## Physics Questions People Ask Fermilab

Special and general relativity
Physics at the speed of light

1. Quantum entanglement and Black holes ...
"What happens if you take 2 quantum-entangled particles, and untangle them and put one of these particles in a blackhole? The other should demonstrate what is going on inside a blackhole, right? Wouldn't this violate the principle that no light, or information, escapes a blackhole?"

2. Centripetal Forces and distances at speed of light
"If space contained only two things and they would rotate relative to each other, would their mass and distance influence the size of the centripetal forces the two things feel? In general relativity, can the distance of any two things increase or decrease faster than the speed of light?"

3. Spin and Frame of Reference
"If I hold a book at arms length with one hand on either side of the book and rotate around in a circle, does the book "spin" on an axis perpendicular to the plane of rotation?"

4. Do blueshifts exist?

5. Adding velocities and increasing mass
"What is the equation for velocity approaching that of the speed of light? Is it true that E=mc^2 is modified in Einstein's special theory of relativity with a factor of sqrt(1-v^2/c^2)?"

6. Light from a fast car
"Theoretical Question: If a vehicle was traveling at the speed of light and a light source was emitted from the vehicle would there be a visible beam of light?"

7. The first speed-of-light measurement
"Who was the first person to measure the speed of light? How was it done?"

8. Lowest speed
"I know very well that there is an upper limit of speed in nature (which is the speed of light), but I wonder a lot if there is a lower speed limit in our universe."

9. Approaching the speed of light
"Why can't anything travel faster then the speed of light?"

10. Faster than speed of light?
"I heard that some of the particles in your collisions were clocked at a speed faster than the speed of light. Is there any truth to this?"

11. New way of thinking about the speed-of-light theory?
"When matter reaches speeds near that of light, it no longer exist in normal time. Does it turn into light when achieving the speed of light?"

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