How do we distinguish science from nonscience
- Modern science seeks explanations for phenomena that rely on natural causes
- Science progresses through the creation and testing of models
- A scientific model must make testable predictions about natural phenomena that would force us to revise the model if the predictions don’t agree with the observations
What is a theory in science
A model that explains a variety of observations in terms of just a few general principles, which has survived numerous tests to verify its predictions and explanations
What is the basic structure of an atom?
An atom consists of a tiny nucleus made of protons and neutrons surrounded by a cloud of electrons
How is light a wave?
Light is a wave of vibrating electric and magnetic fields
In what way is light made of particles?
Light comes in individual photons, each with a specific energy that depends on its frequency
How are wavelength, frequency, and energy related for photons of light?
Frequency increases when wavelength decreases and vice versa. Energy is proportional to frequency.
List the forms of light that make up the electromagnetic spectrum
Radio, infrared, visible light, uv, x-Ray, gamma ray
What are the two rules of thermal radiation?
- Hotter objects emit more total radiation per unit area.
2. Hotter objects emit photons with a higher average energy
Are there any material objects that don’t give off any light
No. All objects radiate light by virtue of their temperatures. This light is thermal radiation.
What is the purpose of a telescope?
A telescope is designed to collect as much light as possible. It also improves resolution and magnifies images.
How do astronomers the light collected by a telescope?
Imaging - use a camera to take pictures, photometry measures total amount of light from an object
Spectroscopy -use a spectrograph to separate the light into different wavelengths
If you had x-ray vision, could you read an entire book without turning the pages
No, a book doesn’t emit x-rays
Some telescopes are put in space for what reasons?
To avoid blurring effects of the Earth’s atmosphere
To avoid the atmosphere absorption of some wavelengths of light
To avoid clouds, high winds, and other inclement weather
The frequency of a wave:
Is measured in hertz, is the number of peaks passing by any point, is measured in cycles per second, and is equal to the speed of the wave divided by wavelength of the wave
The wavelength of a wave is:
The distance between two adjacent peaks of the wave
How are wavelengths, frequency and energy related
Longer wavelength means lower frequency and lower energy
You can see people around you because you
Reflect visible light
Which two wavelength regions cannot be studied with telescopes on the ground?
X-rays and uv
What is the purpose of adaptive optics?
To eliminate distorting effects of atmospheric turbulence for telescopes on the ground
Currently, the largest telescope mirrors have a diameter of
10m
What does interferometry do?
Allows two or more telescopes to obtain the angular resolution of a single telescope much larger than any individual telescope
Why is Polaris special?
It appears near the north celestial pole
Can we see other galaxies?
No, stars, gas and dust block us from seeing them
Why do we see the same face of the Moon at all times?
Because the moons rotational and orbital periods are equal
What conditions are required for a solar eclipse
The phase of the moon must be new, and the nodes of the moons orbit must be nearly aligned with the earth and sun
