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ELI5: Matter sucked into a black hole leaves a gravitational trace, meaning all black holes are gravitational data centres logging the neighbourhoods historical

ELI5: Matter sucked into a black hole leaves a gravitational trace, meaning all black holes are gravitational data centres logging the neighbourhoods historical activities.

edgyquant 5y ago
Wow that’s pretty awesome. Has this been proven?
- detritus 5y ago
  I'm not sure this Could Ever Be proven. Outwith some unknown hyperscience, at least.
  - zardo 5y ago
    We'll have plenty of time to develop hyperscience before we can watch any known black hole start shrinking.
- pdonis 5y ago
  No. What the article is describing is a proposed theoretical model. There is no prospect of gathering any data to test it now or in the foreseeable future.
  - andrewflnr 5y ago
    Mostly just faint hope that Planet 9 both exists and is a primordial black hole.
BobbyJo 5y ago
So the thought here is that particle spins/charges/mass/etc. are all encoded in the gravitational field of the black hole?
danbruc 5y ago
While the previous assumption was that black holes are completely characterized by only three parameters - mass, electric charge, and angular momentum - which is called the no-hair theorem [1]. This is at odds with the time-reversibility of physical laws as there are many ways to make a black hole with a certain mass, electrical charge, and angular momentum but given such a black hole it is not possible to go backwards in time and reconstruct the formation process of the black hole as you have only three numbers and therefore not enough information to figure out when, where and what was thrown into the black hole. [1] https://en.wikipedia.org/wiki/No-hair_theorem https://en.wikipedia.org/wiki/No-hair_theorem
- Terry_Roll 5y ago
  So space archaeology is dead before it got started?
  - danbruc 5y ago
    Not sure if understand what you mean, but if you mean that black holes could eat up the traces of the past and make history inaccessible, then no, at least theoretically. I would assume that the current consensus is that black holes can not do this - which implies that the no-hair theorem is at best approximately true - but we only have unproven ideas which mechanism prevents black holes from destroying information. In practice recovering information from black holes is probably no easier than trying to recover the text of a book by inspecting the smoke of the fire you threw the book into.
    - Terry_Roll 5y ago
      It was a little joke about rooting around inside a blackhole discovering things from the past. ;-)
  - simiones 5y ago
    "Dead" barely even begins to describe the horror of passing the event horizon of a black hole - essentially every particle of your body that gets closer to the center becomes unable to ever, in any possible future, communicate back to the parts that are farther away (according to the GR understanding, which to be fair is not consistent with what we know of QM).

ELI5: Matter sucked into a black hole leaves a gravitational trace, meaning all black holes are gravitational data centres logging the neighbourhoods historical activities.

edgyquant 5y ago

Wow that’s pretty awesome. Has this been proven?

detritus 5y ago
I'm not sure this Could Ever Be proven. Outwith some unknown hyperscience, at least.
- zardo 5y ago
  We'll have plenty of time to develop hyperscience before we can watch any known black hole start shrinking.
pdonis 5y ago
No. What the article is describing is a proposed theoretical model. There is no prospect of gathering any data to test it now or in the foreseeable future.
- andrewflnr 5y ago
  Mostly just faint hope that Planet 9 both exists and is a primordial black hole.

BobbyJo 5y ago

So the thought here is that particle spins/charges/mass/etc. are all encoded in the gravitational field of the black hole?

danbruc 5y ago

While the previous assumption was that black holes are completely characterized by only three parameters - mass, electric charge, and angular momentum - which is called the no-hair theorem [1]. This is at odds with the time-reversibility of physical laws as there are many ways to make a black hole with a certain mass, electrical charge, and angular momentum but given such a black hole it is not possible to go backwards in time and reconstruct the formation process of the black hole as you have only three numbers and therefore not enough information to figure out when, where and what was thrown into the black hole. [1] https://en.wikipedia.org/wiki/No-hair_theorem https://en.wikipedia.org/wiki/No-hair_theorem

Terry_Roll 5y ago
So space archaeology is dead before it got started?
- danbruc 5y ago
  Not sure if understand what you mean, but if you mean that black holes could eat up the traces of the past and make history inaccessible, then no, at least theoretically. I would assume that the current consensus is that black holes can not do this - which implies that the no-hair theorem is at best approximately true - but we only have unproven ideas which mechanism prevents black holes from destroying information. In practice recovering information from black holes is probably no easier than trying to recover the text of a book by inspecting the smoke of the fire you threw the book into.
  - Terry_Roll 5y ago
    It was a little joke about rooting around inside a blackhole discovering things from the past. ;-)
- simiones 5y ago
  "Dead" barely even begins to describe the horror of passing the event horizon of a black hole - essentially every particle of your body that gets closer to the center becomes unable to ever, in any possible future, communicate back to the parts that are farther away (according to the GR understanding, which to be fair is not consistent with what we know of QM).