Relativity Insights: FAQs on Photons, Gravity, Time Dilation, and More!

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* FAQ entries are slowly being migrated to the Insights blog
https://www.physicsforums.com/insights/category/faqs/

Feel free to request future FAQs
 
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Time to update this page. Too many of the links end up at the black hole -- but the threads/insights are still sitting elsewhere on PF.
 
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There must be lots of old posts which link to FAQ pages that no longer exist. Is it technically possible to redirect these to the correct new location? Or, if not, can at least the old FAQ pages still exist each displaying a link to the new page?
 
DrGreg said:
Is it technically possible to redirect these to the correct new location?
Yep!
 
The relativity FAQ list is back, updated and will be updated as more relativity Insights are posted.
 

Thread 'I don't see how a black hole's event horizon can be crossed'

OK, so this has bugged me for a while about the equivalence principle and the black hole information paradox. If black holes "evaporate" via Hawking radiation, then they cannot exist forever. So, from my external perspective, watching the person fall in, they slow down, freeze, and redshift to "nothing," but never cross the event horizon. Does the equivalence principle say my perspective is valid? If it does, is it possible that that person really never crossed the event horizon? The...
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Thread 'Question about Parallel Transport'

In this video I can see a person walking around lines of curvature on a sphere with an arrow strapped to his waist. His task is to keep the arrow pointed in the same direction How does he do this ? Does he use a reference point like the stars? (that only move very slowly) If that is how he keeps the arrow pointing in the same direction, is that equivalent to saying that he orients the arrow wrt the 3d space that the sphere is embedded in? So ,although one refers to intrinsic curvature...
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Thread 'Synchronizing clocks in an inertial frame if light is anisotropic'

ASSUMPTIONS 1. Two identical clocks A and B in the same inertial frame are stationary relative to each other a fixed distance L apart. Time passes at the same rate for both. 2. Both clocks are able to send/receive light signals and to write/read the send/receive times into signals. 3. The speed of light is anisotropic. METHOD 1. At time t[A1] and time t[B1], clock A sends a light signal to clock B. The clock B time is unknown to A. 2. Clock B receives the signal from A at time t[B2] and...
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