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Can "tired light theory" explain the observed redshifts of galaxies?
(Intermediate)
Can gravitational lensing from intervening galaxies cause the observed ripples in the Cosmic Microwave Background?
(Advanced)
Can we look back far enough in time to see the Big Bang?
(Beginner)
Could photons be dark matter?
(Intermediate)
Could the Universe have expanded faster than the speed of light at the Big Bang?
(Intermediate)
How big is the Universe?
(Intermediate)
How do we know the age of the Universe and the Earth?
(Intermediate)
What makes up most of the Universe?
(Beginner)
What's the difference between dark matter and dark energy?
(Intermediate)
Where, in relation to the entire universe, is the Milky Way located?
(Intermediate)
Why is the Cosmic Microwave Background not absorbed by interstellar hydrogen?
(Advanced)
Why is the WMAP picture of the CMB an ellipse?
(Intermediate)
Wouldn't the Big Bang theory be considered a hypothesis and not a theory?
(Intermediate)
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What is at the end of the Universe? (Intermediate)
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Is speed of light the same everywhere ? (Beginner)
How does Venus have sulphuric acid in it's clouds? (Beginner)
Earth's Bow Shock (Advanced)
How much does the Earth "wobble" on its orbit due to the Moon's gravity? (Intermediate)
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)
Editor's Pick
What is the universe expanding into? (Intermediate)
What do I need to do to become an astronomer? (Beginner)
What's the difference between astronomy and astrology? (Beginner)
Why is looking out into space the same as looking back in time? (Beginner)
Can we find the place where the Big Bang happened? (Intermediate)
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Can astronauts produce water in space? (Intermediate)
What are shooting stars? (Beginner)
How are galaxies named? (Beginner)
Does the Mediterranean sea have tides? (Intermediate)
Where did all the water in the universe come from? (Intermediate)
How do supernovae show us that the Universe's expansion is accelerating? (Advanced)
Why are there stars? (Beginner)
Why do we study black holes? (Beginner)
What kind of rock is the moon made of? (Intermediate)
How long does it take the Big Dipper to move in the sky? (Intermediate)
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)
How can the Universe expand faster than the speed of light during inflation? (Advanced)
Why do the planets orbit the sun? (Beginner)
At what speed does the Earth move around the Sun? (Beginner)
How long could life on Earth survive if the Sun stopped shining? (Beginner)
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 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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