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Can we harvest H & O from space to make water?
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Is the reddish dust of Mars biogenic?
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Is there oxygen in the atmospheres of other planets?
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Is speed of light the same everywhere ? (Beginner)
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Why is the sun red? During sunset, Northeastern US, Summer 2021 (Beginner)
Why do rays from Sun appear to converge at a point? (Beginner)
But seriously: what was there before the Big Bang? (Beginner)
How far can photons move freely in the early universe (Advanced)
How likely is it that the Solar System has had or will have a close encounter with another star? (Intermediate)
How do we know what we observe is x light years away? (Beginner)
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What is the universe expanding into? (Intermediate)
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What was the bright, smoothly moving star that I saw? (Beginner)
What would happen if the Moon fell out of its orbit around Earth? (Intermediate)
Are there telescopes that can see the flag and lunar rover on the Moon? (Beginner)
Is it possible for amateurs to do optical interferometry? (Intermediate)
How long could life on Earth survive if the Sun stopped shining? (Beginner)
Earth's Bow Shock (Advanced)
How can we see the Milky Way if we are inside it? (Intermediate)
What kind of eyepieces do I need to look at planets? (Intermediate)
What would happen if an asteroid 10 kilometers across hit the Earth? (Beginner)
How do you measure the distance between Earth and the Sun? (Intermediate)
What was the bright, smoothly moving star that I saw? (Beginner)
Are there telescopes that can see the flag and lunar rover on the Moon? (Beginner)
How far is each planet from Earth? (Intermediate)
What would happen if the Moon fell out of its orbit around Earth? (Intermediate)
Earth's Bow Shock (Advanced)
How do you measure the distance between Earth and the Sun? (Intermediate)
Why do the planets orbit the sun? (Beginner)
Which planet is most similar to Earth? (Intermediate)
At what speed does the Earth move around the Sun? (Beginner)
How are light and heavy elements formed? (Advanced)
Are there telescopes that can see the flag and lunar rover on the Moon? (Beginner)
What was the bright, smoothly moving star that I saw? (Beginner)
How do you measure the distance between Earth and the Sun? (Intermediate)
Which planet is most similar to Earth? (Intermediate)
How far is each planet from Earth? (Intermediate)
Why is the moon in a different place every night? (Beginner)
Earth's Bow Shock (Advanced)
How does the position of Moonrise and Moonset change? (Intermediate)
How are light and heavy elements formed? (Advanced)
Why do the planets orbit the sun? (Beginner)
What's going to happen on December 21st 2012? (Intermediate)
What color is each planet? (Intermediate)
At what speed does the Earth move around the Sun? (Beginner)
How far is each planet from Earth? (Intermediate)
How do you measure the distance between Earth and the Sun? (Intermediate)
Is the Moon moving away from the Earth? When was this discovered? (Intermediate)
Why do the planets orbit the sun? (Beginner)
What is the significance of the Tropic of Cancer, Tropic of Capricorn, Arctic Circle and Antarctic Circle? (Beginner)
When was the last time all of the planets were aligned? (Beginner)
How long does it take for the Sun's light to reach us? (Beginner)
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