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A line drawn perpendicular to a line through the tips of the horns of the crescent moon doesn't point to the Sun! Why not?
(Advanced)
Can we look back far enough in time to see the Big Bang?
(Beginner)
Can we look back in time and see our galaxy forming?
(Intermediate)
Can you use an infinite line of reflectors to send light to the edge of the Universe?
(Intermediate)
Could dark energy come from matter anti-matter pairs forming spontaneously and then annihilating?
(Advanced)
Could photons be dark matter?
(Intermediate)
Has there been an experiment that measured speed faster than the speed of light in vacuum?
(Advanced)
How can we see galaxies if their stars are so faint?
(Intermediate)
How do we know that nuclear fusion is still going on in the Sun?
(Intermediate)
How far can photons move freely in the early universe
(Advanced)
How has light from 13 billion years ago not passed us by?
(Beginner)
How long does the supernova stage of a star last?
(Intermediate)
How much power is contained in a beam of light?
(Intermediate)
If light has no mass, then what draws it into a black hole?
(Intermediate)
If photons have zero mass, why do they feel the effects of gravity?
(Advanced)
Is it possible to measure the temperature of the Sun?
(Beginner)
Is light blueshifted when it is gravitationally lensed?
(Intermediate)
Is the green flash real?
(Beginner)
What color would Mars be if you were standing on it?
(Advanced)
What do a galaxy's colors mean? Are they its true colors?
(Intermediate)
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Earth's Bow Shock (Advanced)
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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)
What do I need to do to become an astronomer? (Beginner)
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How far is each planet from Earth? (Intermediate)
Why is Earth's core molten? (Intermediate)
Why is the moon in a different place every night? (Beginner)
How do you measure the distance between Earth and the Sun? (Intermediate)
Are there telescopes that can see the flag and lunar rover on the Moon? (Beginner)
Why do the planets orbit the sun? (Beginner)
How can the Universe expand faster than the speed of light during inflation? (Advanced)
What was the bright, smoothly moving star that I saw? (Beginner)
Which planet is most similar to Earth? (Intermediate)
At what speed does the Earth move around the Sun? (Beginner)
Are there telescopes that can see the flag and lunar rover on the Moon? (Beginner)
How do you measure the distance between Earth and the Sun? (Intermediate)
How far is each planet from Earth? (Intermediate)
Why is the moon in a different place every night? (Beginner)
Which planet is most similar to Earth? (Intermediate)
Why do the planets orbit the sun? (Beginner)
How can the Universe expand faster than the speed of light during inflation? (Advanced)
At what speed does the Earth move around the Sun? (Beginner)
Is the speed of light constant? (Beginner)
How long could life on Earth survive if the Sun stopped shining? (Beginner)
Are there telescopes that can see the flag and lunar rover on the Moon? (Beginner)
How do you measure the distance between Earth and the Sun? (Intermediate)
How far is each planet from Earth? (Intermediate)
Why is the moon in a different place every night? (Beginner)
How does the position of Moonrise and Moonset change? (Intermediate)
Which planet is most similar to Earth? (Intermediate)
Why do the planets orbit the sun? (Beginner)
What was the bright, smoothly moving star that I saw? (Beginner)
Why do we not have eclipses every month? (Beginner)
At what speed does the Earth move around 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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