Earth is one of eight planets moving in almost circular paths round the Sun which, together with other smaller objects orbiting the Sun (asteroids, dwarf planets, comets) and moons orbiting several planets
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What are comets?
Comets are balls of dust, gas and ice which orbit the Sun in very elongated ellipses with the Sun near one end.
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What are asteroids?
Smallish clumps of rocks between Mars and Jupiter which did not form planets
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When and how was the solar system formed?
Over very long periods from clouds of gases and dust in space being squeezed and pulled together, about five thousand million years ago
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What is one of thousands of millions of stars in the Milky Way galaxy?
Sun
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What makes up the Universe?
Thousands of millions of galaxies, each containing thousands of millions of stars, and that all of these galaxies make up the Universe
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Put in order of size what makes up the Universe from smallest to largest?
1. Diameter of the Earth 2. Diameter of the Sun 3. Diameter of Earth's orbit, 4. Diameter of the Solar System 5. Distance from the Sun to the nearest star 6. Diameter of the Milky Way 7. Distance from the Milky Way to the nearest galaxy.
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Where does all the evidence we have about distant stars and galaxies come from?
Radiation astronomers detect
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What speed does light travel through space (a vacuum)?
300 000 km/s
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What is a light-year?
The distance travelled by light in a year.
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What does the finite speed of light tell us about very distant objects?
We are observing these very distant objects in the past as the light has taken a long time to get to the Earth
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What is parallax?
Parallax can be used to measure how far away a star is because closer stars appear to move more compared to further away stars which appear to move less or not at all.
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How can the distance to a star be estimated?
Relative brightness
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What can interfere with observations of the night sky?
Light pollution and other atmospheric conditions
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Why are there uncertainties about the distances of stars and galaxies?
Nature and difficulty of the observations on which these distances are based and the assumptions made in interpreting them
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What is the source of the Sun’s energy?
Fusion of hydrogen nuclei
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Where were all chemical elements with atoms heavier than helium made?
Stars
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What suggests that distant galaxies are moving away from us?
Light from distant galaxies' wavelength is being stretched, shifting the light to the red end of the spectrum
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What does redshift show us about the distance of a galaxy?
The further away a galaxy is, the faster it is moving away from us
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What does redshift suggest about space?
Sspace itself is expanding
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From oldest to youngest put in order Sun, Earth and Universe
Universe is oldest (14,000 million years) and youngest is Sun and Earth (both approximately 5,000 million years old)
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How do scientists believe the Universe began?
With a ‘big bang’ about 14 thousand million years ago
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What are the two possible ultimate fates of the Universe?
1. Keep expanding forever 2. Stop expanding and begin contracting (big crunch)
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Why is it difficult to predict the ultimate fate of the Universe?
Difficulties measuring: 1. very large distances 2. very large masses 3. motion of very distant objects
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Other cards in this set
Card 2
Front
What are comets?
Back
Comets are balls of dust, gas and ice which orbit the Sun in very elongated ellipses with the Sun near one end.
Card 3
Front
What are asteroids?
Back
Card 4
Front
When and how was the solar system formed?
Back
Card 5
Front
What is one of thousands of millions of stars in the Milky Way galaxy?
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