Comment on Since light cannot pass through a black hole does that mean light has mass? Also why does light form a singularity in a black hole? Is that like a fixed point on a map or something?

HotsauceHurricane@lemmy.world ⁨7⁩ ⁨hours⁩ ago

• davidgro@lemmy.world ⁨7⁩ ⁨hours⁩ ago

  It’s “yes, but not rest mass.” - light has energy and energy is mass. (Specifically m=E/c²)

  In theory a sensitive enough scale could measure the difference between a charged battery and a drained one* without the battery gaining or losing any matter. Not even electrons, since each one leaving the negative end is replaced by one going in the positive end, and vice versa when charging. This is the type of mass light has, just pure energy.

  *I did the math a while back and if I remember right for a typical AA size Ni-MH battery the difference would be about the weight of a bacterium.

  source

  • hoshikarakitaridia@lemmy.world ⁨2⁩ ⁨hours⁩ ago

    So the answer is “kind of”?

    source
  • skankhunt42@lemmy.ca ⁨5⁩ ⁨hours⁩ ago

    So I’m just an idiot when I guess if a battery is good by weight vs other batteries I have. Two heavy ones must be good!

    Maybe I should actually get a battery tester…

    source

    • spizzat2@lemmy.zip ⁨4⁩ ⁨hours⁩ ago

      Or drop them!

      TL:DW version.

      source
    • davidgro@lemmy.world ⁨4⁩ ⁨hours⁩ ago

      Yeah, just get a tester. In reality the weight difference is immeasurably small (like completely swamped by dust particles)

      source
    • OhmeHose@feddit.org ⁨5⁩ ⁨hours⁩ ago

      Just lick the batteries! No need for fancy tech!

      source