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Speed of Light
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How fast do particles travel in space?
(Intermediate)
How has light from 13 billion years ago not passed us by?
(Beginner)
How is it that we see farther out in space (farther back in time) than in the past?
(Beginner)
How long does it take for the Sun's light to reach us?
(Beginner)
How will a change in the speed of light affect the evolution of the Universe?
(Advanced)
If spacetime is curved, is it possible for us to look into space and see light from Earth from long ago?
(Intermediate)
If the universe is 13.8 billion years old, how can it be larger than 13.8 billion light years across?
(Advanced)
Is the speed of light constant?
(Beginner)
Is the universe expanding faster than the speed of light?
(Intermediate)
Is time travel possible?
(Beginner)
Traveling at light speed, how long would it take to get to the nearest galaxy?
(Beginner)
Wait, I'm still confused why information can't travel faster than the speed of light.
(Beginner)
What happens to a substance if its speed is more than the speed of light?
(Intermediate)
What is the size of a black hole?
(Intermediate)
What is the speed of gravity?
(Intermediate)
Who first measured the speed of light?
(Intermediate)
Why can't relative velocities add up to more than the speed of light?
(Intermediate)
Why doesn't gravity change the speed of light?
(Beginner)
Why doesn't light from distant galaxies reach us instantaneously?
(Intermediate)
Why is looking out into space the same as looking back in time?
(Beginner)
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Why do we study black holes? (Beginner)
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What color is each planet? (Intermediate)
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At what speed does the Earth move around the Sun? (Beginner)
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How far is each planet from Earth? (Intermediate)
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Are there telescopes that can see the flag and lunar rover on the Moon? (Beginner)
Is the Moon moving away from the Earth? When was this discovered? (Intermediate)
What color is each planet? (Intermediate)
How far is each planet from Earth? (Intermediate)
At what speed does the Earth move around the Sun? (Beginner)
What is the significance of the Tropic of Cancer, Tropic of Capricorn, Arctic Circle and Antarctic Circle? (Beginner)
Why do the planets orbit 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)
What would happen if an asteroid 10 kilometers across hit the Earth? (Beginner)
What is the difference between a "star" and a "sun"? (Beginner)
Why do stars twinkle? (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)
Is the Moon moving away from the Earth? When was this discovered? (Intermediate)
How do you measure the distance between Earth and the Sun? (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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