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gandalf_der_12te@discuss.tchncs.de ⁨14⁩ ⁨hours⁩ ago

is there a physics limit to the density of energy

the physics limit to the density of energy is literally a black hole. it compresses the maximum amount of mass (energy) into a space. but that’s technologically useless since you can’t extract the energy out of it on-demand.

The densest ways of storing energy that are technologically useful are:

batteries (Na-Ion batteries: 0.2 kWh/kg)
oil/carbon-based fuels (bread: 5 kWh/kg)
uranium (pure uranium: 24 * 10^6 kWh/kg)

There’s also speculative technologies like antimatter (24 * 10^9 kWh/kg) which aren’t available today.

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GraniteM@lemmy.world ⁨9⁩ ⁨hours⁩ ago
The beauty of using uranium as currency is that if anyone hoards too much of it, the problem takes care of itself.

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absentbird@lemmy.world ⁨11⁩ ⁨hours⁩ ago
So one gram of antimatter could power a modern city for like three months? That’s wild.

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brotundspiele@sh.itjust.works ⁨14⁩ ⁨hours⁩ ago
There actually is a method that could be used to extract energy out of a black hole. Probably not something you’d build in a watch-sized device though.

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- gandalf_der_12te@discuss.tchncs.de ⁨14⁩ ⁨hours⁩ ago
  it only seems to work for rotating black holes though?
  
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  - brotundspiele@sh.itjust.works ⁨14⁩ ⁨hours⁩ ago
    Yeah, that’s why you have to wind up your watch every now and then. To spin up its internal black hole again.
    
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  - HeyThisIsntTheYMCA@lemmy.world ⁨12⁩ ⁨hours⁩ ago
    just drink more it’ll start spinning soon enough
    
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  - muts@feddit.nl ⁨14⁩ ⁨hours⁩ ago
    Don’t they all spin though? As in any matter falls in one way or another angular momentum is gained.
    
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    ProfessorPeregrine@reddthat.com ⁨10⁩ ⁨hours⁩ ago
    It is possible, but very unlikely. Maybe two bh merge that has exactly opposite angular momentum.
    
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- WorldsDumbestMan@lemmy.today ⁨14⁩ ⁨hours⁩ ago
  If the well, event horrizon expands when a blackhole takes more mass, why can’t we just figure out how much volume it is compressed into by measuring the event horrizon increase?
  
  We know the matter that goes in is a certain size. Maybe we can deduce the total size it is compressed to? And the size the blackhole gains.
  
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  - rtxn@lemmy.world ⁨14⁩ ⁨hours⁩ ago
    It’s impossible to know based on the current understanding of physics. A black hole is formed when the inward gravitational force exceeds the neutron degeneracy pressure of a sufficiently massive object, which is what keeps neutrons from occupying the same space (not really, it’s complicated). Beyond that, only conjecture exists with no evidence.
    
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