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Cake day: June 12th, 2023

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  • xionzui@lemmy.worldtoMemes@lemmy.mlThe life of a photon
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    1 year ago

    Reflections involve the material absorbing and re-emitting photons back the other direction.

    The curvature of light from gravity is actually space-time itself being curved by mass. The light continues on a straight path through a curved space-time. It looks like it changes direction from the outside, but that’s just the shape of the universe in that area.

    That’s why we feel gravity. The space-time around earth is curved inward, so going forward in time would actually mean falling towards the center if we were stationary in space. The ground is constantly accelerating us upwards. Light does not get accelerated that way, so it follows the curvature.

    If you want to get really deep into the reflection topic: https://youtu.be/rYLzxcU6ROM



  • I’ve been trying to wrap my head around this part and what it means for cause and effect for a while. I think Feynman said something like a photon is only ever emitted when the source and destination agree to exchange one. Which makes sense if the exchange is instantaneous to the photon. But how can billions of years pass for us in the mean time?



  • I use backupninja for the scheduling and management of all the processes. The actual backups are done by rsync, rdiff, borg, and the b2 tool from backblaze depending on the type and destination of the data. I back up everything to a second internal drive, an external drive, and a backblaze bucket for the most critical stuff. Backupninja manages multiple snapshots within the borg repository, and rdiff lets me only copy new data for the large directories.