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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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What color is each planet? (Intermediate)
What is the evidence supporting the nebula theory of Solar System formation? (Intermediate)
Are there telescopes that can see the flag and lunar rover on the Moon? (Beginner)
How does the location of sunrise and sunset change throughout the year? (Advanced)
What is the significance of the Tropic of Cancer, Tropic of Capricorn, Arctic Circle and Antarctic Circle? (Beginner)
Can artificial gravity be created in space? (Intermediate)
What is the difference between a "star" and a "sun"? (Beginner)
Is the distance from the Earth to the Sun changing? (Advanced)
How was the starting point for the Julian Date system chosen? (Advanced)
Why do the planets orbit the sun? (Beginner)
What color is each planet? (Intermediate)
What is the significance of the Tropic of Cancer, Tropic of Capricorn, Arctic Circle and Antarctic Circle? (Beginner)
How far is each planet from Earth? (Intermediate)
How are light and heavy elements formed? (Advanced)
Are aliens or UFOs real? (Beginner)
Are there telescopes that can see the flag and lunar rover on the Moon? (Beginner)
How does the location of sunrise and sunset change throughout the year? (Advanced)
What is the difference between a "star" and a "sun"? (Beginner)
When was the last time all of the planets were aligned? (Beginner)
What is the evidence supporting the nebula theory of Solar System formation? (Intermediate)
What color is each planet? (Intermediate)
How are light and heavy elements formed? (Advanced)
What is the significance of the Tropic of Cancer, Tropic of Capricorn, Arctic Circle and Antarctic Circle? (Beginner)
How far is each planet from Earth? (Intermediate)
What is the difference between a "star" and a "sun"? (Beginner)
How is it proved that the Universe is expanding? (Intermediate)
How does the location of sunrise and sunset change throughout the year? (Advanced)
Are there telescopes that can see the flag and lunar rover on the Moon? (Beginner)
When was the last time all of the planets were aligned? (Beginner)
Is the Moon moving away from the Earth? When was this discovered? (Intermediate)
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)
How long does it take for the Sun's light to reach us? (Beginner)
When was the last time all of the planets were aligned? (Beginner)
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