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50 Cards in this Set
- Front
- Back
- 3rd side (hint)
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What is our place in the universe, our "cosmic address"?
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-me, Earth, solar system, Milky Way Galaxy, Local Group, the Local Supercluster.
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What is a star?
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- a large glowing ball of gas that generates heat and light through nuclear fussion.
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What is a planet?
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-a moderately large object that orbits a star, it shines by reflected light; planets may be rocky, icy or gaseous in composition.
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What is a Moon or (satellite)?
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-an object that orbits a planet.
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What is an asteroid?
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-a relatively small and rocky object that orbits a star.
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What is a comet?-
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-a relatively small and icy object that orbits a star?
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What is a Solar System?
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- a star and all the material that orbits it,including its planets and moons.
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What is a Nebula?
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- an interstellar cloud of gas and/or dust.
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What is a Galaxy?
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- a great islan of stars in space, all held together by gravity and orbiting a common center.
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Universe
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- the sum total of all matter and energy; that is, everything within and between all galaxies.
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How fast does light travel?
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Light travels at a finite speed (300,000 km/s).
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"finite"
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Destination: Moon
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Light Travel time: 1 second
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Destination: Sun
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Light travel time: 8 minutes
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Destination: Sirius
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Light Travel time: 8 years
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Destination: Andromeda Galaxy
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Light Travel TIme: 2.5 million years.
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The farther away we look in distance=
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-the further back we look in time.
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Light-year=
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-The distance light can travel in one year.
-About 10 trillion kilometers (6 trillion miles). |
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Why can’t we see a galaxy 15 billion light-years away?
(Assume the universe is 14 billion years old.) |
-Because looking 15 billion light-years away
means looking to a time before the universe existed. |
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How did we come to be?
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-The matter in our bodies came from the Big Bang, which produced hydrogen and helium.
-All other elements were constructed from H and He in stars and then recycled into new star systems, including our solar system. |
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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. |
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Can we see the entire universe?
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-No, the observable portion of the universe is
about 14 billion light-years in radius because the universe is about 14 billion years old. |
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Let’s reduce the size of the solar system by a factor of
10 billion; the Sun is now the size of a large grapefruit (14 cm diameter). How big is Earth on this scale? |
-a tip of a ball point pen.
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On a 1-to-10 billion
scale: the sun is the size of? |
-of a large
grapefruit (14 cm) |
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On a 1-to-10 billion
scale: the earth is a size of? |
-a tip of a ball
point pen, 15 meters away. |
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On our 1-to-10 billion scale, it’s just a few minutes walk
to Pluto. How far would you have to walk to reach Alpha Centauri? |
-the distance across the United States
(2500 miles) |
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How big is the Milky Way Galaxy?
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The Milky Way has about 100
billion stars. |
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Suppose you tried to count the more than 100 billion stars in our galaxy, at a rate of one per second, how long would it take you?
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- a few thousand years.
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The Milky Way is one of about how many galaxies?
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-100 billion galaxies.
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How big is the universe?
10exp.11 stars/galaxy time 10exp.11 galaxies = |
- It has as many stars as grains of (dry) sand on all Earth’s beaches.
= 10exp.22 stars |
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How do our lifetimes compare to the age of the Universe?
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-The Cosmic Calendar: A scale on which we compress the history of the universe into 1 year.
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How big is the Earth compared to our solar system?
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-On a scale of 1-to-10 billion, the Sun is about the size of a
grapefruit. The Earth is the size of a tip of a ball point pen about 15 m away. The distances between planets are huge compared to their sizes. |
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How far away are the stars?
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-On a scale of 1-to-10 billion, On the same scale, the stars are thousands of kilometers away.
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How big is the Milky Way Galaxy?
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-It would take more than 3,000 years to count the stars in the
Milky Way Galaxy at a rate of one per second. The Milky Way Galaxy is about 100,000 light-years across. |
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How big is the universe?
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—100 billion galaxies in the observable universe
—14 billion light-years in radius —As many stars as grains of sand on Earth’s beaches |
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How do our lifetimes compare to the age of the universe?
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-On a cosmic calendar that compresses the history of the
universe into one year, human civilization is just a few seconds old, and a human lifetime is a fraction of a second. |
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How is Earth moving in our solar system?
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We are moving with the Earth in several ways, and at
surprisingly fast speeds. |
Contrary to our perception, we are not “sitting still.”
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How many times does Earth rotates around its axis?
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-once every day.
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Earth orbits the Sun (revolves):
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-once every year
-at an average distance of 1 AU ≈ 150 million km. -with Earth’s axis tilted by 23.5º (pointing to Polaris). -and rotates in the same direction it orbits, counterclockwise as viewed from above the North Pole. |
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Our Sun moves randomly relative to the other stars in
the local Solar neighborhood: |
-at typical relative speeds of more than 70,000 km/hr.
-it orbits the galaxy every 230 milion years. |
speed and orbit?
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Where does most the Milky Ways light come from?
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- the disk and the bulge
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-most of its mass is in its halo
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How do galaxies move within the universe?
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-Galaxies are carried along with the expansion of the universe.
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But how did Hubble figure out that the universe is expanding?
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-all galaxies outside our Local Group are moving away from us.
-the more distant the galaxy, the faster it is racing away. |
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Earth rotates on axis:
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> 1,000 km/hr
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Earth orbits Sun:
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> 100,000 km/hr
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Solar system moves among stars:
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~ 70,000 km/hr
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Milky Way rotates:
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~ 800,000 km/hr
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Milky Way moves
in: |
Local Group
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How is Earth moving in our solar system?
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-It rotates on its axis once a day and orbits the Sun at a distance of 1 AU = 150 million km
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How is our solar system moving in the Milky Way Galaxy?
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-Stars in the Local Neighborhood move
randomly relative to one another and orbit the center of the Milky Way in about 230 million years |
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How do galaxies move within the universe?
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-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 |
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